Toxicity Analysis of Sewage Sludge Treated with Polyelectrolytes Using Luminescent Bacteria

The aim of this work was to evaluate the ecotoxicity of municipal sewage sludge, after conditioning with polyelectrolytes, coming from a selected wastewater treatment plants (WWTPs). Microtox M500 and Aliivibrio fischeri (luminescent bacteria) were used for the assessment of toxicity. The most common presentation of inhibition result of chosen test is EC50 value, which is equal to concentration causing 50% reduction in light. Ecotoxicity studies were made for water extract of municipal sewage sludge conditioned with polyelectrolytes (polyacrylamide). Samples came from two selected municipal wastewater treatment plants located in the Silesian region, where technology is based on mechanical and biological treatment of sewage (referred to as A and B). At WWTP A all sample solutions were classified as toxic. Sludge after dewatering on the press had a highest toxic effect 64.32 TU after 15 min of exposition. For sewage sludge taken from drying tunnel toxic effect 12.12 TU (after 15 min). In WWTP B sample of sludge before fermentation chamber were toxic: 14.03 TU (after 15 min), raw sludge and sludge after the press weren’t classified as toxic. This study revealed new insights into the acrylamide problem. Furthermore, it showed successful use of Microtox assay to measure acrylamide toxicity in the sewage sludge.