Wisconsin DNR Wastewater Operator Certification Practice Test

These questions are part of the practice quiz. Start practicing

• Flow equalization is used to:
• Name a key performance indicator for secondary treatment performance.
• Which pollutant class is commonly subject to pretreatment before discharge to a municipal wastewater plant?
• In open channel flow measurement, which parameter must be measured to determine flow rate?
• Which equipment is used to dewater sludge?
• Which statement best defines detention time in a wastewater treatment unit?
• Which laboratory or field instrument is used to monitor the pH and temperature of wastewater?
• Which device is used to measure solids settling characteristics and sludge blanket behavior?
• Which parameter is the standard measure of biodegradable organics in wastewater?
• Under what condition is denitrification typically required at wastewater plants?
• Which multi-turn valve is used for fill flow, no flow, OR throttling?
• What does MLSS stand for and why is it important?
• What is the typical shape of an aerated grit chamber?
• Which device is used to physically separate solids from liquid in sludge, typically as a dewatering step?
• What is the main advantage of composite sampling over grab sampling?
• Which statement best describes the difference between primary and secondary wastewater treatment?
• The DMR report due date is the 21st day of the next month.
• In activated sludge systems, what does MLSS stand for?
• Explain return activated sludge (RAS) and waste activated sludge (WAS) ratio and why it matters.
• Which multi-turn valve is used for full open or no flow applications ONLY?
• What is the primary purpose of aeration in activated sludge?
• Define Hydraulic Retention Time (HRT) and state its typical range in a secondary clarifier.
• The activated sludge removed from the secondary treatment process (excluding biomass) is called which of the following?
• What is a common consequence of excessively high MLSS in an aeration basin?
• Which of the following best describes the impact of dairy producers on a treatment plant?
• Which stage of wastewater treatment is primarily designed to remove settleable solids before biological treatment?
• Rotary lobe pumps are self-priming, valveless, positive-displacement pumps.
• In aerobic wastewater treatment, controlling dissolved oxygen (DO) primarily impacts which aspects?
• What term describes the portion of sludge returned from the clarifier to the aeration basin to maintain biomass?
• Which of the following is NOT a component of the sanitary sewer system?
• The activated sludge (bio mass) collected in the final clarifier and returned to the secondary treatment process to mix with the incoming wastewater is:
• What principle underpins composite sampling in wastewater monitoring?
• Describe a good sampling location and procedure for collecting representative influent wastewater samples.
• What is the function of a secondary clarifier in an activated sludge plant?
• Which description best matches rotary lobe pumps?
• In wastewater treatment, what does the acronym RAS stand for?
• Name two common units for wastewater flow and provide a conversion.
• What is a potential impact of cavitation in pumps?
• What is the difference between a check and a relief valve?
• In practice, SCADA systems in wastewater plants are used to...
• Define return activated sludge (RAS) and waste activated sludge (WAS) in an activated sludge system.
• Trickling filters are an example of which treatment type?
• What does RAS stand for in wastewater treatment?
• Give two examples of industrial pollutants requiring pretreatment before discharge to a municipal plant.
• Which valve uses a flexible sleeve that is pinched to stop flow?
• Which device is specifically used to remove floatable materials during primary treatment?
• What is the purpose of flow measurement devices like weirs or flumes on influent lines?
• In wastewater treatment, what does BOD stand for?
• Air lift pumps are prone to plugging, especially as low return flow rates. Thus, operators should closely monitor these pumps to ensure sludge is being returned at all times.
• Which BMP is typically part of a FOG program?
• What does WAS stand for in wastewater treatment?
• What does SCADA stand for in wastewater operations?
• In the F:M ratio, the 'food' is represented by which parameter?
• Stabilization ponds are normally less than 10 feet deep.
• One purpose of a WWTP is to satisfy the oxygen demand of the waste flow before it's discharged to the environment?
• Cavitation occurs when vacuum pressure is lowered to the vapor pressure of the liquid, causing what phenomena?
• A peristaltic pump is a small positive displacement pump commonly used for sampling and chemical addition.
