Potential contribution of water treatment plant (WTP) sludge to river pollution

Abstract

This research aimed to characterize the Water Treatment Plant (WTP) sludge from a tropical coastal city in the Brazilian northeast. Parameters physical-chemical (color, pH, turbidity, total and sedimentable solids, chemical oxygen demand and total aluminum), microbiological (thermotolerant coliforms) and ecotoxicological analyses (lettuce seed - Lactuca sativa) and the marine microcrustacean (Mysidopsis juniae) were analyzed in samples from decanter sludge and washing water from the filters with sludge. As expected, the decanter sludge had a higher amount of solids than the filter, but despite that, the total solids concentration in the filter exceeded 86 times the limit for to be discharge into the water resources, according to Brazilian guidelines. Also, aluminum concentrations were above the guidelines to freshwater (910% - decanter sludge and 210% - filter sludge). Regarding ecotoxicity, sludge from both stages did not affect seed germination and even promoted the growth of 30 to 60% of radicles. On the other hand, the decanter sludge showed to be significative toxic to microcrustaceans in concentrations above than 15%. Considering that these sludges could be released directly into the river in estuarine zone, its potential for toxicity to the aquatic environment is highlighted, and the importance of properly treatment before the discharge in landfills.