Evaluation of Effects of Municipal Sludge Leachates on Water Quality

Abstract

Biosolids made from municipal sludge are an attractive solution instead of chemical fertilization. Nevertheless, their effects on the ecosystem should always be considered. In the present study, anaerobically digested sludge was subjected to two leaching methods (EN 12457-2 and NEN 7341) and the main physicochemical parameters were measured in the leachates. The aquatic organisms Daphnia magna and Vibrio fischeri were exposed to the leachates in order to test for adverse effects. Mixtures of biosolid/solid, simulating the high dose of 80 tn/ha, were also created, and the same parameters were measured for EN 12457-2 leachates. The results show a strong seasonal variation for the results for the municipal sludge, even though the sludge did not originate from a touristic area. The biosolid/solid mixtures did not produce toxic responses to the organism tested. Nevertheless, the parameters nitrites and nitrates in the leachates were increased in relation to control and they continued to increase even at Day 40 post-application. This increase was soil-type-dependent. The biosolids in question could be used for field fertilization, however measures should be taken against underground water nitrate pollution.