Biological treatment of coke plant effluents: from a microbiological perspective
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REVIEW
Biological treatment of coke plant effluents: from a microbiological perspective Tamás Felföldi1 · Zsuzsanna Nagymáté1 · Anna J. Székely2 · Laura Jurecska1 · Károly Márialigeti1 Received: 17 February 2020 / Accepted: 1 July 2020 © The Author(s) 2020
Abstract During coke production, large volume of effluent is generated, which has a very complex chemical composition and contains several toxic and carcinogenic substances, mainly aromatic compounds, cyanide, thiocyanate and ammonium. The composition of these high-strength effluents is very diverse and depends on the quality of coals used and the operating and technological parameters of coke ovens. In general, after initial physicochemical treatment, biological purification steps are applied in activated sludge bioreactors. This review summarizes the current knowledge on the anaerobic and aerobic transformation processes and describes key microorganisms, such as phenol- and thiocyanate-degrading, floc-forming, nitrifying and denitrifying bacteria, which contribute to the removal of pollutants from coke plant effluents. Providing the theoretical basis for technical issues (in this case the microbiology of coke plant effluent treatment) aids the optimization of existing technologies and the design of new management techniques. Keywords Activated sludge · Bioreactor · Phenols · Thiocyanate · Toxic compounds
Introduction In the last decade, global steel demand has kept on growing, leading to a record of 1870 million tons of crude steel production in 2019, which means more than doubling of production in the last 20 years (World Steel Association 2020). Despite the development of alternative ironmaking technologies (Hasanbeigi et al. 2014), more than 70% of crude steel produced worldwide is still manufactured via the blast furnace-basic oxygen furnace route which uses coal to reduce iron oxides in the ores and to generate heat for smelting (World Coal Association 2020). To achieve the purity required for steel making, coal has to be converted into coke. During the coking process, coal is heated to around 1000 °C in the absence of oxygen to drive off the volatile compounds. The resulting coke is a hard porous material composed of almost pure carbon. Hot coke is usually quenched with * Tamás Felföldi [email protected] 1
Department of Microbiology, ELTE Eötvös Loránd University, Pázmány Péter stny. 1/c., Budapest 1117, Hungary
Department of Ecology and Genetics/Limnology, Uppsala University, Norbyvägen 18 D, 75236 Uppsala, Sweden
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water, and the gases containing the volatilized materials are also washed with water resulting in the coking wastewater, which is also referred as coke oven wastewater, coal gasification wastewater or coke plant effluent (Kwiecińska et al. 2017; Nowak et al. 2004). These effluents are high-strength wastewaters, which (in order to accomplish environmental regulations) have to undergo intensive purification processes prior to their discharge; therefore, steel industry has developed a plethora of methods for the treatmen
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