I85PREP
⌘ K
HKIE Professional Assessment - Environmental Discipline study materials
HKIE Professional Assessment - Environmental Discipline study resources

HKIE Professional Assessment - Environmental Discipline practice questions

One question at a time. Build your HKIE Professional Assessment - Environmental Discipline understanding.

First 50 of 200 questions. Each one lists the choices, the correct answer, and an explanation. The checker at the top of this page saves progress in this browser when it is available.

Continue in the practice tool above to load more questions, 50 at a time.

Question 1Environmental engineering (discipline knowledge)

Under Hong Kong's Waste Disposal Ordinance, which authority issues waste disposal licences for the operation of a waste disposal facility?

  1. The Environmental Protection Department, acting through the Authority under the Ordinance Correct answer.
  2. The Buildings Department, acting through the Building Authority
  3. The Electrical and Mechanical Services Department, acting through the Director
  4. The Water Supplies Department, acting through the Water Authority

Explanation

The Waste Disposal Ordinance vests licensing control of waste disposal facilities in the authority administered by the Environmental Protection Department, which assesses facility design, operation and environmental performance before granting a licence. Other departments regulate buildings, water supply and electrical installations, not waste facilities.

Question 2Environmental engineering (discipline knowledge)

In an environmental impact assessment under the Environmental Impact Assessment Ordinance, which mechanism translates predicted impacts into enforceable conditions during construction?

  1. The Environmental Permit issued by the Director of Environmental Protection Correct answer.
  2. The Discharge Licence issued under the Water Pollution Control Ordinance
  3. The Construction Noise Permit issued under the Noise Control Ordinance
  4. The Occupation Permit issued by the Building Authority

Explanation

The Environmental Permit is the statutory instrument that binds the project proponent to the mitigation measures and monitoring requirements in the approved EIA report, and breaching its conditions is an offence. The other permits address occupation, effluent discharge or construction noise individually rather than the whole environmental programme.

Question 3Environmental engineering (discipline knowledge)

A site discharges 2,000 m3/day of effluent with a 5-day biochemical oxygen demand of 30 mg/L into a coastal water. What is the approximate BOD mass load discharged per day?

  1. 600 kg/day
  2. 6 kg/day
  3. 0.06 kg/day
  4. 60 kg/day Correct answer.

Explanation

Mass load equals concentration times flow: 30 mg/L multiplied by 2,000 m3/day, with 1 m3 equal to 1,000 L, gives 30 g/m3 times 2,000 m3/day, or 60,000 g/day, which is 60 kg/day. Consistent unit conversion is the key step.

Question 4Environmental engineering (discipline knowledge)

Which unit is conventionally used to express the sound power level of an industrial plant item radiating noise into the surroundings?

  1. Decibels referenced to one milliwatt
  2. Decibels referenced to one microbar
  3. Decibels referenced to 20 micropascals
  4. Decibels referenced to one picowatt Correct answer.

Explanation

Sound power level is referenced to 1 picowatt (10^-12 W), whereas sound pressure level is referenced to 20 micropascals. Keeping the reference distinct matters because plant manufacturers usually quote power levels while field measurements give pressure levels.

Question 5Environmental engineering (discipline knowledge)

In air pollution control, which device removes fine particulate matter by charging particles and collecting them on oppositely charged plates?

  1. Cyclone separator
  2. Venturi scrubber
  3. Electrostatic precipitator Correct answer.
  4. Fabric filter baghouse

Explanation

An electrostatic precipitator ionises the gas stream so particles acquire charge and migrate to collection electrodes, achieving high efficiency even for sub-micron dust. Cyclones rely on inertial separation, scrubbers on impaction into droplets, and baghouses on physical filtration.

Question 6Environmental engineering (discipline knowledge)

Which gas is the principal target of activated carbon adsorption in the odour control of a sewage treatment works?

  1. Oxygen
  2. Carbon dioxide
  3. Nitrogen
  4. Hydrogen sulphide Correct answer.

Explanation

Hydrogen sulphide is the dominant odorous compound generated by anaerobic conditions in sewage conveyance and treatment, and activated carbon adsorbs it effectively. Carbon dioxide, nitrogen and oxygen are not the malodorous species of concern.

Question 7Environmental engineering (discipline knowledge)

Which parameter is the standard indicator of the organic strength of municipal wastewater for treatment plant design?

  1. Chloride concentration
  2. Total dissolved solids
  3. Turbidity
  4. Five-day biochemical oxygen demand Correct answer.

