Laboratory
What is the most frequently conducted quality control test in a laboratory?
Duplicates
A young sludge
What is the typical drip rate for a pump equipped with a mechanical seal?
In dissolved air flotation thickeners, what mechanism prevents floated solids from entering the effluent?
Effluent baffles
Given a Total Kjeldahl Nitrogen (TKN) concentration of 60 mg/L in a sample where the organic nitrogen is measure at 45 mg/L, what is the concentration of ammonia nitrogen?
15 mg/L
To ensure accurate Biochemical Oxygen Demand (BOD) results, what criteria should an incubated sample meet?
Deplete at least 2 mg/l and have at least 1 mg/L remaining
What is the typical percent solids content in the thickened sludge product produced by a gravity belt thickener?
4% to 8%
Which type of impeller is most suitable for handling large solids in pumping applications?
What is the most effective disinfectant for wastewater treatment?
Ozone
A centrifugal pump operating at 75% efficiency delivers 200 gallons per minute (gpm) against a total dynamic head of 50 feet. If the density of the fluid is 8.34 lbs/gal, which of the following motor sizes would be most appropriate for this duty if each motor has an efficiency of 69%?
5 hp
Toxicity test on effluent shows an LC50 value lower than the regulatory standard. What does this indicate about the effluent?
It is more toxic than regulations permit
What early indication suggests a digester is becoming sour?
rise in the volatile acids to alkalinity ratio
What component is specifically designed to break in order to protect equipment from damage due to excessive forces?
Shear pin
How should a one- ton chlorine cylinder be transported and stored correctly?
transported horizontally and stored horizontally
At a wastewater treatment facility, a piston pump with a 120 mm diameter and 450 mm stroke is tasked with moving bio-solids from the dewatering unit to storage. Operating at 35 strokes per minute over a 9-hour period, how much volume of bio-solids is conveyed daily? (m3)
96.2 m3
In wastewater treatment a 3-log reduction of a pathogen means?
An operator at a wastewater treatment facility using a membrane bioreactor (MBR) system notes an unexpected increase in ammonia level in the effluent, despite normal operating conditions. What should be the first step in troubleshooting this issue to ensure optimal nitrification within the MBR system?
Check the dissolved oxygen levels in the bioreactor and adjust if necessary
What is the potential consequence of excessive biofilm accumulation on a Rotating Biological Contactor?
Shaft deflection
What is a critical maintenance step for ion exchange systems used in the removal of phosphorus from wastewater?
Regeneration
A treatment plant is evaluating the operating cost of a newly installed pump that transfers water at 600 gallons per minute (gpm), or approximately 37.85 liters per second (L/s), works against a total lift of 60 feet (18.29 meters), boasts a pump efficiency of 80%, a motor efficiency of 92%, operates for 10 hours each day, runs 365 days per year, and electricity costs $0.07 per kilowatt-hour (kWh). Calculate the approximate annual operating cost of the pump.
$2,400
Given the equilibrium of hydrogen sulfide in water, which sulfide species predominates at the pH levels of 4, 11, and 14?
4= H2S
11= HS-
14= S2-
when pH is below 4 the dominant sulfide species is H2S, it is a weak acid that does not fully dissociate is acidic conditions. As the pH increases it dissociates into hydrogen ions (H+) and HS-. When the pH is 14 all of the H+ is dissociated leaving just the S2
You are the operator in charge at an activated sludge treatment plant. You have observed a declining chlorine residual despite a recent increase in chlorine dosing. Consider the following: Influent flow and loading are normal, secondary effluent suspended solids are normal, aeration blowers have been out of service for a few weeks. What is the probable cause for decreasing chlorine residual and what should you do to address it?
Insufficient chlorine dosing before reaching the breakpoint, incrementally increase the chlorine dosage
What is an essential maintenance practice for thermal hydrolysis units used in the pre-treatment of sludge before anaerobic digestion?
Periodic temperature recalibration of the system
What are the temperature ranges for psychrophilic, mesophilic, and thermophilic anaerobic digesters?
psychrophilic- 32 to 68 degrees F (0 to 20 C)
mesophilic- 86 to 100 degrees F (30 to 38 C)
thermophilic 122 to 140 degrees F (50 to 60 C)
In an activated sludge treatment system, the theoretical nutrient requirements dictate a BOD:N:P ratio of 100:5:1 for every 100 kg of BOD, requiring 5 kg of nitrogen and 1 kg of phosphorus. Given the following data calculate the actual ratio.
BOD loading: 25,000 kg/day
Ammonia Feed: 5,000 L/day (18% solution, specific gravity 0.93)
TKN loading from wastewater: 400 kg/day
Phosphoric Acid Feed: 700 L/day (55% solution specific gravity 1.52)
Phosphorus Loading from wastewater: 65 kg/day
100:4.3:1.0