SEPTIC TANK VIRUS REMOVAL BY SAND FILTRATION (ONSITE TREATMENT, WASTEWATER, ENTEROVIRUS)

Sand Columns built of ten inches of coarse filter sand, four inches of fine filter sand, and ten inches of glass sand were evaluated for their ability and mechanism of enterovirus removal from household septic tank effluent. Four columns received septic tank effluent without viruses for three months followed by approximately two months of applying septic tank effluent containing attenuated poliovirus, Type 1, Strain LSc. The column effluents were assayed for poliovirus, and at the end of the study period each column was dissected and assayed for poliovirus within the column. Three other columns received septic tank effluent containing poliovirus for periods of approximately three weeks, five weeks, and six weeks. These three filters received poliovirus during the entire time they were operated. Again, the filter effluents were assayed for poliovirus, and the columns were discussed and assayed for poliovirus.;Total Organic Carbon analyses showed that the filters required about 3 weeks to become biologically active, reducing the TOC concentration to less than 10 mg/l. Analyses of the dissected columns indicated that most viruses were removed in the top few inches of biologically active sand, and that the viruses were biodegraded in the filter.;The columns retained viruses when concentrations up to 33 million PFU/l were applied. At this concentration, viruses broke through the filters and were detected in the effluent at concentrations ranging from 220 PFU/l to 2700 PFU/l. The hydraulic loading rate was maintained at 1.5 gallons/day. sq. ft. during the entire study. Upon lowering the virus concentration applied to the columns to less than 200,000 PFU/l, no viruses passed through the filters. The columns receiving viruses during their entire operation never passed any viruses into their effluents even though the influent virus concentration ranged from 1600 PFU/l to 5.7 million PFU/l.