Tannery Expansion Without a Consent
A leather-finishing unit near Kasur processes about 25 tonnes of hides per day and discharges roughly 800 cubic metres per day of process wastewater through a single outfall into an unlined agricultural drain. Last month's sampling by the environmental protection agency laboratory recorded pH 10.4, COD 950 mg/L, BOD5 380 mg/L, total suspended solids 620 mg/L, total chromium 4.6 mg/L and sulphide 45 mg/L. The unit holds an operating consent that expires in four months. The owner wants to add a wet-blue processing line that would raise discharge to about 1,250 cubic metres per day, and has told you that a fresh consent will be applied for after the expansion is running, because the expansion is only an internal change. Your firm has been asked to design the effluent treatment plant and to certify the final design as meeting the applicable national environmental quality standards.
1. Set out the regulatory position and the consequences of proceeding as the owner proposes.
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The owner's plan is a sequence that turns an approval problem into an enforcement problem.
- Discharge authority. Under the Pakistan Environmental Protection Act 1997, discharging effluent into a drain or inland water beyond the national environmental quality standards without a consent is prohibited. The existing consent is time-limited and does not cover a changed or enlarged discharge.
- Expansion triggers assessment. A capacity increase of this order is a modification of an existing project, and modifications are treated as new projects for the purposes of initial environmental examination or environmental impact assessment, as listed in the schedules to the Act and the provincial rules. The Punjab Environmental Protection Act 2012 and the provincial agency's regulations govern the consent and the review.
- Sequencing. The assessment and the revised consent must precede construction and commissioning, not follow them. Applying afterwards does not regularise the intervening discharge.
- Consequences. Enforcement can include fines per day of non-compliance, sealing of the outfall or the plant, prosecution of the occupier, and in practice closure of the unit. A retrospective application also invites a refusal that is far more costly than a compliant one.
- The firm's exposure. Designing and certifying a plant for an unconsented discharge makes the consultancy a party to it.
Advice to the client: submit the assessment and the consent application now, in parallel with design, and time commissioning to follow the consent.
2. Propose an appropriate treatment train for this effluent and state what monitoring would demonstrate compliance.
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Design from the pollutants, not from a catalogue.
- Segregation first. Keep chrome-bearing and sulphide-bearing streams separate from the general wash water. This is cheaper than treating a combined stream and is the single biggest determinant of success.
- Sulphide stream. Catalytic or alkaline oxidation of sulphide, with pH control.
- Chrome stream. Reduce hexavalent chromium if present, then alkaline precipitation of trivalent chromium as hydroxide at controlled pH, followed by settlement; the sludge is a hazardous waste requiring authorised disposal.
- Equalisation. A buffered tank of at least a day's flow smooths the shock loads from batch operations, which is essential here given the pH of 10.4.
- Primary treatment. Screening, grit removal, chemical coagulation and flocculation with settling, to bring suspended solids and part of the COD down before biology.
- Secondary treatment. Activated sludge or sequencing batch reactor with nutrient dosing, since tannery effluent is often deficient in phosphorus; followed by secondary clarification.
- Tertiary. Filtration and, if the receiving drain is sensitive, further polishing.
- Monitoring. Flow-proportional composite sampling across a full production cycle, not grab samples; accredited laboratory analysis for pH, COD, BOD5, suspended solids, total chromium, sulphide and oil and grease, at a frequency agreed with the agency; continuous pH and flow recording; and a log of sludge and chemical consumption. Compliance is demonstrated by a sustained series over the consent period, not by a single good result.
3. What is your professional position on certifying the design as meeting the standards before the plant is built and commissioned?
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Distinguish a design certificate from a performance certificate; conflating the two is how consultants end up guaranteeing outcomes they cannot control.
- What you can certify at design stage. That the design is prepared in accordance with the applicable standards, that the design basis is stated, and that on that basis the plant is expected to meet the effluent limits for the stated flow and influent characteristics. Name the design basis explicitly, including the assumed influent and the 1,250 cubic metres per day flow.
- What you cannot certify. That the plant as built actually complies. That requires commissioning, performance testing over an agreed period, and sampling by an accredited laboratory.
- Conditions to state. Compliance depends on segregation of streams, on the plant being operated by trained staff, on chemical dosing and sludge disposal being maintained, and on the influent not exceeding the design assumptions.
- If the client wants a guarantee. Point out that a compliance guarantee belongs in the construction contract with the contractor, backed by performance testing and retention, not in a consultancy certificate.
- If the client wants certification before consent. Decline. Certifying a design for a discharge the agency has not consented is not a technical opinion but participation in a regulatory breach, and it is exactly the kind of statement that the PEC Code of Ethics requires an engineer to refuse.