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Registered Environmental Protection Engineer practice questions

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Question 1Environmental Laws, Regulations, and Standards

Under China's Environmental Protection Law (2015 revision), which entity bears the primary responsibility for the quality of the atmospheric environment within its administrative region?

  1. The provincial environmental protection department alone
  2. The enterprise emitting the most pollutants
  3. The local people's government at each level Correct answer.
  4. The national ministry in charge of ecology and environment

Explanation

The Environmental Protection Law assigns local people's governments at all levels responsibility for environmental quality in their jurisdictions. Environmental agencies supervise and enforce, but they do not replace the government's quality responsibility. This allocation underpins the environmental target responsibility and assessment system.

Question 2Environmental Laws, Regulations, and Standards

In China's environmental impact assessment (EIA) system, which category of construction project requires preparation of an environmental impact report (报告书)?

  1. Projects funded by foreign investment regardless of scale
  2. Projects with minor impact that only need a registration form
  3. Projects located in industrial parks of any type
  4. Projects that may cause significant environmental impact and require a full assessment Correct answer.

Explanation

China's EIA Law classifies projects into three tiers: report (报告书) for significant potential impact, form (报告表) for lesser impact, and registration form (登记表) for minimal impact. The classification follows the catalogue issued by the ecology and environment authority, not ownership or location. A full report requires a comprehensive assessment including public participation.

Question 3Environmental Laws, Regulations, and Standards

Under China's Law on the Prevention and Control of Water Pollution, which document must a polluter obtain before discharging industrial wastewater into a water body through an outlet?

  1. A land use right certificate
  2. A product quality certification
  3. A pollutant discharge permit Correct answer.
  4. A water resource allocation certificate

Explanation

Direct or indirect discharge of wastewater through an outlet requires a pollutant discharge permit issued by the competent authority. The permit specifies allowable pollutant types, concentrations, and total quantities. Discharge without a permit constitutes unlawful discharge subject to penalties.

Question 4Environmental Laws, Regulations, and Standards

Which principle in China's environmental legal framework holds that parties who cause environmental damage should bear the cost of prevention, remediation, and compensation?

  1. The precautionary principle
  2. The public participation principle
  3. The polluter pays principle Correct answer.
  4. The sustainable development principle

Explanation

The polluter pays principle assigns the cost of pollution prevention, control, and remediation to the party responsible for the pollution. It underpins mechanisms such as pollution liability insurance and ecological damage compensation. The other principles address anticipatory action, procedural rights, and intergenerational equity respectively.

Question 5Environmental Laws, Regulations, and Standards

Under China's Environmental Protection Tax Law, which of the following is a taxable pollutant category?

  1. Heat discharged from cooling systems
  2. Carbon dioxide
  3. Water pollutants Correct answer.
  4. Noise from household appliances

Explanation

The Environmental Protection Tax Law levies tax on four categories: air pollutants, water pollutants, solid waste, and noise. Carbon dioxide is not currently a taxable item under this law. Household appliance noise and waste heat are not within the taxable categories.

Question 6Environmental Laws, Regulations, and Standards

In China's national ambient air quality standard (GB 3095-2012), which pollutant is regulated with a 24-hour average concentration limit but no annual average limit?

  1. PM2.5
  2. Sulfur dioxide
  3. Nitrogen dioxide
  4. Carbon monoxide Correct answer.

Explanation

GB 3095-2012 sets annual and 24-hour limits for sulfur dioxide, nitrogen dioxide, and PM2.5, but carbon monoxide is regulated only by 24-hour and 1-hour average limits. This reflects the acute, short-term nature of CO exposure risk. Candidates should know the averaging periods assigned to each criteria pollutant.

Question 7Environmental Laws, Regulations, and Standards

Under China's regulations on pollution source monitoring, how frequently must key polluting units typically conduct self-monitoring of their emissions?

  1. Only when a complaint is received
  2. Once every five years
  3. Only during the initial environmental acceptance inspection
  4. According to the monitoring plan filed with the authority, which specifies frequency by source Correct answer.

