Controlling sludge retention time to alleviate inhibition of nitrosation and nitration by accumulated aluminum in an A/O-MBR. (October 2019) - Qiu, Chenggang
Abstract: Severe membrane fouling and limited effect of biological phosphorus removal are the major drawbacks for anoxic-oxic membrane bioreactor (A/O-MBR). The dosing of poly-aluminum chloride in A/O-MBR can reduce membrane fouling and improve phosphorus removal certainly, but it may bring potential impacts on the specific oxygen uptake rate of sludge and the activity of ammonia-oxidizing bacteria and nitrite-oxidizing bacteria with accumulated aluminum. Controlling sludge retention time (SRT) was firstly investigated to evaluate the effect on alleviating inhibition caused by accumulated aluminum in A/O-MBR. As compared to the performance without dosing of poly-aluminum chloride, the effluent ammonia concentration in the SRT-15d reactor was increased by 91.80% lower than that of SRT-30d reactor (111.84%). Due to higher sludge yield rate in the SRT-15d reactor, the amount of accumulated aluminum was 39.33 mg Al g −1 VSS less than that of the SRT-30d reactor. Besides, the decline of the activity of ammonia-oxidizing bacteria and nitrite-oxidizing bacteria in the SRT-15d reactor was 4.4% and 18.3%, respectively lower than that of the SRT-30d reactor. Therefore, controlling shorter SRT can be used as an effective tool to alleviate inhibition of nitration and nitrosation by accumulated aluminum in A/O-MBR. Graphical abstract: Image 1 Highlights: Accumulated aluminum would inhibit the activity of AOB and NOB. The sludge yield was high in the short SRT reactor with accumulation of aluminum. Controlling shorter SRT efficiently reduced the accumulated aluminum in the sludge. Controlling shorter SRT alleviated the inhibition of nitration and nitrosation.