A generating station takes once-through cooling water from a lake, passes it through its condensers and returns it to the lake. Which environmental impact arises at the intake rather than at the discharge?

Fish and larvae trapped on screens or drawn through the condensers

Warmer lake water around the outfall, changing which species thrive

Algae growth stimulated by the warmed water near the outfall

Traces of the biocide used to keep the condenser tubes clean

Methane escaping from leaking valves and seals at a gas plant is counted as a serious greenhouse-gas emission, even though far less methane than CO₂ is released, because

a kilogram of methane traps far more heat than a kilogram of CO₂

methane breaks down the protective ozone layer in the stratosphere

methane stays in the atmosphere for far longer than CO₂ does

methane dissolves in rain to form acids that damage lakes and soils

A plant is building a new disposal cell for its fly ash and bottom ash. Which design feature mainly protects the groundwater beneath the site?

A low-permeability liner with a leachate collection system

Groundwater monitoring wells around the edge of the cell

Water sprays that keep the ash damp while it is being placed

Compacting the ash in thin layers as it is placed

A boiler stack's continuous emission monitor is set to alarm in the control room when NOx reaches 80 % of the limit in the plant's operating permit. Why is the alarm set below the permit limit?

To give operators time to correct the cause before the limit is exceeded

To notify the regulator automatically that an exceedance is about to occur

To shut the burner down automatically before the permit limit is reached

To mark the reading at which the plant must file an exceedance report

Mercury in the coal burned at a generating station goes up the stack as a vapour and later settles into lakes downwind. Once in the lakes, the mercury is a serious concern because it

builds up in fish as it moves up the food chain

makes the water acidic, as sulphur dioxide does

feeds a heavy growth of algae that uses up oxygen

sinks into the sediment and stays locked away there

4th Class Environment & Emissions Practice Questions (4A)

Five free practice questions on environment and plant emissions: unit E of paper A (4A) of the 4th Class Power Engineer certificate exam, written to the SOPEEC syllabus. They are in the exam's format: four options, one correct answer. Answer each one before opening the explanation. No account, no email.

01The questions

Procedural · List the types of impacts that operating facilities can have on the environment

A generating station takes once-through cooling water from a lake, passes it through its condensers and returns it to the lake. Which environmental impact arises at the intake rather than at the discharge?
1. Fish and larvae trapped on screens or drawn through the condensers
2. Warmer lake water around the outfall, changing which species thrive
3. Algae growth stimulated by the warmed water near the outfall
4. Traces of the biocide used to keep the condenser tubes clean
Show the answer

A. Correct. The intake pulls in the water and what lives in it: larger fish are pinned against the intake screens (impingement) and eggs, larvae and plankton pass through the pumps and hot condenser tubes (entrainment). Screen design and a low intake velocity reduce it.

Why not the others

B. Warming happens where the heated water is returned, so it is a discharge impact (thermal pollution). At the intake the harm is to organisms drawn in with the water.

C. Any growth spurred by warmth occurs where the heated water is returned, so it is a discharge impact. The intake impact is the trapping and entrainment of fish and small organisms.

D. Biocide residue leaves with the cooling water at the outfall, so it is a discharge impact. The intake harms organisms by drawing them onto the screens or through the system.
Recall · Identify the common greenhouse and acid rain causing gases and describe their effects

Methane escaping from leaking valves and seals at a gas plant is counted as a serious greenhouse-gas emission, even though far less methane than CO₂ is released, because
1. methane breaks down the protective ozone layer in the stratosphere
2. methane stays in the atmosphere for far longer than CO₂ does
3. a kilogram of methane traps far more heat than a kilogram of CO₂
4. methane dissolves in rain to form acids that damage lakes and soils
Show the answer

C. Correct. Methane absorbs infrared radiation much more strongly than CO₂, so kilogram for kilogram it has a far greater warming effect over the years it stays in the air. A small leak can matter as much as a large CO₂ stream, which is why leak detection and repair is part of controlling greenhouse gases.

Why not the others

A. Ozone-layer damage comes from chlorine- and bromine-containing gases such as chlorofluorocarbons and halons. Methane is a concern because it is a strong greenhouse gas.

B. It is the reverse: methane breaks down in the atmosphere within roughly a decade, while much of the CO₂ released stays for centuries. Methane matters because each kilogram traps far more heat.

D. Methane is only slightly soluble in water and forms no acid. The acid-rain gases are sulphur dioxide and nitrogen oxides; methane matters as a strong greenhouse gas.
Procedural · Describe the disposal methods of solid waste from energy plants

A plant is building a new disposal cell for its fly ash and bottom ash. Which design feature mainly protects the groundwater beneath the site?
1. Groundwater monitoring wells around the edge of the cell
2. A low-permeability liner with a leachate collection system
3. Water sprays that keep the ash damp while it is being placed
4. Compacting the ash in thin layers as it is placed
Show the answer

B. Correct. Rain and snowmelt passing through ash dissolve metals and salts, forming leachate. A clay or synthetic liner stops it moving down, and collection pipes on the liner carry it off for treatment, so it does not reach the groundwater.

Why not the others

A. Monitoring wells detect contamination once it is in the groundwater; they check that the liner works but prevent nothing themselves. The liner and leachate collection protect the groundwater.