Explanation

Key polluting units must prepare a self-monitoring plan, file it with the local ecology and environment authority, and conduct monitoring at the frequency the plan specifies. Monitoring results must be recorded and made public. Self-monitoring is a continuing obligation, not a one-time event.

Question 8Environmental Laws, Regulations, and Standards

Which authority is responsible for approving the environmental impact report of a construction project that may have a significant trans-provincial environmental impact?

  1. The national ecology and environment authority Correct answer.
  2. The municipal authority at the project site
  3. The provincial authority where the project is located
  4. The county authority at the project site

Explanation

Projects with significant trans-provincial or cross-regional environmental impact are reviewed and approved by the national ecology and environment authority. Delegation of approval authority is set by the State Council catalogue. Local authorities handle projects within their jurisdiction that do not meet the trans-provincial threshold.

Question 9Environmental Laws, Regulations, and Standards

A factory discharges wastewater with a chemical oxygen demand concentration of 120 mg/L. Its discharge permit allows 100 mg/L, and the applicable industry standard also sets 100 mg/L. Which conclusion is correct?

  1. The discharge complies because it is below 150 mg/L
  2. The discharge exceeds both the permit and the standard and constitutes unlawful discharge Correct answer.
  3. The discharge is lawful if the factory pays the excess discharge fee
  4. The discharge complies because the permit limit is advisory

Explanation

Permit limits and discharge standards are both binding, and exceeding either constitutes unlawful discharge. Paying a fee does not legalize an exceedance. The factory must treat the wastewater to meet the limit and may face penalties for the exceedance.

Question 10Environmental Laws, Regulations, and Standards

A construction company plans a new highway passing near a nature reserve. Under China's EIA Law, when must public participation be conducted?

  1. At the final acceptance inspection stage
  2. During preparation of the environmental impact report, before submission for approval Correct answer.
  3. Only if residents file a formal complaint
  4. Only after the project is approved and under construction

Explanation

For projects requiring an environmental impact report, the developer must solicit public opinion during report preparation, typically through surveys, hearings, or notices. Public comments and the response must be reflected in the report submitted for approval. Public participation after approval or at acceptance is too late to influence design.

Question 11Environmental Laws, Regulations, and Standards

An enterprise generates hazardous waste listed in the National Hazardous Waste List. Which management requirement applies?

  1. It may store the waste on site indefinitely without reporting
  2. It may sell the waste to any recycler without documentation
  3. It may dispose of the waste in a general municipal landfill
  4. It must prepare a hazardous waste management plan, use a permitted operator for transfer, and complete manifest documentation Correct answer.

Explanation

Hazardous waste management requires a management plan filed with the authority, transfer through an operator holding a hazardous waste operating permit, and a manifest tracking each transfer. Indefinite storage, undocumented transfer, and municipal landfill disposal are prohibited. These controls implement the Law on Prevention and Control of Environmental Pollution by Solid Waste.

Question 12Environmental Laws, Regulations, and Standards

Under China's Environmental Protection Law, when an enterprise causes serious environmental pollution and refuses to correct after being ordered to do so, which measure may the authority take?

  1. Order suspension of production for rectification Correct answer.
  2. Transfer the case directly to criminal prosecution without administrative steps
  3. Confiscate the personal property of the legal representative
  4. Immediately revoke the enterprise's business license

Explanation

The law authorizes authorities to order suspension of production or use of equipment for rectification when serious pollution persists despite orders to correct. Revocation of business license and criminal referral follow separate legal procedures and thresholds. Administrative enforcement precedes or accompanies criminal referral where applicable.

Question 13Environmental Laws, Regulations, and Standards

A chemical plant's sudden equipment failure releases a toxic gas plume. Under China's emergency response requirements, what is the enterprise's first obligation?

  1. Immediately launch its emergency plan, take control measures, and notify affected parties and the local authority Correct answer.
  2. Complete a written report within 30 days
  3. Wait for the local government to issue instructions before acting
  4. Continue production until the end of the shift

Explanation

Enterprises must immediately activate their emergency plan, take measures to control the release, and inform those who may be affected and the local authority. Delay in notification or control can escalate harm and liability. Post-incident reporting supplements but does not replace immediate action.

