TSS (TSS)

Total Suspended Solids (TSS) is the mass concentration of undissolved particles in water that are retained on a 1.5 µm or finer glass-fibre filter, expressed in mg/L. It is one of the four core wastewater parameters in every Indian SPCB effluent consent (alongside BOD, COD and pH), and it directly indicates the load of fibre, grit, silt, biomass and process particulate the plant is sending to the receiving stream or sewer.

Measurement follows IS 3025 Part 17. A well-mixed effluent sample is filtered through a pre-weighed 47 mm glass-fibre filter (Whatman GF/C or equivalent, nominal 1.2 µm); the filter is dried at 103-105°C to constant weight; the gain in mass divided by sample volume gives TSS. Sister parameters include volatile suspended solids (VSS) — the fraction that combusts at 550°C, indicating organic suspended matter — and settleable solids (Imhoff cone, 1 hour). TSS does not include dissolved salts, which fall under TDS.

Discharge limits under the Environment (Protection) Rules 1986, Schedule VI: TSS ≤100 mg/L for inland surface water and marine discharge, ≤200 mg/L for land disposal/irrigation, ≤600 mg/L to public sewer. Industry-specific limits in the same Schedule range from 50 mg/L (textile dyeing) to 100 mg/L (general industrial). The CPCB's NGT-driven enforcement since 2018 has reduced tolerance for TSS exceedance — most SPCBs now treat repeated exceedance above 150 mg/L as a closure trigger.

For recycling plants, TSS arises principally from PET, PE and PP wash lines (label particles, paper fibre, mud, glass fines at 800-3,000 mg/L raw effluent), tyre shredding and granulation wash (rubber dust, steel wire fines), e-waste washing (PCB granulate fines, plastic dust), and CBG digestate dewatering (undigested fibre). Treatment is staged: screen + grit chamber + equalisation handles coarse solids; primary clarifier or dissolved air flotation (DAF) at 0.8-1.5 m/h surface loading drops TSS by 60-85%; biological aeration + secondary clarifier takes residual TSS to 30-80 mg/L; sand filter or ultra-filtration polishing achieves below 50 mg/L. Each TSS settling stage produces sludge that itself becomes a hazardous-waste disposal cost — typically Rs 8-25 per kg for cement-kiln co-processing.