TX Class C Wastewater Treatment License Exam Questions and Answers, Exams of Water and Wastewater Engineering

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TX Class C Wastewater Treatment License

2024-2025. Questions and Correct Verified

Answers. Graded A

% reduction formula - ANSincoming - outgoing/incoming X 100 1 acre = - ANS43,560 ft squared 1 acre will treat approximately __________ lb BOD - ANS 1 day = __________ minutes - ANS 1 gallon of water weighs.. - ANS8.34 pounds 1 Liter = - ANS1000 milliliters (mL) 1 mg/L = - ANS1 parts per million (ppm) in water 1 MGAD = - ANS23 gpd/ft cubed 1 mL of water weights - ANS1 gram (g)

1,000,000 gallons per day = - ANS1 MGD 27 ft cubed = - ANS1 yard cubed 43,560 ft cubed = - ANS1 acre-ft 7.48 gal = - ANS1 ft cubed 8.34 lb in 1 MG of water = - ANS1 ppm (8.34 lb/8,340,000) A BOD test is... - ANSa major parameter in quality control A buildup of solids in the tank of the rotating biological contactor may be caused by... - ANSpoor primary clarification A cause of poor quality supernatant liquor could be... - ANSdigester overload A chemical factor influencing the efficiency of wastewater stabilization ponds is... - ANScarbon dioxide A condition(s) that adversely affect(s) the operation of a rotating biological contactor is... - ANStoxic materials from industrial wastes; hydrogen sulfide; high or low pH

A conventional activated sludge process has primary clarifiers that remove about ________ percent of the organic load.. - ANS30-40% A flow totalizer is required when the plant design flow is more than - ANS0.5 MGD A flow-weighted "composite" sample is a... - ANScombination of portions of samples collected at regular intervals and combined according to flow A gas found in treatment systems that is NOT dangerous - ANSdissolved oxygen A low oxygen uptake rate might indicate... - ANStoxic waters, low DO or low BOD A low SVI may indicate... - ANSsludge is settling too fast A minimum value of _________ of oxygen should be maintained in the aerobic digester at all times. - ANS1.0 mg/L A primary clarifier should remove most of what? - ANSsettleable solids Adequate chlorine residuals will... - ANSdestroy pathogenic organisms Administrative penalties, up to __________ per day for each violation, may be assessed against any violator. - ANS$25,

Advanced treatment processes strive to provide a ______________ removal level of specific compounds, suspended solids, and oxygen-demanding materials than cannot be achieved through secondary treatment alone. - ANShigher All anaerobic digester roofs/covers should be equipped with pressure relief, vacuum relief and _________. - ANSflame-trap valves Anaerobic digester mixing methods include - ANSgas mixing and mechanical mixing Anaerobic lagoon dissolved oxygen content... - ANSnone As what materials are decomposed, their phosphorus content is converted to orthophosphate? - ANSorganic At 20'C the HOCl (hypochlorous acid) concentration will vary with the pH as follows: - ANSpH 7 - 80% HOCl Basic elements of a trickling filter are... - ANSfloor and walls; distributor arms; underdrains and media Because UV light is not a chemical, it does not alter the ______________ of the water. - ANSphysical properties Benefit of multiple inlets and outlets in treatment ponds are... - ANSprevention of short-circuiting and will assure an evenly distributed flow

Benefits of removing grit - ANSwear on pump impellers, line stoppages and taking up space Biological denitrification is accomplished under what conditions by heterotrophic bacteria that use nitrate during the fermentation of organic carbon materials? - ANSanaerobic BOD is a measure of what? - ANSoxygen used up By performing Imhoff cone tests on the clarifier inlet and outlet, the operator can determine what? - ANSthe efficiency of the clarifier and a sludge pumping schedule Cause of septic wastewater - ANSbacterial action Chlorine combines with ammonia in wastewater to form.... - ANSChloramines Chlorine contact chamber shall have at least a _____ minute detention time at peak flow - ANS Chlorine could be used as an aid in trickling filter operation to... - ANSbreakup a ponding problem Chlorine equipment shall be capable of... - ANSapplying chlorine continuously; adding highest expected dosage at any time; automatic control of feed