Explanation

Five-day BOD at 20 degrees Celsius is the conventional measure of biodegradable organic content used to size biological treatment processes. Dissolved solids, turbidity and chloride indicate other characteristics and do not quantify biodegradable load.

Question 8Environmental engineering (discipline knowledge)

Which statutory instrument principally controls the discharge of pollutants into Hong Kong inland waters and coastal waters?

  1. Ozone Layer Protection Ordinance
  2. Air Pollution Control Ordinance
  3. Noise Control Ordinance
  4. Water Pollution Control Ordinance Correct answer.

Explanation

The Water Pollution Control Ordinance establishes water control zones and requires discharge licences that set effluent standards for inland and coastal waters. The other ordinances address air, noise and ozone-depleting substances respectively.

Question 9Environmental engineering (discipline knowledge)

A proposed development lies within a water gathering ground and will generate sewage. Which combination of approvals is most relevant to the environmental engineer at the early planning stage?

  1. A water pollution control discharge licence and an environmental permit where the project is a designated project Correct answer.
  2. A waste disposal licence and a dangerous goods licence only
  3. A construction noise permit and an occupation permit only
  4. A trade effluent surcharge agreement and a fire services certificate only

Explanation

Development in a water gathering ground raises effluent quality and catchment protection concerns, so a discharge licence under the Water Pollution Control Ordinance is needed, and if the project is a designated project an environmental permit is also required. The other combinations omit these core environmental controls.

Question 10Environmental engineering (discipline knowledge)

A noise source produces a sound power level of 100 dB and radiates hemispherically over a hard reflective ground. Using Lp = Lw - 20 log r - 8 for hemispherical radiation, what is the approximate sound pressure level at 10 m from the source?

  1. 62 dB
  2. 72 dB Correct answer.
  3. 82 dB
  4. 92 dB

Explanation

Substituting r = 10 m gives 20 log 10 = 20, so Lp = 100 - 20 - 8 = 72 dB. The minus 8 term accounts for hemispherical rather than spherical radiation, and neglecting it would overestimate the level.

Question 11Environmental engineering (discipline knowledge)

During commissioning of an activated sludge plant, the mixed liquor suspended solids are 3,000 mg/L and the sludge age is to be held at 10 days. Which operational adjustment best maintains a stable sludge age if the influent organic load doubles?

  1. Reduce the aeration rate to lower dissolved oxygen
  2. Increase the mixed liquor inventory or wasting rate consistent with the higher biomass production Correct answer.
  3. Stop sludge wasting entirely for several weeks
  4. Decrease the return activated sludge ratio to zero

Explanation

Sludge age equals the mass of solids in the system divided by the daily solids leaving the system, so doubling the load increases biomass production and requires the inventory or wasting rate to be adjusted to hold the target age. Reducing aeration or halting wasting destabilises the process.

Question 12Environmental engineering (discipline knowledge)

In an EIA, which approach best addresses the cumulative impact of several committed developments discharging into the same water body?

  1. Assessing each project in isolation and relying on individual licence limits
  2. Deferring the assessment until each project applies for its discharge licence
  3. Summing the predicted loads from all committed sources and comparing the total against the receiving water's assimilative capacity Correct answer.
  4. Assuming the largest single project dominates and ignoring the others

Explanation

Cumulative impact assessment aggregates the loads from all committed and reasonably foreseeable sources, then tests the combined load against the capacity of the receiving water. Project-by-project assessment can miss the combined effect that exceeds capacity.

Question 13Environmental engineering (discipline knowledge)

Which landfill liner arrangement is normally required for a modern secure landfill receiving municipal solid waste?

  1. A sprayed bituminous seal directly on prepared subgrade
  2. A single layer of compacted clay without any leachate collection
  3. A composite liner of compacted clay with an overlying geomembrane and a leachate collection layer Correct answer.
  4. A gravel drainage blanket over undisturbed natural soil

Explanation

Secure landfills use a composite liner combining a low-permeability clay layer with a geomembrane, plus a drainage layer to collect and remove leachate and reduce head on the liner. Single clay or bituminous seals offer far less containment and no leachate control.

Question 14Environmental engineering (discipline knowledge)

A stack emits 5 g/s of a pollutant from a 50 m chimney. Using a simple Gaussian model with wind speed 5 m/s, the centreline ground-level concentration at the distance of maximum concentration is approximately which order of magnitude?

