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438 Cards in this Set
- Front
- Back
Most important factor in preventing accidents at a wastewater plant?
|
Attitude of the employees. |
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Plant influent appears black and has a foul odor each morning. The cause is traced to a pump station at a subdivision which is oversized for the current number of homes in the subdivision. What corrective action can you take? |
Decrease the distance between the on and off probes in the wet well. |
|
Which of the following best describes the term "public relations"? |
All contacts between the staff of the utility and those outside the staff. |
|
What is a cross connection? |
Result of wastewater coming into contact with potable water. |
|
Why is it recommended that approved backflow prevention devices be installed above grade level? |
To prevent the relief port of the device from ever becoming submerged. |
|
Your plant's discharge permit requires that effluent suspended solids be tested 3 days per week. You test five samples per week. What should you report? |
All five results. |
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At a minimum, how often should contact lists on emergency response plans be verified? |
Quarterly. |
|
According to the Code of Federal Regulations the term "Significant Industrial User" includes. |
A non-domestic discharger that discharges over 25,000 gallons per day of process wastewater or is subject to specific federal pretreatment standards. |
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What document is used to evaluate compliances with personal protective equipment guidelines? |
Occupational Safety and Health Standards. |
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Which term describes the calculated amount by which the value of a utility's physical property declines annually at a predetermined rate? |
Depreciation. |
|
According to 40 CFR, a discharge to a municipal separate storm sewer system that is composed of storm water mixed with industrial waste is defined by EPA as a(n)? |
Illicit discharge. |
|
The main detrimental effect infiltration/inflow has on plant performance is to. |
Cut down the hydraulic detention time. |
|
Which of the following explains how to handle a chlorine release? |
Emergency response plan |
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Which of the following is the most significant problem in using the activated sludge process to treat seasonal cannery waste? |
Nutrient imbalance |
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An auto flow proportional chlorination system is working properly. However in the morning hours when the flow is increasing, the operator is unable to obtain a chlorine residual. What is causing the problem? |
Nitrites in the effluent. |
|
To achieve an overall threat rating for a specific emergency event, a wastewater utility should consider the frequency of past occurrences, the probability of future occurrences, and |
Magnitude of impact. |
|
Uniforms, i.d., and system logos on wastewater system vehicles are critical components of |
public awareness and security program |
|
First step in solving odor problem at plant? |
Make an onsite inspection. |
|
Comprehensive accident report must be posted for review by all employees once per |
year |
|
Delivery of treatment chemicals and materials can pose a security risk. Which of the following is the best way to reduce a treatment plant's vulnerability? |
Match all delivered goods with manifest and purchase order. |
|
The NPDES permit requires an open channel flow measurement system to provide an accuracy of no worse than |
plus or minus 10% |
|
A plant seeks advice to prepare a new ordinance to the use of sewers, which 3 items have the most impact on the operation of the facility? |
The amount of flow, strength of wastewater, and the toxicity of the wastewater. |
|
usual first step in strategic planning for wastewater utilities? |
Setting goals and objectives. |
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Systematic process for evaluating the susceptibility of critical facilities to potential threats and identifying corrective actions that can reduce or mitigate the risk of serious consequences associated with these threats? |
Vulnerability assessment. |
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Wastewaters from manufacturing processes should be kept separate from cooling waters in order to reduce. |
Volume. |
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Wastes from industry can increase the influent temp, what effect can this have on the secondary treatment process? |
Organism activity will increase. |
|
In order to most effectively secure computers used for instrumented process control from cyber-attacks (computer hackers) at wastewater facilities, a utility should |
Not directly connect a scada system to the internet. |
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A wastewater plant has a chlorine leak that results in a release of chlorine gas above reportable quantities. which regulation requires the operator in charge to file a report? |
SARA Title III |
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According to OSHA process safety management regulations, what must the plant management do prior to allowing an outside contractor to upgrade a plant's chlorine feed system? |
Inform the contractor of known hazard potentials in the work area |
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How often should revenue and expense reports be developed for a public wastewater plant |
Monthly |
|
NPDES permits are effective for a fixed term not to exceed how many years? |
5 |
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The superfund amendment and reauthorization act of 1986, referred to as SARA, Title III primarily provides for local community |
Emergency planning and community right to know |
|
Results obtained from pipe roughness coefficient tests can indicate whether or not |
friction losses in the pipe are increasing |
|
a centrifugal pump works on the principle of changing velocity head to |
pressure head |
|
The pump station with variable freq. drives, two complete pumping unites are provided. What flow should each pumping unit be capable of delivering? |
The max daily design flow of the station. |
|
When determining the suction head or lift of a centrifuge pump, measure the distance from the |
Water surface to the center line of the impeller |
|
The head against which a pump must operate |
is the sum of the static head and the friction head |
|
The wet well water level in a lift station controlled by a bubbler system is much lower than normal, the pumps are running constantly, and the level indicator is high. what is most likely the explanation? |
The bubbler tube is blocked. |
|
What may cause a reduction in the pump discharge rate? |
Suction lift higher than anticipated |
|
If other factors remain constant, the capacity of a centrifugal type pump inscreases when the |
Speed of the pump is increased. |
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Which type of pump works on the principle of a decrease in the overall specific weight of a confined column of a gas-water mixture? |
Air lift |
|
Which valve is most suitable for a throttling application? |
Butterfly valve |
|
The term suction lift refers to the pressure measured from the center line of the pump |
Down to the hydraulic grade line |
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Two pumps of the same capacity operate together with a single main. In a typical pump station the discharge will be |
More than one pump, but not twice as much |
|
Which gas is most toxic to humans when inhaled? |
Hydrogen sulfide |
|
What is the safety concern with carbon dioxide |
Carbon dioxide is heavier than air and may cause oxygen-deficient atmospheres |
|
During normal operation of a positive pressure, open-circuit self-contained breathing apparatus, the bypass valve should be |
fully closed |
|
alarm set point for oxygen in an atmospheric monitoring device |
19.5% |
|
Osha requires that three types of atmosphere tests be conducted in a confined space. These must be conducted in a specific order, what test should be done first? |
oxygen content |
|
Threshold limit value time weighted average is what? |
Max. allowable exposure for 8 hours with no harmful effects. |
|
What document is used to evaluate compliance with personal protective equipment guidelines? |
Occupational safety and health standards |
|
Electrical pressure available to cause a flow of current when an electrical circuit is closed? |
Voltage |
|
Besides viscosity, what is an important consideration in the selection of a lubricating oil |
thermal range |
|
A belt driven centrifugal pump was out of service for inspection and impeller replacement. When placed back in service, it produced a lower rate of discharge. The first item to check is whether the |
impeller shaft key was installed. |
|
Maintenance required by mag meters includes checking the |
flow zero |
|
maintenance required for capacitance level indicators includes |
checking and cleaning the connections |
|
the scale that forms on the cathode of an electrolytic process reactor can be removed by flushing the system with |
dilute nitric acid |
|
maintenance required by percent open-closed valve controllers includes |
manually checking the indicator against the valve opening |
|
Erratic performance by pneumatic instruments may be caused by |
water in the air supply |
|
A recently rebuilt centrifugal pump has just been returned to service and is now drawing more amps. What is the most likely cause of this problem? |
packing is too tight |
|
When lubricating electric motors, avoid |
mixing petroleum base grease with silicon base grease |
|
If a gas engine knocks, the most likely cause of the problem is |
Engine is under a heavy load at a low speed |
|
What's the easiest way to determine whether the rotor or the stator on progressive cavity pumps are worn? |
Track the discharge flow rate over time |
|
Improper rotation in a centrifugal pump may cause |
reduced flow or no flow |
|
What are the first external signs of mechanical failure in a gear mechanism? |
excess heat, noise, and vibration |
|
Best way to remove calcium deposits from a hypochlorite solution feed pump? |
use an acid solution to dissolve the calcium deposits |
|
Wear rings are installed in a pump to |
wear instead of the impeller |
|
Misalignment of a driver and a driven piece of equipment can cause |
premature bearing failure |
|
A particular electric motor is wound for 3-phase current. If one phase cuts out while it is in operation |
The motor will heat and will be damaged unless it is stopped by a thermal control device |
|
A condition exists where a large volume of flow is pumped against a low head with a centrifugal pump. This results in the motor getting too hot. The operator closes the valve on the discharge side of the pump so that 20% of the original volume of water is being pumped. Under this new condition, |
The motor temperature would be expected to decrease |
|
If a centrifugal pump vibrates and is noisy, what could be a cause? |
Air is in the pump |
|
The shear pin in a bar screen breaks. the operator removes the unit from service and removes a block of wood from the bar screen, what should the operator do next? |
Replace the shear pin with another of equal strength. |
|
Mechanical seals consist of two subassemblies, which are |
rotating ring assembly and stationary assembly |
|
upon inspecting an idle centrifugal effluent pump, you notice that the shaft is spinning backwards. What should be the first thin you would check in this situation? |
Check valve |
|
Two types of planned maintenance are |
predictive and preventative |
|
if equipment fails, but there is no danger to the public the repair is classified as what? |
Corrective maintenance |
|
The type of maintenance used to extend equipment life, reduce maintenance costs, and increase reliability is referred to as |
preventative |
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establishing a baseline for the performance of equipment over time is a necessary step in __________ maintenance. |
Predictive |
|
Low velocity in a municipal collection system will most likely result in a plant influent which |
is septic and exerts a high oxygen demand |
|
The plant influent has a white opaque appearance and a BOD of 800 mg/L. The most likely cause for this condition is discharge from a |
milk processing plant |
|
A waste with a high BOD and low suspended solids indicates that a major portion of the solids are in |
solution |
|
As wastewater temperature increase, the solubility of oxygen in the wastewater |
decreases |
|
within what wastewater pH range does hydrogen sulfide cause the most serious corrosion problems? |
less than 5.0 |
|
In typical fresh domestic wastewater the ratio of BOD5 to chemical oxygen demand is |
.5 : 1.0 |
|
Pipe friction loss increases as the |
velocity increases |
|
Which open channel flow measurement device offers the greatest accuracy at low flow rates? |
V-notch weir |
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The plant influent becomes septic periodically, which of the following could be added to the influent to help control the problem? |
Potassium permanganate |
|
In wastewater plant influent channels, what is the minimum channel velocity needed to prevent solids from settling out? |
2 ft/sec |
|
Typical range for TSS in domestic influent wastewater is |
100-300 mg/L |
|
Wastewater entering a plant is typically |
somewhat warmer than unheated tap water |
|
What's the best flow velocity to settle out grit? |
.7-1.4 ft/sec |
|
Short circuiting of grit through an aerated grit chamber can be minimized or eliminated entirely by |
installing a submerged transverse baffle along the wall opposite the diffusers |
|
If there is a high head loss across a microscreen, the most probable cause could be |
a plugged screen |
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Which type of pump should be used to transfer a 5% solids primary sludge to a digester? |
positive-displacement pump |
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Primary clarifiers are typically designed to remove____of the settleable solids and ___of the BOD. |
95-99% and 20-50% |
|
What flow device typically measures flow of primary sludge flow? |
magnetic flow meter |
|
Worn wearing shoes are often found on |
the flights of a rectangular clarifier |
|
The withdrawal of sludge from a clarifier should be slow in order to |
prevent the pulling of too much water with the sludge |
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What should an operator do to increase MCRT? |
Decrease the waste rate |
|
What effect does pre-aeration have on downstream secondary plant processes |
it tends to improve the overall efficiency of solids and cbod removal. |
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For a particular plant there is an optimum range in which the mixed liquid solids concentration must be maintained. What could happen if the concentration were allowed to exceed the range |
A cloudy, turbid effluent would result. |
|
The process of nitrification |
Consumes about 7.1 lbs of alkalinity to oxidize 1 lb. of ammonia to nitrate |
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what type of activated sludge process has a detention time of 3 to 24 hours and a design F/M ratio of .03-.1? |
Oxidation ditch |
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When is increased wasting of activated sludge and increasing the aeration tank f/m practiced? |
Denitrication is occurring in the final settling tank causing rising sludge |
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How can an operator decrease the SRT and the MLSS concentration in an activated sludge plant? |
Decrease RAS rate and increase the waste rate |
|
The fecal coliform group is comprised of Escherichia coli and ____________.
