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New York State Department of Environmental
Conservation (NYSDEC) Wastewater Operator
Certification Exam
- What is the primary purpose of a comminutor in a wastewater treatment plant? a. Add oxygen to the water b. Shred large solids into smaller pieces c. Remove grit from wastewater d. Clarify sludge Comminutors are mechanical devices that grind and shred solids to prevent clogging downstream equipment.
- Which unit process is primarily responsible for removing settleable solids? a. Trickling filter b. Primary clarifier c. Aeration basin d. Chlorination tank Primary clarifiers allow gravity settling of solids before secondary treatment.
- What is the optimal pH range for activated sludge microbial activity? a. 3.5โ4. b. 5.0โ6.
c. 6.5โ8. d. 9.0โ10. Microorganisms in the activated sludge process thrive in a neutral to slightly basic environment.
- What is the term for the biological process that converts ammonia to nitrate? a. Denitrification b. Nitrification c. Precipitation d. Flocculation Nitrification is the two-step oxidation of ammonia to nitrate by nitrifying bacteria.
- What is F/M ratio in the activated sludge process? a. Flow to microorganism b. Feed to membrane c. Food to microorganism d. Filtration mass The F/M ratio measures the amount of organic food compared to the biomass available to consume it.
- In a secondary clarifier, the sludge blanket should be: a. Over 6 feet deep b. Maintained at an optimal depth to avoid solids washout c. Nonexistent d. Floating at the surface
10.Which gas is commonly produced in anaerobic digesters? a. Oxygen b. Nitrogen c. Methane d. Carbon monoxide Anaerobic digestion produces biogas, mostly methane, which can be used for energy. 11.What is the purpose of wasting sludge from an activated sludge system? a. Control the solids retention time and microbial population b. Increase BOD c. Boost nitrogen d. Reduce temperature Sludge wasting helps maintain biomass balance and prevents excessive solids buildup. 12.What happens during denitrification? a. Nitrate is converted to nitrite b. Nitrate is reduced to nitrogen gas c. Ammonia is oxidized d. BOD is increased Denitrification reduces nitrate to nitrogen gas in anoxic conditions, completing nitrogen removal. 13.Which parameter is directly related to the clarity of the effluent? a. BOD b. TSS
c. COD d. pH Total Suspended Solids (TSS) influence turbidity and clarity of treated water. 14.Which is the most commonly used disinfectant in municipal wastewater treatment? a. Ozone b. UV light c. Chlorine d. Hydrogen peroxide Chlorine is widely used due to its effectiveness and low cost. 15.What is supernatant? a. Solid portion of sludge b. Oil and grease c. Clear liquid above settled sludge d. Aerated effluent Supernatant is the liquid layer that separates from sludge during settling. 16.A high F/M ratio typically results in: a. Old sludge b. Young sludge c. Stable operation d. Poor BOD removal Young sludge has high microbial activity but low settling characteristics. 17.The main indicator organism for disinfection efficacy is: a. Salmonella
21.What is the acceptable range for effluent BOD under most SPDES permits? a. 60 mg/L b. 30 mg/L or less c. 5 mg/L d. 100 mg/L Standard secondary treatment effluent limits for BOD are 30 mg/L. 22.What is used to dechlorinate effluent before discharge? a. Alum b. Soda ash c. Sulfur dioxide or sodium bisulfite d. Lime These chemicals neutralize chlorine before effluent is released to waterways. 23.What is a common problem in digesters that can lead to foam and poor mixing? a. Cold temperature b. Filamentous bacteria c. Low pH d. Ammonia toxicity Filamentous organisms can cause foaming in anaerobic conditions. 24.What is the normal range of MLSS in the aeration tank for extended aeration systems? a. 100โ200 mg/L b. 2,000โ5,000 mg/L
c. 8,000โ10,000 mg/L d. 12,000โ15,000 mg/L Extended aeration systems operate at higher MLSS than conventional activated sludge. 25.What is the role of alum in chemical treatment? a. pH adjustment b. Coagulation c. Disinfection d. Dechlorination Alum is a coagulant that helps remove fine particles by forming flocs. 26.What condition results from insufficient dissolved oxygen in the aeration tank? a. Alkalinity increase b. Septic conditions c. Nitrification d. Chlorine production Low DO causes anaerobic metabolism and foul odors. 27.How often must a NYSDEC-certified operator renew their certification? a. Every year b. Every 10 years c. Every 5 years d. Every 2 years Certification must be renewed every 5 years with continuing education.