  1. Tens of micrograms per cubic metre Correct answer.
  2. Tens of nanograms per cubic metre
  3. Tens of grams per cubic metre
  4. Tens of milligrams per cubic metre

Explanation

A rough screening estimate uses C approximately equal to Q divided by (pi times u times sigma-y times sigma-z), and with dispersion parameters of the order of tens of metres the result falls in the tens of micrograms per cubic metre range. This is consistent with typical ambient standards expressed in micrograms per cubic metre.

Question 15Environmental engineering (discipline knowledge)

Which strategy most directly reduces the quantity of construction and demolition waste requiring disposal at landfill?

  1. On-site sorting with crushing of inert material for reuse as fill Correct answer.
  2. Covering waste skips to prevent litter escape
  3. Recording waste tonnages in a trip ticket system
  4. Increasing the number of waste collection trips to the site

Explanation

On-site sorting and crushing converts inert rubble into reusable fill, diverting material from landfill and reducing demand for virgin aggregate. Collection logistics, covering skips and record keeping improve control and hygiene but do not reduce the quantity disposed.

Question 16Environmental engineering (discipline knowledge)

In a sequencing batch reactor, which phase immediately follows the fill phase in a conventional cycle?

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

Explanation

A conventional SBR cycle proceeds through fill, react, settle, decant and idle, so reaction follows filling to complete biological treatment before solids are allowed to settle. Decanting before settling would discharge unsettled mixed liquor.

Question 17Environmental engineering (discipline knowledge)

Which monitoring parameter best indicates that anaerobic digestion of sewage sludge has become unbalanced?

  1. Concentration of phosphate in the supernatant
  2. Colour of the digester gas
  3. Ratio of volatile fatty acids to alkalinity in the digester Correct answer.
  4. Turbidity of the digested sludge

Explanation

Rising volatile fatty acids relative to alkalinity signals acid accumulation and impending souring of the methanogenic population before pH collapses. Phosphate, turbidity and gas colour are not reliable early indicators of digester instability.

Question 18Environmental engineering (discipline knowledge)

A developer proposes a 24-hour piling operation adjacent to a residential block. Which control under the Noise Control Ordinance is most directly engaged?

  1. A neighbourhood noise abatement notice
  2. A discharge licence under the Water Pollution Control Ordinance
  3. A construction noise permit with restricted hours and conditions Correct answer.
  4. An environmental permit under the EIA Ordinance

Explanation

Prescribed construction work during restricted hours, including night-time piling, requires a construction noise permit with conditions limiting noise and hours. Neighbourhood abatement notices and the other instruments do not authorise restricted-hour construction noise.

Question 19Environmental engineering (discipline knowledge)

Which design feature most effectively reduces the short-circuiting of flow in a rectangular sedimentation tank?

  1. Increasing the surface overflow rate above design values
  2. Reducing the tank depth while keeping the same volume
  3. Correctly proportioned inlet baffles together with a suitable length-to-width ratio Correct answer.
  4. Removing the outlet weir to lower head loss

Explanation

Inlet baffles distribute flow across the tank and a sufficient length-to-width ratio suppresses density currents and dead zones, improving the fraction of the theoretical detention time actually used. Higher overflow rates, shallower depth and removal of the weir all worsen performance.

Question 20Environmental engineering (discipline knowledge)

In a life cycle assessment of two sludge disposal options, which comparison is methodologically sound?

  1. Comparing only the gate fees charged by each disposal facility
  2. Comparing only the carbon emissions during transport
  3. Comparing the options using different impact assessment methods for each
  4. Comparing the options on a common functional unit with equivalent system boundaries Correct answer.

Explanation

LCA comparisons require the same functional unit and equivalent system boundaries so that burdens are attributed on a like-for-like basis. Comparing only costs, only transport emissions or using inconsistent methods produces misleading conclusions.

Question 21Environmental engineering (discipline knowledge)

A river receives an effluent with high ammonia nitrogen. Which in-stream process converts this ammonia to nitrate and consumes dissolved oxygen?

  1. Nitrification by autotrophic bacteria Correct answer.
  2. Volatilisation of ammonia at neutral pH
  3. Denitrification by heterotrophic bacteria
  4. Phosphorus precipitation by alum dosing

Explanation

Nitrifying bacteria oxidise ammonia to nitrite and then nitrate, consuming about 4.3 mg of oxygen per mg of ammonia nitrogen oxidised and exerting a nitrogenous oxygen demand. Denitrification reduces nitrate to nitrogen gas, and volatilisation is negligible at neutral pH.