Question 14Environmental Laws, Regulations, and Standards

Under China's total emission control system, a new project in a region that has not met its total emission reduction target must generally do what?

  1. Obtain replacement reductions through regional reduction of an equivalent or greater amount before approval Correct answer.
  2. Wait for the next five-year plan period
  3. Proceed without any reduction obligation because it is a new entrant
  4. Pay a fine in lieu of reduction

Explanation

In regions failing to meet environmental quality or total reduction targets, new projects must secure replacement reductions, often through regional reduction or trading, before EIA approval. This ensures no net increase in total emissions. Payment of fines or waiting for the next planning period does not satisfy the requirement.

Question 15Environmental Laws, Regulations, and Standards

In China's pollutant discharge permit system, what is the relationship between the permit and the EIA approval for a project?

  1. The permit replaces the need for EIA approval
  2. The two are unrelated and handled by separate ministries with no coordination
  3. The permit application must be consistent with the approved EIA, and changes triggering re-assessment require EIA revision before permit adjustment Correct answer.
  4. EIA approval is only needed after the permit is issued

Explanation

The pollutant discharge permit must reflect the project as approved in its EIA, including pollutant types, amounts, and control measures. If a change triggers a new or revised EIA, the permit must be adjusted accordingly. The systems are linked, with EIA as the front-end decision and the permit as the operational authorization.

Question 16Environmental Laws, Regulations, and Standards

An environmental monitoring laboratory reports data used in enforcement. Under China's rules on environmental monitoring, what is a key integrity requirement for such data?

  1. Data may be adjusted to match the permit limits
  2. Only the enterprise's own laboratory results are admissible
  3. Monitoring must follow validated methods, and tampering or fabricating data is prohibited and punishable Correct answer.
  4. Sampling records may be discarded after reporting

Explanation

Environmental monitoring data must be produced using validated methods and accurate records, and the law prohibits tampering with or fabricating monitoring data. Violations can lead to administrative penalties and, in serious cases, criminal liability. Records must be retained to support traceability.

Question 17Environmental Laws, Regulations, and Standards

A project is located within a designated drinking water source protection zone (first grade). Which activity is permissible?

  1. Opening a tourist resort with restaurants
  2. Setting up a livestock feedlot
  3. Establishment of a new chemical production line
  4. Construction of a facility for monitoring water quality that discharges no pollutants Correct answer.

Explanation

First-grade drinking water source protection zones prohibit new construction unrelated to water supply and protection, and prohibit discharge outlets and polluting activities. A non-discharging water quality monitoring facility serves protection purposes and is compatible. Industrial, agricultural, and tourism developments with pollution potential are barred.

Question 18Environmental Laws, Regulations, and Standards

Under China's soil pollution prevention law, who bears the responsibility for soil remediation of a contaminated site when the original polluter has disappeared?

  1. The current land user bears no responsibility in any case
  2. No remediation is required once the polluter is gone
  3. The neighboring property owners must remediate
  4. The local people's government may organize remediation, with costs pursued from responsible parties where identifiable Correct answer.

Explanation

Where the responsible party cannot be identified, the local people's government organizes remediation, and where responsibility can later be established, costs may be pursued. Land use rights holders also have obligations to cooperate and, in some cases, conduct investigation. Abandonment of the site does not extinguish the need for remediation.

Question 19Environmental Laws, Regulations, and Standards

A regional ecology and environment bureau issues a fine to an enterprise. The enterprise believes the penalty is unlawful. Which remedy is available under China's administrative law?

  1. Apply for administrative reconsideration or file an administrative lawsuit Correct answer.
  2. Request arbitration by an industry association
  3. Refuse to pay and continue operating
  4. Appeal directly to the national ministry for a binding order

Explanation

A party dissatisfied with an administrative penalty may apply for administrative reconsideration to the appropriate authority or bring an administrative lawsuit before a people's court. These are the statutory remedies. Refusing to comply does not suspend the obligation and may lead to further enforcement.

