Typical Efficiencies and Operating Parameters for Wastewater Treatment Systems, Exams of Water and Wastewater Engineering

Download Typical Efficiencies and Operating Parameters for Wastewater Treatment Systems and more Exams Water and Wastewater Engineering in PDF only on Docsity! Wastewater Treatment Plants Operation Level 1 Exam Prep (2023 – 2024) With Complete Solution An Imhoff cone is used to measure________solids. A. suspended B. colloidal C. volatile D. settleable - D. settleable (Operation of Wastewater Treatment Plants, Volume 1 by Kenneth D. Kerri) A _____ flume is widely used for measuring wastewater flow. - Parshall (Operation of Wastewater Treatment Plants, Volume 1 by Kenneth D. Kerri) Velocity of flow in a grit channel must be reduced to a range of ____ to _____ fps in order for grit to properly settle. - .7 to 1.4 fps (Operation of Wastewater Treatment Plants, Volume 1, 3.33 by Kenneth D. Kerri) With respect to grit removal systems, grit is traditionally defined as particles larger than 0.21mm (0.008 in) (65 mesh) and with a specific gravity of greater than ______. - specific gravity of grit is 2.65 or greater (EPA Wastewater Technology Fact Sheet, Screening and Grit Removal) Mechanically cleaned bar screens feature bars set at _____ to _____ degrees from vertical. - Bars set at 0 to 30 degrees from vertical. (EPA Wastewater Technology Fact Sheet, Screening and Grit Removal) Manually cleaned bar screens feature bars set at _____ to _____ degrees from vertical to facilitate cleaning. - Bars set at 30 to 45 degrees from vertical to facilitate cleaning. Primarily used in older or smaller treatment facilities, or in bypass channels. (EPA Wastewater Technology Fact Sheet, Screening and Grit Removal) The BOD test measures the amount of oxygen that is consumed while a sample of wastewater is incubated in the dark at a temperature of _____ °C for _____ days (± _____ hours) - The BOD test measures the amount of oxygen that is consumed while a sample of wastewater is incubated in the dark at a temperature of 20 °C for 5 days (± 3 hours) (USGS Book 9-A7 (Third Edition) Five-Day Biochemical Oxygen Demand) What do we mean by Total Dissolved Solids (TDS) in wastewater? - All the solids that cannot be filtered out of the water (New Mexico Wastewater Systems Operator Certification Study Manual) What do we mean by Total Suspended Solids (TSS) in wastewater? - All the solids that can be filtered out including: settleable solids and non-settleable solids (colloids) (New Mexico Wastewater Systems Operator Certification Study Manual) The wastewater in a sewer line should move at a speed that will prevent the deposition and buildup of solids in the sewer; this is called a "scouring velocity". A minimum velocity of _____ fps provides this scouring or self-cleaning velocity. - The wastewater in a sewer line should move at a speed that will prevent the deposition and buildup of solids in the sewer; this is called a "scouring velocity". A minimum velocity of 2 fps provides this scouring or self-cleaning velocity. (New Mexico Wastewater Systems Operator Certification Study Manual) Wastewater treatment ponds: Facultative ponds are _____ feet deep - Facultative ponds are 4-8 feet deep (New Mexico Wastewater Systems Operator Certification Study Manual) Wastewater treatment ponds: Anaerobic ponds are _____ feet deep - Anaerobic ponds are >14 feet in depth (New Mexico Wastewater Systems Operator Certification Study Manual) Typical Primary Clarifier Efficiencies: Settleable Solids expected removal efficiency _____% to _____% - Typical Primary Clarifier Efficiencies: Settleable Solids expected removal efficiency 95% to 99% (New Mexico Wastewater Systems Operator Certification Study Manual) Typical Primary Clarifier Efficiencies: Suspended Solids expected removal efficiency _____% to _____% - Typical Primary Clarifier Efficiencies: Suspended Solids expected removal efficiency 40% to 60% (New Mexico Wastewater Systems Operator Certification Study Manual) • Sludge collector is damaged or needs adjusting (Operation of Wastewater Treatment Plants, Volume 1, section 5.16 by Kenneth D. Kerri) What are some causes of black and odorous septic wastewater in primary clarifier effluent? - • Improper sludge removal • Faulty sludge pump • Sludge withdrawal line plugged • Sludge collector worn or damaged • Short circuiting through tank (Operation of Wastewater Treatment Plants, Volume 1, section 5.16 by Kenneth D. Kerri) List the basic laboratory tests used to determine clarifier efficiency. - The basic laboratory tests used to determine clarifier efficiency are DO, settleable solids, pH, temperature, BOD, suspended solids, chlorine residual (if needed), and coliform group bacteria (if needed). (Operation of Wastewater Treatment Plants, Volume 1, section 5.2A by Kenneth D. Kerri) Primary treatment is effective in removing (a) _____________, and (b) _______________, but is not nearly as effective in removing (c) __________________, which