Effluent Guidelines
Technology-based effluent limits for specific categories, established by EPA in 40 CFR Parts 405–471, set the minimum treatment standard for those industries.
Effluent guidelines are based on what treatment technology can achieve, not on what a specific receiving water requires — they set a technology floor, not a water quality floor.
40 CFR Part 133 (Secondary Treatment Regulations) specifies the technology-based limits most POTWs must meet (BOD 30 mg/L monthly average, TSS 30 mg/L monthly average, pH 6–9).
Water quality-based effluent limits can be tighter than the technology floor whenever the receiving water quality requires it.
Effluent guidelines evolve over time; proposed revisions to existing guidelines or new guidelines for an industry typically open multi-year public processes — comments from POTWs receiving those industries' discharges can shape the final rule.
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