Question 20Environmental Laws, Regulations, and Standards

Under China's carbon emission trading framework, which statement best describes the compliance obligation of a covered enterprise?

  1. It must reduce emissions to zero within one year
  2. It may trade allowances only with government agencies
  3. It is exempt if it purchases renewable energy certificates
  4. It must surrender allowances equal to its verified emissions for the compliance period Correct answer.

Explanation

Covered enterprises must report verified emissions and surrender allowances matching those emissions by the compliance deadline. Shortfalls can be covered by purchasing allowances in the market. Zero-emission mandates and renewable certificate exemptions are not part of the allowance compliance rule.

Question 21Environmental Laws, Regulations, and Standards

An EIA report for a project was approved, but the project's scale later increased by 40% with a change in production process. What is the correct procedure under China's EIA Law?

  1. Prepare a new EIA report and resubmit for approval before continuing Correct answer.
  2. Only notify the public without re-approval
  3. No action is needed because the original approval remains valid
  4. Proceed and file a minor change note after completion

Explanation

Significant changes in scale, location, or production process after EIA approval require a new environmental impact assessment and re-approval. A 40% scale increase combined with a process change is a major change. Continuing construction without re-approval constitutes unlawful construction.

Question 22Environmental Laws, Regulations, and Standards

A company discharges air pollutants through an unregistered bypass outlet while its permitted outlet shows compliance. How should enforcement authorities treat this?

  1. As a minor record-keeping issue
  2. As compliant because the permitted outlet meets limits
  3. As unlawful discharge through a concealed outlet, subject to penalties including production suspension and potential criminal referral if thresholds are met Correct answer.
  4. As lawful if total emissions remain below the regional cap

Explanation

Discharging through an unregistered bypass is unlawful discharge and is treated more seriously than a simple exceedance because it evades monitoring. Penalties can include fines, production suspension, and referral for criminal liability where serious pollution is caused. Compliance at the permitted outlet does not cure the bypass violation.

Question 23Environmental Laws, Regulations, and Standards

Under China's ecological damage compensation system, which situation triggers the government's claim against a responsible party?

  1. Activities that cause damage to ecosystems where the responsible party is identified and restoration is not completed Correct answer.
  2. Routine agricultural practices that follow standards
  3. Any lawful discharge within permit limits
  4. Construction that has obtained valid EIA approval and complies with it

Explanation

The ecological damage compensation system allows designated government bodies to claim compensation from parties responsible for ecosystem damage when restoration is not achieved. Lawful, compliant activities within permits and approvals do not trigger such claims. The focus is on restoring ecological service functions.

Question 24Environmental Laws, Regulations, and Standards

A hazardous waste incinerator must meet which regulatory requirement regarding dioxin emissions under China's standards?

  1. Apply municipal solid waste incineration limits instead
  2. Comply with the dioxin emission limit in the hazardous waste incineration standard and conduct periodic monitoring Correct answer.
  3. Emit dioxins without monitoring if the facility is new
  4. Meet only general particulate limits

Explanation

Hazardous waste incineration is governed by a dedicated pollution control standard that sets dioxin emission limits and requires periodic monitoring. General particulate limits are insufficient, and municipal waste incineration standards do not apply. New facilities are not exempt from monitoring.

Question 25Environmental Laws, Regulations, and Standards

In a region where the annual average PM2.5 concentration exceeds the national secondary standard, what does China's Environmental Protection Law require of local governments regarding air quality planning?

  1. They may ignore the exceedance if industry contributes most emissions
  2. They must immediately shut down all industrial activity
  3. They must prepare and implement a plan to meet the standard within a set period and report progress Correct answer.
  4. They may relax the standard for that region

Explanation

Where ambient air quality fails to meet standards, local governments must prepare a plan with measures and timelines to achieve compliance and report progress. Blanket shutdowns and local relaxation of national standards are not lawful responses. National standards set the floor and cannot be loosened by local governments.

Question 26Environmental Laws, Regulations, and Standards

Under China's Environmental Impact Assessment Law, construction projects are classified into three categories for EIA management. Which statement correctly describes the category that requires only an environmental impact registration form (环境影响登记表)?

