Reducing waste strength (the mass of pollutant, e.g. BOD/COD, per unit of production or per litre) means intervening before the pollutant is lost to the wastewater at all, rather than simply diluting it with more water. Five recognized strategies are:
Good housekeeping / dry clean-up. Use dry methods (squeegees, brooms, vacuum recovery) to remove spilled product and residue before washdown, so that spilled material is disposed of as solid waste rather than dissolved into the wash water.
Source segregation of concentrated streams. Keep small, high-strength streams (e.g. a batch dump or a concentrated rinse) separate from large dilute streams so the concentrated fraction can be recovered or treated at high strength instead of averaging its load across the whole plant flow.
In-process material recovery and reuse. Recover and recycle process chemicals or product losses (e.g. countercurrent rinsing that recovers drag-out, or recovery of a solvent for reuse) before they reach the wastewater stream at all.
Raw material and process substitution. Replace a high-BOD/COD or toxic raw material with a lower-impact substitute, or modify the process to generate less waste per unit of product.
Equipment modification to prevent leaks and drips. Improve seals, gaskets, drip trays and containment around process equipment to prevent continuous low-level material loss to the floor drain, which over time is a significant contributor to waste strength.
