ADVANCED TREATMENT AND RE-USE OF HIGH STRENGTH INDUSTRIAL WASTEWATER

High strength (COD = 3,000 − 11,000 mg/l) wastewater (0.3 MGD) from a combined pharmaceutical/dairy products manufacturing site in Singapore is treated using biological treatment (Sequencing Batch Reactors), and chemical oxidation/disinfection using ozone, then is re-used as make-up water in the plant cooling towers. The Treatment System was designed during 1999-2000 and commissioned during the summer of 2001. The treatment process produces a near drinking water quality effluent, reduces water consumption, wastewater disposal and site operating costs.Down-flow continuously back-washed sandfilters are used to remove suspended solids (TSS) upstream of the ozone system. In addition to disinfection, the ozone is also used to reduce the biological oxygen demand (BOD)/chemical oxygen demand (COD). The BOD and COD reduction is required to minimize biological activity and scaling in the cooling towers, and to reduce the COD in the cooling tower blowdown. The biological and tertiary treatment system has proven to be capable of treating high strength loads of up to 11,000 mg/l COD having wide variations in both flow and concentration.This paper presents a summary of: (1) the Basis for Design; (2) Key Design Features with focus on some of the challenging design issues (e.g. high temperature wastewater) and new technology (e.g. Ozone for effluent polishing); (3) Operations Out-Sourcing; (4) Commissioning and Startup Issues; (5) Summary of the First Six Months Operating and Performance Data and (6) Conclusions and Retrospective.