Fate of Sulfate in Municipal Wastewater Treatment Plants and Its Effect on Sludge Recycling as a Fuel Source
Que Nguyen HoA. Giridhar BabuJae‐In KimSomin ParkTae-U LeeJae-Young JeonYun-Young ChoiYoung‐Ho AhnByung Joon Lee
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Abstract:
Wastewater sludge is used as an alternative fuel due to its high organic content and calorific value. However, influent characteristics and operational practices of wastewater treatment plants (WWTPs) can increase the sulfur content of sludge, devaluing it as a fuel. Thus, we investigated the biochemical mechanisms that elevate the sulfur content of sludge in a full-scale industrial WWTP receiving wastewater of the textile dyeing industry and a domestic WWTP by monitoring the sulfate, sulfur, and iron contents and the biochemical transformation of sulfate to sulfur in the wastewater and sludge treatment streams. A batch sulfate reduction rate test and microbial 16S rRNA and dsrB gene sequencing analyses were applied to assess the potential and activity of sulfate-reducing bacteria and their effect on sulfur deposition. This study indicated that the primary clarifier and anaerobic digester prominently reduced sulfate concentration through biochemical sulfate reduction and iron–sulfur complexation under anaerobic conditions, from 1247 mg/L in the influent to 6.2~59.8 mg/L in the industrial WWTP and from 46.7 mg/L to 0~0.8 mg/L in the domestic WWTPs. The anaerobic sludge, adapted in the high sulfate concentration of the industrial WWTP, exhibited a two times higher specific sulfate reduction rate (0.13 mg SO42−/gVSS/h) and sulfur content (3.14% DS) than the domestic WWTP sludge. Gene sequencing analysis of the population structure of common microbes and sulfate-reducing bacteria indicated the diversity of microorganisms involved in biochemical sulfate reduction in the sulfur cycle, supporting the data revealed by chemical analysis and batch tests.Keywords:
Sulfur Metabolism
Industrial wastewater treatment
Sulfate-Reducing Bacteria
Industrial waste
Sulfate-Reducing Bacteria
Zerovalent iron
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The aim of this study was to develop a biological method for the simultaneous removal of sulfate and metals from acidic low-temperature mining effluents. A mixed consortium of cold-tolerant sulfate-reducing bacteria (SRB) and other microorganisms was immobilized on glass beads and exploited in an up-flow biofilm reactor for the continuous treatment of actual and synthetic mining-impacted waters (MIWs) with initial sulfate concentrations between 1580 and 5350 mg L-1. The proton acidity of the mine waters was neutralized by microbial sulfidogenesis. Metals present in the MIWs were precipitated either off-line or in-line, inside the reactor vessel. High sulfate reduction rates (SRRs), from 1000 to 4500 mg L-1 d-1 at a temperature of 11.7 ± 0.2 °C, were achieved (sulfate removal 43–87%). The bacterial consortium was found to be robust and resistant to changes in growth conditions during the bioreactor experiment. The relative abundance of SRB and the SRR increased at higher sulfate concentrations. Sulfidogenic bioreactors have the potential for treatment of acid mine drainage even at low temperature. It was demonstrated that neutral reactor conditions and high SRRs were maintained when acidic influent was fed into the reactor.
Sulfate-Reducing Bacteria
Acid Mine Drainage
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