Environmental engineering - discipline knowledge
What this domain tests
The Environmental Discipline paper assumes you can move in both directions between the Hong Kong statutory framework and engineering numbers: name the instrument that governs a discharge or an impact, then compute whether it complies. Questions usually start from a real activity - a piling site, a sewage discharge, a stack, a landfill - and expect both the legal hook and the arithmetic.
The statutory spine
- EIA Ordinance (Cap. 499) and its Technical Memorandum on EIA Process (TM-EIAO): designated projects need an approved EIA report and an environmental permit before construction and operation. The TM sets the technical content and assessment criteria for air, noise, water, waste, ecology, landscape and hazard, including cumulative impacts.
- Air Pollution Control Ordinance (Cap. 311): Air Quality Objectives for ambient air, and licences for specified processes.
- Water Pollution Control Ordinance (Cap. 358): discharge licences whose conditions derive from the TM on standards for effluents into drainage and sewerage systems, inland and coastal waters.
- Noise Control Ordinance (Cap. 400): construction noise permits, Acceptable Noise Levels for non-percussive work, and separate control of percussive piling.
- Waste Disposal Ordinance (Cap. 354): waste disposal licences and chemical waste producer registration; dredged spoil goes to sea only under the Dumping at Sea Ordinance (Cap. 466).
Numbers you are expected to handle
- Free-field point source: about 6 dB(A) loss per doubling of distance, i.e. 20 log(r2/r1).
- Logarithmic addition: 90 + 90 dB(A) = 93 dB(A), never 180.
- Loading, dilution and mass balance before any comparison with a standard.
Worked example
A factory discharges 50 m3/d of treated effluent at 100 mg/L BOD5 into a stream carrying 500 m3/d at 2 mg/L BOD5, fully mixed. Mixed concentration = (100×50 + 2×500) ÷ 550 = 6,000 ÷ 550 ≈ 10.9 mg/L. If the WPCO licence condition for that discharge is 20 mg/L BOD5, it complies with roughly a factor of two in hand. But the BOD load added to the stream is 5 kg/d, so any later increase in flow must be checked as a load, not only as a concentration.
Traps that cost marks
- Confusing the NCO, which controls when work may happen, with the TM-EIAO, which assesses predicted impact.
- Treating an AQO or a noise criterion as an emission limit; they are ambient or receiver criteria.
- Quoting a standard without naming the receiving water body, the flow band, or the licence condition that fixes it.
- Ignoring that an environmental permit condition, not the EIA report, is the enforceable document at construction stage.