Study On Rapid Start-up Of EGSB And Its Performance Of Pre-treating Black Water At Ambient Temperature

Anaerobic treatment of decentralized sewage is an important research content of wastewater treatment.In this paper,the start-up of EGSB and its pretreatment of black water at ambient temperature were investigated,according to the characteristics of the black water and EGSB reactor.Using flocculent anaerobic fermented sludge and low-concentration domestic wastewater as the seed sludge and raw-water respectively,the EGSB reactor started up smoothly in 65 days by the operational strategies in shortening HRT(14h?7h?4h)and increasing reflux ratio(2:1?2.5:1).The process characteristics of EGSB ensured that the mass transfer and degradation capacity could be enhanced even if the up-flow rate and hydraulic load were elevated gradually.MLSS concentration at the bottom of the reactor increased to 23.6 g/L with a higher VSS/SS ratio of 0.71,and the morphology of sludge changed from the initial floc brown to the coexistence of the dark brown floc and the granular state.It therefore indicated that the high flow rate in EGSB column could induce a slow formation of anaerobic granular sludge,even under the low volume loading of 0.6 kgCOD/m3·d.The effects of operational modes were comparatively analyzed,and the results showed that the organic removal was a little reduced at the lower flow rate.As to the treatment of black water with more COD and complex component,an appropriate extension of HRT for EGSB was necessary.Based on it,the pretreatment of black water by EGSB was carried out under the conditions of inlet COD,TN and NH3-N concentrations of 700-1000,19-21 and 12-15 mg/L and the HRT of 24 h and reflux ratio of 2:1,and the results showed that the anaerobic reactor ran stably in term of 60%,40% and 50% removal efficiencies and the satisfying contents of VFA(3.0-6.0 mmol/L)and alkalinity(20 mmol/L)in effluent.Hereby,considering the limitation in promoting organic loading when EGSB treating medium-low concentration wastewater,ambient temperature was acceptable for the anaerobic process,with aid of the optimization in up-flow rate by controlling the HRT and flux ratio.And it was found that the volume load of ?2.5 kgCOD/m3·d or HRT ?8h was the suitable parameters for EGSB operation.