Study on factors of affecting sedimentation performance of activated sludge in A-step of AB process

The factors including inflow SS, pythogenous sewage, loading rate Ns, dissolved oxygen which affect sedimentation performance of A-step activated sludge were studied in the paper. The experimental results indicated: the inflow SS distinctly improve sedimentation performance of activated sludge; the pythogenous sewage easily worsen sedimentation performance of activated sludge, and canceling primary sedimentation tank and cesspool would avail to stable running of sewage treatment plant. The effect of loading rate Ns on EPS is highly remarkable, and EPS and polysaccharide are correlated evidently with sedimentation performance of activated sludge. When high loading rate Ns is 3.0 kgBOD5/kgMLSS·d, EPS is 17.15mgEPS/gVSS and polysaccharide is 8.15mg/gVSS, which is less 40% than activated sludge of 0.3 kgBOD5/kgMLSS·d loading rate Ns; meanwhile the effect of dissolved oxygen on EPS is less, and dissolved oxygen does not affect sedimentation performance of activated sludge in high loading rate; the polysaccharide content of activated sludge in high loading rate does not benefit the growth of filament, and furthermore the hydrophobicity of activated sludge is good, which cause good sedimentation performance of sludge in high loading rate.