On Site High Rate UASB Anaerobic Demonstration Plant Treatment of NSSC Wastewater

Abstract

Results of a 19 m3 demonstration plant studies are summarized. The plant is located at Sturgeon Falls at a NSSC mill and hardboard plant owned by MacMillan Bloedel. The mill discharges 6300 m3/day of waste effluent containing 50 tonnes of BOD and 127 tonnes of COD. Lab scale testing (1983) and an 18 month 1.4 m3 reactor volume pilot plant study (1985) were completed confirming treatability of the wastewater and suitability of the Upflow Anaerobic Sludge Blanket (UASB) technology among others to successfully treat the mill wastewater. Discharged effluent contains spent sulphite liquor and primary clarifier effluent. As required, the 1.4 m3 Biopaq System successfully achieved BOD reductions in excess of 75 percent at loadings greater than 10 kg COD/m3.d. As a consequence of this and because of economic considerations, the Biopaq System of Paques-Lavalin was selected for on site demonstration during a 12 months period. This period started in spring 1986. Erection of a full-scale plant is planned to take place in 1988. The purpose of the on site demonstration study is to confirm wastewater treatability, optimize design loading rates and confirm granular sludge growth. To achieve the objectives and simulate full-scale operating conditions the MacMillan Bloedel pilot plant has been automated and is controlled via a microprocessor incorporating a customized software program. Start-up performance results and operation at incremental loadings under steady state conditions are presented together with the experience gained during extreme variations in mill effluent quality and flow. Preliminary study results from the first 10 months disclose that a BOD removal efficiency of 80 percent or better is achieved at weekly average loadings of 15 kg COD/m3.d, and the process offers strong resilience to daily swings in wastewater quality. The results also show a net accumulation of granular sludge. The practical application of this technology from a mill operating perspective is discussed, and the layout for a full-scale installation with projected capital and operating costs is provided. Most of the contents of this paper was presented at the Tappi 1987 Environmental Conference (Prong etal, 1987). This paper presents the latest results.