  1. All projects located in ecological protection red-line zones, regardless of scale or pollutant type
  2. Projects with moderate environmental impact, for which an environmental impact statement is prepared and filed after construction begins
  3. Projects with significant environmental impact, for which a full environmental impact report must be prepared and approved before construction
  4. Projects with minimal environmental impact, for which the construction unit files the form online with the ecology and environment authority for record purposes Correct answer.

Explanation

The EIA Law establishes a three-tier system: report (报告书) for significant impact, statement (报告表) for moderate impact, and registration form (登记表) for minimal impact. The registration form is filed by the construction unit through the online filing system and does not require approval by the authority. This tiering is intended to focus regulatory review effort on projects with real environmental consequences.

Question 27Environmental Laws, Regulations, and Standards

China's Environmental Protection Law sets out the principle that parties causing environmental damage bear responsibility for restoration. Under this framework, which statement best describes the liability of an enterprise that has polluted a site it leased rather than owned?

  1. The landowner alone bears remediation liability, because remediation duties follow registered land use rights
  2. Liability is shared equally between the lessee and the landowner by operation of law
  3. The polluter bears remediation liability regardless of land ownership, because liability attaches to the party that caused the pollution Correct answer.
  4. Liability falls on the local government, which must fund remediation and then recover costs at its discretion

Explanation

The soil pollution prevention framework and the Environmental Protection Law assign remediation responsibility to the party that caused the pollution, described as the principle that the polluter remediates. Ownership or leasehold status of the land does not shift this duty away from the causer. Where the responsible party cannot be identified, the government may organize remediation and pursue cost recovery, but that is a fallback rather than the default rule.

Question 28Environmental Laws, Regulations, and Standards

An operator of a municipal wastewater treatment plant must report monitoring data under China's pollution source monitoring rules. The plant's online continuous monitoring system records an exceedance at night, but the operator does not report it and later submits a corrected dataset. How should the ecology and environment authority treat this conduct?

  1. As an issue only for the municipal government, because publicly owned plants are exempt from data rules
  2. As tampering with monitoring data, exposing the operator to administrative penalties and possible liability of responsible persons Correct answer.
  3. As a matter for the equipment supplier, since the continuous monitoring system produced the original record
  4. As a minor technical error that is excused because the corrected dataset was ultimately submitted

Explanation

Environmental monitoring regulations prohibit altering, concealing, or fabricating monitoring data, and withholding a recorded exceedance while submitting a revised dataset falls within that prohibition. Penalties can extend to the operating unit and to directly responsible personnel. Public ownership of the plant does not create an exemption from monitoring-data obligations.

Question 29Environmental Laws, Regulations, and Standards

A provincial ecology and environment department plans to issue a local environmental standard for a pollutant that is already regulated by a national environmental quality standard. Which approach is consistent with China's standardization framework for environmental standards?

  1. The local standard automatically supersedes the national standard nationwide once it is filed
  2. The local standard may be issued only if it is stricter than the national standard, and it applies within the province Correct answer.
  3. The local standard may be more lenient than the national standard where local economic conditions require flexibility
  4. Local standards may not be issued for any pollutant already covered by a national standard under any circumstance

Explanation

Under the Environmental Protection Law and the standardization framework, provincial governments may adopt local environmental quality and pollutant discharge standards for items not covered nationally, and where national standards exist local standards must be stricter. Local standards bind within the issuing jurisdiction and are filed with the national authority. They never relax or replace national requirements.

Question 30Environmental Laws, Regulations, and Standards

A company holds a pollutant discharge permit for a facility. During an inspection, the enforcement officer finds that the company installed an additional production line that raises permitted emission levels, without applying to modify the permit. Under China's discharge permit system, how should this situation be characterized?

  1. A lawful activity, because the original permit remains valid for the site as a whole
  2. A matter governed exclusively by the EIA process, with no consequence under the permit system
  3. Discharging without a permit for the added capacity, because the permit does not cover unapproved changes to the facility Correct answer.
  4. A minor record-keeping lapse correctable at the next routine permit renewal

Explanation

A discharge permit authorizes emissions only for the facilities and quantities described in it, so expanding capacity without a permit modification means the added emissions lack authorization. The operator must apply for a permit change before the new line operates. Permit obligations and EIA obligations operate in parallel, and compliance with one does not excuse non-compliance with the other.

