SU0005060 SSNL - Laserfiche WebLink

Home Browse Search

• Land area—The land area needed is significantly smaller than that for sand filters because loading rates are 5 to 20 times higher(typically, 15 –25 gpd/ft2 based on residential effluent quality as describe above in Table 1). Textile filters for single- family homes typically require a land area between 20 and 40 square feet. • Media quality and availability—The manufactured textile medium ensures consistent quality and availability. • Installation quality—Lightweight textile medium(4.5 lb/ft) and small filter size make pre-manufactured treatment units practical, eliminating onsite construction and reducing installation time, labor, and construction errors. This quality makes these systems ideal for cost saving self-help programs. The textile medium—typically in the form of small chips or"coupons"—has a complex fiber structure which offers an extremely large surface area(>5000 ft2/ft) for biomass attachment. The textile porosity typically exceeds 90 percent,providing high hydraulic conductivity and excellent air movement through the medium. In terms of treatment, a key factor is the water-holding capacity of the textile medium. For the textile medium in current use, it is about 30 percent. It has been shown that treatment in the textile filter is related to retention time of the wastewater within the textile medium and to the overall filter height. Water retention within the textile filter is due mostly to capillary effects in the micropores within the structure of the textile medium. In laboratory column experiments, loading rates as high as 45 gal./ft2/day were used with filter depths as shallow as 12 inches (Roy, 1998). The commercially available filter units are designed with a filter depth of about 18 inches and loading rates from 10 to 25 gal./W/day, depending on the waste strength and system configuration. Just as with sand filters,effluent quality from textile filters is enhanced by relatively small, frequent doses. In more than 10 years of research with textile media, several design variations have been tested in both intermittent and recirculating modes. Today all commercial installations are operating as recirculating filters. In its current configuration, the textile filter has been installed at more than 50 sites across the U.S., including single family homes, commercial sites, and community systems. Because of the relatively high biological loading on the textile filter, a ventilation fan is used to provide oxygen on most systems. This fan—not blower—requires less than 20 watts of power for a residential filter and costs less than 75 cents per month to operate in most regions of the country. The porous nature of the textile medium allows the ventilation fan to circulate air through the filter with very little back-pressure. Figure 3 shows a perspective view of this filter system. NTP-FLT-TRB-ES8-HLB-3 Page 5