A) streptococcus B) Enterobactor C) Klebsiella D) Citrobacter |
C) Klebsiella
The total coliform group consists of Eschericia coli, Enterobacter, Citrobacter, and Klebsiella. But only E. coli and Klebsiella comprise the fecal coliform group. |
|
Coliform bacteria are ____________.
A) pathogens which cause hepatitis
B) more resistant to chlorination than pathogenic bacteria
C) pathogens which cause typhoid
D) less resistant to chlorination than pathogenic bacteria
|
B) More resistance to chlorination.... |
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The typical air-to-solids ratio for a dissolved air floatation unit is __________.
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a. 0.02 to 0.04 kg/kg (0.02 to 0.04 lb/lb) |
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ORP stands for __________.
a. Oxygen Recirculation Pump |
d. Oxidation-Reduction Potential |
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A confined space atmosphere contains a combustible gas. At what percentage of the Lower Explosive Limit (LEL) for that gas is the atmosphere considered "hazardous"?
|
10%
The fact that an atmosphere is considered hazardous when the level of a combustible (or flammable) gas reaches 10% of its Lower Explosive Level (LEL) is part of the definition contained in the OSHA Permit-Required Confined Space regulations. It is important to note that the code actually states E0% of the Lower Flammable Level (LFL)E However, most commercially available gas monitors read the LEL. Therefore, the terms LEL and LFL are used interchangeably. |
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When using an evaporator in disinfection, the chlorine-pressure-reducing valve should be located _________________.
|
Downstream of the evaporator |
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The vapor density of a hazardous gas present in a confined space is 1.15. Where is this gas likely to be found?
|
near the floor |
|
A pH drop in an aerobic digester can be caused by ______________.
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nitrification or CO2 buildup |
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A “dewatering beach is a component of a(n) ________.
|
centrifuge
The dewatering beach of a centrifuge is the conical end of a centrifuge bowl where solids are pushed up and out of the liquid by the screw conveyor. While the solids sit on the beach, some excess water will drain out of the solids by gravity. |
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Potassium permanganate is used for _______________.
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odor control
Potassium permanganate’s uses include odor control and iron removal. |
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If a good floc forms before contacting a gravity belt thickener but the slurry exiting the belt is very wet, the most likely cause is _________________.
|
the belt is dirty and clogged
|
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Mean cell residence time (MCRT) is mathematically described as the mass of solids (lb or kg) in a process _____________________.
|
divided by the mass of solids leaving the process (lb/d or kg/d) |
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Aerobic digesters not only digest sludge, but can also be used to _________________.
|
Thicken the sludge |
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A good way to measure the biological activity and aeration in your biological reactor is to use the ________________ test.
|
SOUR
The specific oxygen uptake rate (SOUR) test provides a measurement of the biological activity and effectiveness of your aeration by looking the amount of DO used by your mixed liquor over a specific period of time. |
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If adding sodium bicarbonate to an anaerobic digester for pH control, care should be taken not to overdose because ___________________________.
|
sodium toxicity can result
Sodium bicarbonate adds alkalinity. When adding to an anaerobic digester, be careful to avoid sodium toxicity from overdosing. |
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The optimum growth of nitrifying bacteria is typically in a pH range of ___________.
|
7.5 to 8.5 The optimum growth of nitrifying bacteria is typically in a pH range of approximately 7.5 to 8.5. If the pH drops below 7 the process begins to slow down substantially. |
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For an activated sludge nitrification process, how much alkalinity is required to oxidize 0.45 kg (1 lb) of ammonia
|
3.2 kg (7.14 lb)
Theoretically, 3.2 kg (7.14 lb) is required to oxidize 0.45 kg (1lb) of ammonia. If this loss of alkalinity is not compensated for during nitrification, the pH will drop and the process can fail. |
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Bacteria associated with fixed film reactors can thrive in water with a pH as low as ________.
|
5.5
|
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Torque overload in a gravity sludge thickener can be caused by ___________________.
|
sludge removal rate is too low
If the sludge removal rate of a gravity thickener is too low, sludge will accumulate. The heavy volume of sludge can cause a torque overload on the thickener’s collection arms. |
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If it is determined you need to add chlorine to your RAS to control a filamentous problem, what is typically the maximum safest dosage used for this process?
|
3 – 5 kg of chlorine for every 1000 kg of MLVSS (2lb chlorine for every 1000 lb MLVSS)
|
|
Hydrogen sulfide is _______________.
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soluble in water, corrosive, and toxic
Hydrogen sulfide gas is corrosive, toxic, and soluble in water. In wastewater, it is usually produced from the anaerobic decomposition of organic matter in the collection system. |
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Class “C” extinguishers are used for ___________.
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Electrical fires
Class C fire extinguishers are used for fires started in electrical wiring, motors, fuse boxes, and other electrical sources. |
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In the wastewater industry, PLC refers to a _______________________.
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Programmable Logic Controller
PLCs (Programmable Logic Controllers) are commonly used in many operational control systems. They allow operators to use control boards and computers to control certain mechanical setpoints and functions in a wastewater plant. |
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Sludge depth should not be greater than ______________ on gravity drying beds.
|
8-12 in.
For gravity drainage drying beds, the sludge depth should only be 20 to 30 cm (8 to 12 in) for optimal performance. |
|
When lime is used in stabilizing solids, how long must a pH of 12 be maintained?
|
2 hrs.
In the standard lime stabilization process, sufficient lime is added to the sludge in order to raise the pH to a level of 12 or higher for a minimum of 2 hours in order to destroy or severely inhibit the growth of pathogens and microorganisms. The final stabilized product not only has a very low bacterial hazard but it also produces few odors. |
|
For efficient removal, phosphorus must be biologically converted to ______________.
|
orthophosphate
For efficient removal, phosphorus must be biologically converted to orthophosphates in under anaerobic conditions. Then, under aerobic conditions, microorganisms use orthophosphates to create polyphosphates which are stored within the cells. |
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For a trickling filter, organic loading is typically expressed as _____________.
|
kg BOD/100m3×d (lb BOD/1000 ft3/d)
|
|
Wastewater solids which have been decomposed to relatively inert solids are called ____________.
|
stable
Stabilization renders solids nonputrescible and inactivates pathogenic organisms. |
|
40 CFR Part 503 provides regulations and guidelines for managing _______________.
|
Biosolids
Part 503 is a rule used in the regulation and management of wastewater biosolids. It outlines procedures and guidelines for biosolid application, incineration, or disposal. |
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Sludge cake is moved through a multiple-health furnace by a process called ______________.
|
rabbling
The furnace consists of a cylindrical steel shell surrounding a number of solid refractory hearths, and a central rotation shaft with rabble arms attached for moving the cake. |
|
Thermophilic anaerobic digesters typically operate at a temperature of _____.
|
60C
Thermophilic aerobic digesters have insulated reactors and reach a normal operating temperature of 60ºC (140 ºF) through heat generated by the biological degreadation of organic solids. |
|
A positive displacement pump should never be started ____________.
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With the discharge valve closed
If the discharge valve of a positive displacement pump is closed when started, pressure will build up inside of the pump and cause severe damage. |
|
Most gas piping systems are rated for _____________service.
|
150psi
Most gas piping systems are rated for 1050 kPa (150 psi)service. Gas pressure from biological processes can exceed this pressure and cause an explosive rupture. Therefore, when isolating a pump or pipe, be sure to allow for venting as a safety precaution. |
|
An aerated grit chamber must maintain a constant velocity of ___________ for proper operation.
|
1 ft/sec
An aerated grit chamber must maintain a constant flow velocity of approximately 0.3 m/s (1 ft/sec). The addition of air in conjunction with this velocity keeps necessary organic material in suspension. |
|
What type of Chlorine Institute cylinder repair kit would be used for 907 kg (2000 lb) containers of chlorine?
|
B
Chlorine Institute cylinder repair kits should be readily available in the event of a cylinder leak. The common types of kits available are A (70 kg/ 150 lb), B (907 kg/2000 lb), and C (tank trucks, tank cars, and barges). |
|
If there is a significant rise in the volatile acid to alkalinity ratio in your anaerobic digester, you should NOT _________________.
|
increase the sludge withdrawal rate
A significant rise in the volatile acid to alkalinity ratio in your anaerobic digester is an indicator of problems such as hydraulic overload or withdrawing too much sludge. Steps to correct this situation are add new seed sludge, decrease the sludge withdrawal rate, extend the mixing time, and check/adjust temperature in the digester as needed. |
|
A water-filled mechanical pump seal not only helps to prevent leaks, but also ___________.
|
prevents pump shaft wear
|
|
Which of the following is a virus?
|
Hepatitis A is a common virus found in wastewater. Its normal route of infection is through ingestion. |
|
In order to control odor from hydrogen sulfide, wastewater containing sulfides should be maintained at a pH of ____________.
|
about 9
In order to prevent the odors released from hydrogen sulfide in septic influent wastewater, the pH should be maintained at approximately 9. This basic pH helps prevent the release of the acidic hydrogen sulfide. |
|
Which of the following tests best simulates the working of a dissolved air flotation unit?
|
rise rate test
|
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A trickling filter loaded at a rate of 64 kg BOD5/100 m3×d (40 lbs. BOD5/ 1000 ft3/day) would be considered a______________.
|
intermediate rate filter
Intermediate rate filters may be loaded up to 64 kg BOD5/100 m3×d (40 lbs. BOD5/ 1,000 ft3/day). Recirculation of trickling filter effluent is commonly practiced to ensure good distribution and blending of filter and secondary effluents. |
|
Jar tests indicate that the best liquid polymer dose for waste stream is 12 mg/L. The flow to be treated is 2.5 mil. gal/day. Determine the gpd setting for the liquid polymer chemical feeder if the liquid polymer is a 60% solution (assume the polymer solution weights 8.34 lb/gal). 1% equals 10,000 mg/L.
|
50 GPD |
|
The primary indicator of an upset in your anaerobic digester is _________________.
