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|Title:||Investigation of Optimum Operating Conditions for Recirculating Sand Filters|
|Keywords:||operating conditions;sand filter;recirculating;septic system|
|Abstract:||<p> Recirculating Sand Filters (RSFs) provide a compact method of secondary treatment to septic systems and lagoons, are relatively easy to operate and require little maintenance. Together, these characteristics render RSFs particularly appropriate for small communities and municipalities, as they offer a number of economic and operational advantages over conventional technologies. A preliminary study investigating RSF effluent quality, conducted jointly by McMaster University, the Great Lakes Sustainability Fund (GLSF) and the Ontario Ministry of the Environment (MOE) in 1999-2001, conducted pilot-scale experiments and demonstrated that municipal sewage can be successfully treated year-round by RSFs. The results of the preliminary study recommended that further work be conducted to investigate the selection of media size, dosing frequency, recycle ratio, and hydraulic loading rate. </p> <p> The primary objective of this study was to develop design and operating conditions under Ontario climatic conditions with respect to media size, dosing frequency, recycle ratio and hydraulic loading rate by conducting further pilot-scale studies. Three pilot-scale RSFs, operating in parallel, were loaded intermittently with septic tank effluent to evaluate the above mentioned operating parameters on the removal of total suspended solids (TSS), 5-day carbonaceous biochemical oxygen demand (cBOD5), total ammonia-nitrogen (TAN) and total nitrogen (TN). The addition of alum was also implemented to evaluate the removal of total phosphorus (TP). The effluent objectives for this study were based on the MOE general secondary treatment level requirements of monthly averages based on a minimum of four weekly samples. The four-phase experimental program began in April, 2004 and ended in June, 2005. Three media sizes were investigated, with d10 of 2.6, 5 and 7.7 ·mm. The applied hydraulic loading rates were 0.2 and 0.4 rnlday. Dosing frequencies of 24 and 48 times/day were observed. Recycle ratios of 300% and 500% were also evaluated. </p> <p> It was found that the RSF operating with 2.6 mm media, 500% recycle ratio and 24 times/day dosing frequency under a hydraulic loading rate of 0.2 rnlday produced the best quality effluent, and achieved the effluent objectives required by the MOE. These operating criteria, however, must still be investigated under cold weather conditions to ensure acceptable year-round performance in Ontario. With proper addition of alum, the TP effluent objective was achieved under the optimum operating conditions. </p>|
|Appears in Collections:||Digitized Open Access Dissertations and Theses|
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