Study On The Formation Of Improved Aerobic Granular Sludge By Ce And The Performance In SBR

Rare earth Cerium has widely biological effect on animal, plant and bacteria. Suitable concentration Cerium can enhance the activity of enzyme, increase the amount of microorganism, promote the formation of aerobic granular sludge, and improve the performance of aerobic granular sludge. Today, the nitrogen and phosphorus removal technology aimed for eutrophication control has been the study focus in the wastewater treatment area. Acetic acid and propionic acid are the main composition of short chain fatty acid (SCFA) in real wastewater. This paper studied the effect of carbon source on activated sludge and the formation of aerobic granular sludge in two same SBR which took sodium acetate or sodium propionate as single carbon source respectively while Ce3+(50 mg/L) was added, so as to further study the biological effect of Cerium on the formation of aerobic granular sludge. We studied effects of the changes of sodium acetate/sodium propionate on the nitrogen and phosphorus removal of aerobic granular sludge. Performance, characteristic of operation cycle and denitrifying phosphorus removal kinetics of improved aerobic granular sludge by Cerium under optimum composition of carbon source were also researched. Conclusions as follows:1) Research showed that the amount of EPS, the ratio of Protein/Amylose of the sludge had the same change trends in two SBR, but the amount of EPS of the sludge which took sodium propionate as single carbon source was bigger, this indicated suitable concentration of Ce3+ can improve growth, enhance the activity of enzyme, improve surface of activated sludge which had different carbon source while the same concentration of Ce3+ had different effect on different carbon source, sodium propionate was more sensitive.2) Changes of Ce3+ in the sludge in the formation of aerobic granular sludge indicated that sludge had optimum absorb concentration of Cerium. The concentration of Ce3+ in sodium acetate aerobic granular sludge bigger than that in sodium propionate aerobic granular sludge indicated that different carbon source had different optimum absorb concentration of Cerium. Distribution of Ce3+ in the sludge also has great importance to the performance of aerobic granular sludge.3) Pollutants removal effect of the wastewater indicated that the sludge in two SBR all had high COD removal rates (95.5% and 96.7% respectively) while sodium acetate aerobic granular sludge had better TP removal effect (91.2% and 86.8% respectively) and sodium propionate aerobic granular sludge had better TN removal effect (77.3% and 84.4% respectively).4) The study on performance of aerobic granular sludge showed that sodium acetate aerobic granular sludge had smaller particle size (0.4-0.6mm and 2-5mm respectively), SVI (27.4 ml/g and 42.5 ml/g respectively), moisture (85.1% and 91.2% respectively) while sodium propionate aerobic granular sludge had better performance on hydrophobicity (63.2% and 68.3% respectively) and settling velocity (51.97m/h and 86.96m/h respectively).5) The study on microstructure of aerobic granular sludge showed that sodium acetate aerobic granular sludge was solider, the kinds of microorganism was more, the volume of microorganism was smaller, the distance of interstice was shorter while sodium propionate aerobic granular sludge had internal holes, the number of spore was smaller, biological activity was worse.6) Batch experiments showed that improve the ratio of sodium propionate/ sodium acetate can promote the nitrogen and phosphorus removal of aerobic granular sludge, the best the ratio of sodium propionate/sodium acetate (COD) was 3:1.7) Studies on characteristic of operation cycle and denitrifying phosphorus removal kinetics of improved aerobic granular sludge by Cerium under optimum composition of carbon source showed that COD,TN,TP removal rates of improved aerobic granular sludge are 95.8%,82.8% and 96.7% respectively. The denitrifying phosphorus removal kinetic parameters of improved aerobic granular sludge were below:νmaxNO3-of the aerobic granular was 0.107 mg NO3--N/mg MLVSS·d, Ks,NO3- of the aerobic granular was 0.326 mg NO3-N/L; The aerobic granular would absorb 1.31mgPO4--P average when it reducing per mgNO3-N in the process of denitrifying phosphorus removal.