Cultivation Of Anaerobic Granule In ABR And Its Characteristics And Application

In anaerobic wastewater treatment systems,the formation of granules is essential to the stable operation of biological systems.Granulation not only significantly enhances the settleability of biomass,leading to effective bacterial retention in the reactor,but also improves physiological conditions making them favorable for bacteria and their interactions,especially syntrophisms in the anaerobic system.Granular sludge was inoculated with digested sludge from urban sewage treatment plant and cultivated using synthetic wastewater under different methods(with or without inert matters).Effect of inert matters to performance of granules and disposal efficiency of granules to simulated dyeing wastewater were studied.Running conditions of granular reactor were also optimized.Anaerobic granules with good performance were successfully cultured with digested sludge from urban sewage treatment plant.Granular diameter ranged from 0.8mm to 2(?)mm,and decreased along the direction of water flow.The results indicated that addition of inert matters could decrease granulation time,enhance colonisation of suspended solids and increase the granular diameter.Effluent alkalinity,upflow velocity and organic loading rate(OLR)also affected sludge granulation significantly.Researches showed that over high sludge bed and systemic acidification would prolong the formation of granules.Twenty days after acidification,the reactor restored to normal by adding fresh sludge combined with increasing influent alkalinity.It was of importance to modify the sludge height lower than 2/3 of the effective water depth to avoid overflow between compartments.Observation and analysis of granule biological phase illustrated that anaerobic microbe distributed appropriately in different compartments.Granules in front several compartments composed predominantly of spherical bacteria and granules in latter parts mainly composed of rod-shaped bacteria resembling Methanothrix soehngenii in short chains or single cells and intertwined filamentous bacteria resembling Methanothrix soehngenii.COD removal efficiency decreased with the decrease of hydraulic retention time (HRT).The optimal HRT should be above 30 h to keep high COD removal rate.At high HRT,hydrolysis acidification reaction mainly occurred in the front two compartments.The reaction moved backward latter compartments with the increase of OLR.In these circumstances,to maintain stable operation of reactor, acid-producing chambers increased and methanogenesis reaction moved backward. Variations of effluent pH responding to running time were consistent with changes of COD removal rate.At identified HRT,effluent pH gradually increased from the first to sixth chambers, illustrating the variation of the function and reaction in the reactor from another aspect.Effluent volatile fatty acids(VFA)decreased along the direction of water flow, reflecting the separation of acidogenic and methanogenic phases.The accumulation of VFA inhibited metabolic activity of methanogenic bacteria as the increase of OLR, which leaded to the decline of COD removal rate.Optimum OLR was below 8.0 kg COD/(m~3·d),by keeping the effluent pH varying from 7.0 to 7.2.As the effect of temperature on reactor performance was significant,it was better to keep the reactor running at medium-high temperature.After successful domestication,light fastness black dye removal rate exceeded 90% treated by granular sludge from ABR with addition of inert matters.The removal rate could keep at high OLR.After granulation ABR was dominant to treat refractory wastewater.Composition of bacteria in granules and granular diameters had great impact on degradation of light Fastness black dye.The granules with prevailing acidogenic bacteria and bigger diameters from the first chamber performed better than that with prevailing methanogenic bacteria and smaller diameters from the fifth chamber.Addition of glucose has stress effect on dye decomposition in first and third chamber,while enhanced dye decomposition in fifth chamber.HRT affected dye removal obviously.The dye removal rate decreased with the decrease of HRT which still reached 84.1%at HRT of 10 h.Adjustment of pH was favorable to improvement of treatment efficiency.