Chemical wastewater treatment: A concept for optimal dosing of coagulants

Abstract

A concept for optimisation of the coagulant dosing for domestic wastewater treatment is presented and evaluated. The concept is based on the real-time estimation of the optimal coagulant dosage using on on-line water quality measurements of the raw water. A preliminary project was established in 1992 and was completed in 1993. Laboratory- and pilot scale evaluation of the concept was followed. Finally, a consortium between NIVA, ANØ (Avløpssambandet Nordre Øyeren) and Alfa Laval Automation (earlier Satt Control AS) implemented full scale tests at a small scale treatment plant (Bårlidalen WWTP, Eidsvoll) and a large/medium scale treatment plant (TAU WWTP, Tønsberg). A dosing concept based only on one or two influent parameters like flow and turbidity are not efficient, although they could be intersting for small WWTPs. At Bårlidalen WWTP, such a concept could save over 8% of the chemical costs. Dosing concepts based on more influent parameters enabling a comprehensive description of the influent are needed for larger WWTP. At small treatment plants such a system demonstrated savings up to 25% on chemical costs, while over 4-10% saving at larger WWTP are expected.