Wastewater Treatment Plant Operations, Exams of Water and Wastewater Engineering

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WASTEWATER B TEST

QUESTIONS WITH THE LATEST

AND UPDATED SCORE.

Percent of volatile solids normally in sludge -- Correct Answer ✔✔ 70- 80% D.O. levels in a primary clarifier -- Correct Answer ✔✔ 0.5-1.0 MG/L Why are precautionary measures needed around an aeration basin? -- Correct Answer ✔✔ undertow and turbulence O.S.H.A. approved trench -- Correct Answer ✔✔ narrow excavation in which the depth is greater than the width; the width must be less than 15 feet What causes bulking? -- Correct Answer ✔✔ 1. Excessive hydraulic loading,

2. Solids not promptly removed from clarifier
3. Inadequate weir length
4. Improper ratio of depth to surface area of the final clarifier What are the 5 elements of a trickling filter? -- Correct Answer ✔✔ 1. Floor
5. under drain
6. Wall containing the filter bed
7. media
8. filter distribution arm When and where are monthly reports submitted? -- Correct Answer ✔✔ by the 20th of the following month; submitted to Austin

How and when do you report a bypass? -- Correct Answer ✔✔ as soon as possible by phone within 24 hours; followed by in writing within 5 working days What are the 5 events of stream purification? -- Correct Answer ✔✔ 1. Pollution

2. Degradation
3. Decomposition
4. Recovery
5. Clear What are the 2 methods for measuring D.O.? -- Correct Answer ✔✔ 1. Winkler method
6. meter What is needed for good communication? -- Correct Answer ✔✔ good listening How much chlorine gas comes from one part liquid chlorine? -- Correct Answer ✔✔ 450 What does the "F and M" stand for in the F:M Ratio? -- Correct Answer ✔✔ Food to Microorganism What feeds the nitrification organisms? -- Correct Answer ✔✔ fatty volatile acids An explosive atmosphere contains what 2 things? -- Correct Answer ✔✔ 1. Oxygen
7. flammable gas vapor or dust How deep should the drying bed sludge be? -- Correct Answer ✔✔ 8- inches Why is a low flow rated important when filling a drying bed? -- Correct Answer ✔✔ to prevent undigested sludge from breaking through the ripe sludge blanket in the digester

Under a microscope what 2 organisms should be predominant? -- Correct Answer ✔✔ 1. SILIATE

2. rotifers The detention time in a contact stabilization plant is more or less than other extended aeration plants? -- Correct Answer ✔✔ Less What 2 things are chlorine used for? -- Correct Answer ✔✔ 1. disinfection
3. odor control What will a leaking chlorine container do? -- Correct Answer ✔✔ freeze up How are plant goals best accomplished? -- Correct Answer ✔✔ planning, PM, records, analysis What is the function of the bottom float in a lift station? -- Correct Answer ✔✔ turns the pump off What must be used when connecting a potable water supply to a lift station? -- Correct Answer ✔✔ an air gap between the pump and the water line twice the diameter of the water line or at least 1", whichever is greater What is the problem if the supernatant in the settleometer is clear but the effluent is not? -- Correct Answer ✔✔ 1. Bulking
4. An equipment malfunction such as a plugged R.A.S. or W.A.S. line
5. problem in secondary clarifier Why does flow through a clarifier move up slowly? -- Correct Answer ✔✔ to keep floc particles from coming over the wiers when should a manhole be placed? -- Correct Answer ✔✔ at least every 500 feet or whenever necessary

Where should the sludge in the clarifier be kept in the activated sludge process? -- Correct Answer ✔✔ bottom quarter An S.V.I. of 180 represents what? -- Correct Answer ✔✔ old bulking sludge What should be done to remove microorganisms from an activated sludge plant? -- Correct Answer ✔✔ waste What is the preliminary treatments main purpose? -- Correct Answer ✔✔ remove large solids what are the considerations for writing a permit? -- Correct Answer ✔✔ impact on receiving stream What is an adequate B.O.D. for the contact stabilization ponds best function? -- Correct Answer ✔✔ at least 35 lbs/acer/day what is fecal coliform measured in? -- Correct Answer ✔✔ a geometric mean how should the bell end of a pipe be laid? -- Correct Answer ✔✔ uphill what 5 types of pipe are commonly used in collection systems? -- Correct Answer ✔✔ 1. PVC