|
volatile acids increases/alkalinity decreases
The primary measurable warning sign for anaerobic digestion failure is an increase in volatile acid production as bicarbonate alkalinity decreases. You will also see a fall in pH, decrease in gas production, and excess carbon dioxide in the off-gas. |
|
If solids in water have a specific gravity of 1.30, then they are _______________.
|
30% heavier than water
The specific density of a particle is the ratio of its mass to that of an equal volume of water at the same temperature. Water’s specific density is 1.0. Therefore, the particle is 1.3 times heavier than the water it is in or : (1.3 x 100%) E00% = 30% heavier than water. |
|
A pH drop in an aerobic digester can be caused by ______________.
|
nitrification or CO2 buildup
In an aerobic digester, the oxidation of ammonia to nitrate (nitrification) or the dissolution of carbon dioxide into the digester contents in a covered tank can lower pH. Both reactions produce acidic compounds that consume alkalinity and lower pH. |
|
Blowers can produce discharge temperatures in excess of ____________.
|
200F
Air piping is often insulated in order to protect operators from burns. Blowers typically have discharge temperatures in excess of 93°C (200°F). This temperature is close to the boiling temperature for water. |
|
Heat exchangers are typically used in a wastewater treatment plant for _______________.
|
heating sludge for anaerobic digestion
|
|
After a settleometer test you have a thin layer of clear supernatant over a poorly settling sludge and your SVI is greater than 150 mL/g. This condition is referred to as ________________.
|
sludge bulking
Typically poorly settling sludge with a thin layer of supernatant and excessively high SVI are symptoms of sludge bulking problems. |
|
What factor is a main contributor to the growth of Nocardia?
|
low F:M
Nocardia foam is usually a problem in activated sludge systems that have very long SRTs. This filamentous microorganism is a slow-grower but can become a nuisance quickly because it floats and can become trapped in tanks where the effluent leaves via a submerged opening. Nitrifying systems, which require a long SRT in order to allow for a sufficient population of nitrifiers to develop, are often plagued with Nocardia problems. |
|
Which of the following forms of plant life is necessary for the proper functioning of an aerobic/facultative stabilization or oxidation pond?
|
Algae
Aerobic and facultative lagoons rely on algal photosynthesis to help provide DO to the system. |
|
A dirty filtrate coming from your pressure filter dewatering system indicates either too high a feed pressure or ___________.
|
torn/punctured filter media
A dirty filtrate is typically an indicator of too a high a feed pressure forcing some solids through the filter into the filtrate or a ripped/punctured filter media allowing solids to escape. If your pressure system filtrate is high in solids, first try reducing the feed pressure before checking the filter media.
|
|
You have decided to use chlorine to help control a Nocardia foaming problem. A typical benchmark is to initially apply __________ for every 1000 kg (1000 lb) of mixed liquor volatile solids (MLVSS).
|
4 lb
Care must be taken when using chlorine to control filamentous organisms. Too much chlorine can completely destroy the floc structure and create a very turbid effluent. A good benchmark is to initially apply 4 kg (4lb) for every 1000 kg (1000 lb) of mixed liquor volatile solids (MLVSS). |
|
The best method for protecting a steel tank from rust is _____________.
|
adding a protective coating
Adding special protective coatings (some are available in certain paints) is the best method for rust prevention. |
|
A total chlorine dosage of 6.9 mg/L is required for disinfection. If the effluent flow is 3.1 mil.gal/day and the hypochlorite used has 65% available chlorine, how many pounds /day of hypochlorite will be required?
|
274 lbs/day |
|
The maximum weir loadings for secondary clarifiers range from _____________.
|
125 – 250 m3/m·d (10 000 – 20 000 gpd/ft)
For the secondary clarifiers of most facilities, benchmarks of clarifier operation include maximum weir loadings of 125 – 250 m3/m·d (10 000 – 20 000 gpd/ft) and overflow rates ranging from 24 – 33 m3/m2·d (600 – 800 gpd/ft2). |
|
Dominance of flagellates in your mixed liquor indicate ________ ?
|
high F:M, low SRT
The dominance of flagellates in your mixed liquor indicates a high F:M ratio and a low SRT. The other organisms typically present during these conditions are amoeboids and free-swimming ciliates. |
|
Which type of incinerator uses graded silica?
|
fluidized bed
Fluidized bed incinerators use graded silica. The bed is put into a boiling motion by the combustion of the air allowing the combustion air optimum contact with incoming sludge solids. |
|
The adverse effect a substance has on a living entity defines that substance’s _________________.
|
Toxicity
Toxicity is the adverse effect a substance has on a living entity. It is the primary function of any sort of wastewater treatment to reduce or eliminate a waste stream’s toxicity. |
|
A viscous, jelly-like slime covering a trickling filter or RBC is known as a(n) _____________.
|
Biological growth
A biological growth or fixed film is a viscous, jelly-like substance comprised of a large and diverse population of microorganisms to be used for treatment. |
|
A ____________ controller receives sensor output from the process variable and compares it to the setpoint or desired result then adjusts the system accordingly.
|
feedback
A feedback controller receives sensor output from the process variable, compares it to the setpoint, and then adjusts the system accordingly. A feedforward controller uses information about the inputs to a process to prevent process errors. |
|
Auxiliary fuel requirements in a multiple hearth incinerator are lower for sludges with a high percentage of volatiles. The volatile content of a sludge may be maximized by:
|
All of the above |
|
A vertical column of fluid is also known as _________.
|
head
The pressure exerted by a height or level of fluid is often referred to as head. If the fluid is not moving, it is often known as static head. Conversely, if the fluid is moving, there is velocity head. Head is typically measured in feet or meters of column height. |
|
The detention time of an aerated grit chamber typically ranges from __________ minutes.
|
3 to 5 minutes
The typical detention time of an aerated grit chamber ranges from 3 to 5 minutes (peak). The rotation speed in the chamber should also be maintained to approximately 0.3 m/s (1 ft/sec). |
|
The most probable cause of sludge floating to the surface of a secondary clarifier is _________.
|
Settled sludge is not being removed quickly enough
Rising sludge in a secondary clarifier is typically caused by sludge being held too long in the tank and going anaerobic. This accumulation can usually be attributed to worn or damaged scraper blades, problems with the sludge removal pumping, low flows through the clarifier, or low-DO mixed liquor entering the clarifiers. |
|
A chlorine demand test shows the __________________________.
|
amount of chlorine needed to provide a specific residual after a given time
Chlorine demand is typically determined by subtracting the residual chlorine from the applied dosage. Therefore, a demand test will help determine the dosage needed to supply a desired residual after the appropriate contact time. |
|
A flow of 3700 gpd of sludge is pumped to a 37 000 cu ft digester. The solids concentration of the sludge is 6% with a volatile solids concentration of 75%. If the digester reduces volatile solids by 55%, how many lbs/day volatile solids are destroyed per cu ft of digester capacity. Assume the sludge weights 8.34 lbs/gal. Round to the nearest hundreth.
|
0.02 lbs VS destroyed/cu ft |
|
Which type of incinerator uses graded silica?
|
fluidized bed
Fluidized bed incinerators use graded silica. The bed is put into a boiling motion by the combustion of the air allowing the combustion air optimum contact with incoming sludge solids. |
|
The discharge pressure for a positive displacement blower in wastewater treatment plant can run as high as _______________.
|
210 kPa (30 psig)
Blower setups must be designed to meet varied airflow requirements. However, there are certain limits to the design criteria for the pumps used in these systems. For a positive displacement blower, the recommended maximum discharge pressure is 210 kPa (30 psig). Often these limits are related to the stresses placed on piping, the equipment, and for safety concerns. |
|
The two bacteria primarily associated with nitrification are Nitrosomonas and ________ ?
|
Nitrobacter
Nitrosomonas and Nitrobacter are aerobic bacteria commonly referred to as "nitrifiers". Because these are the only bacteria involved in nitrification, the process must be carefully maintained. |
|
1 cu ft/sec is equal to ________.
|
.65 mgd |
|
Why is the COD test preferred for process control over the BOD test?
|
results are obtained faster |
|
What type of microorganisms are most prevalent in a young (Low MCRT, High F:M) mixed liquor?
|
amoebas, flagellates
The dominance of amoebas and flagellates in your mixed liquor indicates a low MCRT and high F:M ratio. The dominance of nematodes and rotifers indicates a high MCRT and low F:M ratio. |
|
Which of the following devices is used to measure chlorine flow rates?
|
rotameter
Rotameters are most often used with chlorinators to measure the flow to the disinfection process. |
|
The maximum weir loadings for secondary clarifiers range from _____________.
80 – 120 m3/m·d (6400 – 9600 gpd/ft) |
125 – 250 m3/m·d (10 000 – 20 000 gpd/ft)
For the secondary clarifiers of most facilities, benchmarks of clarifier operation include maximum weir loadings of 125 – 250 m3/m·d (10 000 – 20 000 gpd/ft) and overflow rates ranging from 24 – 33 m3/m2·d (600 – 800 gpd/ft2). |
|
Operators begin to note that the wastewater in the 2 primary sedimentation tanks occasionally looks black and has a strong odor. You look back through the operating logs and note the following: Influent flows through the plant have been fairly constant.
|
Poor quality (high BOD) digester supernatant is being returned to the primary sedimentation tanks.
Since the problem has not been reported in upstream processes (such as the grit removal system), the problem appears to be developing in the primary sedimentation tanks rather than coming into the plant from the collection system. Since the problem is only noted occasionally, the cause is probably not the centrate which is discharged to the primary sedimentation tanks every day. |
|
From a meatpacking plant, food industry, or dairy you would expect to find all of the following pollutants EXCEPT _____________.
|
volatile organics
It is expected to have high BOD, FOG, and even variations in pH from a food industry’s effluent. However, it is uncommon to see volatile organics, such as fuels, and organic acids in such an effluent. |
|
How many pounds of polymer must be added to 30 gallons of water to make a 0.1% polymer solution?
|
.25 lbs |
|
Which of the following would be least likely to be a problem in wastewater flows from industries such as commercial laundries and paper manufacturers?
|
trace metals |
|
Which of the following is a sign your trickling filter is organically overloaded and hydraulically underloaded?
|
ponding
Ponding occurs when the spaces of the media become clogged. To help correct this problem, decrease the organic loading and increase the hydraulic loading to promote sloughing. |
|
When using a centrifuge, the highest performance and results will be obtained when processing ________________________ sludge.
|
anaerobically digested primary
Centrifuges achieve optimal results when processing anaerobically digested primary sludge. When processing this sludge type a cake with 35-40% total solids, 95% solids recovery, can be produced using only 4-6 lbs polymer per dry ton solids. |
|
To decrease the heating requirements of an anaerobic digester, _________.
|
increase the total solids concentration of the feed sludge
Sending the highest possible solids concentration to the digester will decrease the volume of sludge to be digested, increase the detention time and therefore reduce the heating requirements. |
|
Reasons for flow equalization include all of the following, EXCEPT _________________.
|
temperature fluctuation control
Influent flow equalization is used for controlling variations and fluctuations in flow, BOD, solids, and pH as well as dealing with toxic materials or “slugs”. |
|
An anaerobic digester is failing when __________.