• What is a limitation of UV disinfection?
• Stabilization ponds are aerated.
• In a vortex-type grit chamber, where does the water–grit mixture primarily rotate?
• How does an operator determine what preventative maintenance a piece of equipment requires?
• Which of the following is explicitly prohibited from discharge into the collection system due to potential interference with the treatment process?
• Which of the following is NOT considered a type of preliminary treatment?
• What are two common chemical dosing steps in wastewater treatment and their purpose?
• Trash pumps are non-clogging up to what size?
• What does the BOD5 test measure and why is it important in wastewater treatment?
• What is the primary purpose of preliminary treatment in a wastewater treatment plant?
• What is the most common triangular weir notch used for open-channel flow measurement?
• Breweries commonly contribute which combination of wastewater characteristics, often requiring equalization?
• In an aerated grit chamber, how are settled solids typically removed?
• Sludge disposal provides which resource to soils?
• What is the primary purpose of primary treatment?
• Which of the following are tertiary treatment methods? Choose the option that lists all true methods.
• What is the correct ratio of BOD to Nitrogen to Phosphorus in typical wastewater design?
• Which valve is commonly used on sludge lines or high solids content to minimize clogging?
• What percent of sewage is solid?
• Denitrification occurs under which conditions?
• What is a selector?
• To measure the influent entering a treatment plant from the community, where should flow measurements be taken?
• In a vortex-type grit chamber, how are solids separated from the wastewater?
• Which two disinfection methods are commonly used in wastewater plants?
• What is meant by sludge age, and why is it controlled?
• What is the biological process called when nitrifying bacteria oxidize ammonia to nitrite and nitrate under aerobic conditions?
• Sand is an example of organic matter found in raw sewage?
• In the activated sludge process, which statement describes Return Activated Sludge (RAS)?
• How can you tell if nitrification is occurring effectively in the plant?
• Cleaning agents can impact a treatment plant by which of the following?
• What is a restriction in an open channel used to measure flow?
• What DO concentration is typically targeted in the aeration basin to support nitrification?
• Metal finishing industries can discharge wastewater with which features?
• Which of the following is NOT a common method of sludge disposal?
• Which statement best describes diaphragm pumps compared with other positive displacement pumps?
• If cavitation is occurring, what is the recommended action?
• Secondary biological treatment consists of _______, either mixed in suspension in a basin or attached to a media of some type where the _____ material is broken down and consumed. Most secondary treatment processes require _____ for the bacteria.
• Which locations are typically used for Class A sludge application?
• Which instrument is used to measure dissolved oxygen in an activated sludge process?
• A structure that allows a pipe to dip below an obstruction by forming a U-shaped path, forcing liquid to rise and exit the other end, is called an:
• Which equipment is designed to remove grit solids from wastewater before clarification?
• What is the role of digestion gas collection and flare in anaerobic digestion?
• What type of pump is a diaphragm pump?
• What are the two main reasons for treating wastewater?
• Distinguish inflow from infiltration in a collection system.
• Which option best describes the method used to determine flow in an open channel by measuring depth?
• What is the typical hazard associated with confined-space entry and how is it mitigated?
• What is sludge thickening and what are two common methods used?
• What is the purpose of the spiral flow created by the injected air in an aerated grit chamber?
• What are diaphragm pumps commonly used for?
• What is inflow and infiltration (I/I) mitigation, and why is it important?
• Which statement about diaphragm pumps is true?
• What is the primary purpose of a digester in sludge management?
• A rise in influent ammonia at a plant typically indicates which condition?
• Which situation would indicate nitrification is not occurring?
• Which analysis among the following is used to reduce vector attraction in Class B sludge?
• Which statement best describes the impact of the food industry on a wastewater treatment plant?
• Which of the following is among the required records kept when land spreading biosolids and sludge?
• RBC stands for Rotating Biological Contactor.
• Which part of the treatment process uses biological processes?
• Which units are commonly used for reporting average daily flow in wastewater operations?
• Which of the following is a preventative spill measure for WWTPs?