Question 31Water Pollution Control and Wastewater Treatment

In conventional activated sludge treatment, which group of microorganisms is the primary indicator of a healthy, well-settling floc with good organic removal?

  1. Sulfur-oxidizing autotrophs forming dense granular aggregates
  2. Free-swimming nematodes dominating the mixed liquor
  3. Filamentous bacteria such as Microthrix parvicella at high abundance
  4. Ciliate protozoa grazing on dispersed bacteria in a floc-forming community Correct answer.

Explanation

A healthy activated sludge floc contains floc-forming bacteria plus a trophic community of ciliates and other protozoa that graze dispersed bacteria and contribute to clear effluent. Their presence with modest filament abundance signals stable sludge age and good settling.

Question 32Water Pollution Control and Wastewater Treatment

A wastewater flow of 0.05 m3/s is dosed with alum at 30 mg/L. What mass of alum is required per day?

  1. 259.2 kg/d
  2. 64.8 kg/d
  3. 12.96 kg/d
  4. 129.6 kg/d Correct answer.

Explanation

Convert flow to L/d: 0.05 m3/s x 86400 s/d = 4320 m3/d = 4.32 x 10^6 L/d. Multiply by 30 mg/L to get 1.296 x 10^8 mg/d, which equals 129.6 kg/d.

Question 33Water Pollution Control and Wastewater Treatment

Which parameter is the standard design basis for sizing the aeration tank volume of a conventional activated sludge system?

  1. Primary clarifier overflow rate
  2. Hydraulic retention time at average dry-weather flow Correct answer.
  3. Sludge volume index of the return sludge
  4. Chlorine contact basin detention time

Explanation

Aeration tank volume in conventional activated sludge is set from the selected hydraulic retention time applied to the design flow, then checked against solids retention time and loading. SVI and clarifier overflow rate inform solids handling, not tank volume.

Question 34Water Pollution Control and Wastewater Treatment

In primary sedimentation, which design parameter most directly controls the removal of discrete settleable particles?

  1. Dissolved oxygen concentration
  2. Surface overflow rate Correct answer.
  3. Solids retention time
  4. Food-to-microorganism ratio

Explanation

For discrete settling the overflow rate, expressed as flow per unit surface area, equals the settling velocity of particles that are just removed. It is therefore the governing design parameter for primary clarifiers.

Question 35Water Pollution Control and Wastewater Treatment

Which condition most commonly causes filamentous bulking in an activated sludge plant?

  1. Excessive aeration producing high dissolved oxygen
  2. Addition of a supplemental carbon source to the anoxic zone
  3. Low dissolved oxygen or low F/M favoring filamentous organisms Correct answer.
  4. Overdosing of polymer in the return sludge line

Explanation

Filamentous bulking typically arises from conditions that favor filamentous bacteria over floc formers, such as low dissolved oxygen, low F/M, nutrient deficiency, or septicity. These conditions let filaments extend beyond the floc and impair settling.

Question 36Water Pollution Control and Wastewater Treatment

Which disinfection approach produces a residual that persists in the distribution system?

  1. Medium-pressure UV irradiation
  2. Membrane filtration
  3. Chloramination Correct answer.
  4. Ozonation

Explanation

Chloramination leaves a combined chlorine residual that persists for a long time and is favored where disinfection byproduct control matters. UV, ozone, and membranes provide essentially no persistent residual.

Question 37Water Pollution Control and Wastewater Treatment

A sample has a 5-day BOD of 200 mg/L and a first-order BOD rate constant k of 0.23 per day. What is the ultimate BOD?

  1. About 293 mg/L Correct answer.
  2. About 460 mg/L
  3. About 200 mg/L
  4. About 137 mg/L

Explanation

For first-order kinetics, BOD5 = L0(1 - e^(-kt)). With k = 0.23/d and t = 5 d, the factor is 1 - e^(-1.15) = 0.683, so L0 = 200/0.683 = about 293 mg/L.