Chlorine is a heavy, non-combustible, ______________ gas with a pungent, irritating odor and very low electrical conductivity. - ANSgreenish-yellow Chlorine is available as.... - ANSpure chlorine in a cylinder; sodium hypochlorite solutions from 5% to 15% chlorine; calcium hypochlorite of about 65% effective chlorine Chlorine may be used for... - ANSbulking control, disinfection and odor control Chlorine may be used to... - ANSincrease BOD; kill psychoda bacteria and destroy grease Circumference = - ANSpie X diameter Classifications of solids in wastewater - ANSfixed/ash, suspended/dissolved, organic/inorganic Clean Water Act - ANSgives the basic structure for regulating discharges of pollutants into the waters of the United States Clogged orifices on influent distributor arms may be corrected by... - ANScleaning and flushing Control parameters for activated sludge plants - ANSoxygen levels, wasting rates, sludge quality, return rates and aerator solids levels

Control tests on pond effluents include - ANSBOD, TSS and pH Cycles of decay include - ANScarbon, nitrogen and sulfur Define F/M ratio - ANSfood to microorganism ratio Depth of facultative lagoons is - ANS5-8 ft deep Depth of wastewater stabilization pond - ANS3-5 ft deep Describe activated sludge... - ANSis fluffy and difficult to settle with approximately 99% moisture content Different treatment plants have different requirements for wastewater treatment (true or false). - ANSTrue Digester gas may be used to ________ digesters. - ANSheat Digester gas should contain about _____________ methane - ANS65-75% Digester trouble signs include... - ANSan increase in CO2 content and a decrease in volatile solids reduction

Direct filtration of secondary effluent is often used to reduce _____ solids to low levels. - ANSsuspended Disinfection may also be accomplished by... - ANSozone, bromine and ultraviolet radiation Dissolved oxygen is necessary in... - ANSsecondary treatment processes During normal operations, the __________ will concentrate sludge, making it 2- times denser than that of the mixed liquor. - ANSclarifier Electrons pass from the ______ source (the electron donor) to nitrate and nitrite (the electron acceptor) to promote the conversions to nitrogen gas. - ANScarbon Essential needs of an efficient wastewater stabilization pond... - ANSDO, algae and bacteria Every city with more than ________ in population needs to establish a water pollution control program and hire qualified personnel to administer it. - ANS10, Facultative lagoon dissolved oxygen content... - ANSDO on top and none at bottom Filter operational problems include... - ANSponding; filter flies (psychoda); odors

Filter ponding may be caused by... - ANSpoor quality rock; excessive organic loading; inefficient primary clarifier For an activated sludge process to work properly, an operator much insure that... - ANSenough return activated sludge is sent tot he aerator to maintain the process; solids do not accumulate in the clarifier; excess solids that develop in the process are removed frequently enough to avoid build-up For anaerobic digesters, good sludge, supernatant and gas production is realized at a pH of about... - ANS7. Forms of chlorine used in wastewater treatment include... - ANSgas, granular and solution Gas chlorination facilities should be equipped with.... - ANSbottle of ammonium hydroxide Good activated sludge will contain... - ANSa high percentage of stalked ciliates and large numbers of rotifers Good housekeeping around ponds includes... - ANSkeeping dike clean Grab samples must be used to determine.... - ANSchlorine residual Hazardous gases can be composed of... - ANScombustibles and explosive gases; asphyxiation-producing gases; poisonous or toxic gases

Hazardous wastes include - ANScyanide, sulfides, organics and gasoline How are protozoa (cause of amoebic dysentery) destroyed? - ANSdisinfection How can grease be removed before sedimentation? - ANSby chlorination, aeration and skimming How deep should the clarifier blanket be? - ANSfilling the bottom 1/ How is F/M ratio calculated? - ANSby dividing the pounds of incoming BOD (food) by the pounds of MLVSS (microorganisms) in the aeration tank How many basic cell structures are there? - ANS How many cubic feet of screenings per million gallons of wastewater will coarse screens remove? - ANS0.5 to 6. How many gallons per day will each person contribute to the wastewater treatment plant? - ANS How many times should a clarifier concentrate mixed liquor solids? - ANSat least two times How much BOD is removed in primary settling? - ANS35%

How much BOD will each person contribute to the wastewater treatment plant each day? - ANS0. How much raw influent should return pumps be able to provide? - ANS50-150% How much settleable solids is removed in primary settling? - ANS90-95% How much suspended solids is removed in primary settling? - ANS50-70% How much total organic matter is removed in primary settling? - ANS20-30% How should raw sludge be pumped to a digester? - ANSslowly when it is adequately thickened If a chlorine dosage of 12 mg/L is added to a wastewater effluent containing ammonia and the chlorine demand is 11.5 mg/L, the residual would be ________.