2. concrete
3. asbestos concrete
4. ductile iron
5. clay what are 3 characteristics of fresh domestic sewage? -- Correct Answer ✔✔ 1. dishwater color
6. slight fecal odor
7. 99.9 percent water What test should be run within 15 minutes of grabbing the final effluent sample? -- Correct Answer ✔✔ PH test

What does S.V.I. mean? -- Correct Answer ✔✔ sludge volume index what is the formula for S.V.I.? -- Correct Answer ✔✔ 30 minute settled sludge volume in ML/L, times 1000, divided by the M.L.S.S. concentration in MG/L x 1000 What are the 3 different cycles of decay? -- Correct Answer ✔✔ 1. nitrogen

2. sulfur
3. carbon What percent of moisture should the sludge from a primary clarifier contain? -- Correct Answer ✔✔ 94-96% What is sludge in a trickling filter that goes to a clarifier called? -- Correct Answer ✔✔ humous sludge What is B.O.D. in an extended aeration activated sludge process reduced by? -- Correct Answer ✔✔ 90-95% What problems can chlorine be used to treat? -- Correct Answer ✔✔ bulking; foaming How many gallons of waste water are contributed each day per person? -- Correct Answer ✔✔ 100 gallons what are 4 characteristics of water? -- Correct Answer ✔✔ 1. physical
4. chemical
5. bacteriological
6. radiological How many MG/L of B.O.D. does raw domestic waste water have? -- Correct Answer ✔✔ 100-300 MG/L How many pounds of B.O.D. are contributed daily by each person? -- Correct Answer ✔✔ 0.17 lbs

How many hours does a C.O.D. test require? -- Correct Answer ✔✔ 2- What is the minimum velocity of waste water in a collection system? -- Correct Answer ✔✔ 2 feet per second (3 ft/sec recommended) what is a depressed sewer that crosses under a road or creek and has a reversal in grade called? -- Correct Answer ✔✔ Inverted siphon what should storm sewers only carry? -- Correct Answer ✔✔ rainwater How many feet should water and sewer lines be kept apart in all directions? -- Correct Answer ✔✔ 9 feet what is the main purpose of sewage treatment? -- Correct Answer ✔✔ to stabilize and dispose of organic material what is the best way to hook up potable water to the packing gland on a pump? -- Correct Answer ✔✔ by an air gap or not at all what is the most important thing protected by pretreatment? -- Correct Answer ✔✔ employees what are the 3 exceptions to turning in a monthly permit? -- Correct Answer ✔✔ 1. under construction

2. a new plant
3. not running yet B.O.D. or C.O.D is what in the F:M ratio? -- Correct Answer ✔✔ F - Food when denitrification occurs what is used instead of oxygen? -- Correct Answer ✔✔ nitrate What does a trickling filters efficiency dependant on? -- Correct Answer ✔✔ recirculation

When should a manhole be located? -- Correct Answer ✔✔ 1. change of pipe size

2. pipe intersections
3. change of depth or slope
4. every 500 feet why is grit washed? -- Correct Answer ✔✔ decrease the concentration of organic matter what is the simpler activated sludge process to operate? -- Correct Answer ✔✔ extended aeration what 2 things are sludge volume readings used to observe? -- Correct Answer ✔✔ 1. sludge quality
5. clarity what should sludge hauled to the landfill be? -- Correct Answer ✔✔ 20% solids what should a plant manager be most concerned about? -- Correct Answer ✔✔ plant effluent what should you do if a chlorine cylinder is leaking liquid chlorine? -- Correct Answer ✔✔ rotate the cylinder to position the frosted area on the upper most side so that it becomes a gas leak instead of a liquid leak What law provides the Texas Water Commission with the authority to regulate domestic wastewater treatment plants? -- Correct Answer ✔✔ Texas Water Code If a waste water spill occurs that endangers human health or environmental safety, when must the Texas Water Commission be contacted? -- Correct Answer ✔✔ within 24 hours by phone; within 5 days by written report

