Wastewater Treatment Exam: 121 Questions and Answers, Exams of Water and Wastewater Engineering

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Wastewater B Test with 121 complete questions and answers exam

Percent of volatile solids normally in sludge - >>>70-80% D.O. levels in a primary clarifier - >>>0.5-1.0 MG/L Why are precautionary measures needed around an aeration basin? - >>>undertow and turbulence O.S.H.A. approved trench - >>>narrow excavation in which the depth is greater than the width; the width must be less than 15 feet What causes bulking? - >>>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? - >>>1. Floor
5. under drain
6. Wall containing the filter bed
7. media
8. filter distribution arm When and where are monthly reports submitted? - >>>by the 20th of the following month; submitted to Austin How and when do you report a bypass? - >>>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? - >>>1. Pollution

2. Degradation
3. Decomposition
4. Recovery
5. Clear What are the 2 methods for measuring D.O.? - >>>1. Winkler method
6. meter What is needed for good communication? - >>>good listening How much chlorine gas comes from one part liquid chlorine? - >>> What does the "F and M" stand for in the F:M Ratio? - >>>Food to Microorganism What feeds the nitrification organisms? - >>>fatty volatile acids An explosive atmosphere contains what 2 things? - >>>1. Oxygen
7. flammable gas vapor or dust How deep should the drying bed sludge be? - >>>8-12 inches Why is a low flow rated important when filling a drying bed? - >>>to prevent undigested sludge from breaking through the ripe sludge blanket in the digester

Under a microscope what 2 organizms should be predominant? - >>>1. SILIATE

2. rotifers The detention time in a contact stabilization plant is more or less than other extended aeration plants? -

Less What 2 things are chlorine used for? - >>>1. disinfection

2. odor control What will a leaking chlorine container do? - >>>freeze up How are plant goals best accomplished? - >>>planning, PM, records, analysis What is the function of the bottom float in a lift station? - >>>turns the pump off What must be used when connecting a potable water supply to a lift station? - >>>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? - >>>1. Bulking
3. An equipment malfuntion such as a plugged R.A.S. or W.A.S. line
4. problem in secondary clarifier Why does flow through a clarifier move up slowly? - >>>to keep floc particles from coming over the wiers when should a manhole be placed? - >>>at least every 500 feet or whenever necessary

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

2. concrete
3. asbestos concrete
4. ductile iron
5. clay what are 3 characteristics of fresh domestic sewage? - >>>1. dishwater color
6. slight fecal odor

3. 99.9 percent water What test should be run within 15 minutes of grabbing the final effluent sample? - >>>PH test What does S.V.I. mean? - >>>sludge volume index what is the formula for S.V.I.? - >>>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? - >>>1. nitrogen
4. sulfur
5. carbon What percent of moisture should the sludge from a primary clarifier contain? - >>>94-96% What is sludge in a trickling filter that goes to a clarifier called? - >>>humous sludge What is B.O.D. in an extended aeration activated sludge process reduced by? - >>>90-95% What problems can chlorine be used to treat? - >>>bulking; foaming How many gallons of waste water are contributed each day per person? - >>>100 gallons what are 4 characteristics of water? - >>>1. physical
6. chemical
7. bacteriological

4. radiological How many MG/L of B.O.D. does raw domestic waste water have? - >>>100-300 MG/L How many pounds of B.O.D. are contributed daily by each person? - >>>0.17 lbs How many hours does a C.O.D. test require? - >>>2- What is the minimum velocity of waste water in a collection system? - >>>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? -

Inverted siphon what should storm sewers only carry? - >>>rainwater How many feet should water and sewer lines be kept apart in all directions? - >>>9 feet what is the main purpose of sewage treatment? - >>>to stabilize and dispose of organic material what is the best way to hook up potable water to the packing gland on a pump? - >>>by an air gap or not at all what is the most important thing protected by pretreatment? - >>>employees what are the 3 exceptions to turning in a monthly permit? - >>>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? - >>>F - Food when denitrification occurs what is used instead of oxygen? - >>>nitrate What does a trickling filters efficiency dependant on? - >>>recirculation When should a manhole be located? - >>>1. change of pipe size
4. pipe intersections
5. change of depth or slope
6. every 500 feet why is grit washed? - >>>decrease the concentration of organic matter what is the simpler activated sludge process to operate? - >>>extended aeration what 2 things are sludge volume readings used to observe? - >>>1. sludge quality
7. clarity what should sludge hauled to the landfill be? - >>>20% solids what should a plant manager be most concerned about? - >>>plant effluent

what should you do if a chlorine cylinder is leaking liquid chlorine? - >>>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? - >>>Texas Water Code If a waste water spill occurs that endangers human health or environmental safety, when must the Texas Water Commission be contacted? - >>>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? - >>>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? - >>>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? - >>>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? - >>>Black ink The electric current flowing in a 120 volt circuit that lights a 75 watt bulb is sufficient to cause what? -

severe muscular contractions How often should the self-contained breathing apparatus be checked? - >>>Monthly and after each use

