Wastewater Treatment Processes and Operations, Exams of Water and Wastewater Engineering

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Wastewater Class B Texas Questions with Complete Verified Solutions 2024/2025 The name of the State Agency responsible for enforcing pollution control laws in Texas Texas Commission of Environmental Quality The term pathogenic means Capable of causing disease The minimum separation between sewer lines and potable water lines is 9 feet A licensed wastewater operator is a professional consistently does best job possible, practices personal safety, strives to improve job knowledge, strives to keep the plant and collection system in the best appearance and working order An important step in testing a sample for Total Suspended Solids is Filtering a sample The Biochemical oxygen Demand (BOD) of a sample is based on Measuring the dissolved oxygen (DO) used The results of Biochemical Oxygen Demand (BOD) sample taken at a treatment plant tells the operator How the plant was operating 5 days ago Which of the following are dangerous gasses that are likely to be present in lift stations and manholes? Natural gas, gasoline fumes, hydrogen sulfide and carbon dioxide A preferred hydraulic method of cleaning sewer lines is Hydro Jet Cleaner Ways to reduce bad odors coming from a collection system routinely cleaning slow running or low flow lines, adding chlorine or hydrogen peroxide to the collection system Types of pipe that are commonly used in wastewater collection system ductile iron, Poly Vinyl Chloride (PVC) Before entering a confined space a worker should Use approved monitoring device and check for the presence of dangerous gasses, ventilate the space with a blower, wear a safety harness and attach a life line A properly designed and operated primary sedimentation tank should remove _____ percent of incoming BOD 30-40% Devices that may be used to determine the level of sewage in a lift station air bubbler, floats, electrodes, Acoustic (sonic) What is the most important role of aerobic bacteria in the treatment of wastewater? decompose organic matter The hydraulic loading of a trickling filter may be determined by flow rate and filter area These can be used to dewater sludge belt press, drying beds, solid bowl centrifuge, gravity thickener Most important to providing adequate sewage treatment in a stabilization pond sunlight, algae, bacteria and time Offensive and objectionable odors which sometimes occur in trickling filters usually indicate septic conditions are present Dissolved Oxygen (DO) in aeration tank of an activated sludge plant should be maintained at or about 2 to 4 mg/L Contributes to the infiltration in a collection system breaks in the main lines, high ground water levels, heavy rains, hydro jet cleaning plugged mains When a centrifuge pump loses prime the pump is no longer moving liquid A Rotating Biological Contactor (RBC) is fixed firm biological treatment process Needs to be checked regularly to properly operate an activated sludge treatment plant aeration equipment and mixed liquor solids Point source discharges are discharges that come from pipes or ditches that are monitored, controlled and inspected Non-point discharges are discharges that have intermittent, dispersed flows having little or no control The Texas Water Code establishes the protection of water quality and quantity of the state by setting stream standards, issues permits for discharges, identifies non-point source controls, and establishes water reuse. The wastewater plant operator is primarily responsible for Inflow and Infiltration (I&I) typically refers to unaccounted for water in the system after heavy rains If the ____ loading on the plant is high, the operator would need to ____Dissolved Oxygen (DO) levels. Organic/Increase A simple method for indicating when to waste sludge is 30 minute settling test Organic loading of a stabilization pond is about ____ pounds of BOD/acre/day with a detention time of at least ___ days. 35 BOD/ 30 Days Anaerobic digesters are covered to keep out ____, and to trap useful methane which can be used to keep the digester warm. free oxygen Unstable anareobic sludge contains streaks of _________ or ________. gray/green Aerobic digestion is an ____process whereby the aerobic bacteria consume themselves Endogenous Approved disposal methods for digested, dewatered, sludge's are landfill, ____ and ____. Incineration & Land Application Landfill applied sludge must have a solids content of at least _________percent 20 Calcium Hypochlorite (HTH) is a strong _______ and reacts violently with _________. Oxidizer/Oil & Hydrocarbons When added to water chlorine forms _____&_______acid Hydrochlorous and Hydrochloric When ammonia is present in wastewater and reacts with chlorine_________are formed Chloramines Effluent dosage of chlorine in the contact chamber must produce a total combined residual of 1.0 mg/L after 20 minutes Besides disinfection, chlorine has other uses at the wastewater treatment plant such as Reduces BOD, Odor, Algae growth, Helps with Grease TCEQ allows the reuse of wastewater, some of these include Irrigation, aquifer recharge, cooling towers and fire protection All reclaimed water piping must be _______in color purple Before entering a manhole the operator should test for ________and oxygen levels and ________the manhole before entering. all hazardous gasses