Industrial wastewater discharge is governed by increasingly stringent regulations worldwide. In Egypt, Law 48/1982 and its amendments set effluent limits for discharge to public waterways, while Law 93/1962 covers discharge to public sewers. Similar frameworks exist across the Gulf (MEWA standards in Saudi Arabia, Abu Dhabi EAD regulations) and internationally (US EPA NPDES permits, EU Industrial Emissions Directive). Non-compliance carries financial penalties, legal liability, and risk of forced shutdown.
The most commonly regulated parameters for industrial discharge are: pH (typically 6.0–9.0), total suspended solids (TSS < 50–100 mg/L), chemical oxygen demand (COD < 100–500 mg/L depending on receiving body), biochemical oxygen demand (BOD₅ < 30–60 mg/L), oil and grease (< 10–20 mg/L), heavy metals (varies by metal — typically < 0.5–2.0 mg/L), and specific pollutants relevant to the industry.
Chemical treatment is the most cost-effective first step for most industrial effluents. A typical physico-chemical treatment train consists of: pH adjustment using NaOH or H₂SO₄, rapid mixing with a coagulant (ferric chloride or PAC), slow mixing with an anionic polymer flocculant, clarification by sedimentation or dissolved air flotation (DAF), and final pH adjustment before discharge. This sequence can achieve 80–95% removal of TSS, 60–80% COD removal, and near-complete removal of phosphorus and heavy metals.
For facilities with high organic loading (food processing, pharmaceutical, textile dyeing), biological treatment may be needed after chemical treatment to meet BOD and COD limits. However, chemical pre-treatment is still essential to remove toxic compounds that would inhibit biological activity. Monitoring and record-keeping are equally important — continuous pH monitoring, daily composite sampling, and quarterly lab analysis are typical requirements.