Question 22Environmental engineering (discipline knowledge)

A factory installs a new boiler and must demonstrate compliance with the Air Pollution Control Ordinance. Which document issued under the Ordinance authorises the emission of air pollutants from the specified process?

  1. A construction noise permit
  2. A licence for the specified process Correct answer.
  3. A waste disposal licence
  4. A water discharge licence

Explanation

Specified processes such as furnaces and boiler plants require a licence under the Air Pollution Control Ordinance that sets emission limits and operating conditions. The other instruments belong to noise, water and waste regimes and cannot authorise air emissions.

Question 23Environmental engineering (discipline knowledge)

A site investigation reports soil contaminated with lead at concentrations above the relevant risk-based standard, and the groundwater is also affected. Which remediation approach is most appropriate for the soil where excavation to landfill is not feasible?

  1. Diluting the contaminated soil by mixing with clean fill in place
  2. Applying a temporary odour suppressant and continuing construction
  3. Capping the area with clean soil and taking no groundwater action
  4. In-situ soil washing or stabilisation combined with monitored natural attenuation of the groundwater plume Correct answer.

Explanation

Where excavation is impractical, treatment or immobilisation of the lead-bearing soil combined with management of the groundwater plume addresses both source and pathway. Capping alone leaves the source and plume uncontrolled, dilution is not accepted as treatment, and odour suppressants do not remediate contamination.

Question 24Environmental engineering (discipline knowledge)

A consultant claims a 99.9 percent removal efficiency for a secondary treatment upgrade. Which statement correctly interprets the corresponding log removal?

  1. Nine log removal, meaning one billionth of the influent concentration remains
  2. One log removal, meaning one tenth of the influent concentration remains
  3. Three log removal, meaning one thousandth of the influent concentration remains Correct answer.
  4. Two log removal, meaning one hundredth of the influent concentration remains

Explanation

Each log unit corresponds to a tenfold reduction, so 99.9 percent removal leaves 0.1 percent, which is a factor of one thousand or three logs. Confusing percentage removal with log removal is a common reporting error.

Question 25Environmental engineering (discipline knowledge)

A noise-sensitive receiver is 200 m from a proposed ventilation plant. The predicted level at the facade is 3 dB above the noise criterion. Which combination of measures is technically most defensible?

  1. Applying administrative controls to restrict receiver occupancy
  2. Relocating the receiver and ignoring the plant
  3. Doubling the fan speed to improve dispersion of the noise
  4. Source enclosure with acoustic louvres and silencers, plus a barrier where line of sight permits Correct answer.

Explanation

A 3 dB exceedance requires a modest but reliable reduction, best achieved by attenuating at source with enclosures, louvres and silencers, supplemented by a barrier where the geometry allows. Increasing fan speed raises both sound power and tonal content, and measures aimed at the receiver are not engineering controls.

Question 26Environmental engineering (discipline knowledge)

Under the Air Pollution Control Ordinance, which authority issues the Specified Process Licence for a scheduled industrial process such as a cement works?

  1. The Buildings Department
  2. The Fire Services Department
  3. The Environmental Protection Department Correct answer.
  4. The Town Planning Board

Explanation

Specified processes listed in the Air Pollution Control Ordinance require a licence administered by the Environmental Protection Department as the controlling authority. Other departments have separate statutory roles and cannot issue this licence.

Question 27Environmental engineering (discipline knowledge)

In Hong Kong, which legislation is the principal control on the import and export of hazardous and other controlled waste?

  1. The Water Pollution Control Ordinance
  2. The Waste Disposal Ordinance Correct answer.
  3. The Ozone Layer Protection Ordinance
  4. The Noise Control Ordinance

Explanation

The Waste Disposal Ordinance provides the framework for waste import and export permits, implementing the Basel Convention controls. The other ordinances address different environmental media and do not govern transboundary waste movements.

Question 28Environmental engineering (discipline knowledge)

Which unit process is primarily used to remove dissolved heavy metals from an industrial wastewater by precipitation as insoluble hydroxides?

  1. Chlorination for disinfection
  2. Chemical precipitation with lime or caustic soda Correct answer.
  3. Aeration in a diffused air basin
  4. Screening through a bar rack

Explanation

Adding lime or sodium hydroxide raises pH so dissolved metal ions form insoluble hydroxide precipitates that can be settled or filtered out. Aeration, chlorination and screening do not deliberately convert dissolved metals into settleable solids.

