RESUMEN
The effects of microbial electrolysis cell (MEC) integration stage on two-stage anaerobic digestion (TSAD) of food waste (FW) were studied via semi-continuous experiments. The results showed that both MEC (with 1.2 V) integrations enhanced the performances of the TSADs, with the enhancement of electro-two stages being higher. The methane production of TSAD increased from 1.36 ± 0.04 L/L/d to 1.53 ± 0.05 L/L/d (electro-methanogenic stage) and 1.54 ± 0.04 L/L/d (electro-two stages) during the steady period. Electro-acidogenesis decreased propionic acid production and enhanced hydrogen production, while electro-methanogenesis promoted the conversion of volatile fatty acids to methane. The MEC integration improved energy recovery from the organic matter in FW by 11.65-16.15% and reduced the mass loss, with those of the electro-two stages being higher and the electro-methanogenic stage being dominant in the electro-two stages. The integration of MEC enhanced anaerobic fermentation by enriching Olsenella, norank_f__ST-12K33 and Proteiniphilum and improved methanogenesis by enriching Methanobacterium and Candidatus_Methanofastidiosum.
Asunto(s)
Reactores Biológicos , Eliminación de Residuos , Anaerobiosis , Reactores Biológicos/microbiología , Alimentos , Electrólisis , Metano , Aguas del Alcantarillado/microbiologíaRESUMEN
The effects of microbial electrolysis cells (MECs) at three applied voltages (0.8, 1.3, and 1.6 V) on simultaneously enhancing methanization and reducing hydrogen sulfide (H2S) production in the anaerobic digestion (AD) of sewage sludge were studied. The results showed that the MECs at 1.3 V and 1.6 V simultaneously enhanced the methane production by 57.02 and 12.70% and organic matter removal by 38.77 and 11.13%, and reduced H2S production by 94.8 and 98.2%, respectively. MECs at 1.3 V and 1.6 V created a micro-aerobic conditions for the digesters with oxidation-reduction potential as -178â¼-232 mv, which enhanced methanization and reduced H2S production. Sulfur reduction, H2S and elemental sulfur oxidation occurred simultaneously in the ADs at 1.3 V and 1.6 V. The relative abundances of sulfur-oxidizing bacteria increased from 0.11% to 0.42% and those of sulfur-reducing bacteria decreased from 1.24% to 0.33% when the applied voltage of MEC increased from 0 V to 1.6 V. Hydrogen produced by electrolysis enhanced the abundance of Methanobacterium and changed the methanogenesis pathway.
Asunto(s)
Aguas del Alcantarillado , Electrólisis , Aguas del Alcantarillado/microbiología , Sulfuro de Hidrógeno , Reactores Biológicos/microbiologíaRESUMEN
In this study, Fe-Al layered double hydroxide (Fe-Al LDH) was prepared and applied to activate persulfate to condition sewage sludge and improve its dewaterability. The results showed that Fe-Al LDH activated persulfate to generate a large amount of free radicals, which attacked extracellular polymeric substances and reduced their content, disrupted microbial cells, released bound water, decreased sludge particle size, increased sludge zeta potential, and improved sludge dewaterability. After sewage sludge was conditioned with Fe-Al LDH (0.20 g/g total solids (TS)) and persulfate (0.10 g/g TS) for 30 min, the capillary suction time of the sludge dropped from 52.0 s to 16.3 s, while the moisture content of the sludge cake decreased from 93.2% to 68.5%. The dominant active free radical produced by the Fe-Al LDH-activated persulfate was SO4-â¢. The maximum Fe3+ leaching of the conditioned sludge was only 102.67 ± 4.45 mg/L, thus effectively alleviating the secondary pollution of Fe3+. The leaching rate of 2.37% was significantly lower than that of the sludge homogeneously activated with Fe2+ (738.4 ± 26.07 mg/L and 71.00%).