Study On Disinfection Of Hospital Wastewater Treated By Membrane Bioreator (MBR) Using Sodium Hypochlorite

Hospital wastewater, containing a great number of bacteria, viruses and other deleterious components, should be treated properly before discharged to aquatic environment. Nowadays, the most commonly used method for hospital wastewater treatment is direct chlorination or primary treatment followed by chlorination. As several water-born diseases were broke out, more and more attentions have been paid on the treatment of hospital wastewater. The effluent discharge standard and requirements of hospital wastewater will be upgraded.Traditional hospital wastewater treatment method has several disadvantages, such as low level of automatization, pollution from aeration off-gas and poor safety. However, the above defects can be overcome by using membrane bioreactor (MBR). Moreover, the disinfection efficiency is enhanced and the harm to the environment caused by disinfected effluent is reduced because of the improved quality of the effluent.In order to verify the advantages that MBR has in hospital wastewater disinfection, testing samples, the raw wastewater and the MBR effluent from Tianjin First Central Hospital, were studied after disinfection by using sodium hypochlorite.The experimental results showed that total count of bacteria in the disinfected MBR effluent was not detectable when the contact time was controlled to 1.5 min and the dosage of sodium hypochlorite (calculated as available chlorine) was 1.0～2.0 mg/L. As for the raw hospital wastewater, the same disinfection effect couldn't be attained even the dosage of sodium hypochlorite and contact time were increased to 50.0 mg/L and 1.0 h; The content of trichloromethane in the MBR effluent and the raw hospital wastewater after disinfection, were 5.14μg/L(2.0 mg/L, 2.0 min)and 19.70μg/L(20.0 mg/L, 1.0 h)respectively. The acute toxicity test with Daphnia magna showed that the median effect concentration of the MBR effluent and the raw hospital wastewater after disinfection, were 11.49%(1.0 mg/L, 2.0 min)and 2.55%(15.0 mg/L, 1.0 h)respectively.The decreasing dosage of disinfectant, less disinfection by-products (DBPs) formation and lower acute toxicity were achieved as for disinfection of MBR effluent. Currently, MBR is a preferable treatment method for hospital wastewater. Some details in the Requirements for medical organization sewage discharge...