|
all of the above
Instability in digestion occurs when the biological process becomes unbalanced and acid-formers are out-producing methane-formers. Warning signs of this condition are decreased alkalinity and increased volatile acid concentrations. |
|
The required polymer dose for your gravity thickener is 8 mg/L. The flow to the thickener is 0.91 mgd. If the polymer solution contains 70% active polymer agent, what should the chemical feeder setting be in mL/min? Remember, 1% = 10 000 mg/L and assume the polymer to weigh 8.34 lb/gal.
|
27 mL/min |
|
The destabilization of sludge particles by decreasing the repulsive forces between particles is called ____________.
|
coagulation
Coagulation involves the destabilization of sludge particles by decreasing the repulsive forces between the particles. Flocculation is the agglomeration of coagulated particles. |
|
If the ammonia concentration in an anaerobic digester exceeds ____________, the environment becomes toxic.
|
3000 mg/L
An ammonia concentration range of 50 to 200 mg/L is beneficial to anaerobic digestion. Most digesters can handle a concentration up to 1000 mg/L without serious adverse effects. An ammonia level of 3000 mg/L or better is toxic to the digester. |
|
Steps used to control filter flies on your trickling filter include increased hydraulic loading, cleaning spray nozzles, occasionally flooding the filter, and __________.
|
chlorinating the filter
A step that can be used to control filter flies (Psychoda) is to chlorinate the for several hours each week until the situation is controlled. You should maintain a residual in the filter of at least 1 to 2 mg/L to ensure you are destroying the flies and their eggs. |
|
The primary method of nitrogen removal in constructed wetland treatment system is ______________________________.
|
nitrification/dentrification In a constructed wetland system, microbes transform ammonia to nitrate through nitrification and other microbes convert nitrate to nitrogen gas through denitrification. |
|
Typically, foaming problems are found in _______________.
|
biological reactors
Even a properly working activated sludge biological reactor will have some foaming (10-25% of the reactor surface). Excess foaming is an indicator to a system upset. |
|
Operators that may be required to wear SCBAs cannot ______________.
|
grow beards
Opertors that may be required to wear SCBA units must have good lung capacity, and must keep cheeks and chin free of facial hair. This means no beards, but properly trimmed mustaches are acceptable. |
|
Vane, gear, and lobe all describe what type of pump?
|
positive displacement pumps
Gear, vane, and lobe pumps are all types of positive displacement pumps. Positive displacement pumps effectively handle thicker sludges. |
|
The desired solids loading rate for a 80-ft diameter clarifier is 40 lbs/day/ sq ft. If the flow to the clarifier is 6.5 MGD, what is the required MLSS concentration?
|
3707 mg/L |
|
Theoretically, how much influent alkalinity would be required for a nitrification process to have 65 mg/L of alkalinity left in the effluent when the influent ammonia concentration is 17.8 mg/L and the process is achieving 98% conversion of ammonia?
|
189 mg/L |
|
The first step in shutting down a centrifuge is to __________.
|
turn off the feed sludge
The first step is to manually decrease the feed sludge flow to zero. Close the isolation valve to ensure positive shutoff. Then start flushing water and stop polymer feed and polymer dilution water. |
|
The typical rotational speed of a RBC is ______________.
|
1.0 – 1.6 rpm
For an RBC, a rotational speed of 1.0 to 1.6 rpm allows for adequate contact time with the waste stream. |
|
You have just installed a new electrical circuit that uses a 50-ohm resistor and supports 2 amps of current. What is the voltage across this circuit?
|
100 volts
Voltage is the electric potential across a circuit and is linearly related to the resistance and amperage of that circuit. Therefore: V = IR Where V is voltage, I is amperage, and R is resistance. Based on this equation: V = (2 A)(50 ohms) = 100 volts |
|
Through the biological nitrogen removal process, influent ammonia and TKN are converted into ______________ and released into the atmosphere.
|
nitrogen gas
The end result of the biological nitrogen removal process is the disassociation of nitrates into oxygen (used by microorganisms) and nitrogen gas. |
|
Muriatic acid is also known as _____________.
|
Muriatic is a common name for hydrochloric acid |
|
Upflow fluidized bed reactors are typically used to achieve
|
denitrification
Upflow fluidized bed reactors use an attached-growth process for denitrification. Upflow reactors can achieve biomass concentrations in the range of 25 000 to 30 000 mg/L, which allows much smaller reactor volumes than typical suspended growth processes. |
|
Chlorine can be used to control filter flies in trickling filters. The chlorine residual recommended for filter fly control is _______.
|
1 to 2 mg/L
In order to control the proliferation of filter flies on a trickling filter, maintain a chlorine residual of 1 to 2 mg/L to help destroy eggs and possible food sources. |
|
Which of the following ions do NOT contribute to alkalinity?
|
SO4-2
The alkalinity of many surface waters is primarily a function of carbonate, bicarbonate, and hydroxide content. Borates, silicates, and other bases also contribute. |
|
Typically the largest source of pollutants for natural bodies of water is _____________.
|
nonpoint
Nonpoint sources of pollution, such as urban runoff, are typically the primary polluters of natural bodies of water. Other forms of waste are usually collected and treated before release. |
|
Treatment processes for wastewater sludges (biosolids) include all of the following EXCEPT __________.
|
disinfection
Wastewater biosolids can be treated using, thickening, dewatering, stabilization, incineration, composting, and heat drying. Disinfection is a primary concern only for wastewater effluent. |
|
A screen system that can be internally or externally fed influent is the ___________.
|
rotary drum screen
Rotary drum screens can be internally fed (flow enters the drum from the inside and goes out radially into a channel or tank). Rotary drum screens can also be externally fed (flow enters the drum from a channel or tank and flows into the open drum). |
|
A low solids content in the aeration basin is typically indicated by the presence of _________________.
|
a white fluffy foam
A low solids content in the aeration basin leads to a high food-to-microorganism ratio that is indicated by the presence of stiff, fluffy, white foam. |
|
When chlorine is introduced to hydrogen sulfide gas, the hydrogen sulfide is ____________.
|
oxidized and made odorless
Chlorine, ozone, hydrogen peroxide, and other chemicals are used to oxidize hydrogen sulfide and render it odorless. |
|
The desired solids loading rate for a 80-ft diameter clarifier is 40 lbs/day/ sq ft. If the flow to the clarifier is 6.5 MGD, what is the required MLSS concentration?
|
3707 mg/L |
|
Predominance of free-swimming cillates and flagellates in activated sludge indicate?
|
High F/M, Low SRT
Studying a sludge sample under a microscope and determining which microorganisms are predominant can tell a lot about an activated sludge system. The presence of mostly free-swimming ciliates and flagellates usually indicates that you are dealing with a young sludge from a recent plant start-up or that the biomass is recovering from a fairly severe upset. |
|
Typically denitrified sludge floating on your secondary clarifier indicates ______________.
|
sludge is being held too long in the clarifier blanket
Denitrification may occur in your secondary clarifier if DO levels are too low in your biological reactors or if sludge is being held long enough in the clarifier blanket to allow the DO level to drop to zero. |
|
The most common pressurization mode used to operate dissolved air flotation thickeners is __________ pressurization.
|
recycle
DAF units can typically operate in total, partial, and recycle pressurization modes. The most common mode used is recycle. |
|
Potassium permanganate is used for _______________.
|
odor control |
|
A control system that uses information about the inputs to a process in order to prevent process errors is known as a ________________ controller.
|
feed forward
Feed forward control use input information, such as plant influent or secondary effluent, to adjust the rate of a chemical feed like chlorine. By using a programmed setpoint for dosage, the feed forward controller will be able to adjust the dosage as conditions change and prevent a process upset. |
|
Which of the following chemicals would NOT be used as a coagulant for phosphorus removal?
|
potassium phosphate
Lime, aluminum sulfate, ferric chloride, and organic polymers are all coagulants that can be used in phosphorus removal. Potassium phosphate is not a coagulant. |
|
The typical F:M ratio for an extended aeration process ranges from ______________.
|
0.05 to 0.15
The F:M ratio for an extended aeration process typically ranges from 0.05 to 0.15. An F:M of 0.2 to 0.4 is used for most conventional processes. This low F:M means the extended operation runs using little food for the microorganism population. |
|
A secondary clarifier is 75 ft in diameter and receives a combined RAS and primary effluent flow of 4.0 mgd. If the MLSS concentration is 2450 mg/L, what is the solids loading rate on the clarifier?
|
19 lb/d/ft2 |
|
The surface overflow rate for a settling tank is determined from the ___________.
|
volumetric flow divided by the tank surface area
The surface overflow rate for any settling tank is simply the volumetric flow rate divided by the tank’s surface area. This will give the rate in terms of distance per unit time. |
|
The vapor density of a hazardous gas present in a confined space is 1.15. Where is this gas likely to be found?
|
near the floor
The vapor density of air is 1.0. Since the gas has a higher density than air, it is heavier than air. Therefore, it will collect in the lower levels of the confined space. |
|
The theoretical dosage of sulfur dioxide when used for dechlorination is ______________.
|
0.9 mg/L SO2 per 1.0 mg/L chlorine residual
|
|
The two chemicals used in an amperometric chlorine analyzer are pH buffer (pH 4) and ____________________.
|
potassium iodide reagent
Most online chorine analyzers use amperometric titration. The two solutions used are pH buffer and potassium iodide reagent. |
|
Which of the following causes the greatest increase in chlorine demand?
|
increase in organic matter
While the pH of an effluent can have an impact on the effectiveness of chlorine; the levels of ammonia, organic materials, iron compounds, and sulfur compounds present in the effluent significantly increase chlorine demand. |
|
The typical solids loading range for a gravity thickener treating primary sludge is __________.
|
100 to 150 kg/m2·d (20 to 30 lb/d/sq ft)
To operate a gravity thickener efficiently and ensure optimum performance, an operator must monitor the solids loading and overflow rates and keep them within a prescribed range. When thickening primary sludge, the typical range for solids loading is 100 to 150 kg/m2„ªd (20 to 30 lb/d/sq ft). |
|
Which of the following is NOT a type of positive displacement pump?
|
axial
Axial- and radial-flow are types of centrifugal pumps. |
|
In order to promote nitrification in an activated sludge process, the ____________ can be lowered.
|
F:M
In order for nitrification to occur, bacteria present need to use ammonia as food. Since carbon is a more desirable food source, reducing the amount of carbon readily available is a good step to take to promote nitrification. Additional steps to take include: Maintain the pH at neutral (or slightly above), the temperature needs to stay up to maintain the respiration rate of the microorganisms and the RAS should be increased. |
|
Stuffing boxes are primarily used to keep _____________ out of pump shafts.
|
air
Stuffing boxes and packing seals are used primarily to prevent air from entering the pump and to prevent excess leakage at the pump shaft. |
|
NPDES permits outline all of the following parameters EXCEPT _________________.
|
plant safety requirements
NPDES permits outline discharge location, allowable flows, allowable effluent concentrations, monitoring and reporting requirements, and more stringent treatment requirements if necessary. Plant safety is typically outlined by the plant management and OSHA (Occupational Safety and Health Administration). |
|
A limiting factor for digester loading is ___________.
