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In this study, two lab-scale UASB reactors were established to testify S 0 recovery efficiency, and one of which (M-UASB) was improved from the previous T-UASB by shortening reactor height once S 2− over oxidation was observed. After the height was shortened from 60 to 30 cm, S 0 recovery rate was improved from 7.4% to 78.8%, and while, complete removal of acetate, nitrate and S 2− was simultaneously maintained. Meanwhile, bacterial community distribution was homogenous throughout the reactor, with denitrifying sulfide oxidization bacteria predominant, such as Thauera and Azoarcus spp., indicating the optimized condition for S 0 recovery. The effective control of working height/volume in reactors plays important roles for the efficient regulation of S 0 recovery during DSR process. [ABSTRACT FROM AUTHOR]

Influence of acetate-C/NO 3 − -N/S 2− ratio to the functional microbial community during the denitrifying sulfide removal process is poorly understood. Here, phylogenetic and functional bacterial community for elemental sulfur (S 0 ) recovery and nitrate (NO 3 − ) removal were investigated with the switched S 2− /NO 3 − molar ratio ranged from 5/2 to 5/9. Optimized S 2− /NO 3 − ratio was evaluated as 5/6, with the bacterial genera predominated with Thauera , Enterobacter , Thiobacillus and Stappia , and the sqr gene highly expressed. However, insufficient or high loading of acetate and NO 3 − resulted in the low S 0 recovery, and also significantly modified the bacterial community and genetic activity. With S 2− /NO 3 − ratio of 5/2, autotrophic S 2− oxidization genera were dominated and NO 3 − reduction activity was low, confirmed by the low expressed nirK gene. In contrast, S 2− /NO 3 − ratio switched to 5/8 and 5/9 introduced diverse heterotrophic nitrate reduction and S 0 over oxidization genera in accompanied with the highly expressed nirK and sox genes. [ABSTRACT FROM AUTHOR]

Highlights: [•] A novel combined process for waste activated sludge dewatering was proposed. [•] Extracellular polymeric substances (EPS) were characterized by ultraviolet visible spectra. [•] Loosely, tightly bound EPS and bacterial cells in sludge flocs together affected the dewatering. [•] Tightly bound EPS provided some protective shielding allowing cells to survive. [•] The process disrupted EPS and cells, released the trapped water and promoted the dewatering. [Copyright &y& Elsevier]

Abstract: The individual effects and interactive effects of substrate concentration, ratio of inoculum to substrate, Ca2+ concentration on the methane yield from the effluent of bio-hydrogen fermentation of food waste were investigated in this study. A central composite design (CCD) and response methodology (RSM) were employed in designing the experiments, in order to determine the optimum conditions for methane fermentation. The experiment results showed that the effects of substrate concentration, ratio of inoculum to substrate, Ca2+ concentration were statistically significant at 5% level. The interactive effect of substrate concentration and ratio of inoculum to substrate was significant, however the interactive effect of substrate concentration and Ca2+ concentration, ratio of inoculum to substrate and Ca2+ concentration were found to be insignificant at 5% level. A maximum yield of 565.76ml CH4/g VSadded was estimated under the optimum conditions for substrate concentration 7.77g of VS/l, inoculum to substrate ratio of 2.81 and calcium concentration of 380.82mg/l. Verification experiment of the estimated optimum conditions confirmed that the RSM was useful for optimizing the methane yield from effluent of bio-hydrogen fermentation of food waste. [Copyright &y& Elsevier]