Question 29Environmental engineering (discipline knowledge)

Which descriptor is used in the Noise Control Ordinance for an area that is predominantly residential and where a low noise level is expected?

  1. Industrial Area
  2. Rural Area
  3. Commercial Area
  4. Noise Sensitive Area Correct answer.

Explanation

The Noise Control Ordinance and its technical memoranda use the concept of a Noise Sensitive Area, typically residential or institutional, where tighter acceptable noise levels apply. Area designations such as industrial or commercial are not the statutory trigger for the lowest noise limits.

Question 30Environmental engineering (discipline knowledge)

In a municipal solid waste incinerator, what is the main purpose of the secondary combustion zone operating above about 850 degrees Celsius?

  1. To cool the flue gas before the stack
  2. To precipitate heavy metals as hydroxides
  3. To increase the moisture content of the ash
  4. To ensure destruction of organic compounds and dioxins Correct answer.

Explanation

A high-temperature secondary zone with adequate residence time and turbulence completes combustion of organics and destroys dioxin precursors. Cooling, metal precipitation and ash moisture are handled by other parts of the plant.

Question 31Environmental engineering (discipline knowledge)

Which parameter is normally measured to assess the strength of leachate from a landfill for design of a leachate treatment plant?

  1. Sulphur dioxide concentration
  2. Sound power level
  3. Biochemical oxygen demand and ammoniacal nitrogen Correct answer.
  4. Radon activity

Explanation

Landfill leachate strength is characterised mainly by BOD, COD and ammoniacal nitrogen, which drive treatment plant sizing. Sulphur dioxide, sound power and radon relate to air or noise, not leachate strength.

Question 32Environmental engineering (discipline knowledge)

Which term describes the process by which wind-driven soil particles are lifted and transported from an exposed construction site?

  1. Flocculation
  2. Leaching
  3. Wind erosion Correct answer.
  4. Sedimentation

Explanation

Wind erosion is the detachment and transport of loose soil particles by wind, which is why exposed sites require watering, covering or stabilisation. Sedimentation, leaching and flocculation describe water-based or chemical processes, not wind-driven soil loss.

Question 33Environmental engineering (discipline knowledge)

Which gas is the principal greenhouse gas targeted by methane recovery at a landfill?

  1. Methane Correct answer.
  2. Nitrogen dioxide
  3. Carbon monoxide
  4. Hydrogen sulphide

Explanation

Methane is generated by anaerobic decomposition of organic waste and has a high global warming potential, so landfill gas recovery targets it. Carbon monoxide, nitrogen dioxide and hydrogen sulphide are not the main greenhouse gas from landfills.

Question 34Environmental engineering (discipline knowledge)

A consultant must predict noise from a proposed fixed plant using the standard Hong Kong methodology. Which document provides the accepted calculation method for industrial noise assessment?

  1. The Hong Kong Planning Standards for open space
  2. The Water Quality Objectives
  3. The Waste Disposal Plan
  4. The technical memorandum on noise from places other than domestic premises Correct answer.

Explanation

The Noise Control Ordinance technical memorandum for places other than domestic premises sets out the accepted approach for assessing and predicting industrial and commercial noise. The other documents address waste, water and open space planning rather than industrial noise prediction.

Question 35Environmental engineering (discipline knowledge)

An effluent has a 5-day BOD of 200 mg/L and a COD of 500 mg/L. What does the BOD to COD ratio of 0.4 most reasonably indicate about the wastewater?

  1. It is strongly alkaline and needs neutralisation first
  2. It is substantially biodegradable and suited to biological treatment Correct answer.
  3. It is dominated by non-biodegradable recalcitrant organics
  4. It contains no organic matter at all

Explanation

A BOD to COD ratio around 0.4 suggests a large biodegradable fraction, so biological treatment is appropriate. A very low ratio would indicate poorly biodegradable organics, and no ratio can establish alkalinity or the total absence of organics.

Question 36Environmental engineering (discipline knowledge)

A rectangular grit chamber must remove particles with a settling velocity of 0.02 m/s at a design flow of 0.1 cubic metres per second. Using the surface overflow rate concept, what minimum surface area is required?