• ANSa monochloramine - 0.5 mg/L Important factors to a well operating trickling filter... - ANScontinuous food supply, aerobic conditions and a moist zoogleal mass In an Imhoff tank, the lower compartment serves as the... - ANSdigester In an Imhoff tank, the upper compartment serves as the... - ANSclarifier

In small concentrations hydrogen sulfide has a __________ odor. - ANSrotten-egg In the removal process, what must bacteria do? - ANSgather food, digest food, utilize food and give off by-products In what ways are bacteria classified? - ANSshape, oxygen needs, temperature and metabolism Inflow - ANSdirect discharges of storm water or surface water into a wastewater collection system (storm drains, roof gutters, yard drains, basement sump pumps and broken manholes and wastewater lines). Is activated sludge aerobic or anaerobic? - ANSaerobic Laboratory tests on an anaerobic digester may be used to determine... - ANSdigester loading and quality of supernatant and digested sludge Laboratory-scale studies have shown that the changes occurring in the settlement of the floc are greatly influenced by what? - ANSbiological activity Main purpose of sedimentation tank - ANSallow scum to rise and solids to settle under quiescent (low velocity) conditions Many over look what kind of oxidizing agent as an oxidant because of its relative ineffectiveness in conventional waste treatment? - ANSozone

Methane is a ____________________ and highly flammable gas which acts to deprive body tissues of oxygen and will not support life. - ANScolorless, odorless, tasteless Methods of controlling filter flies include... - ANSflood the filter Non-hazardous wastes include - ANSchlorides, alkalinity, color, phosphorous and iron Normal range for SVI (sludge volume index) - ANS70- One of the benefits of pre-aeration is - ANSgas and grease removal Organic compounds in wastewater include - ANScarbon, hydrogen and oxygen (animal and vegetable in nature) Other than stream discharge, what are other ways to dispose of effluent wastewater? - ANSaquifer recharge, evaporation in a pond, and application to farm land by irrigation Percent (%) formula is - ANSPart/Whole X 100 pH is important in the operation of... - ANSanaerobic digesters; chlorination of wastewater; oxidation ponds

Physical causes of sludge bulking are... - ANSexcessive hydraulic loading, settled sludge that is not promptly removed from the clarifier, inadequate weir lengths and improper ratio of depth to surface area of the final clarifier pie = - ANS3. Preaeration benefits - ANSfreshen wastewater, scour gases and remove grease Preliminary Treatment - ANSthe 1st stage of sewage treatment where large debris, such as sticks, grit, and rags pas through a screen followed by a grit chamber, where the flow of water is slowed enough to allow for sedimentation. Primary volatile acids are converted by methane bacteria to... - ANSmethane and carbon dioxide Proper __________ is essential to filter performance. - ANScleaning Purpose of advanced (tertiary) treatment - ANSreduces specific contaminants such as suspended solids, ammonia or phosphorous to very low levels to achieve struct effluent standards Purpose of primary treatment - ANSremoves solids that readily settle or float Purpose of return activated sludge - ANSto reseed the biological reactor with treatment microorganisms

Purpose of secondary treatment - ANSmicroscopic living creatures (microorganisms) remove additional contaminants Purpose of wasting solids from an activated sludge system is... - ANSremove excess biological solids, inert solids and old/dead microorganisms Raw wastewater anaerobic ponds are usually used by... - ANSlivestock feedlots, meat packing operations and industrial wastes generators Reclaimed water piping must be color-coded __________. - ANSpurple Reclaimed water providers must report monthly to TCEQ the _____________ and __________ of reclaimed water delivered to a user. - ANSvolume/quality Required minutes of detention time for design flow? - ANS Required minutes of detention time for peak flow? - ANS Rising sludge and gas bubbles can be caused by... - ANSdenitrification in the final clarifier Rotating Biological Contactor - ANSa type of biological secondary treatment process Rotating biological contactors are usually covered to... - ANSprevent algae growth on the media

Rotating biological contactors may be... - ANSdriven by electric motors or trapped air Scum in a digester is mostly... - ANSundigested grease Since the majority of _______ digesters are open tanks, digester liquid temperatures are dependent on weather conditions and can fluctuate extensively.