• Which statement accurately describes gravity belt thickening in sludge treatment?
• Which Wisconsin administrative codes regulate municipal and industrial sludge?
• Denitrification requires which condition for nitrate to be used as an electron acceptor?
• Which wastewater treatment process removes suspended solids and nutrients to achieve a level of treatment greater than secondary?
• Which term refers to the mixture of microorganisms and wastewater in an aeration tank?
• Surfactants from cleaners can cause which issues in a wastewater treatment plant?
• Which parameter must be present for bacteria to effectively treat wastewater in secondary treatment?
• Why is oxygen transfer efficiency (OTE) important in aeration systems?
• What safety procedures should be followed when entering a confined space such as a digester or manhole?
• What makes diaphragm pumps unique from other positive displacement pumps?
• To know actual flow and loading to treatment units, side streams need to be included or excluded from flow measurements?
• In activated sludge, what condition leads to bulking and how is it typically corrected?
• What does MLSS stand for in activated sludge processes?
• Biogas produced during anaerobic digestion consists mainly of methane and carbon dioxide. Which gas is also a major component?
• Which statement best describes the function of preliminary treatment?
• Which valve would you choose for rapid on/off operation using a simple stem and ball mechanism?
• Flow meters must be calibrated annually. Which type of record should be kept?
• Where do common recycle streams originate in a wastewater treatment plant?
• What is the primary purpose of coagulant and flocculant dosing in wastewater treatment?
• What is the optimal DO range for typical aerobic wastewater treatment?
• Which statement most accurately describes a limitation of UV disinfection?
• Why is it important to measure wastewater flow?
• Which treatment stage primarily removes dissolved organics through biological processes?
• Which two valves are self-actuated?
• Trickling filters are a form of secondary treatment.
• Debris lodged in bottom of a v-notch weir would cause the flow meter reading to read higher, lower, or the same?
• Which of the following describes problems that can result when sewage goes septic?
• What type of solids does a clarifier remove?
• Define F:M using BOD and MLSS
• Dewatered sludge typically contains what percent solids, and what is its common nickname?
• Which statement best describes how ammonia is measured in wastewater and what rising ammonia indicates?
• Why is energy efficiency important in wastewater treatment and what are two effective strategies?
• Disinfection destroys all microorganisms.
• Which of the following is a common open-channel flow measurement device?
• Which valve is typically used for on/off service with minimal leakage and high reliability and requires turning a wheel to move the gate into the flow path?
• How does a variable-frequency drive (VFD) on an aeration blower contribute to plant performance?
• Which of the following is a required land spreading record related to nitrogen?
• What is a potential safety hazard with anaerobic digestors?
• A ______ pump contains an impeller that rotates in a casing to pump large volumes of liquid through a pipe. This pipe is most commonly used for raw wastewater pumping; at lift stations, recirculation flows, for RAS/WAS, and final effluent pumping.
• Which type of bacteria primarily performs nitrification in wastewater treatment?
• What is the term for solids returned from the clarifier back to the aeration tank?
• Which component is typically the final settling unit in an activated sludge plant?
• In an aerated grit chamber, what causes heavier grit particles to settle?
• In raw sewage, the solid content is closest to:
• What is the purpose of secondary (biological) treatment?
• What is the typical pH range for domestic wastewater?
• Which byproduct is produced during anaerobic digestion and why are they managed?
• A ________ pump is a type of pump and motor combination used for lift stations and wet wells. It is a type of centrifugal pump.
• Which of the following is considered a control measure for industrial discharges?
• Compare primary treatment to secondary treatment.
• Which statement best describes how energy can be saved in aeration systems?
• What is the primary purpose of equalization in an industrial wastewater system?
• In open channel flow measurement, which parameter is used to infer the flow rate as part of a weir measurement?
• Which of the following is a typical location for in-plant flow meters?
• Which of the following is not a quarter-turn valve?
• What is the typical detention time for lagoon or small pond wastewater systems?
• Which statement best describes the purpose of pretreatment before discharge to a municipal wastewater plant?