may exert a strong oxygen demand on the receiving waters. - Primary treatment is effective in removing (a) settleable solids, and (b) scum or floatable solids, but is not nearly as effective in removing (c) lighter suspended solids or dissolved solids, which may exert a strong oxygen demand on the receiving waters. (Operation of Wastewater Treatment Plants, Volume 1, section 6.0A by Kenneth D. Kerri) The major consideration for daily operation of a trickling filter is to use the ______ recirculation rates that will produce good results (meet NPDES permit requirements), but not cause ponding and other problems. - The major consideration for daily operation of a trickling filter is to use the lowest recirculation rates that will produce good results (meet NPDES permit requirements), but not cause ponding and other problems. (Operation of Wastewater Treatment Plants, Volume 1, section 6.4A by Kenneth D. Kerri) Trickling filter recirculation rates should be adjusted to maintain a DO from _____ to _____ mg/L in the filter effluent from rock media and from _____ to _____ mg/L in the filter effluent from synthetic media. - Trickling filter recirculation rates should be adjusted to maintain a DO from 3 to 6 mg/L in the filter effluent from rock media and from 4 to 8 mg/L in the filter effluent from synthetic media. (Operation of Wastewater Treatment Plants, Volume 1, section 6.4B by Kenneth D. Kerri) The tiny, gnat-sized filter fly is known also as _____? - Psychoda (Operation of Wastewater Treatment Plants, Volume 1, section 6.412 by Kenneth D. Kerri) Trickling filter flies can be controlled by what methods? - 1. Increasing the recirculation rate 2. Keeping orifice openings clear, including end gates of the distributer arms 3. Applying approved insecticides with caution to filter walls and other plant structures 4. Flooding the filter for 24 hours at intervals frequent enough to prevent completion of the life cycle 5. Dosing with about 1 mg/L chlorine for a few hours each week 6. Keeping the area around the filter clean, including removing weeds, cutting grass, and pruning shrubbery (Operation of Wastewater Treatment Plants, Volume 1, section 6.4F by Kenneth D. Kerri) True or False: A trickling filter should be taken out of service during icy conditions? - A trickling filter should not be taken out of service during icing conditions because the quality of the effluent will be reduced and additional maintenance problems could develop (Operation of Wastewater Treatment Plants, Volume 1, section 6.4G by Kenneth D. Kerri) MPN is the _____ _____ _____ of coliform-group organisms per unit volume of sample water. Expressed as a density of population of organisms per _____ mL of sample water. - MPN is the Most Probable Number of coliform-group organisms per unit volume of sample water. Expressed as a density of population of organisms per 100 mL of sample water. (Operation of Wastewater Treatment Plants, Volume 1, section 7.0 by Kenneth D. Kerri) What is the RPM rate in which RBC units rotate? - 1.5 RPM (Operation of Wastewater Treatment Plants, Volume 1, section 7.0 by Kenneth D. Kerri) For rotating biological contactors, what is the approximate percentage of media surface immersed in wastewater while in operation? - 40% (Operation of Wastewater Treatment Plants, Volume 1, section 7.0 by Kenneth D. Kerri) Why is the RBC process divided into four or more stages? - The RBC process is divided into four or more stages to increase the effectiveness of a given amount of media surface area. Organisms on the first-stage media are exposed to high levels of BOD and reduce the BOD at a high rate. As the BOD levels decrease from stage to stage, the rate at which the organisms can remove BOD decreases and nitrification starts. (Operation of Wastewater Treatment Plants, Volume 1, section 7.0B by Kenneth D. Kerri) Nitrification in nature is a two-step oxidation process of ammonium (NH4+) or ammonia (NH3) to nitrate (NO3−) catalyzed by two ubiquitous bacterial groups. The first reaction is oxidation of ammonium to nitrite by ammonia oxidizing bacteria represented by the (a.)______ genus. The second reaction is oxidation of nitrite (NO2−) to nitrate by nitrite- oxidizing bacteria, represented by the (b.) ______ genus. - (a.) Nitrosomonas, (b.) Nitrobacter _______ is an aerobic process in which bacteria change the ammonia and organic nitrogen in wastewater into oxidized nitrogen (usually nitrate). The second-stage BOD is sometimes referred to as the "nitrogenous BOD" (first-stage BOD is called the "carbonaceous BOD"). - Nitrification is an aerobic process in which bacteria change the ammonia and organic nitrogen in wastewater into oxidized nitrogen (usually nitrate). The second-stage BOD is sometimes referred to as the "nitrogenous BOD" (first-stage BOD is called the "carbonaceous BOD"). (Operation of Wastewater Treatment Plants, Volume 1, section 7.0 by Kenneth D. Kerri) ______ is the anoxic biological reduction of nitrate