|
hydraulic detention time
Two criteria may determine a digester’s capacity Ethe hydraulic detention time and the volatile solids loading rate of the incoming sludge. The detention time deals with the flow while the volatile concentration deals with how much treatment time will be required for that particular sludge. |
|
Which of the following pH values fall into the range of a well-operated anaerobic digester?
|
6.9
The typical operating range of an anaerobic digester is 6.8 E7.2. At a pH below 6, the volatile acids become toxic to methane-forming bacteria. At a pH above 8, dissolved ammonia levels will become toxic to the methane-forming bacteria. |
|
Which of these industries produces the highest BOD wastewater?
|
fruit juice processors
Any industries that discharge large quantities of organic wastes or sugars generate high BOD levels in wastewater. |
|
In the contact stabilization process, where is the food absorbed into the process?
|
contact reactor
The contact stabilization mode requires a short-term contact reactor in which food is adsorbed, a clarifier, and a sludge reaeration reactor with approximately six times the detention time of the contact reactor. In the sludge reaeration reactor, previously adsorbed organics are hydrolyzed and then re-released to the liquid before final stabilization in the contact reactor. |
|
Some pressure filter systems for dewatering use a __________ system to help dewater sludges high in oils and grease.
|
precoat
Precoat systems may provide performance benefits in systems that have feed sludge that contains high levels of oil and grease or fine materials. To prevent oil, grease, or fines from blinding the filter cloth, a coating of filter aid such as diatomaceous earth is applied to the filter cloth before the injection of the conditioned feed sludge. |
|
There are several odor models that can be used to simulate the dispersion of short-term peak concentrations of odors in order to predict when and where odors will be detected around collection system and treatment plant structures. These models include a
|
modified Lutzack-Ettinger model
The modified Lutzack-Ettinger process is a variation of the activated sludge process that is able to achieve biological nutrient removal. The Hogstom model, the fluctuating plume model, the TRACE model, the odor impact model and the Illinois Institute of Technology Research Institute model are several odor models that are available in the public domain. |
|
In terms of mechanical equipment in a treatment plant, MCC stands for _________.
|
motor control center
Motor control centers (MCCs) are made up of series of steel cabinets that contain motor starters and breakers for the main electrical service to individual pieces of equipment. |
|
The primary limitation of low pressure sprays (fixed nozzles with pressures < or = 103 kPa (15 psi) for overland flow systems is:
|
nozzles are subject to plugging
The limitations of overland flow systems that use low pressure sprays for wastewater distribution are that the nozzles are subject to clogging and they produce more aerosols than slotted pipes or bubbling orifice distribution methods. |
|
Wastewater that contains no measurable DO and nitrate is referred to as __________.
|
anaerobic
Anaerobic wastewater contains no dissolved oxygen as well as no nitrate. |
|
The maximum kilowatts drawn over a short period of time (usually 15 minutes) is called the electrical _________.
|
demand
The electrical demand is the basis for demand charges which are meant to compensate the electric utility for its investment in additional capacity required to meet theoretical maximum load. |
|
Which of the following activated sludge process modes is typically operated with the shortest solids retention time (SRT)?
|
modified aeration
A modified aeration activated sludge process can operate with a MLSS concentration as low as 200 mg/L, an aeration time as low as 1.5 hours and an SRT as low as 0.2 days. |
|
The presence of large amounts of filter flies could be caused by any of the following conditions except ____________.
|
excessive hydraulic loading
Filter flies thrive in environments that get periodic light sprays of wastewater. High hydraulic loading to a trickling filter will keep media continually wet which is not conducive to filter fly breeding. Filter flies can also breed in grass and weeds around a trickling filter that receive occasional sprays of wastewater such as that carried by wind blowing across the trickling filter. |
|
The mesophilic temperature range, used in relation to anaerobic digestion, is ____________
|
90-100 F
32 – 38°C (90 – 100°F) is the mesophilic temperature range. Most anaerobic digesters are operated in this range. |
|
A ____________ controller receives sensor output from the process variable and compares it to the setpoint or desired result then adjusts the system accordingly. |
feedback A feedback controller receives sensor output from the process variable, compares it to the setpoint, and then adjusts the system accordingly. A feedforward controller uses information about the inputs to a process to prevent process errors.
|
|
A visual indicator of a chlorine leak ______________.
|
is green or reddish brown deposits on metal
Chlorine is a very corrosive substance. If there is leak in a chlorine system in the presence of metal, it will corrode that metal and create discolorations of the metal. These discolorations are typically reddish or green in nature. If a visual indicator is present, use an ammonia solution to find the exact location of the leak. |
|
Which of the following statements best describes the nitrifying bacteria Nitrosomonas and Nitrobacter?
|
slow-growing autotrophic bacteria that oxidize inorganic compounds such as ammonia for energy
Nitrifying bacteria are slow-growing autotrophic bacteria that oxidize ammonia nitrogen for energy. It is this slow growth that contributes to an extended mean cell residence time for the nitrification process. |
|
What is the proper pH range for maintaining methane-forming bacteria in an anaerobic digester?
|
6-8
In a healthy environment for methane-forming microorganisms, the pH ranges from 6 to 8 with a typical operating range of 6.8 to 7.2. |
|
In terms of sludge thickening (primarily gravity thickening), WAS typically can be described as __________.
|
forming a light, fluffy floc that settles poorly
WAS is typically more difficult to thicken by gravity than primary sludge. Since WAS has undergone treatment, it tends to form a light, fluffy floc that settles poorly. |
|
|
26 lbs/day/sq ft |
|
An ideal carbon to nitrogen ratio for composting sludge is _______________.
500:1 |
30:1
A carbon to nitrogen ratio of approximately 30:1 allows for optimum microbial growth during composting. |
|
In the wastewater industry, PLC refers to a _______________________.
|
PLC
PLCs (Programmable Logic Controllers) are commonly used in many operational control systems. They allow operators to use control boards and computers to control certain mechanical setpoints and functions in a wastewater plant. |
|
For preventive maintenance of a comminutor, how often should the channel be drained and the unit cleaned?
|
monthly
For preventive maintenance of a comminutor, the channel should be drained and the unit cleaned on a monthly basis. As always, the maintenance recommendations of the manufacturer of a particular piece of equipment should be carefully followed. |
|
To neutralize a sour digester, assume that 1 mg/L of lime need to be added for every mg/L of volatile fatty acids present in the sludge. If the digester contains 242,000 gallons of sludge with a volatile fatty acid concentration of 760 mg/L, how many pounds of lime should be added?
|
1534 lb |
|
The recommended oil change frequency for gear reducers operating under favorable conditions and using petroleum-based lubricants is ___________.
|
6 months or 2500 hours of operation, whichever comes
The typical recommended oil change frequency for equipment operating under favorable conditions and using petroleum-based lubricants is 2500 hours or 6 months, whichever comes first. Intervals of 1 to 3 months may be necessary if the unit operates under conditions that tend to deteriorate oil or cause condensation. As always, follow the recommendations of the equipment manufacturer. |
|
A properly functioning heated anaerobic digester can have an alkalinity as high as ___________.
|
5000 mg/L
With the addition of lime to control pH and the production of ammonium bicarbonate during digestion, the alkalinity in a typical heated anaerobic digester can be as high as 5000 mg/L |
|
A sludge pump has a bore of 10 in (0.83 ft) and a stroke length of 3 in (0.25 ft). If the pump operates at 32 strokes/minute, how many gpm are pumped? Assume 100% efficiency and volume displacement. Density of the sludge is 7.48 gal/cu ft.
|
32 gpm |
|
A centrifugal pump must acheive a flow rate of 550 gpm against a total dynamic head of 75 ft. What would be the water horsepower requirement for this pump, assuming that the liquid to be pumped has a specific gravity of 1.2?
|
12.5 whp |
|
The primary compound formed when chlorine gas is introduced to water is ____________.
|
hypochlorous acid
Chlorine dissolves quickly into water to form a mixture of hypochlorous and hydrochloric acids. |
|
If your RAS rate is too high, what is typically the primary result?
|
solids will overload the clarifier and wash out
Solids overload occurs when solids enter the clarifier faster than they can be removed. Overload is related to plant flow, RAS flow, and MLSS concentration. Typically, sludge settleometer readings are normal; however, clarifier blankets are high, return rates are high, and effluent solids concentrations are elevated. Adjusting the RAS rate can quickly verify whether solids loading is a problem. |
|
As part of the national pretreatment program (40 CFR Part 403), plants with a design flow of more than ____________ must develop an industrial waste pretreatment program. |
19 000 m3/d (5 mgd)
The General Pretreatment Regulations of Existing and New Sources of Pollution outline the national pretreatment program for the United States. The regulation requires any plant with a design flow over 19 000 m3/d (5 mgd) to develop an industrial waste pretreatment program. |
|
Which of the following is NOT a probable cause for excessive sloughing in a rotating biological contactor?
|
high dissolved oxygen levels
In rotating biological contactors, excessive sloughing is caused by: toxic materials in the influent, excessive pH variations, and drastic changes in flow and loading. These factors cause sloughing because they create conditions that damage the biomass.
|
|
Wearing rings on a pump are used to _______________.
|
minimize internal leakage
Wear rings and other forms of packing are used to minimize internal leakage of the fluid being pumped through the stuffing box.
|
|
Which of the following conditions will lead to the predominance of Thiothrix bacteria in your activated sludge process?
|
high sulfide levels
High sulfide levels, septic wastes, and nutrient deficiencies can all lead to the predominance of Thiothrix bacteria in your activated sludge process.
|
|
A biotower is an alternative to what wastewater treatment process?
|
trickling filter
A biotower is a larger form of a trickling filter system. It uses special media to allow high-rate treatment. It is typically used in conjunction with other wastewater processes. |
|
Typically the presence of light, stiff, billowy white foam on the surface of an aeration tank is an indicator of ________. Also what action should you take to correct the problem?
|
high F:M, decrease wasting
Typically the presence of stiff, white foam is an indicator of high F:M, meaning there are not enough microorganisms to consume your pollutants. Therefore, the best solution is to decrease your wasting rate to increase your microorganism population. |
|
At temperatures less than _______, the rate of volatile solids reduction drops so low that aerobic digestion processes are rendered ineffective.
|
10°C (50°F)
At process temperatures less than 10„aC (50„aF) aerobic digestion will almost come to a complete stop. This is true of many biological processes. |
|
Calcium hypochlorite contains ___________% available chlorine.
|
65
Calcium hypochlorite contains 65% available chlorine. Care should be taken when handling calcium hypochlorite to make sure it does not to come into contact with water. This will release hypochlorous and hydrochloric acids which are extremely dangerous. |
|
What type of respirator is needed when entering an IDLH (Immediately Dangerous to Life or Health) atmosphere?
|
supplied air respirator or self-contained breathing apparatus (SCBA)
In a IDLH atmosphere, SCBA gear must be worn and properly used to protect workers from injury. |
|
The precipitation of magnesium ammonium phosphate throughout an anaerobic digester system is referred to as _______________.
|
scaling
The precipitation of magnesium ammonium phosphate or scaling in side the digester system can complicate the process. This scale can hamper pumping and temperature control in the digester. |
|
Which of the following is a low-DO filament that is most likely to be found under low F:M conditions?
