Performance And Methanogenic Community Analysis Of Anaerobic Digestion For Food Waste Treatment And Biogas Production

In this study,a new pilot anaerobic treatment system was used for the treatment of food wastewater and residue.The anaerobic treatment system is mainly composed of 800L high-solid reactor,200L Buffer Tank and 1000L new Up flow Solid Reactor(USR).Compared with the traditional Up flow Anaerobic Sludge Bed(UASB)reactor,the new type of USR reactor remove the three-phase separator and other components,and the spatial structure is used to realize the purpose of solid-liquid separation in the reactor.The main research contents include:start-up of a new USR reactor,effect of feed concentration on the operation of single phase USR reactor,effect of total solids(TS)of feed concentration on the operation of two phase reaction system and changes of methanogenic community structure and dominant methanogenic species in USR reactor.The main results are shown as following:(1)The new pilot USR reactor was initiated with 5%feed concentration,and operated at 1 kgCOD/(m3·d)organic loading rate(OLR).On the 30th day,pH and concentration of volatile fatty acid(VFA)in the reactor was stable.In the meantime,the treatment efficiency of reactor and the rate of methane production reached a stable level.(2)In the single-phase operation of USR reactor,the Chemical Oxygen Demand(COD)removal efficiency was greater than 82%,and the methane yield reached 303.8 L/kg CODremoval,when the feed concentration was 11.1%and the OLR reached between 7.0 and 7.6 kg COD/(m3·d).When the feed concentration was 33.3%and the OLR reached approximately 18 kgCOD/(m3·d),the COD removal efficiency was less than 50%,and the methane yield decreased to 104L/kg CODremovai.(3)In the two phase operation of anaerobic system,the food waste residue was largely removed in High Solid Reactor.The TS in the High Solid Reactor remained below 1.5%.At the same time,the COD removal efficiency was kept at 81%,291 L/kgCODremoval of methane production rate.When the TS of feed was larger than 6%,the TS in the High Solid Reactor increased to 1.8%or more,and the COD reamoval efficiency and methane production rate in the USR reactor was also negatively affected.(4)The community structure of methangens and dominant methangen changed in different stages.When Methanosaeta was the dominant species in the USR reactor,the COD removal efficiency and methane production rate were higher than that of Methanospirillum.A methanosaeta-dominated methanogenic community was successfully established,with 7.0-7.6 kgCOD/(m3·d),less than 300mg/L of VFA and 2.2-2.5%of TS.