nitrogen to nitrogen gas. - Denitrification is the anoxic biological reduction of nitrate nitrogen to nitrogen gas. In secondary clarifiers the nitrogen bubbles produced as a result of denitrification can attach to the biological floc and float the floc to the surface. This condition is often the cause of rising sludge. (Operation of Wastewater Treatment Plants, Volume 1, section 7.0 by Kenneth D. Kerri) The ________ stage is a stage of decomposition that occurs in the biological treatment processes when aerobic bacteria, using dissolved oxygen, change carbon compounds to carbon dioxide. - The carbonaceous stage is a stage of decomposition that occurs in the biological treatment processes when aerobic bacteria, using dissolved oxygen, change carbon compounds to carbon dioxide. (Operation of Wastewater Treatment Plants, Volume 1, section 7.0 by Kenneth D. Kerri) (Operation of Wastewater Treatment Plants, Volume 1, comprehensive review questions #2 by Kenneth D. Kerri) When evaluating trickling filter operation records, operators should adjust the process according to which main principle? 1. To minimize all operational costs 2. To obtain the best possible results for the least cost 3. To use the least amount of cholorine 4. To use the lowest recirculation rates - 2. To obtain the best possible results for the least cost (Operation of Wastewater Treatment Plants, Volume 1, comprehensive review questions #2 by Kenneth D. Kerri) What could be the cause of the RBC media appearing black and producing odors that are not normal? 1. Industrial discharges containing sulfur compounds 2. Influent wastewater containing toxic or inhibitory substances 3. Solids or BOD overloading 4. Solids or BOD underloading - 3. Solids or BOD overloading (Operation of Wastewater Treatment Plants, Volume 1, comprehensive review questions #23 by Kenneth D. Kerri) How can foaming be controlled in an aeration tank? 1. By increasing aeration rates 2. By introducing foam-devouring organisms 3. By removing detergents 4. By water sprays - 4. water sprays (Operation of Wastewater Treatment Plants, Volume 1, comprehensive review questions #26 by Kenneth D. Kerri) When a pond turns dull green, gray, or colorless what condition is generally indicated? 1. The loading is satisfactory and the pond is working properly 2. The pH and DO are too high 3. The pH and DO have dropped too low 4. The pH is steady and weather conditions have deteriorated - 3. The pH and DO have dropped too low (Operation of Wastewater Treatment Plants, Volume 1, comprehensive review questions #34 by Kenneth D. Kerri) How can an operator locate a small chlorine leak? By using a paint brush or rag dipped in 1. Caustic soda 2. Hydrochloric acid 3. Hypochlorite 4. Strong ammonia solution - 4. Strong ammonia solution (Operation of Wastewater Treatment Plants, Volume 1, comprehensive review questions #38 by Kenneth D. Kerri) The concerns of the treatment plant designer and operator usually are to remove which substances in the wastewater? 1. Dissolved inorganic solids 2. Dissolved organic solids 3. Organic and inorganic solids 4. Radioactive wastes 5. Thermal wastes - 2, 3 (Operation of Wastewater Treatment Plants, Volume 1, comprehensive review questions #4 by Kenneth D. Kerri) Normally, the slime growth or biomass on the media of a rotating biological contactor should have which of the following characteristics? 1. Algae present 2. Brown to gray color 3. Few or no bare spots 4. Offensive odor 5. Shaggy appearance with a fairly uniform coverage - 2, 3, 5, (Operation of Wastewater Treatment Plants, Volume 1, comprehensive review questions #26 by Kenneth D. Kerri) True or False: A white, fluffy foam indicates low solids content in the aerator while a brown, leathery foam suggests high solids concentrations. - True (Operation of Wastewater Treatment Plants, Volume 1, comprehensive review questions #29 by Kenneth D. Kerri) What is the typical removal efficiency of settleable solids in a primary clarifier? A. 10 to 15% B. 20 to 50% C. 40 to 60% D. 95 to 99% - D. 95 to 99% (Operation of Wastewater Treatment Plants, Volume 1, section 5.23 by Kenneth D. Kerri) What is the maximum holding time of a sample before performing a BOD5 test (providing that the sample is kept at 4 degrees C and above freezing)? - 48 hours maximum. The 48 hours starts when the very first aliquot of a composite sample is collected (i.e. when the composite sampler starts collecting a composite sample). (PA Dept. of Environmental Protection, BOD doc) Drying oven temp to determine Total Solids in sample - 103-105 degrees C ("Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy) Drying oven temp to determine Total Dissolved Solids (TDS) in sample - 180 +/- 2 degrees C ("Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy) Drying oven temp to determine Total Suspended Solids (TSS) in sample - 103-105 degrees C ("Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy) Chemical used to dechlorinate samples for BOD