Progress in Mechanism and Control Strategy of Anaerobic Ammonium Oxidation(Anammox) Granular Sludge Floating

To solve the problem of breaking and floating of anaerobic ammonium oxidation(anammox)granular during reaction may lead to instability or collapse of the treatment system,the mechanism and control strategy of anammox granular sludge floating were summarized in this paper.The previous studies showed that the density of the anammox granule decreased which was thought to be the main mechanism of granular sludge floating.Therefore,at high nitrogen loading rates(NLRs) level,floating would occur which might be the fact that the anammox granular sludge produced a large amount of nitrogen gas(N₂)and the gas could not release easily.Then the gas trapped in the granular sludge inside or attached to the granular sludge surface.There were some strategies which were adopted to control the anammox sludge floating,such as controlling the particle size of the sludge(1.5 ~4.0 mm);controlling the NLRs(4.0~ 34.5 kg/(m³·d));improving the concentrations of phosphorus and calcium in the influent(p(KH₂PO₄) = 10 mg/L,p(CaCl₂-2H₂O) =0.15 ~5.65 mg/L);using the reactor with stirring;adjusting the location of outlet and controlling the time of output,etc.