REMOVAL EFFICIENCY OF OPPORTUNISTIC PATHOGENS AND ORGANIC MATTERS IN SECONDARY EFFLUENT BY SLOW FILTRATION WITH BIOFILM
The secondary effluent of municipal sewage treatment plants contains a large number of opportunistic pathogens,which poses a potential threat to human health.In this study,the efficacy of the slow filtration process on the removal of opportunistic pathogens(Pseudomonas aeruginosa,Legionella,and Mycobacterium avium)and DOC in water under different operating conditions(influent C/N ratio,Ca2+concentration,pH value)was investigated,and the correlation analysis between the removal of opportunistic pathogens and DOC and E.coli was conducted,respectively.The results showed that under the condition of a filtration rate of 5 cm/h and changing the influent water quality conditions,the effect of biofilm slow filtration on the removal of opportunistic pathogens was greater than that without biofilm slow filtration.When the C/N ratio was 10,Ca2+concentration was 60 mg/L and pH value was 7,the best effect of biofilm slow filtration on the removal of opportunistic pathogens was achieved.Under the optimal operating conditions,the content of opportunistic pathogens in the effluent of biofilm slow filtration was positively correlated with the DOC content;except for the Ca2+concentration,the content of opportunistic pathogens by biofilm slow filtration was positively correlated with E.coli in other operating conditions.In conclusion,the biofilm slow filtration process can effectively remove opportunistic pathogens and organic matter in secondary effluent,which is an effective way to treat the secondary effluent in depth and provide a safety guarantee for the water risk in the reuse process of reclaimed water.
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