Use of non woven textile in intermittent filters

Abstract

Intermittent filters are widely used in North America for on-site wastewater treatment However, availability or transportation of the treatment medium can become a limiting factor. The use of non-woven textile coupons, a light, and compressible material, to replace the sand or gravel has been tested. Test columns containing textile coupons over a height of 90 cm were operated at hydraulic loading rates (HLR) of 20 to 60cm/d, with or without recirculation. During the eighteen months test period, the two most efficient columns, single pass (HLR = 20 cm/d) and recirculating (HLR = 60 cm/d), met treatment goals of 10 mg/l biological oxygen demand (BOD5) and total suspended solids (TSS). Detailed analysis of water quality at different depths and HLRs indicated that water detention time in the coupons might be a factor in organic matter removal. A new filter configuration was then developed to take advantage of this feature; it comprised three hydraulically independent layers of coupons. The new column was tested in the recirculating mode and in the single pass mode at HLRs of 123 and 188 cm/d respectively for six months. In both cases, BOD5 values at the effluent were below 10 mg/l; in the recirculation mode, TSS values were below 15 mg/l.