|
Sphaerotilus natans
Sphaerotilus natans is a bacteria that is associated with low DO conditions and an excess of food in the activated sludge process. |
|
|
algae
Aerobic and facultative lagoons rely on algal photosynthesis to help provide DO to the system.
|
|
The primary use for methanol in wastewater treatment is __________.
|
as a carbon source to fuel denitrification
The primary use of methanol is to provide additional carbon needed to fuel the denitrification process. In a system where all of the organics have been previously removed, the average dosage is 3 mg/L methanol per 1 mg/L NO3- N. |
|
The concentration of your polymer is 0.8%. If the feed rate of your polymer is 0.2 L/s (3 gpm), what is the feed rate of the polymer in kg/d (lb/d)?
|
288 lb/d |
|
Which of the following could lead to cavitation in a centrifugal pump?
|
pump speed is higher than recommended
If the speed of the pump is increased, often so is the velocity of the fluid. This increase in fluid flow can lead to a reduction on fluid pressure and vapor pressure of the liquid. This in turn can lead to cavitation. |
|
Gravity thickeners are similar in many ways to a _____________.
|
clarifier
Gravity thickeners create calm flow conditions allowing sludge to settle out of the wastewater similar to the way clarifiers remove solids from the waste stream. |
|
Hypochlorite (OCl-) and hypochlorous acid (HOCl) constitute _____________.
|
free residual chlorine
Chlorine in the form of hypochlorous acid and/or hypochlorite ion is defined as free available or free residual chlorine. Both of these are weak and disassociate easily, therefore their presence indicates an excess or “free” amount of chlorine. |
|
Thermophilic anaerobic digesters typically operate at a temperature of _____.
|
140 F
Thermophilic aerobic digesters have insulated reactors and reach a normal operating temperature of 60ºC (140 ºF) through heat generated by the biological degreadation of organic solids. |
|
The typical depth of a rock media trickling filter is ______________.
|
1.2 – 3.0 m (4 – 10 ft)
The term trickling filter often applies to shallow rock media filtration systems with a depth of 1.2 E3.0 m (4 E10 ft). Trickling filter systems with greater depths are often referred to as biotowers or biological towers, and the meadia in these systems is usually plastic. |
|
Certain soluble organic materials (refractory organics) are resistant to biological breakdown in secondary treatment. The most effective way to remove these organic materials is by using ___________.
|
activated carbon filtration
Activated carbon can remove soluble COD and refractory organics by chemical adsorption on its surface as the water is filtered through it. |
|
Typically, chlorine is __________________ before entering solution and introduced to the effluent.
mixed |
evaporated
Chlorine in large quantities is usually transported in liquid form. Therefore when it is used for disinfection, it is first evaporated and the gas is mixed into a solution before entering the effluent. |
|
Motors, couplings, and pumps used for grit removal should be checked ____________ for signs of damage.
|
daily
Because of the damaging nature of grit and debris, the sensitive mechanical equipment (motors, couplings, pumps) used to handle these materials should be checked daily for signs of damage. |
|
For a confined space entry, all of the following safety equipment is required for each entrant except
|
portable eye-wash station
All of the other requirements listed here Ean attached retrieval system with adequate attendant support, a 5 to 10 minute escape breathing system, and gas detection capability are all required by the OSHA Permit-Required Confined Space regulations for each entrant into the confined space. |
|
The pump most commonly used for transferring sludge to a dewatering process is a(n) __________.
|
progressing cavity pump
A progressive cavity positive displacement pump is typically used to transfer sludge to a dewatering process |
|
Which of the following is a device used for level measurement
|
bubbler tube
A bubbler tube system uses a small air supply and the backpressure created by the static head of a tank’s contents to measure the level inside the tank. All other devices listed are typically used for flow measurement. |
|
A total of 270 ml/L sludge settled during a 30 min. settleability test. The secondary influent flow is 11 000 m3/d (2.9 mgd). Calculate the RAS flow in m3/d (mgd) as a ratio of the secondary influent flow.
|
4069 m3/d (1.1 mgd) |
|
What is the best method to prevent short-circuiting in a clarifier?
|
use of properly designed baffles on the stilling well and/or around the perimeter of the tank.
Clarifier influent structures such as baffles help distribute flow evenly throughout the clarifier as well as reduce entrance velocity. |
|
Fine bubble diffusers are ________ susceptible to fouling than coarse bubble diffusers.
|
more
Fine diffusers are more susceptible to fouling due to their small pore size, making the pores easier to clog. |
|
UEL and LEL are terms related to gases and vapors in wastewater treatment. What do these terms typically define?
|
the explosive limits of common gases
UEL and LEL stand for the upper and lower explosive limits of a gas or vapor. These are the concentrations at which there is a possibility of explosion from contact with heat or other chemicals. |
|
Which of the following disinfection options is typically most effective against viruses?
|
UV
UV disinfection is proven to be more effective than chlorine and ozone against viruses in certain cases, regardless of the virus involved. |
|
Secondary clarifier sludge blankets are typically maintained between __________.
|
0.15 and 0.9 m (0.5 and 3 ft)
Typically, clarifiers are operated so that the solids blanket depth is between 0.15 and 0.9 m (0.5 and 3 ft) from the bottom of the clarifier, with an optimal depth typically between 0.3 and 0.6 m (1 and 2 ft). |
|
Which of the following chemicals is used to precipitate phosphorus from wastewater
|
aluminum sulfate
Alum (aluminum sulfate), polyaluminum chloride, and ferric chloride are the chemicals typically used for orthophosphate precipitation. |
|
If ozone is used for disinfection, the threshold limit for exposure for operators is ____________ for an eight-hour period.
|
0.2 mg/m3 (0.1 ppm)
Prolonged exposure to ozone can lead to potential respiratory problems. The threshold limit for exposure to ozone is 0.2 mg/m3 (0.1 ppm) for an eight-hour workday. |
|
An oxidation ditch is most similar to a(n) ______________ process.
|
extended aeration
The oxidation ditch is a reactor layout that is a variation of the extended aeration process. Typically, wastewater is pumped around a circular or oval pathway by a mechanical aerator or pumping device at one or more points along the flow pathway. |
|
All of the following are possible problems that can occur when operating a belt filter press EXCEPT ______________.
|
improper air-to-solids ratio
Typical problems to troubleshoot on a belt filter press include: belt mistracking, plugged (blinded) bet, and low quality filtrate due to poor conditioning. |
|
If there is insufficient alkalinity in your wastewater initially, the _____ of an aerobic digester tends to _____ over time
|
pH, decrease
During aerobic digestion, alkalinity is often consumed and carbon dioxide is generated during the process. If there is insufficient alkalinity in your wastewater for buffering, these two factors contribute to a decrease in pH for the digester contents. |
|
Chemicals such as ammonia and/or trisodium phosphate may at times be added to your wastewater prior to biological treatment in order to ________________.
|
correct a nutrient imbalance
Nitrogen and phosphorus are nutrients that are required in significant amounts to support biological processes. In some instances it is necessary to add these nutrients prior to biological treatment. |
|
Typically, primary sludges from a clarifier can be thickened to __________.
|
2 to 7% solids
Primary sludge is typically easier to thicken and dewater than any other sludge produced during treatment. A primary clarifier can be used as a thickening unit by maintaining a sludge blanket and only intermittently removing sludge. The sludge can be thickened to 2 to 7% solids in this manner. |
|
At an ammonia (NH3-N) concentration less than _________, the nitrification rate is significantly reduced.
|
2 mg/L
Ammonia is the food of nitrosomonas. If the ammonia concentration is low, the nitrification rate will slow. Significantly slowing of the nitrification rate is noticeable at ammonia concentrations less than 2 mg/L.
|
|
Oxidation Reduction Potential (ORP) is most often associated with ___________.
|
chlorine control
ORP is based on millivolt readings of potential across bipolar electrodes. There is a millivolt change in this potential as chlorine is added to water. These units measure those changes and can provide detailed residual information to be used in control chlorine dosage. |
|
A total of 4000 gpd of sludge is pumped to a digester. If the sludge has a 6% total solids content and a volatile solids content of 75%, how many lbs/day volatile solids are pumped to the digester?
|
1500 ld/day |
|
If there are not enough filamentous organisms present in your mixed liquor, the sludge floc tends to __________.
|
shear into small pieces
If there are not enough filamentous microorganisms present in the biomass, the floc structure may be weak, have a tendency to shear into small pieces, and not settle well. However, if the floc contains an overabundance of filamentous microorganisms, the activated sludge will settle very poorly. |
|
The most common type of centrifuge used for thickening or dewatering sludge in wastewater treatment is the _________________.
|
solid bowl centrifuge
The most common type of centrifuge used is the solid bowl centrifuge. In this type of centrifuge, a solid-walled bowl rotates on a horizontal axis |
|
Typically UV disinfection dosage is measured during operation by the intensity of the lamps and ____________.
|
contact time
Although solids, microorganisms, and hardness affect the performance of a UV system, its dosage is measured the intensity of the lamps coupled with the contact time in the effluent channel.
|
|
You should decrease your wasting rate if __________________________.
|
billows of white foam appear on the aeration tank surface
If billows of white foam appear on the aeration tank surface, decrease the WAS rate in order to reduce the F:M ratio. High F:M is a typical cause of stiff, white foam. |
|
What is the maximum safe level of ammonia a worker can be exposed to during an 8-hour workday?
|
50 ppm (mg/L)
A worker should not be exposed to more than 50 ppm (mg/L) of ammonia during an 8-hour workday. |
|
At pH levels below __________, the activated sludge process will completely stop.
|
2.0
|
|
Which of these pumps uses a flexible membrane between the sludge it is moving and the driving force of the sludge? It uses this membrane along with valves or ball checks to provide the necessary suction and discharge pressures.
|
diaphragm
Diaphragm pumps use a flexible membrane between the sludge it is moving and the driving force of the sludge. The membrane and valves or ball checks provide the suction and discharge pressures. The driving force is often provided by a mechanical device or fluid pressure. |
|
A useful method of determining a WAS rate is to base it on ___________.
|
a constant F:M ratio
A useful control method is to waste solids to maintain a constant F:M ratio. By maintaining this F:M, the proper amount of microorganisms are available for the loading conditions. |
|
In an aerated grit chamber, diffused air ______________.
|
allows the heavier grit particles to settle while keeping the lights organic particles in suspension
Aerated grit chamber use diffused air to “roll the wastewater and allow the heavier grit particles to settle while keeping organic matter in suspension for use in the remainder of the treatment process. |
|
To detect a chlorine leak in a cylinder or valve, what type of chemical or solution should be used?
|
ammonia
A spray bottle filled with ammonia can be used to spray down the valves and hosing to check for any chlorine gas leaks. If any chlorine comes into contact with the ammonia, a yellow gas will form giving a visual verification of where the leak is occurring. |
|
The final product of denitrification is __________.
|
nitrogen gas
In denitrification, microorganisms break down nitrates formed during the nitrification process into oxygen and nitrogen gas. After all of the free oxygen is consumed, the microorganisms start to use the nitrate as an alternate oxygen source. The nitrogen gas produced collects into bubbles which rise to the surface and are released to the atmosphere. |
|
Sodium bisulfite is used for all of the following functions EXCEPT ____________.
