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This paper presents the results from a pilot study that evaluated two chemically enhanced primary treatment (EPT) technologies for the treatment of wet weather flows at the Gold Bar WWTP. The EPT technologies evaluated were ballasted flocculation and inclined plate settling. EPT in the existing clarifiers was also given limited testing, however that test work is not part of this paper.The pilot study is a continuation of the City's Combined Sewer Overflow (CSO) Control Strategy. That strategy includes the use of EPT followed by the disinfection of CSO received as wet weather flow (WWF) at the Gold Bar Wastewater Treatment Plant (WWTP). Full secondary treatment is provided for the first 420 MLD received at the plant. Enhanced primary treatment is being considered for the next 600 MLD. Based on the results of the pilot study, the City was able to make a rational judgement concerning the most appropriate EPT and disinfection technologies to implement for the treatment of wet weather flows.This pilot test program is unique in that the EPT performance criterion being tested and evaluated is ultraviolet transmissivity (%UVT), in addition to the removal of total suspended solids (TSS). KEYWORDSEnhanced primary treatment (EPT), ballasted flocculation, inclined plate settling, combined sewer overflow (CSO), ultraviolet transmissivity (%UVT), total suspended solids (TSS).

A continuous bench-scale treatability study determined the most desirable design and operating parameters for waste treament of effluent from an integrated Canadian TMP newsprint operation. An initial batch study indicated that the effluent was biologically treatable and provided initial biological kinetic (biokinetic) parameters for this wastewater. This information was used to design the continuous study. Conventional activated sludge treatment of the mill wastewater can produce an effluent which meets the federal regulations for BOD5, suspended solids, and toxicity to D. magna. Predictions using cumulative toxicity units (CTU) indicate that the treated effluent would also be non-toxic to O. mykiss as well. Analyses of ammonia in the treated effluent indicated that un-ionized ammonia concentrations would be non-toxic to rainbow trout. Mass balances incorporating the results of the bench-scale studies and the effect of fibre carry-over from the primary clarifier, defined the full-scale operating conditions selected as: an F/M of 0.35 d−1, HRT of 0.5 days, SRT of 6 days and an MLSS of 4400 mg/L (when no polymer is used at the primary clarifier). These conditions were arrived at by selecting the smallest HRT which still corresponded to an MLSS < 5000 mg/L, an F/M < 0.4 d−1 and an SRT > 5 days. Based on the kinetics for biological treatment of mill effluent, at the maximum mill production, adequate BOD5 removal will still easily be obtained under the above operating conditions, even during cold weather periods. Operational concerns identified by bench-scale testing indicated that a full-scale facility should incorporate an anoxic selector (although the anoxic selector did not show measurable improvement in the bench-scale tests) and micronutrient addition for filamentous bulking control.