  1. 5 square metres Correct answer.
  2. 50 square metres
  3. 0.002 square metres
  4. 2 square metres

Explanation

For an ideal settling basin the required surface area equals flow divided by the particle settling velocity, so 0.1 divided by 0.02 gives 5 square metres. Larger areas would over-design, while smaller areas would fail to capture the target particle size.

Question 37Environmental engineering (discipline knowledge)

A stack emits a pollutant at 2 g/s. Under neutral conditions the maximum ground-level concentration from a Gaussian dispersion model is estimated at 40 micrograms per cubic metre per unit emission rate per second. What is the predicted maximum ground-level concentration?

  1. 8 micrograms per cubic metre
  2. 80 micrograms per cubic metre Correct answer.
  3. 40 micrograms per cubic metre
  4. 20 micrograms per cubic metre

Explanation

The concentration scales linearly with emission rate, so multiplying 40 micrograms per cubic metre by the 2 g/s emission gives 80 micrograms per cubic metre. The other values either ignore the emission rate or apply it incorrectly.

Question 38Environmental engineering (discipline knowledge)

A noise barrier is proposed between a road and a nearby residential block. Which condition most limits the achievable insertion loss of the barrier?

  1. The barrier is close to the noise source
  2. The receiver has a direct line of sight over the top of the barrier Correct answer.
  3. The barrier is continuous along the road
  4. The barrier is made of dense concrete

Explanation

Barrier performance depends on breaking the line of sight and creating a diffraction path; if the receiver still sees the source over the top, insertion loss is small. Density, proximity to the source and continuity generally help rather than limit performance.

Question 39Environmental engineering (discipline knowledge)

A water treatment works uses coagulation with alum followed by flocculation. What is the main purpose of the slow flocculation stage?

  1. To promote collisions so flocs grow to settleable size Correct answer.
  2. To strip dissolved gases by aeration
  3. To disinfect the water with chlorine
  4. To remove dissolved salts by reverse osmosis

Explanation

Slow mixing after coagulant addition encourages particle collisions and the growth of flocs large enough to settle in the following clarifier. Disinfection, gas stripping and desalination are separate processes achieved by other units.

Question 40Environmental engineering (discipline knowledge)

A site has soil contaminated with petroleum hydrocarbons above the risk-based standard. Which remediation approach destroys the contaminant in situ by supplying air to stimulate microbial activity?

  1. Solidification and stabilisation
  2. Thermal desorption
  3. Bioventing Correct answer.
  4. Soil washing

Explanation

Bioventing injects air into the unsaturated zone to supply oxygen to indigenous microbes that biodegrade hydrocarbons in place. Soil washing, solidification and thermal desorption rely on physical separation, immobilisation or heat rather than in-situ biological destruction.

Question 41Environmental engineering (discipline knowledge)

In an environmental impact assessment, which approach is most appropriate for predicting the impact of a proposed tunnel on groundwater levels in an overlying aquifer?

  1. Reference to a single nearby borehole log
  2. Application of a Gaussian plume dispersion model
  3. Coupled numerical groundwater modelling with sensitivity analysis Correct answer.
  4. Simple mass balance of rainfall alone

Explanation

Groundwater drawdown from tunnelling depends on aquifer properties, boundary conditions and geometry, which a calibrated numerical model with sensitivity testing can represent. Rainfall mass balance, a single borehole or a plume model cannot capture the spatial groundwater response.

Question 42Environmental engineering (discipline knowledge)

A developer proposes to install a diesel generator near a residential block and must demonstrate compliance with the Noise Control Ordinance. Which action best establishes the predicted noise impact before installation?

  1. Wait until after commissioning and respond to complaints
  2. Assume the generator will be inaudible because it is enclosed in a container
  3. Rely on the manufacturer's sound power level alone without propagation calculation
  4. Carry out a noise assessment using the approved calculation method and compare with the applicable criteria Correct answer.

Explanation

Predicting impact requires applying the approved calculation method to the sound power data and comparing the result with the applicable noise criteria at the receiver. Waiting for complaints, using bare sound power data or assuming inaudibility does not demonstrate compliance.

Question 43Environmental engineering (discipline knowledge)

A wastewater treatment plant must discharge to a stream with a low dry-weather flow. Which design decision most directly protects the receiving water's dissolved oxygen?

  1. Increasing the discharge volume
  2. Removing the final clarifier
  3. Raising the effluent temperature
  4. Increasing the effluent quality standard for BOD and ammonia Correct answer.