|
coagulant
Sodium bisulfite is used for dechlorination, pH control, chromium treatment, and as a bactericide. |
|
Higher than normal influent grease levels is one of the problems that can lead to __________ in secondary clarifiers.
|
ashing
Excessive grease levels can lead to ashing in the secondary clarifiers. The grease, entrained with floc, will float on the surface of the clarifier and have a slightly white, flaky appearance, similar to ash. Ashing can be caused by other process problems, also. |
|
What type of unit removes grit from wastewater?
|
vortex separator
|
|
RBCs can be designed to be rotated by all of the following EXCEPT:
|
wastewater flow
Mechanical drives and air can be used to rotate RBCs through the wastewater that is being treated. |
|
Lime slakers convert quicklime (CaO) to __________.
|
calcium hydroxide
Lime slakers add water to quicklime (CaO) in order to form hydrated lime, calcium hydroxide – Ca(OH)2. This change in form allows for quicker dissolution in water and better mixing into a wastewater stream. |
|
You currently have 10% by volume polymer solution in stock, but you need a 6% solution for your belt press. How much of the 10% solution should be diluted with water to give you 75 L (20 gal) of 6% solution? Assume the specific gravity of both the polymer solution and dilution water are 1.0.
|
45 L (12 gal) |
|
The primary sludge flow to a gravity thickener is 4 L/s (66 gpm). This is blended with a 6 L/s (95 gpm) secondary effluent flow. If the thickener diameter is 8 m (25 ft), what is the hydraulic loading rate in L/s•m2 (gpd/ft2)?
|
472 gpd/ft2 |
|
Which of the following is NOT one of the main diseases caused by pathogenic organisms found in wastewater?
|
Nocardia
Nocardia is not a disease. It is a type of filamentous bacteria which can cause dark brown foam to build-up on the biological reactors. |
|
The two design configurations typically available for solid-bowl centrifuges are ___________.
|
cocurrent and countercurrent
The two design configurations typically available for solid-bowl centrifuges are cocurrent and countercurrent. The major differences in design pertain to the location of the feed ports, the removal of the centrate, and the internal flow patterns of the liquid and solid phases. |
|
The actual output of a pumpfs motor is referred to as _______________.
|
brake horsepower
|
|
“Classifying” grit refers to __________________.
|
washing and dewatering the grit
Grit classifiers are used for the final washing of organics from grit and dewatering the grit before final disposal. It is important to wash these organics from the removed grit and return the organics to the wastewater treatment process to maintain proper organic levels throughout the treatment process. |
|
The valve of a 70 kg (150 lb) chlorine cylinder has a fusible plug in its valve body designed to melt at _______________.
|
70 to 74 ºC (158 to 165 ºF)
The 70 kg (150 lb) chlorine cylinder has a fusible plug in its valve body designed to melt at 70 to 74 ºC (158 to 165 ºF) in order to prevent a hydrostatic rupture of the cylinder. |
|
A settling tank’s hydraulic performance depends on surface area, volume, and ___________.
|
influent and effluent structures
The hydraulic performance of a settling tank depends on its surface area, volume, and the structure for influent and effluent. The influent structures should insure flow is even and calm to promote settling. And the effluent structures should be able to handle flow variations. |
|
Psychoda is another name for what trickling filter pest organism?
|
filter flies
Psychoda or filter flies usually appear when there is insufficient wetting of the filter media which allows for breeding and egg-laying. |
|
One of the most frequent causes of poor activated sludge process performance is ________________.
|
poor control of solids inventory
|
|
Proper conditioning chemical dosage is typically determined by _____________.
|
jar tests
Conditioning chemical dosage is determined by such tests as jar, filter leaf, buchner funnel, and capillary suction tests. |
|
For personal safety, operators need to protect themselves from high ________ levels around blower equipment.
|
noise
Operators should be careful of high noise levels around blower equipment. Noise levels of 85 dbA for a 24-hour or more exposure period require hearing protection. |
|
Grit is washed in order to _________.
|
remove organic matter
Grit is washed in order to remove organics from the grit. Organic material must be removed before the grit can go to a landfill. |
|
How is phosphorus removed from wastewater?
|
chemical addition and sedimentation/filtration
Phosphorus cannot be converted to a gaseous form and then removed (or vented) from the process like nitrogen. Therefore, phosphorus must be converted to solid form and removed by sedimentation, filtration, or some other solids removal process. |
|
Which of the following may be caused by overaeration/mixing in the aeration tank?
|
pin floc
|
|
If 5 ounces of a dry polymer are added to 15 gallons of water, what is the percent strength of the polymer solution? Remember that there are 16 ounces in a pound.
|
0.25 % |
|
Which process removes the most suspended solids from the water in the wastewater treatment process?
|
primary treatment
|
|
What is the typical cause of ponding on a trickling filter?
|
excessive biological growth on the media
Ponding is typically caused by excessive biological growth on the media. A few possible corrective actions are reduction of organic loading; increase in hydraulic loading; and flooding of the filter for 24 hours. |
|
Phosphorous is typically removed from wastewater using some or all of the following EXCEPT _____________.
|
comminution
|
|
Nitrogen and ___________ are essential nutrients for microbial growth.
|
phosphorus
Both nitrogen and phosphorus are essential nutrients for microbial growth in biological treatment systems. They can also cause algal blooms and other pollution issues in receiving waters if too much of these substances are released in the plant’s effluent. |
|
A trickling filter employed in combination with an additional biological treatment step is called a ___________________.
|
roughing filter
Roughing filters are generally designed to allow a substantial amount of soluble BOD bleed through. An additional treatment process follows the trickling filter in order to complete BOD oxidation. |
|
Which of the following methods of wastewater treatment can be best adapted for crop production?
|
slow rate land treatment
Type 2 slow rate systems, also known as crop irrigation systems, are designed primarily for crop irrigation with wastewater treatment as a secondary objective. |
|
Which of the following thickening processes mixes incoming sludge with a pressurized recycle stream as it enters the thickener?
|
dissolved air flotation thickener
Prior to entering a DAF unit, the feed sludge is mixed with a recycle stream that has been pressurized with air. This pressurized stream is used as the air source to float thickened sludge to the top of the unit. |
|
Raw domestic wastewater typically contains approximately _______ total phosphorus.
|
6 – 20 mg/L
Domestic wastewater typically contains 6 E20 mg/L of total phosphorus. Approximately 5 E10% is removed during primary treatment and 10 E20 % is removed by conventional secondary treatment. |
|
For gravity and dissolved air flotation thickeners, the solids loading rate is defined as the weight of solids coming into the thickener divided by the _________________.
|
surface area of the thickener
|
|
Chemical methods for removing nitrogen involve all of the following EXCEPT ___________.
|
ferric chloride coagulation
|
|
PVC stands for ____________.
|
Polyvinyl Chloride |
|
A _________________ consists of a set of windings around a core (coil) and is installed on a line to either step-down or step-up voltage for the electricity traveling through the line.
|
transformer
A transformer consists of a set of windings around a core (coil) with a primary side that receives power and a secondary side that releases power. Step-down transformers decrease the voltage and step-up transformers increase the voltage. |
|
The optimal range for solids loading on a secondary clarifier is __________________.
|
200 – 300 kg/m2·d (40 – 60 lb/d/sq ft)
If solids loading for a clarifier is the amount of solids distributed over the surface area of a clarifier in a given time. The optimal solids loading for a secondary clarifier is 200 E300 kg/m2·d (40 E60 lb/d/sq ft). |
|
A common measure for preventing soil erosion around a lagoon treatment system is through the use of _____________.
|
riprap
Riprap (large stones) are often used with lagoon and wetland systems to minimize soil erosion effects, protect inlet/outlet equipment, control vegetation, and protect bed liners. |
|
Which of the following types of diffusers produce large bubbles and turbulent mixing?
|
nonporous (fixed orifice) diffusers
Fixed-orifice type diffusers usually consist of piping or plating with moderate sized holes drilled into them. Examples of this type are spargers and wide-band non clog units. These diffusers produce large bubbles are used when mixing is more important than oxygen transfer. |
|
A common operational problem associated with using lime is the _________ of pumps and feed lines.
|
clogging
Quicklime can readily absorb moisture and form semi-solid clumps. Also lime slurries will coat the inside of pipes and pumps and lead to clogging, stoppages and reduced flow. Flushing your lime-pumping system with fresh water on a regular basis may help to alleviate the clogging. |
|
Daily consumption of chlorine is typically measured based on ___________.
|
weight of chlorine vessels
The most accurate method for determining the amount of chlorine used over any period of time is to take readings from the scale on which the containers sit.
|
|
What type of clarifier uses suction tubes to remove settled sludge?
|
RSR (rapid sludge return)
A RSR clarifier uses siphon tubes or direct pumping to remove solids from the bottom of the clarifier. |
|
At a pH above ____, hydrogen sulfide gas will stay in solution.
|
8
At a pH of 9.0, 99% of hydrogen sulfide is dissolved in water as the nonodorous hydrosulfide ion. Consequently, at a pH above 8, hydrogen sulfide gas cannot escape from the water it is dissolved in. |
|
The pretreatment of wastewater typically takes place ___________________.
|
before a waste stream enters the collection system
Pretreatment of wastewater is typically the responsibility of an establishment or industry before their waste enters the collection system. Over the past several years, the regulations for pretreatment have become stringent. |
|
What condition/situation might require an operator to chlorinate the RAS?
|
the presence of excessive filamentous organisms
In the event of an overpopulation of filamentous organisms, it may be necessary to chlorinate the RAS in order to control the population. However, care should be taken because the chlorine will also destroy useful organisms as well. |
|
Which of the following chemicals is NOT typically used to precipitate phosphorus?
|
Aluminum sulfate (alum), ferrous sulfate, and lime are the coagulants used to precipitate phosphorus from wastewater. |
|
A rotary drum screen is classified as a __________ screen.
|
fine
Rotary drum screens are fine screens that are either internally- or externally-fed. Both types of systems use a spray wash system to remove screenings. Externally-fed units also employ the use of a doctor (scraper) blade to help remove screenings. |
|
Today, the color of ggroundh wires used in electrical wiring is ___________.
|
green |
|
What is the average detention time of a primary clarifier?
|
1-2 hours
|
|
When foam covers the entire surface of a biological reactor, a device known as a __________ can be used to obtain a representative sample of the contents.
|
bomb sampler
|
|
One of the most effective chemicals for dechlorination is _______________.
|
sulfur dioxide
Sulfur dioxide, hydrogen peroxide, sodium metabisulfite, and sodium bisulfite are chemicals used in dechlorination. |
|
In clarifiers, a non-uniform flow condition in which a small percentage of the water travels faster and through a shorter path than the rest of the water in the tank is described as ________ ?
|
short-circuiting |
|
Sludges with longer detention times generally require _________________ polymer for the processes of coagulation and flocculation.
|
more
Sludges like aerobically digested or extended aeration sludges are difficult to dewater. The longer they are kept under aeration the more difficult they are to flocculate. They require more polymer to treat because of this condition. |
|
The first indicator of a high organic load coming into a facility is a decrease in ____________.
