Research On Start-up And "Acidification" Of Productive Internal Circulation Anaerobic Reactor

In this paper, regarding anaerobic biological treatment expansion project (I) of pharmaceutical wastewater treatment project of one Pharmaceutical Co., Ltd. in Anhui Province as a research object, through consulting a large number of domestic and foreign literatures, the theory and development of anaerobic biological treatment technology, the basic structure and the working principle of IC reactor were discussed briefly. The productive start-up characteristics of IC reactor treating pharmaceutical wastewater inoculated with high-temperature digestion sludge for alcohol wastewater was mainly studied, and the acidification phenomenon, which was prone to happening in anaerobic biological process for the purpose of methane-producing, was focused on especially. The major conclusions obtained were listed as follows:(1) IC reactor inoculated with high-temperature digestion sludge for alcohol wastewater could be started up successfully under mesophilic condition, achieving volume loading of 3.5-4.0 kgCOD/(m3·d), but the start-up lasted 171 days. When the start-up was finished, the efficiency of COD removal reached 80%, the COD and pH in effluent stabilized at around 2100mg/L and 7.5 separately, and a small amount of granular sludge was discovered in the 3m sampling port of the reactor.(2) The appropriate temperature is essential for IC reactor. Under the condition of the temperature less than 30℃in the reactor, the VFA in effluent rised rapidly, and the efficiency of COD removal decreased accordingly, which could be alleviated by adjusting the temperature timely to avoid the "acidification phenomenon"; The variation trend on the VFA in effluent was nearly similar to that in 3m zone at the reactor; due to the larger ALK in wastewater, the pH in effluent was more stable, not varying with fluctuation in the VFA in effluent.(3) The COD volume loading increased dramaticly and lasted several days, leading to the "acidification phenomenon" in the reactor, i.e. the VFA in effluent increased dramatically to 1800mg/L or even higher, which needed prompt control measure to avoid more serious acidification, which may made the reactor collapse. To sovle the problem of acidification, the following measures were adopted:first, to reduce the volume loading, that is stopping the water of hydrolytic acidification tank into the reactor; second, to introduce a large amount of water into the reactor to wash away VFA in the reactor; to return the reactor effluent when the VFA in 3m zone at the reactor below 500mg/L; Sequently, increase the COD concentration in influent gradually. Finally, the reactor regained normal operating condition, like that before the acidification, which spent nearly a month.(4) By analyzing all monitoring indicators of the reactor operation, it was found that, before the acidification was occuring, first and foremost there were changes in the amount of gas, followed by sharp increase of the VFA in effluent, then the COD in effluent changed, followed by slight fluctuation in the pH in effluent in the end. Although the amount of gas producing was more sensitive in response to abnormal changes in the reactor, the reason for this situation was not known for sure. So the VFA in effluent should be monitored to reflect the operation state of the system in practical terms.