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Wastewater Class 2 ABC part 2 Exam
Questions
What is the proper pH range for maintaining methane-forming bacteria in an anaerobic digester? 4 - 6 6 - 8 2 - 4 8 - 10 - โ โ B In terms of sludge thickening (primarily gravity thickening), WAS typically can be described as __________. compacting easily has a low sludge volume index settling rapidly forming a light, fluffy floc that settles poorly - โ โ D 65 000 gal/day of sludge from a primary clarifier is pumped to a gravity thickener. If the solids content of the sludge is 4% and the surface area of the thickener is 850 sq ft, what is the solids loading rate of the thickener? Assume the weight of the sludge is 8.34 lbs/gal. 12lbs/day/sq ft 26 lbs/day/sq ft 3 lbs/day/sq ft
19 lbs/day/sq ft - โ โ B An ideal carbon to nitrogen ratio for composting sludge is _______________. 500: 1: 30: 1:30 - โ โ C In the wastewater industry, PLC refers to a _______________________. Programmable Logic Controller Pump Level Circuit Pressure Limit Control Plastic-Lined Conduit - โ โ A For preventive maintenance of a comminutor, how often should the channel be drained and the unit cleaned? monthly weekly annually daily - โ โ A To neutralize a sour digester, assume that 1 mg/L of lime need to be added for every mg/L of volatile fatty acids present in the sludge. If the digester contains 242,000 gallons of sludge with a volatile fatty acid
are pumped? Assume 100% efficiency and volume displacement. Density of the sludge is 7.48 gal/cu ft. 12 gpm 32 gpm 26 gpm 20 gpm - โ โ B A centrifugal pump must acheive a flow rate of 550 gpm against a total dynamic head of 75 ft. What would be the water horsepower requirement for this pump, assuming that the liquid to be pumped has a specific gravity of 1.2? 10.8 whp 12.5 whp 15.3 whp 6.4 whp - โ โ B The primary compound formed when chlorine gas is introduced to water is ____________. sodium chloride chloroform bromine chloride hypochlorous acid - โ โ D If your RAS rate is too high, what is typically the primary result?
solids will overload the clarifier and wash out the solids level to the final effluent decreases aeration in the basin would increase anaerobic conditions would develop in your secondary clarifier - โ โ A As part of the national pretreatment program (40 CFR Part 403), plants with a design flow of more than ____________ must develop an industrial waste pretreatment program. - โ โ 19 000 m3/d (5 mgd) Which of the following is NOT a probable cause for excessive sloughing in a rotating biological contactor? excessive pH changes high dissolved oxygen levels excessive changes in flow and/or organic loading toxic materials in the influent - โ โ B Wearing rings on a pump are used to _______________. hold the impeller in place wear out prior to pump failure minimize internal leakage hold the pump shaft in place - โ โ C Which of the following conditions will lead to the predominance of Thiothrix bacteria in your activated sludge process?
30ยฐC (86ยฐF) - โ โ B
Calcium hypochlorite contains ___________% available chlorine. 85 65 20 40 - โ โ B What type of respirator is needed when entering an IDLH (Immediately Dangerous to Life or Health) atmosphere? supplied air respirator or self-contained breathing apparatus (SCBA) NIOSH-approved filtering facepiece full-face cartridge respirator powered air purifying respirator (PAPR) - โ โ A The precipitation of magnesium ammonium phosphate throughout an anaerobic digester system is referred to as _______________. scaling decaying crystallization fouling - โ โ A Which of the following is a low-DO filament that is most likely to be found under low F:M conditions? Nocardia
Sphaerotilus natans Microthrix parvicella H. hydrossis - โ โ B Which of the following forms of plant life is necessary for the proper functioning of an aerobic/facultative stabilization or oxidation pond? algae weeds water lilies cattails - โ โ A Thermophilic anaerobic digesters typically operate at a temperature of _____. 80ยบC (176ยบF) 60ยบC (140ยบF) 20ยบC (68ยบF) 40ยบC (104ยบF) - โ โ B A positive displacement pump should never be started ____________. with the discharge valve closed with the discharge valve open without being primed before relieving all pressure in the discharge pipe - โ โ A
extend the mixing time adjust the digester temperature for an extended period of time - โ โ A A water-filled mechanical pump seal not only helps to prevent leaks, but also ___________. keeps the pump primed cools the material being pumped acts as a reserve water supply prevents pump shaft wear - โ โ D Which of the following is a virus? Shigella Clostridium Salmonella Hepatitis - โ โ D In order to control odor from hydrogen sulfide, wastewater containing sulfides should be maintained at a pH of ____________. less than 7 about 7 about 9 less than 4 - โ โ C