and ventilate When a municipal wastewater effluent has a high nitrate level and low ammonia level this most likely means the effluent has received a high degree of aerobic treatment Total solids in wastewater are the sum of Settleable and volatile solids This treatment device is commonly used to separate and remove large solids from raw wastewater A Mechanically raked bar screen ___________would have an adverse effect on the proper settling of solids in a clarifier. A short circuiting flow pattern This test would give the best information on how efficiently a trickling filter was operating Percent BOD Removal This trickling filter problem could be reduced by increasing the recirculation ratio Filter files What gases are produced by the controlled anaerobic digestion of wastewater sludge's Methane & Carbon Dioxide These diseases are caused by pathogenic organisms that may be present in raw wastewater Hepatitis, typhoid, paratyphoid,dysentery, cholera, gastroenteritis, polio, hookworm and giardiasis During heavy rain it is possible that manholes and lift stations may overflow, discharge waste materials into roadways or ditches. This type of discharge (SSO) would be considered an unavoidable discharge, a violation of the Texas Water Code, a bypass that must be reported within 24 hours and considered a health hazard An effective way for the collection system worker to prevent infection by waterborn pathogenic organism is to Wear protective clothing and avoid direct contact with waste water _________will increase the chances that sewage will turn septic Stoppages in the main line Extensive use of garbage disposals (grinders) in a community would likely have the following effect on the collection system Increase the amount of flow, solids, and grease The minimum size for a gravity flow sewer line on city right-of-way and the minimum grade is 6 inch and a grade of 0.50 percent The most accurate way to find the average wastewater flow rate in an existing 10-inch sewer main is Obtaining actual flow data & verifying with field data What is the greatest advantage for using fiberglass manholes in areas with high groundwater? fiberglass is not subject to infiltration A __________ pump would most likely be used when discharging into a 10" diameter pressure sewer main. Centrifugal Excessive power consumption by a pump could be caused by Worn bearings and worn impeller Trench safety is a great concern in Texas. OSHA requires that anytime an excavation is greater than __ feet deep it must be protected by ______. 5 feet / An approved Trench Box, Shoring, or Sloping In an excavation if a ladder is used as a means of exit, it must extend ________feet above the ground and be secured and within ____ feet laterally of anyone in the excavation. 3 feet / 25 feet laterally A ____________ would be the best to determine if a storm drain is connected to a sanitary sewer line. Smoke Test _________ would most commonly be used to seal a number of joint leaks on a main with minimal interruption internal grouting Pre-treatment of wastewater would include: Coarse or fine screening, grinding and grit removal and grease removal and pre-aeration Primary treatment of wastewater would include settling tanks or basins, scum collection and removal, sludge collection and removal Secondary treatment typically used today would include Stabilization ponds, trickling filters, rotating biological contractors (RBC) & activated sludge Essential components of the wastewater collection system include Sewer mains & piping, Lift Stations, Pumps, Grease & Sand traps, & Manholes Grit removal would be considered A part of Primary Treatment The protozoa that causes dysentery would most likely be destroyed by Disinfection Using final plant effluent in cooling towers would be a Beneficial way to reuse treated effluent TCEQ may authorize discharge of untreated wastewater into or near a receiving stream in extreme cases. This is referred to as Bypass Enforcement action from TCEQ may be taken if pollution or waste violates the Texas Water Code. Violations of Water Code may include Unauthorized discharge, accidental discharge & health hazard The Activated Sludge process is an ________process. Aerobic In the activated sludge process aeration tanks provide the space necessary to _______, ________, & _______ and return biological solids. Mix, aerate, & Hold Influent In the active sludge process, Utilization is the process where Food supply is changed into a liquid state for use In the activated sludge process, Stabilization is Wastes biologically converted to water, carbon dioxide, or new cells In the activated sludge process, the _______ is called the heart of the activated sludge process. Clarifier In the activated sludge process, factors that will influence the operation of the final clarifier are Loading, solids applied, settling, thickness of solids, rate of return & Wasting In the activated sludge process, the clarifier will concentrate return sludge and waste sludge about ___ to__ times the solids concentration of the mixed liquor two (2) to four (4) In the activated sludge process, for the clarifier to do its job, the ____ must be retained long enough to allow ______ to settle and liquid to rise. water/ solids In the activated sludge process, as more mixed liquor flows to the clarifier, the thickness of the sludge blanket will Increase as solids accumulate In the activated sludge