|
DO
Typically the first measurable indicator of a high organic load is a decrease in DO due to the substantial increase in BOD. |
|
A rotary spray distribution unit is a component of what treatment process?
|
trickling filter
A rotary spray distribution unit is one of the primary components of the trickling filter. This unit is designed to evenly distribute primary effluent over the entire surface of the trickling filter. |
|
An operator will control the sludge thickness (solids concentration) from a primary clarifier in order to meet the requirements of the _____________.
|
downstream solids handling units
The necessary thickness of the sludge removed from primary clarifiers is typically depends on the type of downstream solids handling processes downstream. For example if you plan to immediately dewater your primary sludge, if you have primary sludge degritting you will want a very thin sludge (about 0.5% solids) |
|
All of the following cations are typically used to precipitate phosphorus from wastewater EXCEPT _______________.
|
sulfur
When introduced under the right conditions, aluminum, iron, and calcium will form insoluble precipitates with phosphorus and can then be removed by physical means from the wastewater.
|
|
In a electrical circuit, a(n) ______________ is used to measure current.
|
ammeter
An ammeter is used to measure current, while an ohmmeter is used to measure resistance. |
|
Venturi tubes, orifice plates, and pitot tubes are all types of ___________ flow meters.
|
differential
Venturi tubes, orifice plates, and pitot tubes are types of differential flow meters. Differential head flow meters use an in-pipe constriction that produces a temporary and measurable pressure drop across it. |
|
Of the following, which is chlorine MOST LIKELY to be added to?
|
secondary clarifier effluent
|
|
The final product of denitrification is __________.
|
nitrogen gas
In denitrification, microorganisms break down nitrates formed during the nitrification process into oxygen and nitrogen gas. After all of the free oxygen is consumed, the microorganisms start to use the nitrate as an alternate oxygen source. The nitrogen gas produced collects into bubbles which rise to the surface and are released to the atmosphere. |
|
Which of the following air filters will efficiently remove large quantities of dust and larger particles in order to protect blowers?
|
viscous impingement
Viscous impingement filters trap dust and larger particles on an oil-coated mesh screen. They can handle a large quantity of dust, but often smaller or lighter particles can slip through. |
|
Which of the following air filters will efficiently remove large quantities of smoke and small particles in order to protect blowers?
|
electrostatic precipitators |
|
For most trickling filter systems, operators can use ___________ to control parameters such as the strength of the applied wastewater and the hydraulic loading to the filter.
|
recirculation
|
|
Most often the RAS rate for an activated sludge process is based on ____________.
|
MCRT or SRT The RAS rate is typically calculated as a percentage of a facilityfs influent flow based on a target mean cell residence time or solids retention time your facility requires. For example, the lower the MCRT required, the lower your RAS rate will need to be. |
|
LOX stands for ________________.
|
Liquid Oxygen
LOX stands for liquid oxygen. It is one of the methods for supplying oxygen to high-purity oxygen activated sludge treatment facilities.
|
|
In an activated sludge process, a reactor that is designed to have influent fed at 2 or more points along the length of the reactor is referred to as ___________.
|
step feed
A step-feed activated sludge reactor is designed to have influent fed at 2 or more different points along the reactor length. This helps to evenly distribute the organic load or to adjust distribution if there is a problem with aeration in the reactor. |
|
At pH levels below __________, the activated sludge process will completely stop.
|
2.0
For most activated sludge processes, a range of 6.5 to 8.5 must be maintained. If the process is nitrifying, a more stringent pH range of 7.0 to 8.0 is recommended. At pH levels below 2.0 and above 10.0, the activated sludge process will stop altogether. |
|
Ferric is typically supplied to wastewater treatment facilities as a _______________.
|
liquid
Due to its physical properties and storage requirements, ferric chloride is almost always supplied as a bulk liquid. |
|
The microorganisms typically involved in the activated sludge treatment are bacteria and protozoa such as _____________.
|
rotifers
Rotifers are a type of protozoa useful to the activated sludge process. Algae and fungi are microscopic plants and Nocardia is detrimental bacteria. |
|
|
volume
Thickening is primarily designed to reduce the volume of material to be removed or treated in downstream processes. It accomplishes this by removing water from sludge and thereby concentrating or thickening the sludge. |
|
Waste activated sludge is typically ___________ raw primary sludge.
|
thinner than
Typically the percentage of total solids in raw primary sludge is 3-4% while the percentage in waste activated sludge is 1-2%. Therefore it is thinner than raw sludge. |
|
Excess oil and grease in the influent will often lead to the formation of __________ in primary clarifiers.
|
scum
|
|
Alum, ferrous sulfate, lime, ferric chloride, and polymers are chemicals used to precipitate_________ from wastewater.
|
phosphorus
Alum, lime, ferrous sulfate, ferric chloride, and organic polymers are chemicals used for precipitating phosphorus from wastewater. |
|
Tertiary wastewater treatment plants ________________.
|
use chemical precipitation and filtration
Tertiary treatment processes involve chemical-physical treatment of the wastewater. It utilizes processes such as chemical clarifiers and activated carbon filters for treatment. |
|
Chloramines are easily defined as _________________.
|
chlorine combined with nitrogen compounds
|
|
In an aerated lagoon, the minimum dissolved oxygen level that must be maintained is ________ ?
|
1 mg/L
Typical practice is to maintain 1 to 2 mg/L DO in an aerated lagoon. A minimum of 1 mg/L should be kept during heavy loading periods. |
|
In an aerated lagoon, a minimum DO of 1.0 mg/L should be maintained during the highest demand period which usually occurs __________________.
|
at night
|
|
Chlorine gas is a hazardous material. Which of the following is a similar, but a safer, disinfection product?
|
Sodium hypochlorite
Sodium hypochlorite can be just as effective for effluent disinfection as chlorine and it is much less hazardous. However, it can be very expensive and, unlike chlorine, it has a limited storage period before it begins to degrade. |
|
Oxygen transfer is dependent upon |
the liquid temperature |
|
Which of the following provides an estimate of the quantity of solids to be wasted from an activated sludge aeration tank? |
The rate of settling and settleometer reading |
|
Flagellates predominate in a system with a low bacteria population and a high organic load. The floc is light and dispersed. The process change needed to keep the light, dispersed floc from becoming a problem is to |
increase the mcrt |
|
pin floc is present in the effluent of a conventional activated sludge plant. The mixed liquor settling test shows rapid settling and cloudy supernatant. |
Increase the WAS rate. |
|
Based on the results shown in the table below, if no process changes are made, the expected results in the aeration tank are:
influent cbod & tss month 1 200 mg/l, 150 month 2 550 mg/l, 600
|
Mlss and cbod increase; DO decrease |
|
Compared to normal operating results, you observe a steady increase in oxygen uptake rate from your aeration tank effluent sample. This indicates |
There is a need to increase your mlss concentration |
|
What is indicated if a mixed liquor sample from an activated sludge process has large number of amoebas and other flagellated protozoa. |
young sludge |
|
Which of the following bod:n:p ratios represents a nitrogen deficiency? |
200:5:2 |
|
What should the bod:n:p ratio be? |
100:5:1 |
|
micro organisms that obtain carbon from organic matter for the synthesis of cell tissue are called |
heterotrophic |
|
micro organisms that obtain carbon from inorganic matter and sunlight |
autotrophic |
|
micro organisms that nitrify are |
autotrophic |
|
When there are a large amount of micro organisms and very little food or BOD, they will not reproduce as much but will keep using oxygen to metabolize food stored in cells. This is called |
endogenous respiration |
|
When collecting nocardia samples where is it highly concentrated? |
in the foam |
|
a properly operating activated sludge plant normally has a mixed liquor which contains what percent volatile solids? |
70-80% |
|
In a biological nutrient removal system in which phosphorus removal has declined, it is appropriate to test the mixed liquor in the anaerobic zone for the presence of |
nitrates |
|
Which activated sludge process would handle shock loads of organics most effectively? |
step feed |
|
When used for disinfection ozone is generated on-site because |
ozone is unstable |
|
Three forms of alkalinity |
bi-carbonate, hydroxide, carbonate |
|
Max storage time for a BOD sample? |
48 hrs |
|
Which of the following describes the best way to remove calcium deposits from a hypochlorite solution feed pump? |
an acid solution to dissolve the calcium deposits |
|
cod test results are obtained by a strong chemical procedure |
oxidation |
|
After dechlorinating a BOD sample, what would you do next? |
Seed the sample |
|
Samples for fecal coliform tests should be incubated at |
44.5 C
|
|
Samples for E. Coli MPN should be incubated at |
35C |
|
Which of the following samples cannot be preserved by cooling alone prior to analysis? |
COD |
|
What is the chlorinator withdrawing if it is connected to the bottom valve of a half full 1-ton cylinder? |
liquid chlorine |
|
Proper sample container for an oil and grease sample is |
wide mouth glass bottle |
|
what's the normal average contact time required for a chlorination system |
30-60 min |
|
The dilution water used in a BOD test should have an initial dissolved oxygen content of about |
7-9 mg/L |
|
Which acid is used to lower the pH less than 2 for a sample collected for COD analysis? |
sulfuric acid |
|
total toxic organics include |
chlorinated hydrocarbons |
|
What chemicals reduce or eliminate chlorine residual? |
sulfur dioxide and sodium metabisulfite |
|
What happens during breakpoint chlorination |
ammonia-nitrogen is oxidized to nitrogen gas |
|
What disinfection system produces the fewest disinfection by products? |
UV |
|
When fecal coliform samples are preserved at 10C or less, what's the max allowable time between collecting and testing? |
6 hours |
|
Glassware used for phosphorus testing must be |
rinsed with hydrochloric acid and distilled water |
|
Biosolids records must be kept for how long? |
5 yrs |
|
In the endogenous respiration phase, the mass of bacteria |
Decreases |
|
What's an advantage of aerobic digestion compared to anaerobic digestion? |
Close operational control of the VA/ALK relationship is not necessary |
|
CFR 503 says that sour must be less than |
1.5 mg/hour/gram |
|
In an anaerobic digester gas pressure is maintained by a controlling mechanism that is commonly regulates |
6-8 inches of water column pressure |
|
Thermophilic bacteria thrive at temperatures |
above 45 degrees C |
|
When first starting up a DAF unit the operator should |
close all the drain line valves from all the tanks, compartments, and the dump valves within the system |
|
If an anaerobic digester starts foaming what should you do |
reduce feed rate and monitor ph, add alkalinity if needed |
|
Buffer capacity in an anaerobic digester is measured by |
alkalinity |
|
What gases are produced in the highest concentrations during the initial start up of an anaerobic digester? |
Carbon dioxide and hydrogen sulfide |
|
During aerobic digestion, why does the pH in the digester decrease? |
Utilization of alkalinity |
|
What will most likely occur if sludge is pumped to a vacuum filter faster than it is being dewatered by the filter? |
filter vat will probably overflow onto the floor |
|
how can stack gases from a sludge incinerator be deodorized? |
raise the temperature of the gases sufficiently so that they burn |
|
a concentration of _____percent digester methane gas in air is explosive |
5-15% |