• ANSaerobic Sludge bulking is corrected by.... - ANSrestoring environmental balance to favor floc-forming bacteria over filamentous organisms Sludge conditioning is the process of removing water by thickening or by adding polymers or _________________ materials to improve the loading rate - ANSinorganic Sludge drying time is affected most by... - ANSdegree of digestion Sludge from a primary clarifier should have a moisture content of what? - ANS94- 96% Sludge types may include... - ANSactivated State law requires that reports are to be submitted no later than the ________th day of the following month. - ANS

SVI Formula (Sludge Volume Index) - ANS30 min settle test/MLSS x 1000 Synergistic Effect - ANSreaction between waste streams Texas Water Code - ANSgives the TCEQ jurisdiction over discharges of waste into or adjacent to water in the state The air requirements in an activated sludge process are governed by... - ANSorganic loading on the plant The biological growth on the disc of a rotating biological contactor should... - ANScontain approximately 50,000 mg/L solids; be 0.05-0.1 inch thick after one or two weeks; and be gray to brown in color The depth of sludge drawn to a drying bed should be... - ANSabout 9 inches The digester temperature should not change more than ______ degree C per day.

• ANS The following processes are used to dewater sewage sludge: - ANSvacuum filters, filter presses and centrifuges The following tests are important in the control of an activated sludge process... - ANS30 min setteability test; oxygen uptake rate; microscopic examination

The ideal orientation of a wastewater stabilization pond would be... - ANSparallel with prevailing winds The materials found practical for phosphorus precipitation include the ionic forms of what? - ANSaluminum, iron and calcium The materials resulting from the stabilization of waste material as it passes through a trickling filter are... - ANSwater, nitrates and carbon dioxide The moisture content of sludge transported to a municipal landfill should be less than __________. - ANS80% The most expensive method for the final disposal of sludge is... - ANSincineration The most important factor affecting filter performance is the _____ of the secondary effluent applied to the filter. - ANSquality The organic loading on wastewater stabilization ponds should not exceed - ANS lb. BOD/acre/day The proper pH for anaerobically digested sludge will... - ANSbe from 6.8 to 7. The purpose of laboratory tests is to... - ANSdetermine the overall efficiency of the plant; determine the effect of the discharge on the receiving stream; determine the characteristics of the waste being treated

The purpose of sludge digestion is... - ANSstabilize the organic matter The RBC (rotating biological contactor) unit must be preceded by a... - ANSprimary clarifier or fine screen The recirculation ratio of a trickling filter has an effect on... - ANSorganic matter removal; odors; filter flies The rotating discs should be... - ANSpartially submerged in the wastewater The SVI should range from... - ANS70- The TCEQ allows the reuse of treated wastewater for... - ANSgolf course irrigation; aquifer recharge; agricultural irrigation The TCEQ monthly effluent report must be submitted to the TCEQ in Austin by the ______ day of the month following the month being reported - ANS20th The TCEQ requires at least _____ mg/L residual after _____ minutes contact. - ANS 20 The test(s) that best indicate(s) the condition of an anaerobic digester is (are)... - ANSvolatile acid concentration

The underdrain system of a standard rate trickling filter should be... - ANSdesigned to flow half-full The use of granular activated carbon (GAC) for ______________ removal is common. - ANSorganic The zoogleal mass on a filter is composed mainly of what? - ANSbacteria and algae To control odors at a trickling filter plant, the operator can... - ANSincrease recirculation, practice good housekeeping and chlorinate the influent Too high a velocity in a grit chamber can result in what? - ANSexcess grit in primary clarifier Total suspended solids are... - ANSdetermined by filtration Treatment pond classifications are... - ANSwastewater stabilization ponds, aerated lagoons, facultative lagoons, anaerobic lagoons and hyacinth ponds Trickling filters may be classified as.... - ANShigh-rate; roughing; standard-rate Type of organic matter present in wastewater - ANSproteins