testing - Sodium Sulfite (pg 76 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy) At a WWTP, what can the following color codes on piping indicate? Brown Orange Green Blue Methane gas production decreases, while CO2 content of gas increases pH drops below 6 and possible foaming (pg 18 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy) Gasses that make up anaerobic digester gas - Methane approx 70% Carbon Dioxide approx 30% Hydrogen, nitrogen, and hydrogen sulfide are also present in small amounts. (pg 19 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy) operational temp of most (mesophilic) anaerobic digesters - 90-100 degrees F (pg 21 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy) The pH of an aerobic digester can be lowered by these byproducts of aerobic biological activity - Carbon Dioxide, produced during normal aerobic respiration Nitric Acid, produced during the process of nitrification (pg 22 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy) Pathogens associated with sewage sludge - Salmonella bacteria Enteric (intestinal) viruses Helminth ova (eggs of parasitic worms) (pg 26 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy) Polymer terminology: "aging" - The 30-90 minutes required for polymer to unfold and activate in freshly prepared feed solutions (pg 28 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy) Polymer terminology: feeding polymer "neat" - polymer fed directly, without dilution (pg 28 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy) Regulations that govern the use and disposal of sewage sludge - 40 CFR (Code of Federal Regulations) Part 503, often referred to as "Part 503." (pg 28 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy) Organic loading to a wastewater treatment pond is expressed in these units - Pounds of BOD per day per acre (pg 29 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy) The function of sodium nitrate, when added to a waste stabilization pond - Sodium nitrate may be used to minimize odor problems during brief overload conditions in an un-aerated waste stabilization pond. (pg 31 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy) The normal color of a wastewater treatment pond, especially during the summer months - Green, due to the growth of algae near the pond surface (pg 32 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy) typical F/M ratio in the conventional activated sludge process - .2-.5 F/M (pg 32 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy) Excessive tan "greasy" foam can indicate what in the activated sludge process? - Possible Nocardia infestation (pg 36 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy) White crispy billowy foam can indicate what in the activated sludge process? - Start up or recovery from upset condition (low F/M, young sludge) (pg 36 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy) Moderately light brown foam can indicate what in the activated sludge process? - Normal operation (pg 36 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy) Process control test most often used to determine the settling characteristics of activated sludge - Sludge Volume Index (SVI) (pg 37 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy) The loading to an RBC is measured in these units - Pounds of soluble BOD/day/1000 sq ft. of surface area (pg 38 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy) Aerobic biological treatment process capable of at least 85% removal of BOD and total suspended solids. - Secondary treatment (pg 39 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy) Microorganisms associated with good quality activated sludge - free swimming ciliates and stalked ciliates (pg 40 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy) RBC slime growth that appears white could indicate what? - Excess sulfide in wastewater promotes growth of sulfur bacteria Beggiatoa (pg 45 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy) This chemical, when present in wastewater effluent, can cause serious interference with disinfection - nitrite, produced during nitrification, can cause high chlorine demand (pg 58 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy) The most commonly used chemical for effluent dechlorination - sulfur dioxide (pg 60 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy) The characteristics (values present) of typical domestic raw sewage: BOD Suspended Solids Total Solids - BOD= 150-250 mg/L Suspended Solids= 175-275 mg/L Total Solids= 1000 mg/L or .1% (pg 69 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy) The relationship between the COD and BOD levels in raw domestic sewage - COD is approximately 2.2 times the BOD content (pg 69 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy) Standard bottle volume for BOD5 test - 300 ml What should be done if the pH and DO in a wastewater stabilization pond are dropping dangerously low? - Check the loading. The loading may need to be reduced or stopped.