The efficiency of the one-stage and two-stage simulated biogas digester reactors for the anaerobic pretreatment of the rural toilet black water from the south hilly area was studied. The results showed that when the average influent concentrations of TCOD and SCOD were 862 and 718 mg/L, the HRT were 12, 24, 36 and 72 h respectively, the average removal efficiencies of TCOD and SCOD were 12.5%, 57.5%, 60.8%, 67.1% and -15.7%, 53.6%, 55.3%, 64.7% accordingly under the steady-state phase. The removal efficiency of 72 h HRT reactor was higher than those of three other HRTs reactors. The TCOD and SCOD removal efficiencies of the two-stage simulated biogas digester reactors were improved by 6.4% and 8.9% respectively compared with the one-stage reactor at the 72 h HRT. This indicated that both one-stage and two-stage simulated biogas digester reactors achieved good COD removal efficiencies and the efficiency of the two-stage reactor was a little higher than that of the one-stage reactor for the toilet black water anaerobic pretreatment. Considering the economic factor, the 72 h HRT one-stage simulated biogas digester reactor could be used as the key biological treatment unit to combine with the follow-up ecological treatment equipments such as the constructed wetland for the rural toilet black water treatment.
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