process, biological solids from the bottom of the clarifier must be returned to the aeration basin for re-seed. This process is accomplished by Air lift pumps, centrifugal pumps, Diaphragm pumps, Screw pumps & Gravity Flow In the activated sludge process, no sludge process will work properly without Regular removal of excess solids In the activated sludge process, Mass Balance refers to Maintaining the balance between Return Sludge Flow, Return Sludge, Aeration tank volume, Mixed liquor suspended solids In the activated sludge process, the terms F/M ratio is important because this refers to Food to Microorganism Ratio In the activated sludge process, the F/M Ratio is calculated by ______ the pounds of _________ by the pounds of MLVSS in the ___________. Dividing/ Incoming BOD/ aeration tank In the activated sludge process, the term Gould Sludge Age refers to How long in days a pound of solids stays in the aerator In the activated sludge process, Gould Sludge Age (GSA) is calculated by Dividing the total pounds of TSS in the aerator by the pounds of TSS entering the aerator as raw In the activated sludge process, the term Mean Cell Residence Time (MCRT) refers to The amount of time the living cells are kept in the plant In the activated sludge process, daily observation of the aeration basin treatment processes are essential. The operator should pay close attention to Surface turbulence, Foam, Odors, & Color In the activated sludge process, daily observation of the final clarifier is also essential. The operator should pay close attention to Surface scum, Sludge blanket, Weir Flow, Rising solids, & Clarifier overflow In the activated sludge process, five (5) Important control parameters are Dissolved Oxygen level, Aerator solids level, Solids quality, Rate of returned sludge, & Wasting rate In the activated sludge process, Dissolved Oxygen levels throughout the aeration basins are measured using a portable DO meter. The operator should keep DO levels between ______ and _______. 2 mg/L and 4.0 mg/L In the activated sludge process, "Classic Bulking" is a common problem typically caused by Low density sludge In the activated sludge process, Sludge Rising differs from "Sludge Bulking" and "Sludge Rising" is typically associated Nitrification - De-nitrification process In the activated sludge process, techniques used to reduce "Frothing & Foaming" typically include Adjusting sludge age, Reducing the amount of air, Spraying the frothing area with water, Applying de- foaming agents In the activated sludge process, floc is very important to the settling process. Floc is composed primarily of Bacteria, Protozoa, Microscopic Animals, & Fungi In the activated sludge plants, the operator will experience problems. Some of the common Treatment plant problems include Insufficent capacity, Equipment failures, Design inadequacies, Poor maintenance, & Inflow rates exceed plant capacities. In the activated sludge plants the operator will experience problems. Some of the common Influent problems include Septic inflow, Organic overloading, and under loading, Hydraulic overloading, Solids washout during storm inflow, Toxic substances, Shock loads, & Nutrient deficiencies In the activated sludge plants, the operator will experience problems. Some common Operational problems include Sludge quality, foaming, improper operating techniques In the activated sludge plants, the operator will experience problems. Some common Environmental problems include. Low temperatures, System pH out of range, & Excessive algae growth In the activated sludge plants, to properly set the clarifier return rate the operator must know three things Return activated sludge rate, Sludge blanket thickness, & the Solids concentration of the return flow The typical sludge age for extended aeration plants is 20 to 40 days In the activated sludge plant, good quality sludge will settle _________& _______ over _________ minute period. Gently & Uniformly over 15 to 20 minutes In the activated sludge plant, old sludge quality will settle ________& _________ over ________ minute period. Rapidly and ragged over 5 minutes. In the activated sludge plant, there are (5) important nitroen transformation processes that occur by microorganisms. They are- Assumilation, Ammonification, Nitrification, Denitrification, & Nitrogen fixation. __________in the effluent from an activated sludge process is a pollutant and may create toxic conditions for aquatic life in the receiving stream Nitrogen Denitrification occurs in an activated sludge system when there is __________ to maintain the aerobic metabolism of the carbon stabilizing bacteria. Insufficient Dissolved Oxygen The lack of _________ triggers the facuitative bacteria to change from aerobic and anaerobic Dissolved Oxygen In the activated sludge system, "Hydraulic Wash Out" is When the upward movement of the water in the clarifier exceeds the downward settling velocity In the activated sludge system, Hydraulic Wash Out can be controlled by flow equalization, Additional clarifier capacity or inflow reduction In the activated sludge system, if the operator observed Boiling action, Violent turbulence throughout the aeration tank surface, Large air bubbles 1/2 inch or greater, the operator would suspect- Over aeration resulting in high DO and or floc shearing therefore the operator should reduce the air SCFM to get DO into the proper range