Question 38Water Pollution Control and Wastewater Treatment

In a wastewater treatment context, which statement best describes the role of the anoxic zone in biological nutrient removal?

  1. It provides high dissolved oxygen for nitrification of ammonia
  2. It aerates the return sludge to strip dissolved gases
  3. It precipitates phosphorus as struvite by raising pH
  4. It allows denitrifiers to reduce nitrate using influent carbon under oxygen-limited conditions Correct answer.

Explanation

An anoxic zone has no free oxygen but contains nitrate, allowing denitrifying bacteria to oxidize influent carbon while reducing nitrate to nitrogen gas. This recovers oxygen demand and removes nitrogen.

Question 39Water Pollution Control and Wastewater Treatment

A plant operates at a solids retention time of 5 days with a mixed liquor temperature of 15 degrees C. Nitrification is observed to be incomplete. Which change is most likely to improve nitrification?

  1. Increase the solids retention time to provide a safety factor above the minimum nitrifier SRT Correct answer.
  2. Decrease the solids retention time to wash out slow-growing organisms
  3. Increase the influent ammonia load without changing aeration
  4. Reduce the dissolved oxygen setpoint to save energy

Explanation

Nitrifying bacteria grow slowly, so the minimum SRT for nitrification at 15 degrees C is several days, and design practice requires a safety factor. Raising the SRT retains enough nitrifiers to complete oxidation of ammonia.

Question 40Water Pollution Control and Wastewater Treatment

A secondary clarifier shows a rising sludge blanket and floating clumps in the effluent, with gas bubbles visible in the blanket. What is the most probable cause?

  1. Excessive polymer addition to the aeration basin
  2. Hydraulic overload from excessive surface overflow rate
  3. Low sludge volume index indicating poor flocculation
  4. Denitrification in the sludge blanket releasing nitrogen gas Correct answer.

Explanation

When nitrate reaches the anoxic blanket and sufficient carbon is present, denitrification produces nitrogen gas bubbles that lift sludge to the surface. This is the classic rising-sludge symptom, distinct from hydraulic washout.

Question 41Water Pollution Control and Wastewater Treatment

Which membrane process configuration is typically used for direct filtration of secondary effluent in water reclamation where the goal is removal of suspended solids and pathogens but not dissolved salts?

  1. Microfiltration or ultrafiltration Correct answer.
  2. Electrodialysis reversal
  3. Reverse osmosis
  4. Thermal distillation

Explanation

Microfiltration and ultrafiltration are low-pressure porous membranes that reject particles, colloids, and microorganisms while passing dissolved salts. Reverse osmosis and thermal processes remove dissolved salts and are used only when desalting is required.

Question 42Water Pollution Control and Wastewater Treatment

A chemical precipitation step uses ferric chloride to remove phosphorus. Which mechanism best explains the removal?

  1. Ion exchange of phosphate onto cationic resin beads
  2. Formation of ferric phosphate and ferric hydroxide flocs that incorporate phosphate Correct answer.
  3. Volatilization of phosphorus as phosphine gas
  4. Biological uptake of phosphate under anaerobic conditions

Explanation

Ferric salts hydrolyze to form hydroxide flocs that adsorb and coprecipitate phosphate, and ferric phosphate itself is sparingly soluble. The combined precipitate is removed in downstream clarification or filtration.

Question 43Water Pollution Control and Wastewater Treatment

An industrial discharger must meet a monthly average limit of 30 mg/L for oil and grease. Which pretreatment technology is most appropriate for a free-floating oil layer in the influent?

  1. UV oxidation
  2. Activated carbon adsorption
  3. API gravity separator Correct answer.
  4. Anion exchange

Explanation

An API separator uses gravity differential to float and skim free oil from water and is the standard first-stage treatment for oily wastewater. Activated carbon, ion exchange, and UV address dissolved organics or microorganisms, not free oil.

Question 44Water Pollution Control and Wastewater Treatment

A nitrifying activated sludge system experiences a sudden drop in pH from 7.2 to 6.1 after an increase in influent ammonia. What is the most likely explanation?

