Texas Wastewater A Exam Quuestions and Complete Solutions

Texas Wastewater A Exam Quuestions and Complete Solutions What is TCEQ doing to control "point source" pollution of the Texas waterways? - Answer: *Permitting of domestic wastewater plants *Permitting of industrial wastewater plants Describe proper design of force main wastewater lines. - Answer: Minimum two fps velocity with the smallest pump operating alone. Minimum four inch diameter pipe with 150 psi rating. What is Standard Dimension Ratio? - Answer: Ratio of outside pipe diameter (OD) to wall thickness (PVC) Describe proper design of gravity wastewater lines. - Answer: Designed to flow half full ,under normal conditions, at a minimum of two fps and a maximum of ten fps. Manholes should have a minimum opening of? - Answer: 24 inches and be at least 4 feet wide. pH meters should be calibrated how often? What standards should be used for calibration purposes? - Answer: Daily with at least two buffers. What is the standard chlorine residual and minimum contact time on Texas wastewater permits? - Answer: a. 1.0 mg/L for a minimum 20 minutes detention time at peak flow b. No chlorine residual needed if detention time is greater than 21 days As the complexity of an organization increases, what management function becomes most important? - Answer: Planning What is the effective chlorine disinfecting agent? - Answer: Hypochlorous Acid (HOCl) Does pH affect the chlorination process? Explain your answer. - Answer: When using free chlorine the disinfectant is HOCl acid. As such it is much more effective at pH's below 7.0. Above 7.0 pH the acid begins to be neutralized. What is the effluent chlorine residual in Texas that is standard on permits and the minimum detention time? What is the maximum residual allowed? - Answer: Texas standard is 1.0 mg/L for a minimum 20 minutes detention time at peak flow. Maximum residual allowed is 4.0 mg/L. A treatment plant has a clarifier that is 60 feet in diameter and is 10 feet deep. The weir is 2 feet inside the outer clarifier wall. The flow is 1.0 MGD. The weir and outflow channel is 3 feet deep. a. What is the detention time in hours? - Answer: Formula What activated process cannot nitrify in a single stage? - Answer: Contact Stabilization What is the GPM output of a piston pump with an 8-inch diameter piston with a 10-inch stroke operating at 50 strokes per minute? - Answer: Formula A treatment plant has a clarifier that is 60 feet in diameter and is 10 feet deep. The weir is 2 feet inside the outer clarifier wall. The flow is 1.0 MGD. The weir and outflow channel is 3 feet deep. a. What is the detention time in hours? b. What is the surface loading in gal/ft2/day? c. What is the weir loading in gal/linear ft/day? - Answer: Formulas A primary clarifier has a flow of 3.0 MGD and has a diameter of 100 feet. It is 12 feet deep and has 24 inches of freeboard. What is the detention time in hours? - Answer: Formulas Anaerobic digester gas should contain? - Answer: 65-75% methane, 25-35% carbon dioxide and 1-5% nitrogen. An activated sludge plant has an average daily flow of 3.5 MG. The aeration tank capacity is 1.2 MG with a MLSS concentration of 3200 mg/L. The clarifier has a capacity of 400,000 gallons with a MLSS concentration of 6,000 mg/L. The wasting rate is 40,000 gallons per day with a MLSS concentration of 8, 000 mg/L. The effluent TSS is 18 mg/L. Assuming volatile concentrations of 70%, what is the MCRT and what type of activated sludge plant should this be? - Answer: Formulas MCRT What are some of the causes of filaments in the aeration basin? - Answer: a. low DO b. low organic loading c. septic wastes d. nutrient deficiencies . e. high sulfur content Good sludge quality will have a predominance of what organisms in the MLSS? - Answer: Ciliated protozoa When an RBC is operating correctly, how will the slime appear on the media? - Answer: Grey to brown 0.05 to 0.1 inches thick According to design criteria, what are the minimum allowable diameters for a manhole? - Answer: 24 inch opening and 48 inch inside diameter What activated sludge process does not achieve complete nitrification? - Answer: Contact Stabilization In the selection of forced main wastewater piping, what is the minimum working pressure? - Answer: 150 psi The oxygen depletion of BOD dilution water should not exceed - Answer: 0.2 mg/L. What is the minimum air gap when making water and wastewater connections? - Answer: Minimum of one inch or twice the inlet pipe size whichever is greater. What is the minimum useful size pipe to prime a centrifugal pump? - Answer: 1 inch An anaerobic digester must maintain an average year round temperature of - Answer: 95 degrees F. How do you remove shoring from a trench? - Answer: From the bottom up Which of the following methods would you use to increase the degree of nitrification in an activated sludge plant? - Answer: increase dissolved oxygen levels and increase the sludge age Which of the following are considered normal operator controls on an activated sludge plant? - Answer: *aeration rates *return and wasting rates Reducing the return sludge flow rate for an activated sludge system which has a good settling sludge will ________. - Answer: increase the RAS concentration and the clarifier sludge blanket thickness An extended air activated sludge plant has a fast settling sludge and high amounts of pin floc leaving the clarifier. One way to correct this problem is to ________. - Answer: * reduce the MCRT by wasting more * increase the F/M ratio by wasting more The primary causes of wastewater stoppages are ________. - Answer: roots and grease The inside diameter of a manhole must be how wide? - Answer: 48 inches On a construction job site, equipment booms must maintain at least how many feet of clearance from overhead electric lines? - Answer: 10 feet Digester gas should contain about ________. - Answer: a. 65% - 75% methane A treatment plant has two primary clarifiers. Each has a diameter of 40 feet and a depth of 12 feet. If the design flow is 1.2 mgd, find the surface loading on each clarifier in gallons/ft2/day. Assume the flow is equally split between the two clarifiers. 