Surcharge Assessment is a procedure for recovering costs incurred, while treating high strength waste discharged by industrial and commercial users into the wastewater system. It is an additional charge applied to industries, which discharge industrial waste into the wastewater system that is amenable to treatment by the wastewater system but exceeds the strength of domestic wastewater.  

Surcharges are calculated based on the concentrations of (carbonaceous) biochemical oxygen demand (C/BOD), ammonia and total suspended solids (TSS) in the discharge.