The Granule Development And Performance Of ABR

A sequence of baffled planks are setted along the flow in the Anaerobic Baffled Reactor(ABR), so the reactor is separated into several serial chambers. The sewage flow along the reactor with upward and downward flow. The ABR reactor has the advantages of simple structure, strongely intercepting sludge, better stablization and so on. So many researchers are attracted by ABR since it appeared. Two identical ABR models with four chambers are used and the valid volume is 90 litres . COD, VFA, pH and alkalinity of outflow were systemly measured . The development and characteristics of the granule sludge and the performance are studied in each chamber due to the change of alkalinity and organic load in this paper.The conclusions of this thesis are as followed:(1) The granulation of the sludge is affected by the ammount of inoculated sludge. Channel will appear if the sludge bed is too high. In this reaserch the height of the sludge bed is adjusted within 2/3 of the valid water level and the channels disappear. The peoriod of development will be prolonged due to acidification of the system. Acidification can be solved by adding fresh sludge, increasing alkalinity of influent, decreasing load and backflow. In this study inoculating some fresh sludge and increasing the alkalinity of influent are used and the acidification disappeared after 20 days.(2) The important factors affecting granulation are alkalinity of effluent, upflow and organic load. In this study granule sludge is cultivated successfully with load of 0.34kgCOD/ (kgVSS.d), upflow of 0.11m/h, alkalinity of effluent of CaCO₃1000mg/L and temperature above 25℃.(3) The size of the granule sludge in each chamber reduced along the flow. The organic compound is hydrolyzed and acidified in the front chambers. The main bacterium of the back chamber are Methanosarcina SP and Methanothrix SP.(4) In the course of cultivating granule sludge, some degree of alkalinity needed to be maintained in ABR. When the load is increased, the more alkalinity will be needed to maintain certain buffer. In start-up, the reactor may be acid due to lack of alkalinity. Theneeded alkalinity decreases gradually along the granulation in the course of cultivating granule sludge. In this study high alkalinity (CaCO3750¹100mg/L) is maintained in the initial stage of cultivating granule sludge. The alkalinity of effluent decreases a little (above CaCO3524.3mg/L) along the granulation and good effect can be achieved. When sucrose is treated by ABR with granule sludge, the removal rate of COD and alkalinity have no direct proportion. The reactor has enough buffering ability with no risk of acidification and high removal rate of COD can be attained when the alkali in influent is 0.25g/gCOD and the alkalinity of effluent maintains above CaCO3600mg/L.(5) The alkalinity of the reactor increases along the flow. The second and third chambers appear the biggest increasing that suggest the buffering of the reactor is provided mainly by the second and third chambers. The higher the alkalinity of effluent is, the higher the pH is. The pH can indicate alkalinity and buffering capacity of the reactor.(6) The first two chambers have important effect to remove COD. The removal rate of COD in the first chamber is 70%. 50% of the total VFA comes from the first chamber, 70-80% of the total VFA is produced in the first two chambers. When the effluent alkalinity is high (CaCO3l500mg/L), the chamber of acidfication phase moves to the next chamber, the amount of VFA in effluent increases.(7) It is found that when the volumetric load is 2.67⁸.0 kgCOD /m3.d, pH increases along the flow. As long as the pH is above 6.4 in one chamber, the reactor can operate normally. The pH in more chambers is above 6.4, the smaller the possibility of acidification of the reactor.(8) When the COD in influent is 2000mg/L, the alkalinity is more than CaCO3524.3mg/L, more than 88.9% COD is removed. When the load is below 6.67kgCOD/m3.d and the alkalinity is more than CaCO3700mg/L, the removal rate of COD is more than 90%.