CHARACTERIZATION OF NOVA-SCOTIA SURFACE WATERS AND TREATMENT OPTIONS FOR REMOVAL OF COLOR AND TRIHALOMETHANE PRECURSORS

This paper provides an overview of the results of a study undertaken t o provide a basis for predesign evaluation of the effectiveness of opt ions for treatment of municipal surface waters in the province of Nova Scotia. Seasonal samples of raw water were obtained from the fall of 1992 through the fall of 1993 from five sites. Results were compared w ith a Nova Scotia Department of Health data base of randomly collected samples. For project samples, strong relationships were evident betwe en raw water total organic carbon (TOC) and both colour and trihalomet hane formation potential. Laboratory batch tests, supported by plant r esults, indicated that percentage removals of TOC increase with raw wa ter TOC, and that settling-filtration was more effective than direct f iltration for waters with higher raw TOC concentrations. Results of so lids sealing tests were consistent with TOC results. A treatment optim ized for TOC removal also ensured removal of colour. TOC removals by d issolved air flotation followed by filtration exceeded removals by dir ect filtration or settling-filtration, based an laboratory bench tests , particularly at sites with higher values of raw TOC. Colour removal by dissolved air flotation was consistently higher at all sites.