Which of the following tests best simulates the working of a dissolved air flotation unit? free drainage test centrifugal test jar test rise rate test - โ โ D A trickling filter loaded at a rate of 64 kg BOD5/100 m3รd (40 lbs. BOD5/ 1000 ft3/day) would be considered a______________. intermediate rate filter roughing filters low rate filter high rate filter - โ โ A Jar tests indicate that the best liquid polymer dose for waste stream is 12 mg/L. The flow to be treated is 2.5 mil. gal/day. Determine the gpd setting for the liquid polymer chemical feeder if the liquid polymer is a 60% solution (assume the polymer solution weights 8.34 lb/gal). 1% equals 10,000 mg/L. 100 gpd 50 gpd 25 gpd 10 gpd - โ โ B
58ยฐC (136ยฐF)
45ยฐC (113ยฐF) - โ โ A
Heat exchangers are typically used in a wastewater treatment plant for _______________. warming cold influent dissolving powder polymer into solution warming the contents of small clarifiers in cold weather heating sludge for anaerobic digestion - โ โ D After a settleometer test you have a thin layer of clear supernatant over a poorly settling sludge and your SVI is greater than 150 mL/g. This condition is referred to as ________________. septic sludge ashing sludge bulking pin floc - โ โ C What factor is a main contributor to the growth of Nocardia? low F:M lower temperatures the startup of an activated sludge process shorter MCRT (Mean Cell Residence Time - โ โ A
Which of the following forms of plant life is necessary for the proper functioning of an aerobic/facultative stabilization or oxidation pond? algae water lilies weeds cattails - โ โ A A dirty filtrate coming from your pressure filter dewatering system indicates either too high a feed pressure or ___________. the feed sludge solids concentration is too low lime scales on the edges of your pressure plates torn/punctured filter media too little sludge being fed to the system - โ โ C You have decided to use chlorine to help control a Nocardia foaming problem. A typical benchmark is to initially apply __________ for every 1000 kg (1000 lb) of mixed liquor volatile solids (MLVSS). 120 kg (120 kg) 80 kg (80 lb) 4 kg (4 lb) 20 kg (20 lb) - โ โ C The best method for protecting a steel tank from rust is _____________.
high F:M, high SRT high F:M, low SRT - โ โ D Which type of incinerator uses graded silica? induced draft double stack multiple-hearth fluidized bed - โ โ D The adverse effect a substance has on a living entity defines that substance's _________________. acidity toxicity alkalinity demand - โ โ B A viscous, jelly-like slime covering a trickling filter or RBC is known as a(n) _____________. anaerobic film population biological growth filter fouling - โ โ C
A ____________ controller receives sensor output from the process variable and compares it to the setpoint or desired result then adjusts the system accordingly. manual feedforward compound feedback - โ โ D Auxiliary fuel requirements in a multiple hearth incinerator are lower for sludges with a high percentage of volatiles. The volatile content of a sludge may be maximized by: All of the above Removing sludge inorganics such as grit Avoiding the use of ferric chloride and lime in the dewatering process Not digesting the sludge - โ โ A A vertical column of fluid is also known as _________. friction factor viscosity level head density height - โ โ C The detention time of an aerated grit chamber typically ranges from __________ minutes.
0.06 lbs VS destroyed/cu ft 0.1 lbs VS destroyed/cu ft 0.02 lbs VS destroyed/cu ft 0.04 lbs VS destroyed/cu ft - โ โ C Which type of incinerator uses graded silica? multiple-hearth fluidized bed induced draft double stack - โ โ B The discharge pressure for a positive displacement blower in wastewater treatment plant can run as high as _______________. 210 kPa (30 psig) 190 kPa (28 psig) 130 kPa (19 psig) 150 kPa (22 psig) - โ โ A The two bacteria primarily associated with nitrification are Nitrosomonas and ________? Nitrofer Nitrobacter Nocardia
Nitrothiothrix - โ โ B 1 cu ft/sec is equal to ________. 30024 gph 500 gpm 0.72 mgd 0.65 mgd - โ โ D Why is the COD test preferred for process control over the BOD test? much safer to perform than the BOD test does not take into account chemical content results are obtained faster the results give a better view of the biological activity - โ โ C What type of microorganisms are most prevalent in a young (Low MCRT, High F:M) mixed liquor? amoebas, flagellates free swimming ciliates, flagellates stalked ciliates, rotifers, flagellates nematodes, rotifers - โ โ A Which of the following devices is used to measure chlorine flow rates? rotameter sonic flow meter