Never work in confined spaced where the oxygen percent is less than what? - >>>19.5% Why are the presence of dangerous gases not always identified by an unpleasant odor? - >>>Some dangerous gases have no odor What 2 major defects can cause hydraulic overloading of wastewater collection systems and treatment plants? - >>>1. Infiltration

2. Inflow What should be done when utility lines are encountered in the excavation of a trench? - >>>contact the utility company and use extreme care to support the utility line during construction How can roots in a sewer be cleared? - >>>power rodders what is the minimum flow velocity required in sewage collection and transfer systems in order to keep the solids in suspension? - >>>2.0 feet per second When does algae in a facultative pond consume oxygen? - >>>Day - sunlight The chlorine demand is the difference between what? - >>>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? -

90% or more

Black ink The electric current flowing in a 120 volt circuit that lights a 75 watt bulb is sufficient to cause what? - >>>severe muscular contractions How often should the self-contained breathing apparatus be checked? - >>>Monthly and after each use Never work in confined spaced where the oxygen percent is less than what? - >>>19.5% Why are the presence of dangerous gases not always identified by an unpleasant odor? - >>>Some dangerous gases have no odor What 2 major defects can cause hydraulic overloading of wastewater collection systems and treatment plants? - >>>1. Infiltration 2. Inflow What should be done when utility lines are encountered in the excavation of a trench? - >>>contact the utility company and use extreme care to support the utility line during construction How can roots in a sewer be cleared? - >>>power rodders what is the minimum flow velocity required in sewage collection and transfer systems in order to keep the solids in suspension? - >>>2.0 feet per second When does algae in a facultative pond consume oxygen? - >>>Day - sunlight The chlorine demand is the difference between what? - >>>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? - >>>90% or more What is one short term corrective measure for the subsequent loss of D.O. caused by overloading of a stabilization pond? - >>>sodium nitrate

What has the least influence on the settle-ability of solids in a clarifier? - >>>soluble B.O.D. Proper operation of a facultative pond system requires what? - >>>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? - >>>Wastewater is passeing 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? - >>>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? - >>>maintain the F:M ratio near 0.5 (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? - >>>inspect and clean periodically How should the proper temperature be achieved if the anaerobic digester is several degrees below? -

as slow as possible A predominance of what 2 things in the M.L.S.S. is a sign of good sludge quality? - >>>Ciliates and rotifers What causes the white thick billowing foam common during the startup of an activated sludge wastewater treatment plant? - >>>low M.L.S.S. Why are the volatile acids/ alkalinity relationship useful in digester control? - >>>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? - >>>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? -

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

2. pre-chlorinate influent for control of hydrogen sulfide
3. remove nitrogen by breakpoint chloination
4. dose R.A.S. for control of bulking foam
5. reduce plugging in trickling filter for a 5 M.G.D. priamry 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? - >>>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? - >>>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? - >>>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? - >>>370 cubic yards LxWxH= cubic feet/27 = cubic yards

What is meant by S.V.I.? - >>>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? - >>>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? - >>>toxic materials Why is it best to use as few different types of lubricants in a plant as possible? - >>>reduce the chances of making an error in application What 3 things can aquifer recharge with plant effluent be used for? - >>>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? - >>>velocity will increase How can you tell that an anaerobic digester is functioning well? - >>>CO2 concentration decreases CH increases What does bio-monitoring test? - >>>toxicity of water by exposing living organisms to plant effluent

How can phosphates be removed from secondary effluent? - >>>Luxury uptake, alum precipitation, and lime precipitation What are 3 indications of denitrification - >>>1. gas bubbles

2. chunks of sludge rising in the secondaryy clarifier
3. S.S.T. inverts in 1-4 hours what is the most important function of the management at a treatment plant? - >>>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? - >>>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? - >>>other activated sludge processes the sludge is bulking if the S.V.I. equals what? - >>> what is the purpose of return activated sludge? - >>>remove solids accumulating in the clarifier; reseeding aeration tank with biologically activated solids 450 parts gas chlorine is yielded by how much liquid chlorine? - >>>1 part the nitrifying bacteria will tend to make the mixed liquor PH what? - >>>decrease