Zero-valent Iron Enhanced Anaerobic Digestion Of Pre-concentrated Domestic Wastewater: Characteristics And Mechanisms

In the 21st century,with rapid social and economic development,energy issues have become a huge challenge of human society.In order to solve the huge problems brought by wastewater,anaerobic biological treatment technology came into being.According to the concentration,the low-concentration domestic wastewater discharge accounts for 71.4%of the wastewater discharge.The wastewater pre-concentration technology that can effectively capture a large amount of organic matter promotes the anaerobic digestion of wastewater in order to recover bioenergy.In general,there are various types of wastewater pre-concentration technologies.The use of forward osmosis membrane filtration and dynamic membrane filtration are the most effective technologies to obtain the organic matter.As the main research reported,the effect of adding zero-valent iron?ZVI?during anaerobic digestion was excellent,and the mechanism of ZVI enhancing the methane production of concentrated wastewater was explored preliminary.The main results of this research are as follows:?1?The classification of pre-concentrated domestic wastewater and F/M?Food to Microorganism Ratio?experiments indicated the biodegradability of pre-concentrated domestic watewater.The results showed that the easily degraded polysaccharide andprotein in the small particle COD of less than 40?m is the main component.In therange of F/M 0.2-1.0,the most suitable F/M for anaerobic digestion of pre-concentrated domestic wastewater is 0.5.At this time,the maximum methane production of pre-concentrated domestic wastewater is 0.275 L CH₄/g COD.Pre-oncentrated domestic wastewater is a suitable substrate,but it still needs to increase its methane production and shorten the time of duration.?2?In order to improve the BMP of pre-concentrated domestic wastewater,the zero-valent iron technology was used to carry out batch experiments to explore the role and related mechanisms of ZVI on the methane production performance of pre-concentrated domestic wastewater.ZVI dosing experiments have indicated that when F/M is 0.5,the optimal dosing concentration of ZVI is 6 g/L,and the BMP of pre-concentrated domestic wastewater is 15.2%higher than that without ZVI.ZVI significantly improves the hydrolysis process and has little effect on the acidification process.But it needs to be further verified in a larger reactor.?3?Further continuous process experiments to explore the effect of ZVI on the AnDMBR and related mechanisms.?1?After the addition of ZVI,the COD of effluent was reduced by 14.28%-25.51%,the polysaccharide and protein contents were reduced by 59%and 78%,the removal rate of TP and PO₄^3-was as high as 95%,and the methane production rate was increased by 17.7%-37.1%.?2?The removal rate of turbidity is higher than 95%after adding ZVI,but the average increase of TMP is increased to 0.18 kPa/d.?3?The iron ions,especially Fe²⁺,converted from ZVI,can act as flocculants and electron donor,which can remove more phosphorus,COD and other impurities.?4?ZVI can increase the hydrogenotrophic methanogenesis process by 57%and the abundance of Methanolina,and then increase the methane production.The more compact dynamic membrane is formed by adding ZVI.The analysis of material morphology,composition and microbial community of reactor sludge and dynamic membrane provided new data support for preliminary reveal of the mechanism by which ZVI can enhance function of AnDMBR.But it should still consider negative impacts of ZVI on membrane fouling.