Sand filters and biofilters can effectively treat wastewater — even in areas with poor soils JANUARY JLC 1997 Around a quarter of America's homes have an on-site sewage disposal system, usually consisting of a septic tank and leach field. On-site septic systems are popular because they cost much less than connecting to a sewer line, especially in spread-out suburban or rural areas. But on many sites, the classic septic tank and leach field system won't work because the soils aren't suitable for adequately treating septic effluent. In soils that drain too slowly, septic systems can fail by causing effluent to pond on the surface or even to back up into the house (an "operational failure"). In soils that drain too fast, or