What 4 reasons can result in up to $10,000/day fines levied against a wastewater facility by the Texas Water Commission? -- Correct Answer ✔✔ 1. Violation of the TWC rule, a waste permit or order of the commission

2. Failure to seek an amendment of a permit or secure an order to construct prior to expansion of a facility
3. Failure to submit monthly self reporting forms
4. Bypassing an essential treatment unit without authorization What is the 2 hour peak flow determination at a domestic wastewater treatment plant? -- Correct Answer ✔✔ The maximum flow sustained for a two hour period during the period of daily discharge What is the daily average flow reported for a domestic wastewater plant? -- Correct Answer ✔✔ arithmetic average of all determinations of the daily discharge within a period of one calendar month What should be used to record permanent data in a treatment plant's log? -- Correct Answer ✔✔ Black ink The electric current flowing in a 120 volt circuit that lights a 75 watt bulb is sufficient to cause what? -- Correct Answer ✔✔ severe muscular contractions How often should the self-contained breathing apparatus be checked? -- Correct Answer ✔✔ Monthly and after each use Never work in confined spaced where the oxygen percent is less than what? -- Correct Answer ✔✔ 19.5% Why are the presence of dangerous gases not always identified by an unpleasant odor? -- Correct Answer ✔✔ Some dangerous gases have no odor What 2 major defects can cause hydraulic overloading of wastewater collection systems and treatment plants? -- Correct Answer ✔✔ 1. Infiltration

2. Inflow What should be done when utility lines are encountered in the excavation of a trench? -- Correct Answer ✔✔ contact the utility company and use extreme care to support the utility line during construction How can roots in a sewer be cleared? -- Correct Answer ✔✔ power rodders what is the minimum flow velocity required in sewage collection and transfer systems in order to keep the solids in suspension? -- Correct Answer ✔✔ 2.0 feet per second When does algae in a facultative pond consume oxygen? -- Correct Answer ✔✔ Day - sunlight The chlorine demand is the difference between what? -- Correct Answer ✔✔ amount of chlorine added and the amount of chlorine remaining after a contact period An efficient primary clarifier is expected to remove what percent of the influent settleable solids? -- Correct Answer ✔✔ 90% or more What is one short term corrective measure for the subsequent loss of D.O. caused by overloading of a stabilization pond? -- Correct Answer ✔✔ sodium nitrate What has the least influence on the settle-ability of solids in a clarifier? -- Correct Answer ✔✔ soluble B.O.D. Proper operation of a facultative pond system requires what? -- Correct Answer ✔✔ adequate D.O. at the surface at all times What would cause a colored dye solution added to raw wastewater entering a primary settling tank to be noticeable in 15 minutes but passed through within 40 minutes? -- Correct Answer ✔✔ Wastewater

is passing through the tank so fast that settling is probably not effective. the amount of organic matter removed by a trickling filter is dependant on what? -- Correct Answer ✔✔ recirculation ratio What is the best method of preventing the recurrence of small, dense, pinpoint floc in the secondary clarifier of a conventional activated sludge plant? -- Correct Answer ✔✔ maintain the F:M ratio near 0. (based on B.O.D. analysis), and D.O. between 1 - 3 ml/L What should you do to the plates of a flame arrester in the gas line between a waste gas burner and an anaerobic digester? -- Correct Answer ✔✔ inspect and clean periodically How should the proper temperature be achieved if the anaerobic digester is several degrees below? -- Correct Answer ✔✔ as slow as possible A predominance of what 2 things in the M.L.S.S. is a sign of good sludge quality? -- Correct Answer ✔✔ Ciliates and rotifers What causes the white thick billowing foam common during the startup of an activated sludge wastewater treatment plant? -- Correct Answer ✔✔ low M.L.S.S. Why are the volatile acids/ alkalinity relationship useful in digester control? -- Correct Answer ✔✔ they are the first indicators that the digestion process is going sour What is the best solution to an excessively thick scummy dark tam foam that occurs on the aeration tank surface in a conventional activated sludge plant? -- Correct Answer ✔✔ increase W.A.S. rate What steps should be taken when volatile acids in an anaerobic digester begin to increase beyond twice the buffering alkalinity capacity of the digester while both pH and gas production are

