USE OF NON WOVEN TEXTILE IN INTERMITTENT FILTERS

Intermittent filters are widely used in North America for on-site wast ewater treatment. However, availability or transportation of the treat ment medium can become a limiting factor. The use of non-woven textile coupons, a light, and compressible material, to replace the sand or g ravel has been tested. Test columns containing textile coupons over a height of 90 cm were operated at hydraulic loading rates (HLR) of 20 t o 60 cm/d, with or without recirculation. During the eighteen months t est 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 bi ological oxygen demand (BOD5) and total suspended solids (TSS). Detail ed analysis of water quality at different depths and HLRs indicated th at water detention time in the coupons might be a factor in organic ma tter removal. A new filter configuration was then developed to take ad vantage 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.