  1. Increased denitrification releasing hydroxide
  2. Alkalinity consumption by nitrification exceeding the available buffering Correct answer.
  3. Phosphate precipitation consuming hydrogen ions
  4. Carbon dioxide stripping caused by excessive aeration

Explanation

Nitrification consumes about 7.14 mg of alkalinity as CaCO3 per mg of ammonia nitrogen oxidized, so a sudden ammonia load can exhaust buffering and depress pH. This inhibits nitrifiers further if not corrected.

Question 45Water Pollution Control and Wastewater Treatment

Which statement correctly describes the purpose of the return activated sludge stream?

  1. It provides chlorine contact for disinfection
  2. It removes excess sludge from the system to control solids retention time
  3. It supplies alkalinity to the nitrification process
  4. It maintains the desired mixed liquor suspended solids concentration in the aeration basin Correct answer.

Explanation

Return activated sludge recycles settled biomass from the secondary clarifier back to the aeration basin to hold the target MLSS and food-to-microorganism ratio. Wasting, not returning, controls the solids inventory.

Question 46Water Pollution Control and Wastewater Treatment

A treatment plant must reduce total nitrogen in the effluent. Which sequence of zones supports simultaneous nitrification and denitrification with internal recycle?

  1. Aerobic, anaerobic, and anoxic zones with no recycle
  2. Anaerobic zone followed by chlorination
  3. Aerobic zone only with high dissolved oxygen
  4. Anaerobic, anoxic, and aerobic zones in series with internal mixed liquor recycle to the anoxic zone Correct answer.

Explanation

Nitrate produced in the aerobic zone is returned by internal recycle to the upstream anoxic zone, where influent carbon drives denitrification. The anaerobic zone ahead of the anoxic zone supports biological phosphorus removal in the same train.

Question 47Water Pollution Control and Wastewater Treatment

A biosolids sample has 4 percent total solids. What is the approximate volume reduction achieved if the same solids mass is dewatered to 20 percent total solids?

  1. To about one-half of the original volume
  2. To about one-twentieth of the original volume
  3. To about one-fifth of the original volume Correct answer.
  4. To about four-fifths of the original volume

Explanation

For a fixed solids mass, volume is inversely proportional to solids concentration. Raising the concentration from 4 to 20 percent, a factor of five, reduces the volume to one-fifth.

Question 48Water Pollution Control and Wastewater Treatment

Which condition is required for reliable biological phosphorus removal in an enhanced biological phosphorus removal system?

  1. Alternating anaerobic and aerobic (or anoxic) conditions with volatile fatty acids available in the anaerobic zone Correct answer.
  2. Continuous aerobic conditions with no anaerobic contact
  3. Continuous anaerobic conditions with no oxygen reintroduction
  4. High nitrate concentration in the anaerobic zone

Explanation

Phosphorus-accumulating organisms take up volatile fatty acids and release phosphate under anaerobic conditions, then store excess phosphate aerobically. Nitrate in the anaerobic zone interferes because it is a preferred electron acceptor.

Question 49Water Pollution Control and Wastewater Treatment

A plant is required to meet a total coliform limit in reclaimed water. Which combination best provides both inactivation and a measurable residual for distribution?

  1. Filtration followed by UV with no chemical addition
  2. Filtration followed by chlorination with residual monitoring Correct answer.
  3. Equalization followed by pH adjustment
  4. Primary clarification followed by grit removal

Explanation

Filtration reduces turbidity and shields organisms from disinfectants, and chlorination then provides inactivation plus a residual that can be monitored downstream. UV alone inactivates well but leaves no residual.

Question 50Water Pollution Control and Wastewater Treatment

A sequencing batch reactor completes fill, react, settle, decant, and idle phases. Which phase allows solids to separate before the treated supernatant is withdrawn?

  1. Settle Correct answer.
  2. Idle
  3. React
  4. Fill

Explanation

In the settle phase aeration and mixing stop so biomass can form a blanket and clarify the supernatant. The decant phase then removes the clarified effluent above the sludge blanket.