Question 2 of 7: Environmental Ethics and Water/Wastewater Treatment Design Principles

Question 2: Environmental Ethics and Water/Wastewater Treatment Design Principles (20 marks)

Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.

(i) Ethical Obligations of an Engineer Retained by the Disinfectant Supplier

Although the engineer's contract runs to the disinfectant supplier, principle (a) — holding paramount the health, safety and welfare of the public — overrides the ordinary duty of loyalty to a paying client whenever the two conflict. The engineer's first obligation is therefore to document the finding rigorously: quantify the mixing deficiency (e.g., short-circuiting past the intended contact time, uneven dispersion of disinfectant into the flow) and estimate its effect on disinfectant dose and resulting trihalomethane (THM) formation, distinguishing this technical finding from the bacteriological compliance result the supplier is expecting to hear.

Next, principle (c) requires the engineer to report the finding — in writing, promptly, and to both parties named in the contract's scope (the supplier and the municipality), not just the party that hired him — together with a clear recommendation for corrective action (baffling or mixer modifications to eliminate the overdosing while still meeting the bacteriological CT requirement, and interim monitoring of THM levels in the distribution system). Because THMs are a public-health hazard governed by the Guidelines for Canadian Drinking Water Quality, this is not a discretionary courtesy notice; it is the engineer's professional duty regardless of whether the supplier would prefer the finding stayed quiet.

If the supplier and/or municipality fail to act within a reasonable time and the elevated THM risk to public health remains unresolved, the final sentence of principle (c) becomes operative: the engineer may — and, given the magnitude of a known-carcinogen exposure, arguably should — escalate beyond the two contracting parties, first to the relevant drinking-water regulator (the provincial drinking-water authority and/or EGBC) and, only if the risk still remains unaddressed, make the concern known publicly. This sequence (document → report to both parties with a remedy → escalate to the regulator → disclose publicly only as a last resort) keeps the engineer's paramount duty to the public intact while respecting professional channels before public disclosure.

(ii) Four Key Design Principles for a Drinking-Water Treatment Facility

Choosing a drinking-water treatment facility, four design principles govern a sound facility, blending technical and non-technical (institutional, social and economic) considerations:

1. Multi-barrier treatment (technical). No single unit process is relied upon to remove every class of contaminant; source-water protection, coagulation/flocculation/sedimentation, filtration and disinfection are layered so that the failure of any one barrier does not compromise finished-water safety — the backbone principle behind the Guidelines for Canadian Drinking Water Quality.
2. Reliability and redundancy (technical). Duty/standby equipment (pumps, filters, disinfection trains), backup power, and online water-quality monitoring with automatic process control ensure the plant continues to meet health-based standards through equipment failure, power outages or a sudden raw-water quality upset.
3. Appropriate technology matched to community capacity (non-technical). The selected process train must be operable and maintainable by the local operating authority long-term — a technically "optimal" but operationally complex plant that a small municipality cannot staff, fund or supply spare parts for is a design failure; affordability (capital and lifecycle O&M cost relative to the community's rate base) is itself a design constraint.
4. Public health protection, regulatory compliance and community engagement (non-technical). The design must be validated against the applicable provincial drinking-water regulation and the Guidelines for Canadian Drinking Water Quality, include a monitoring/reporting program the operating authority can sustain, and reflect consultation with the served community (including, where relevant, Indigenous communities relying on the same source water) on siting, cost recovery and service-level expectations.