C. Damping the ash controls windblown dust, an air-quality measure. It adds water rather than keeping it out of the ash; the liner and leachate collection protect the groundwater.

D. Compaction makes the fill stable and saves space, but water still works its way through the ash. The liner with leachate collection is what keeps the leachate out of the groundwater.
Recall · Describe the alert processes related to environmental problems of plants

A boiler stack's continuous emission monitor is set to alarm in the control room when NOx reaches 80 % of the limit in the plant's operating permit. Why is the alarm set below the permit limit?
1. To notify the regulator automatically that an exceedance is about to occur
2. To give operators time to correct the cause before the limit is exceeded
3. To shut the burner down automatically before the permit limit is reached
4. To mark the reading at which the plant must file an exceedance report
Show the answer

B. Correct. An early alarm is the plant's first alert step: it tells the shift that emissions are trending up while there is still margin, so the cause (air-fuel ratio, flue gas recirculation, firing rate) can be found and corrected before a permit exceedance occurs.

Why not the others

A. The alarm is internal: it alerts the people who can act on the boiler. A reading at 80 % of the limit is inside the permit, so there is no exceedance to tell the regulator about.

C. An alarm alerts; it does not trip the burner. Shutting down at every pre-alarm would cut steam to the load for a reading that is still inside the permit. The point is to warn operators early.

D. A reading at 80 % of the limit complies with the permit, so it is not an exceedance to report. The pre-alarm exists to warn the operators while they can still act.
Recall · Identify the sources and effects of common gases and vapours that have an adverse environmental impact

Mercury in the coal burned at a generating station goes up the stack as a vapour and later settles into lakes downwind. Once in the lakes, the mercury is a serious concern because it
1. makes the water acidic, as sulphur dioxide does
2. builds up in fish as it moves up the food chain
3. feeds a heavy growth of algae that uses up oxygen
4. sinks into the sediment and stays locked away there
Show the answer

B. Correct. Bacteria in lake sediments and water convert deposited mercury to methylmercury, which fish take up mainly from what they eat. Each step up the food chain concentrates it further, so large fish-eating fish carry the most, and the people and wildlife that eat them are exposed.

Why not the others

A. Mercury is a toxic metal, not an acid-forming gas; acid deposition comes from sulphur dioxide and nitrogen oxides. Mercury's harm is that it builds up in fish through the food chain.

C. Algae blooms are fed by nutrients such as phosphorus and nitrogen. Mercury is not a nutrient; its harm is that it builds up in fish as it passes up the food chain.

D. Much of the mercury does reach the sediment, but it does not stay locked away: bacteria there convert it to methylmercury, which enters the food chain and builds up in fish.

02Answer key

Question	Answer	Learning outcome
Q1	A	List the types of impacts that operating facilities can have on the environment
Q2	C	Identify the common greenhouse and acid rain causing gases and describe their effects
Q3	B	Describe the disposal methods of solid waste from energy plants
Q4	B	Describe the alert processes related to environmental problems of plants
Q5	B	Identify the sources and effects of common gases and vapours that have an adverse environmental impact

03What unit E covers

How a plant affects the environment around it: the carbon and nitrogen cycles, ecosystems and food webs, alert processes and operator attitude, effects that last after a plant closes, smog, greenhouse gases and acid rain, NOx and SO2 control, noise, fly ash and fine particulates, electrostatic precipitators and baghouses, ash disposal, thermal pollution, spill containment and liquid waste.

The SOPEEC 4th Class syllabus names this unit “Environment” (ABSA numbers it A5) and lists three objectives under it. SOPEEC does not publish how many exam questions come from each unit, and neither do the ABSA, Technical Safety BC, TSASK or TSSA pages we checked. The right-hand column is how many questions our bank holds on each objective, Standard and Advanced together, not a count from the exam.

Syllabus objective	In our bank
E-21 Explain how the environment is related to the operating plant.	11
E-22 Explain how gas and noise emissions affect plant operation.	9
E-23 Explain how liquid and solid emissions affect plant operation.	10

04What the questions turn on

Lower the flame temperature for NOx

Most NOx from a gas flame is thermal NOx, formed when nitrogen and oxygen from the air combine at high flame temperature. Recirculating cooled flue gas into the combustion air lowers the peak flame temperature and so the NOx formed.

Work SO2 from the fuel sulphur

Sulphur burned to SO2 doubles in mass, since 32 kg of sulphur and 32 kg of oxygen give 64 kg of SO2. Apply the scrubber's removal percentage to that total to find what it captures and what leaves the stack.

Sound levels add by energy

Decibels are on a logarithmic scale, so two identical sources do not double the reading. Each doubling of identical sources adds 3 dB: two fans giving 87 dBA each give 90 dBA together.

Read the collector from the monitors

An opacity monitor measures how much of a light beam across the stack the particles stop. Rising opacity with steady O2 and CO points to the collector, and a drop in baghouse differential pressure points to a torn or loose bag.

05The other units

Paper 4A has twelve units, A to L. Each has its own page of free questions:

The 4th Class Power Engineering practice exam (4A) page describes the full question bank. How these questions are written and checked: how our questions are made. Found a mistake? Tell us and we will fix it.