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Septage, the solids accumulated in septic tanks, has traditionally been applied to agricultural land without treatment in Ontario (Canada). New regulations will treat septage as a biosolids with strict pathogen, metal and nutrient limits to land application. Reed bed filters provide a promising alternative to treat septage. Two pilot reed bed filters and one pilot sand drying bed were constructed in the fall of 2006 in Eastern Ontario. The pilot filters have been studied extensively over a 5 year period with solid loading rates (38-157 kg TS/m2/yr) and hydraulic loading rates (1.9-6.4 m/yr) varied along with filter dose/rest period. The effect of plants (phragmites) on filter performance was also investigated. The system operates year round with the filters acting as sludge freezing beds during the winter months. Solids are accumulating in the beds at 20-25 cm/year, with percent solids increased from 2.6 percent in raw septage to 23.0 percent in the dewatered septage. The dewatered sludge meets both metals and E.coli criteria for land application. Exceptional filtrate quality is consistently observed with removal rates of 99 percent for BOD5, TSS and TP and removal rates of 95% for TKN-N. Effluent water quality is comparable to a low strength domestic wastewater which can be easily be treated by any conventional municipal or onsite wastewater treatment system. Reed bed filters are a passive low cost technology which can effectively treat septage under cold climatic conditions. Reed beds are particularly applicable to rural communities were the stabilized sludge can be applied to agricultural land.
reed bed, septage, biosolids