Units commonly used to measure the rate of hydraulic loading are... - ANSlb/ft/day Units commonly used to measure the rate of organic loading include... - ANSlb BOD/acre ft/day and lb BOD/1000 ft3/day Wastewater is treated by what organisms? - ANSbacteria, fungi, algae, plants, animals and protozoa Wastewater stabilization pond dissolved oxygen content... - ANSDO throughout (top, bottom and middle) Wastewater stabilization ponds are... - ANSaerobic, dependent upon sunlight and shallower than facultative lagoons Water quality fees may be as high as ____________ per permit? - ANS$115,000 Ways that oxygen can be depleted in streams - ANSuntreated waste discharges, algae masses at night, and high BOD in the effluent Weir loadings should not exceed _________ gal/day/linear foot of weir at peak flow (1 MGD or less plant). - ANS20,000

Weir loadings should not exceed ___________ gal/day/linear foot of weir at peak flow (1 MGD or above plant). - ANS30,000 What activated sludge process parameters can an operator change directly? - ANSaeration rates, waste rates, and return sludge rates What are major surface waters classified as for the purposes of water quality management and designation of site-specific standards? - ANSsegments What are zoogleal solids called that are washed off a trickling filter? - ANSsloughings (which settle in the final clarifier) What by-products are excreted by microorganisms? - ANSCO2, H2O and NH3 and polysaccharides What can cause problems in granular activated carbon (GAC) treatment? - ANSbiological growth What chapter of the Texas Water Code gives the TCEQ jurisdiction over the discharge of waste into adjacent water in the state? - ANSCh 26 What conditions can influence settling of solids? - ANStemperature, condition of solids and flow velocity What conditions should an operator observe in a well controlled activated sludge process? - ANSsurface turbulence/uniform roll pattern; foam/small amount of light-colored, crisp foam; odors/mild, earthy; color/medium-brown

What conditions should an operator observe in a well controlled clarifier? - ANSvery little surface scum; a sludge blanket covering 1/4 of the bottom; uniform weir flow (all the way around); almost no rising solids and overflow should be clear and free of floc What DO levels (in aeration) are optimal to maintain health of aerobic microorganisms? - ANS2-4 mg/L What does short-circuiting in a pond cause? - ANSreduction in detention time What factors affect biological growth? - ANSdissolved oxygen level, temperature, pH and available food What happens when the return sludge rate is too low? - ANSthere will be insufficient organisms to treat the waste load entering the aeration basin and the sludge blanket in the secondary clarifier could become too high What has been tried as oxidizing agents in wastewater treatment? - ANSchlorine dioxide (ClO2) Ozone (O3) Chlorine (Cl2) What is a common coagulant used for chemical precipitation? - ANSaluminum sulfate; sodium aluminate and ferric sulfate

What is a factor that influences the operation of sludge thickeners? - ANSsolids surface loading, temperature of the sludge entering the unit and biological activity of the sludge What is a flow equalization used for? - ANSto reduce excessive flows or organic loads What is the absorbent most commonly used for water treatment? - ANSActivated carbon What is the most important microorganism in wastewater treatment? - ANSbacteria What limiting factors affect bacteria growth? - ANSpH, temperature, moisture and food What must be durable and provide enough surface for bacterial growth with a trickling filter? - ANSfilter media What must the operator control in order for microorganisms to do their job? - ANSthe environment What occurs when solutions of two different concentrations are separated by a semipermeable membrane such as cellophane? - ANSosmosis What percentage of suspended solids will settle out within 2 hours? - ANS70%

What problem is short-circuiting in a clarifier? - ANSflow problem What stage of treatment is grit removal usually accomplished in? - ANSpreliminary treatment What substances should NOT be dumped into the collection system? - ANSacids; caustics; chemical fertilizers What test best indicates the efficiency of a trickling filter? - ANSpercent BOD removal What test can give operators a visual check on sludge quality? - ANS30-minute settling test What type solids cannot go onto a trickling filter? - ANSlarge suspended solids What was the first major law to address water pollution? - ANSThe Federal Water Pollution Control Act of 1948 What will a wastewater stabilization pond effectively reduce? - ANSBOD and bacteria When gas chlorine is added to water, the following is formed... - ANSHOCl (hypochlorous acid) and HCl (hydrochloric acid)