• Which of the following is NOT among the five common pieces of equipment used in suspended growth secondary biological treatment?
• How do you calculate the average flow for a given day from the daily total?
• What materials are the bafflers in a clarifier typically made of?
• Progressive cavity pumps are unreliable and can often run dry and fill with excessive grit.
• Flow measurement devices on influent lines help with which outcome?
• Which statement best describes preliminary treatment?
• Differentiate nitrification and denitrification in wastewater treatment.
• What does MLSS stand for in wastewater treatment?
• Why is pH control important in disinfection and in overall process chemistry?
• Relief valve prevents excessive pressure.
• What is the most common way to dispose of sludge in Wisconsin?
• Which gas is commonly recognized as a toxic gas at wastewater plants?
• Odor control is considered a type of preliminary treatment.
• What is the term for solids wasted from the treatment system?
• Define primary treatment.
• The microorganisms used to treat wastewater are the same as those found in rivers and lakes.
• What is the purpose of grit removal in a municipal wastewater treatment plant?
• Which gas is NOT listed as a potential toxic gas at a WWTP?
• In lagoon systems, what best describes the typical detention time?
• Why is keeping an operation log or daily log important?
• Which valve type uses a ball inside as the sealing element and is operated by a quarter-turn to open or close?
• Into which two main locations can settled solids be returned or wasted?
• Which of the following is NOT an attached growth wastewater treatment system?
• The mixture of microorganisms and wastewater in an aeration tank is referred to as ________.
• _____ are flows generated within the plant, usually from solids processing that has been recycled back through the plant.
• Which valve is commonly known for rapid operation due to a simple stem and ball mechanism?
• Which multi-turn valve is used on sludge lines or wastewater with high TSS?
• What is a slug load and why is it problematic?
• How much of the sampler bottle should be filled with liquid when composing a composite sample?
• Which sampling approach provides a better composite representation?
• What is the key difference between grab sampling and composite sampling?
• What are two common disinfection byproducts formed with chlorination?
• Which parameter most directly reflects organic strength of wastewater and is widely tracked in treatment?
• What does WAS stand for in wastewater treatment?
• This type of pump uses a piston in a reciprocating motion and is commonly used for pumping sludges.
• What hazard does hydrogen sulfide pose in wastewater plants and how is it controlled?
• What are common methods of sludge disposal?
• DMR stands for Discharge Monitoring Report.
• Anaerobic activity results in which gas that is extremely toxic even at low concentrations?
• Which analyses must sludge go through before being applied as Class B sludge?
• Cavitation may occur in which parts of a flowing liquid system?
• What percent of TSS/BOD can a secondary treatment system achieve?
• What is the process by which bacteria convert nitrate and nitrite to nitrogen gas under anoxic conditions?
• List three common plant hazards and the PPE typically required when working in wastewater facilities.
• What is an NPDES permit and what does it require of facilities?
• What is the purpose of the final clarifier?
• Why is calibration of DO probes and pH meters essential?
• What is the purpose of daily sampling and reporting requirements in a Wisconsin plant?
• In pipe flow measurement, which device is commonly used?
• In chlorine disinfection, how does pH affect disinfection efficiency?
• What is the purpose of lockout/tagout in confined-space safety?
• Grit removal protects pumps by removing which type of solids early in treatment?
• Which consequence is a typical result of inflow and infiltration (I&I) exceeding treatment plant capacity?
• Which combination of operational metrics is commonly used to assess the stability of a secondary treatment system?
• Which statement about peristaltic pumps is true?
• What is the function of a mechanical bar screen in a wastewater plant?
• Which multi-turn valve is used for corrosive wastewaters?
• Define wet well.
• What is the function of Waste Activated Sludge (WAS) in the activated sludge system?
• Within how many hours should the DNR and local emergency response agencies be notified after a chemical spill?
• Why is equalization often necessary for discharges from certain industries?
• What issue can FOG (fat, oil, grease) cause in wastewater systems?
• Progressive cavity pumps are unreliable and can often run dry and fill with excessive grit.