3.14 x 20 x 20 = 1256 1,200,000 /2 = 600,000 gallons each 600,000/ 1256 - Answer: b. 478 gallons/ft2/day Distilled water used for the BOD analysis should not exceed ________. - Answer: 0.2 mg/L depletion One element of being an effective communicator is to ________. - Answer: a. be a good listener In order to promote a collaborative management style, one thing a supervisor can do is ________. - Answer: join the team as a member rather than as boss One thing an employee can do to be a good team member is to ________. - Answer: try to understand other people's needs and desires Seeding of BOD samples is necessary when samples ________. - Answer: a. have a chlorine residual b. have previously been chlorinated c. have been subjected to high temperatures d. contain high or low pH industrial wastes A 30-inch diameter wastewater interceptor is observed to be flowing half-full at about two fps. The approximate volume of wastewater flowing through the pipe is ________. - Answer: 2,200 gallons per minute A one-cylinder reciprocating sludge pump with a 10-inch bore and a 5-inch stroke pumps at a rate of 50 cycles per minute. How many minutes must the pump be operated to pump 5,000 gallons of sludge? - Answer: 60 minutes Review exhibit E in the separate package. According to the DMR, the TSS data shows ________. a. a violation of the daily average b. a violation of the number of grab samples c. a violation of the 7-day average d. a violation of the daily max e. no violation - Answer: Need DMR Review exhibit E in the separate package. According to the DMR, the cBOD data shows ________. a. a violation of the daily average b. a violation of the number of grab samples c. a violation of the 7-day average d. a violation of the daily max e. no violation - Answer: Need DMR Review exhibit E in the separate package. According to the DMR, the NH3-N data shows ________. a. a violation of the daily average b. a violation of the number of grab samples c. a violation of the 7-day average d. a violation of the daily max e. no violation - Answer: Need DMR When is blue-green algae the most dominant on a pond treatment system? - Answer: Summer Motivating workers to increase long-term productivity is best accomplished by ________. - Answer: giving the workers a participatory role in setting goals What is the purpose of biomonitoring of a plant's effluent? - Answer: Test for toxicity A zone in a body of water that was recently polluted might show signs of ________. - Answer: low DO, scarce aquatic life, low turbidity When testing for effluent toxicity, how is it determined? - Answer: survival rate of aquatic organisms When must TCEQ be notified about expansions of a treatment facility? - Answer: Before construction In an anaerobic digester, the percentage of methane and carbon dioxide gas content should be ________. - Answer: 70% methane, 30% carbon dioxide The temperature of an anaerobic digester should be maintained at a minimum of ________. - Answer: 95ᵒ F What type of wastewater treatment plant operates in the endogenous growth phase? - Answer: Extended air Disinfection with chlorine is the more effective at a pH of 9 rather than 6. a. True b. False - Answer: b. False The biomass of a normal functioning RBC has what appearance? - Answer: Grey to brown and 0.05 to 0.1 inch thick A complete mix activated sludge plant has a fast settling sludge and high amounts of pin floc leaving the clarifier. One method of correcting the problem is to ________. - Answer: Increase F/M ratio by wasting more How often should pH meters be calibrated? - Answer: Daily A wastewater treatment plant has a clarifier that is 80 feet in diameter and is 12 feet deep. The flow is 2.5 mgd. The single weir is two feet inside the outer wall and is 3 feet deep What is the clarifier detention time in hours? a. 3.9 b. 3.5 c. 5.3 d. 4.2 - Answer: Formula A wastewater treatment plant has a clarifier that is 80 feet in diameter and is 12 feet deep. The flow is 2.5 mgd. The single weir is two feet inside the outer wall and is 3 feet deep What is the hydraulic loading on the clarifier in gal/sq. ft/day? a. 598 b. 698 c. 551 d. 614 - Answer: Formula A wastewater treatment plant has a clarifier that is 80 feet in diameter and is 12 feet deep. The flow is 2.5 mgd. The single weir is two feet inside the outer wall and is 3 feet deep. What is the weir loading in gal/linear ft/day? a. 10,000 b. 10,460 c. 11,276 d. 11,400 - Answer: Formula How should shoring be removed from a trench? - Answer: from the bottom up Effective communication depends on ________. - Answer: being a good listener According to 30 TAC Chapter 317, all pipe and fittings used in wastewater pressure mains shall have a minimum psi pressure rating of ________. - Answer: 150 The smallest pipe size for air recirculation of a self-priming centrifugal pump is ________. - Answer: 1 inch The goal of a sanitary wastewater survey is to ________. - Answer: identify problems in the system needing rehab Sewer balls and pigs are what type of wastewater cleaning equipment? - Answer: mechanical cleaning equipment When setting goals for an employee, the goals should be ________. - Answer: accompanied by an action plan According to Chapter 317 Design Criteria, a manhole can be installed within nine feet of an existing waterline if ________. - Answer: the manhole is completely watertight and tested for no leakage As the population of a collection system increases, the ratio of peak flow to average daily flow will ________. - Answer: decrease If a wastewater pipe has a slope of 4 feet in 200 feet, it is referred to as ________. - Answer: two times the inlet pipe diameter One of the requirements of the Texas Hazard Communication Act of 1985 is that the employer mush hold annual training in which the utilities' written policies and the employee's rights are explained to ________. - Answer: all employees The Federal Clean Water Act________. - Answer: requires a permit for disposal of sludge brequires a permit for ocean discharges of sewer requires a permit for disposal or placement of dredge material creates a national permit system for all wastewater discharge e. all the above If an employee is guilty of misconduct as defined by the utilities personnel policies, the supervisor should________. - Answer: *attempt to modify the employee's behavior through training and other forms of assistance *inform the employee of the consequences if the behavior is not modified When fighting an electrical fire, you should________. - Answer: *Use non-conductive extinguishing methods *Use Class A or B extinguishers if you are certain electricity to the unit has been shut-off If the float that turns on the lead pump in a wastewater lift station is situated above a gravity influent line, the line will________. - Answer: tend to have a grease problem If an operations company ceases its operation or is sold such that the control of the company is transferred to another party, ________. - Answer: the company's operations certificate is revoked The sludge from a primary clarifier should contain what percent solids? - Answer: 4% to 6% What are the hazards of using powdered activated carbon? - Answer: *fire/explosive *inhalation *uncomfortable working conditions How often must a facility conduct TCLP on its sludge if its sludge disposal is equal to or greater than 15,000 metric tons annually? - Answer: monthly Most gas protection instruments do not latch. That means that________. - Answer: the instrument stops alarming when removed from the contaminated atmosphere A. What are the three major characteristics of "point source" water pollution in Texas? - Answer: a. Can be easily identified. For example, "This is where they discharge." b. Can be monitored for effluent characteristics. c. Can be permitted by regulators. What is TCEQ doing to control "point source" pollution of the Texas waterways? - Answer: a. Permitting of domestic wastewater plants b. Permitting of industrial wastewater plants c. Permitting of storm water run-off. d. Assessment of fines and penalties for violators. How does a "non-point source" of water pollution differ from a "point source"? - Answer: *Point source is easily to identify, monitor, and permit. *A non-point source, while we may know it exists, it difficult to identify where it is discharged. In most cases the discharge may be gradual over a very large area at multiple locations. Therefore it is also hard if not impossible to monitor. D. Give three examples of "non-point source" pollution. - Answer: a. Storm water run-off in areas not under storm water permitting. b. Run-off from agricultural land c. Run-off from a mining operation d. Run-off from cattle, hog, or chicken operation Your activated sludge plant has thick blackish brown foam on it. What are the possible problems and possible solutions? - Answer: This is characteristic of Nocardia filamentous bacteria. This filament and its relatives will be predominate when sludge is old and food supply does not match the organisms available. Operating conditions that support Nocardia are low food to microorganism ratio (F/M) and high mean cell residence time (MCRT). Proper operational response would be to increase wasting and get F/M and MCRT in line with the activated sludge process being utilized. If the problem is extremely severe, chlorine may need to be applied to kill some of the filamentous bacteria. List at least six control tests which should be used to optimize the activated sludge process. Provide a brief explanation of the purpose of each control test. - Answer: a. Dissolved oxygen b. Return activated sludge (RAS) flows and MLSS concentration c. Waste Activated sludge (WAS) flows and concentrations d. pH e. 30 Minute settleability test (SV30) f. COD (BOD5 or CBOD5) required for permit compliance g. MLSS and MLVSS concentration in the aeration basin h. Influent flow, BOD and TSS concentration i. Calculate F/M ratio, MCRT, and SVI List and discuss three reasons why lift stations are used in a collection system. - Answer: a. When the gravity line is so deep that we cannot go any deeper and have to pump. b. When we have to convey wastewater from a gravity line over a hill or rise where we can gravity flow again. c. Where we have to transport the wastewater a substantial distance such as an outfall line to the treatment plant. d. A lift station (one pump) is used at every tap in a low pressure system. There is no gravity flow in these type systems.