Operation Of MBR Treating Hospital Sewage And Monitoring Of Aerosol Microorganisms In The Off-Gas

Hospital sewage, which contains a great deal of bacteria, virus and other deleterious components, should be treated and disinfected properly before discharge. After several public health incidents breaking out, more and more attentions have been attracted on the treatment of hospital sewage.The traditional treatment of hospital sewage has several disadvantages, such as complex process flow, large occupied area, low standard of automatization and secondary pollution to ambient air, which can be overcome by using membrane bioreactor (MBR) process. Moreover, the disinfection efficiency is enhanced due to the high quality effluent from MBR.In order to estimate the operational effect of hospital sewage treatment with MBR, the mixed liquor and the effluent collected from the MBR of Tianjin No.1 Hospital, were monitored. To verify the advantages that MBR under nagative pressure status has in prevention of air pollution, this study monitored the aerosol microorganisms in the MBR workshop, inside of the reactor and ambient air, and emphasized on their quantity and particle size distribution using Andersen sampler.The experimental results showed that the difference between effluent quality of the two reactors was small when they run alternately in the way of aerobic-anoxic. The average effluent turbidity was 0.27 NTU; the removal efficiency of COD was 89.93%; the removal efficiency of NH3-N was 97.30%. Under nagative pressure status, the average concentration of the bacteria and fungi was 815 CFU/m3 and 792 CFU/m3 respectively in the workshop, smaller than that under the normal pressure (1016 CFU/m3 and 804 CFU/m3) and the reactor partially open status (1241 CFU/m3 and 836 CFU/m3). Obviously, the bacteria concentration (388 CFU/m3) in the off-gas treated by high efficiency air filter was smaller than that inside of the reactor (8039 CFU/m3) without treatment, the removal rate was up to 95.2%. The concentration of the bacteria and fungi was 2841 CFU/m3 and 1329 CFU/m3 respectively in the treated off-gas emission area; while that in ambient air around the hospital was 2878 CFU/m3 and 1248 CFU/m3 respectively.The effluent indexes such as COD, NH3-N and etc can reach Discharge Standard of Water Pollutants for Medical Organization (GB18466-2005) when hospital sewage is treated by MBR. Membrane fouling can be slow down under the alternate operation mode. Moreover, the dosage of disinfectant is reduced due to high quality effluent which has much less organic materials and microorganisms, compared to the effluent from conventional treatment process. Under negative pressure status, MBR can prevent the aerosol microorganisms from emitting to ambient air effectively, and the off-gas of MBR treated by high efficiency air filter is not lead to secondary pollution.