Behaviour of a nitrifying and denitrifying submerged filters in the treatment of urban wastewater

The system studied consists of two submerged filters, the first one working in anoxic conditions keeps denitrifying activity using inlet wastewater as carbon source, the second one works in aerobically oxidizing organic nitrogen and ammonia to nitrate. Biofilm microbial community have been characterized by enumeration of heterotrophic bacteria, persistence of indicators of fecal pollution and nitrifying and denitrifying population. As it has been expected, the bacteria attached and the exopolymers synthesized was higher in the denitrifying bioreactor (anoxic column) than in the nitrifying one (oxic column). The amount of exopolymers extracted was 5mg/g in denitrifying biofilm and less than 1mg/g in nitrifying. The biopolymer was composed of 52% of carbohydrates and 36% of proteins. Efficiency of biorreactors was evaluated by measuring the following parameters: suspended solid, organic matter, nitrogen and pathogens (indicators of fecal pollution). The mean values obtained were 86% of suspended solid removed, 85% of organic matter, 97% of fecal enterococci, 93.3% of fecal coliforms and 79.5% of phages. Otherwise, denitrifying yield reached more than 80% of removal and nitrifying activity was 90%.