Adsorption and survival of faecal coliforms, somatic coliphages and F-specific RNA phages in soil irrigated with wastewater

This study was carried out to compare the adsorption and survival of faecal coliforms, somatic coliphages and F-specific RNA phages in soil irrigated with wastewater. Adsorption isotherms showed that 3-10x more faecal colifor ms than somatic coliphages were adsorbed from wastewater onto soil. The ads orption behavior of F-specific RNA phages was intermediate between those of these two microorganisms. In wastewater, the inactivation factor of somati c coliphages at 8-22 degreesC was 5-7 lower than those of faecal coliforms. F-specific RNA phages have a decrease close to faecal coliforms. In soil, at temperatures of 8-22 degreesC and at moistures of 15-35%, somatic coliph ages survived longer than the two other microorganisms. These results seeme d to be confirmed by the soil column experiments. The rate of inactivation of all microorganisms was lower in soil than in wastewater and depended ext ensively on soil temperature and moisture content. Survival was optimal at low temperature (8 degreesC) and low moisture content (15%). Thus, somatic coliphages seemed to be a better indicator of faecal contamination than fae cal coliforms under our experimental conditions and based only on the two c riteria tested (survival and adsorption). Somatic coliphages were able to c ontaminate the soil over greater distances and survive better in both waste water and soil than faecal coliforms. These results need to be confirmed by studies on several soil columns using different kinds of soil and differen t kinds of wastewater.