Study On The Effect Of Extracellular Polymer Substances On The Settleability Of The Sludge And Its Role In Biological Removal Of Phosphorus

From the angle of EPS in activated sludge, the effects of nutriment (nitrogen and phosphorus) and operation conditions (Ns and DO) on the settleability of activated sludge were studied deep in the paper. The regression equation was deduced in orthogonal experiment of nitrogen, phosphorus and Ns, DO. Moreover the synthetical effect of EPS and the content of its constitutes or surface charge (Zeta) on SVI were deep studied. Meanwhile some researches were done in the paper to understand the function and mechanism of EPS in biological removal of phosphorus from wastewater.The main conclusions are as follows:1) By means of the experiment of the effect of nitrogen and phosphorus on the settleability of activated sludge, the results of the experiment indicated: The effect of the content of nitrogen and phosphorus in the substrate on the total EPS and the constitutes of EPS was remarkable. When the ratio of BOD5/TN (100/5～100/0) or BOD5/TN 100/1～100/0) increaseed gradually (N-depleted or P-depleted), the total EPS and the concentration of the three main polymers carbohydrate, proteins and DNA in the extracted EPS increased individually. Thus the SVI of the sludge increased and the settleability of the sludge become poor. The regression equation was deduced in orthogonal experiment of nitrogen and pHospHorus: EPS =56.7751-0.09293(BOD5/TN)-0.03169(BOD5/TP)-0.00041(BOD5/TN)·(BOD5/TP) The effect of phosphorus on EPS was highly remarkable and the effect of nitrogen on EPS was commonly remarkable. The effect of their interaction on EPS was remarkable.2) By means of the experiment of the effect of DO and Ns on the settleability of activated sludge, the results of the experiment indicated: The Effect of the loading rate Ns and DO in the system on the total EPS and the constitutes of EPS was remarkable. When DO or Ns decreased gradually in the system, the total EPS and the concentration of the three main polymers carbohydrate, proteins and DNA in the extracted EPS increased individually. Thus the SVI of the sludge increased and the settleability of the sludge become poor. The regression equation was deduced in orthogonal experiment of DO and Ns: EPS=48.31-13.60Ns-1.59DO .The effect of Ns on EPS was highly remarkable and DO on EPS was commonly remarkable. The effect of their interaction on EPS was unremarkable.3) The results of the experiment indicated: An stronger positive correlation was...