Explanation

Tighter limits on oxygen-demanding substances reduce the oxygen sag in a low-flow stream, protecting dissolved oxygen. Larger discharge volumes, higher temperatures and loss of clarification would all increase oxygen demand or reduce dilution.

Question 44Environmental engineering (discipline knowledge)

A landfill is being designed with a composite liner. Which function does the compacted clay layer perform beneath the geomembrane?

  1. It provides drainage to collect leachate
  2. It acts as the gas extraction layer
  3. It provides a low-permeability secondary barrier and attenuates leachate Correct answer.
  4. It supports vegetation for final restoration

Explanation

In a composite liner the compacted clay layer acts as a low-permeability barrier and can attenuate contaminants if the geomembrane is breached. Drainage, gas extraction and vegetation support are provided by separate layers.

Question 45Environmental engineering (discipline knowledge)

An anaerobic digester shows rising volatile fatty acids and falling pH. Which action best restores stable digestion?

  1. Raise the temperature sharply above the operating range
  2. Reduce the organic loading rate and allow the methanogens to recover Correct answer.
  3. Stop mixing the digester completely
  4. Increase the feed rate to dilute the acids

Explanation

Accumulated volatile fatty acids with falling pH indicate that acid-forming bacteria are outpacing methanogens, so reducing loading lets the methanogens catch up. Adding feed, stopping mixing or overheating would worsen the imbalance.

Question 46Environmental engineering (discipline knowledge)

A river has a low reaeration capacity. Which in-stream condition most strongly controls the recovery of dissolved oxygen downstream of an effluent discharge?

  1. The chloride concentration of the effluent
  2. The colour of the effluent
  3. The balance between oxygen demand and atmospheric reaeration Correct answer.
  4. The turbidity of the effluent

Explanation

Downstream oxygen recovery depends on the oxygen sag created by demand and the rate at which oxygen is replenished by reaeration. Colour, chloride and turbidity are not the controlling factors for the oxygen balance.

Question 47Environmental engineering (discipline knowledge)

A proposed development will generate construction waste. Which measure at the design stage most directly reduces the quantity sent to landfill?

  1. Extending the construction programme
  2. Using a larger number of subcontractors
  3. Increasing the size of the site hoarding
  4. Designing for standard modular dimensions to minimise off-cuts Correct answer.

Explanation

Designing to standard modular dimensions reduces off-cuts and waste generation at source. Hoarding size, subcontractor numbers and programme length do not directly reduce the quantity of waste material produced.

Question 48Environmental engineering (discipline knowledge)

A regional air quality model predicts that a proposed power plant will raise annual average nitrogen dioxide at a nearby town by 2 micrograms per cubic metre where the existing level is already close to the objective. Which interpretation is most defensible?

  1. A 2 microgram increment is always negligible regardless of the baseline
  2. The increment may cause exceedance of the objective and should be assessed against headroom Correct answer.
  3. The model result should be ignored because annual averages are irrelevant
  4. The plant should be approved because nitrogen dioxide is not a pollutant of concern

Explanation

Where the baseline is near the objective, even a small increment can cause exceedance, so the available headroom must be examined and mitigation considered. Dismissing small increments, ignoring annual averages or denying the pollutant's significance is unsound.

Question 49Environmental engineering (discipline knowledge)

A carbon footprint study compares two sludge disposal routes. Which methodological choice is essential for a fair comparison?

  1. Selecting the route with the lowest capital cost
  2. Ignoring transport emissions for both routes
  3. Reporting only the direct on-site emissions
  4. Using the same system boundary and functional unit for both routes Correct answer.

Explanation

A defensible comparison requires an identical functional unit and consistent system boundaries so that the same services and life-cycle stages are counted for each option. Cost, omission of transport or reporting only direct emissions would bias the comparison.

Question 50Environmental engineering (discipline knowledge)

A noise model predicts a level 1 dB above the relevant criterion at a facade. Which conclusion is most technically sound?

  1. The exceedance proves the development is unacceptable and must be refused
  2. The prediction can be ignored because 1 dB is inaudible
  3. The criterion must be relaxed to accommodate the plant
  4. The predicted exceedance is within model uncertainty and should be examined with measurement and sensitivity checks Correct answer.

Explanation

A 1 dB predicted exceedance is comparable to typical model and measurement uncertainty, so verification by measurement and sensitivity analysis is warranted before a firm conclusion. Automatic refusal, relaxing the criterion or dismissing the result are not technically defensible responses.