decreasing? -- Correct Answer ✔✔ decrease sludge feeding rate and temperature What equipment may be used by maintenance to inspect sewer lines? -- Correct Answer ✔✔ camera What 5 things can chlorination be used for in wastewater treatment? -- Correct Answer ✔✔ 1. disinfection

2. pre-chlorinate influent for control of hydrogen sulfide
3. remove nitrogen by breakpoint chlorination
4. dose R.A.S. for control of bulking foam
5. reduce plugging in trickling filter for a 5 M.G.D. primary plant, if the raw sludge solids volatile content is 81% and the digested sludge solids volatile content is 69%, what percent of the volatile solids are being converted into gas? -- Correct Answer ✔✔ 15% A treatment plant receives a flow of 3.5 M.G.D., if the clarifier is 100 feet wide and 15 feet deep, what is the surface loading rate? -- Correct Answer ✔✔ 1170 gal/ft.2/day Primary sludge containing 5% solids is pumped into a digester continuously at a rate of 25 G.P.M. How many pounds of volatile solids are added to the digester each day if the volatile solids content is 73% of the total solids? -- Correct Answer ✔✔ 10969 lbs/ day A trench 2 feet wide, 500 feet long and an average of 10 feet deep will produce what amount of excavated material? -- Correct Answer ✔✔ 370 cubic yards LxWxH= cubic feet/27 = cubic yards What is meant by S.V.I.? -- Correct Answer ✔✔ 30 min settled sludge volume in MG/L x 1000, divided by the M.L.S.S. concentration in MG/L

What 3 things could be the cause of a 30 minute settling test with high S.V.I. , dark color sludge and clear supernate that took a long time to form? -- Correct Answer ✔✔ 1. bulking sludge

2. presence of fulking filamentous bacteria
3. low D.O. in the aeration basin An oxygen uptake rate that is falling which is performed in an aeration chamber indicates the presence of what? -- Correct Answer ✔✔ toxic materials Why is it best to use as few different types of lubricants in a plant as possible? -- Correct Answer ✔✔ reduce the chances of making an error in application What 3 things can aquifer recharge with plant effluent be used for? -- Correct Answer ✔✔ 1. prevention of salt water intrusion
4. reduction of substance
5. replenishing ground water if a force main size is too small what can result? -- Correct Answer ✔✔ velocity will increase How can you tell that an anaerobic digester is functioning well? -- Correct Answer ✔✔ CO2 concentration decreases CH4 increases What does bio-monitoring test? -- Correct Answer ✔✔ toxicity of water by exposing living organisms to plant effluent How can phosphates be removed from secondary effluent? -- Correct Answer ✔✔ Luxury uptake, alum precipitation, and lime precipitation What are 3 indications of denitrification -- Correct Answer ✔✔ 1. gas bubbles
6. chunks of sludge rising in the secondary clarifier
7. S.S.T. inverts in 1-4 hours

what is the most important function of the management at a treatment plant? -- Correct Answer ✔✔ maintaining treatment and maintenance records What is the reason for slow movement of grit by way of a screw on an incline in a grit washing type removal system? -- Correct Answer ✔✔ removal of organic material from grit In the contact stabilization mode of activated sludge the contact tank detention time is designed to be less than what? -- Correct Answer ✔✔ other activated sludge processes the sludge is bulking if the S.V.I. equals what? -- Correct Answer ✔✔ 180 what is the purpose of return activated sludge? -- Correct Answer ✔✔ remove solids accumulating in the clarifier; reseeding aeration tank with biologically activated solids 450 parts gas chlorine is yielded by how much liquid chlorine? -- Correct Answer ✔✔ 1 part the nitrifying bacteria will tend to make the mixed liquor PH what? -- Correct Answer ✔✔ decrease