32.What is an SPDES permit? a. Storage document b. Discharge authorization c. Waste manifest d. Lab report SPDES permits authorize discharge of treated wastewater to surface waters. 33.What agency regulates SPDES permits in New York? a. EPA b. NYSDEC c. NYDOH d. OSHA The NYSDEC issues and enforces SPDES permits in New York. 34.What should be done during a chlorine leak? a. Vent area with fans b. Evacuate and wear SCBA c. Call local newspaper d. Use baking soda Chlorine leaks require emergency response and protective equipment. 35.What is the term for excess microbial growth in receiving water from nutrients? a. Eutrophication b. Flocculation c. Chlorination
d. Precipitation Eutrophication leads to algal blooms and oxygen depletion. 36.What is one sign of short-circuiting in a clarifier? a. High BOD removal b. Solids in effluent c. Grease on surface d. Warm temperature Short-circuiting allows flow to bypass proper settling. 37.Which chemical raises pH? a. Alum b. Lime c. Ferric chloride d. Bisulfite Lime increases pH and alkalinity. 38.What should be monitored daily at a treatment plant? a. Payroll b. Building codes c. Flow, DO, pH, temperature, BOD/TSS samples d. Permit renewals Operators must routinely track process and effluent parameters. 39.A grab sample is: a. 24-hour composite b. A single sample at a specific time c. Historical average
d. Wearing PPE Confined space entry without proper permits and monitoring is hazardous and illegal. 44.Which component removes floating grease and scum? a. Grit chamber b. Skimmer mechanism c. Diffuser d. Chlorinator Skimmers collect surface debris in clarifiers. 45.What effect does filamentous bacteria have on sludge? a. Improves settling b. Causes bulking c. Reduces volume d. Increases pH Filamentous growth prevents proper compaction and settling. 46.High chlorine residual in effluent can: a. Improve algae growth b. Harm aquatic life c. Increase oxygen d. Reduce solids Excess chlorine is toxic to fish and must be dechlorinated. 47.What is the acceptable DO in the aeration basin? a. 0.1โ0.5 mg/L b. 0.5โ1.0 mg/L
c. 1.0โ3.0 mg/L d. 5.0โ10.0 mg/L This range supports aerobic microbial metabolism. 48.What test evaluates sludge dewaterability? a. BOD b. Capillary suction time (CST) c. pH d. UV absorbance CST measures how easily sludge releases water during dewatering. 49.What component supplies oxygen in an aeration tank? a. Clarifier b. Diffuser or mechanical aerator c. Chlorinator d. Coagulator These systems transfer air/oxygen into the wastewater. 50.What is one purpose of the NYSDEC certification? a. Issue lab results b. Promote chlorine use c. Ensure qualified operators manage treatment plants d. Reduce payroll Certification ensures public health and environmental protection through skilled operators.
55.What is the primary concern when handling chlorine gas? a. Flammability b. High pH c. Toxicity and corrosiveness d. Radioactivity Chlorine gas is highly toxic and corrosive, requiring strict safety protocols. 56.What is the result of filamentous bulking? a. Better sludge compaction b. Sludge that wonโt settle well in clarifier c. Higher BOD removal d. Increased DO Filamentous bacteria cause sludge to remain suspended. 57.What does SCBA stand for? a. Standard Chemical Buffer Application b. Self-Contained Breathing Apparatus c. Safety Compliance Breathing Aid d. Surface Clean Biological Agent SCBA provides breathable air in hazardous environments. 58.What effect does short-circuiting have in a clarifier? a. Increases DO b. Improves settling c. Reduces detention time and treatment efficiency d. Increases sludge age
Short-circuiting reduces settling effectiveness by allowing flow to bypass intended paths. 59.Why is mixing important in anaerobic digesters? a. Reduce odors b. Prevent scum and improve digestion efficiency c. Increase pH d. Produce DO Mixing ensures even microbial contact and prevents floating scum. 60.What should you do if your plant experiences a permit exceedance? a. Ignore it b. Report immediately to NYSDEC as required c. Call local police d. Re-test and wait 7 days Permit exceedances must be reported promptly as part of SPDES compliance. 61.What causes grease to accumulate in a treatment plant? a. Low pH b. High BOD c. Discharge from kitchens and restaurants d. High DO Grease typically comes from food service discharges. 62.What is a confined space? a. A limited or restricted space with limited entry/exit and potential hazards
66.What does the acronym MLSS stand for? a. Minimum Level Solids Suspension b. Mixed Liquor Suspended Solids c. Micro-Level Sludge Solids d. Major Liquid Suspended Solids MLSS measures solids concentration in the aeration basin. 67.Why is alkalinity important in nitrification? a. Removes BOD b. Supports chlorine residual c. Maintains pH stability during ammonia oxidation d. Aids in scum removal Nitrifying bacteria consume alkalinity, so buffering is essential. 68.What is the color of healthy activated sludge? a. White b. Black c. Brown d. Green Brown sludge indicates active microbial populations. 69.What can happen if you overdose chlorine? a. Incomplete disinfection b. Improved pH c. Toxicity to aquatic life d. Increased BOD Excess chlorine can exceed effluent limits and harm receiving waters.
70.What is the goal of secondary treatment? a. Settle grit b. Biologically remove organic matter and BOD c. Add nutrients d. Remove heavy metals Secondary treatment uses biological processes to reduce organics. 71.The purpose of a flow equalization basin is to: a. Balance inflow rate and load to downstream processes b. Remove odors c. Increase sludge d. Neutralize pH Flow equalization prevents hydraulic overloads. 72.What personal protective equipment (PPE) should be worn when handling chemicals? a. Safety glasses only b. Gloves, goggles, apron, face shield c. Sunglasses d. Lab coat PPE protects operators from splashes, fumes, and contact hazards. 73.What is the main danger of hydrogen sulfide (HโS) in collection systems? a. Toxicity and corrosion b. Freezing c. Alkalinity
