HYDROGEN SULFIDE EMISSIONS FROM MUNICIPAL SEWAGE TREATMENT FACILITIES UNDER CONDITIONS OF ACTIVATED SLUDGE BUCKLING - Науково-технічний журнал «Техногенно-екологічна безпека»

Abstract. The presence of hydrogen sulfide in wastewater poses serious environmental and operational challenges for municipal wastewater treatment plants. The objective of this study is to monitor the formation of hydrogen sulfide at various stages of municipal wastewater treatment at existing treatment plants under conditions of filamentous bulking of activated sludge and to provide a predictive assessment of the resulting environmental risks. The subject of the study is the dynamics of the concentration of reactive forms of sulfur-hydrogen sulfide and sulfates – in wastewater during mechanical and biological treatment at operating treatment plants, as well as the microbiological processes that cause their transformation. We monitored the concentration of sulfides and redox conditions in wastewater and identified filamentous bacteria responsible for activated sludge bulking. It was established that the sulfur cycle at wastewater treatment plants triggers active microbiological sulfate reduction in mechanical treatment facilities due to highly reducing conditions (rH2 £10), caused by excessive hydrogen sulfide content (up to 5.9 mg/L) in the influent wastewater. It is precisely with the products of sulfate reduction that all subsequent microbiological transformations of the sulfur cycle occur, including: filamentous bulking of activated sludge in aeration tanks due to the massive growth of filamentous sulfur bacteria Type 021N and the formation and release of hydrogen sulfide. Using our own methodology, we performed a preliminary calculation of hydrogen sulfide emissions from wastewater treatment plants. It was established that the development of filamentous bulking of activated sludge causes a 15- to 18-fold increase in hydrogen sulfide emissions into the atmosphere. The scientific innovation of the study lies in the scientifically substantiated demonstration of the impact of filamentous bulking of activated sludge (caused by the massive proliferation of filamentous sulfur bacteria) on increased hydrogen sulfide emissions from wastewater treatment plants. To prevent the development of filamentous bulking of activated sludge, and in the event of its occurrence at wastewater treatment plants – to actively suppress this operationally hazardous phenomenon-technological methods of practical significance are proposed.

Key words: municipal wastewater treatment plants, emissions, sulfides/hydrogen sulfide, sulfate reduction, redox conditions, filamentous bulking of activated sludge, sulfur cycle, environmental hazard.

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