Abstract
The effect of reduced form of sulfur compounds on granular sludge was investigated. Significant release of extracellular polymeric substance (EPS) from the granular sludge occurred in the presence of sulfide and methanethiol according to various concentrations. Granular sludge also showed a rapid increase in turbidity and decrease in diameter in accordance with sulfide concentration during the long-term shaking, suggesting that the strength of the granules was reduced with high-concentration sulfide. A continuous experiment of up-flow anaerobic sludge blanket reactors with different concentrations of sulfide (10, 200, 500 mg-S/L) influence demonstrated that the reactor fed with higher concentration of sulfide allowed more washout of small particle-suspended solid (SS) content and soluble carbohydrate and protein, which were considered as EPS released from biofilm. Finally, the presence of sulfide negatively affected methane production, chemical oxygen demand removal and sludge retention in operational performance.
Highlights
Granular sludge-based system including up-flow anaerobic sludge blanket (UASB) and expanded granular sludge bed (EGSB) is commonly employed for biological treatment of industrial wastewater around the world [1,2]
The Extracellular Polymeric Substance (EPS) extracted from the granule using cation exchange resin (CER) method was as follows: protein 13.2 ± 2.5 mg/g-suspended solid (SS), and carbohydrate 42.8 ± 3.6 mg/g-SS
These values were at similar levels to those of anaerobic granules obtained by other researchers [29]
Summary
Granular sludge-based system including up-flow anaerobic sludge blanket (UASB) and expanded granular sludge bed (EGSB) is commonly employed for biological treatment of industrial wastewater around the world [1,2]. Granule is a kind of concentrated multilayered biofilm including different microbial trophic groups: acidogenic bacteria, syntrophic acetogenic bacteria and methanogenic archaea. These microbial groups produce EPS around the cells, which help the microorganisms attach each other and create large cell aggregations [3]. The granulation and the stability of the granules are commonly considered to be strongly affected by various environmental and operational conditions [4]. Since there is wide variety of wastewater providing different environmental and operational conditions in reactors due to different industries, it has become clear that some kinds of wastewaters are difficult to form granules and retain biomass successfully. Chou and Huang [14] observed that smaller granules were formed in the phenol-fed UASB reactor than in the sucrose-fed reactor
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