Effect Of Chemical Uncoupler On Sludge Reduction, Nitrogen And Phosphorus Removal Efficiency

It is more and more difficult to dispose the sludge coming from wastewater treatment plant, and the wastewater treatment technology and method that have low sludge production become the focus and difficulty. Many studies showed adding chemical uncoupler in the wastewater treatment system could inhibit anabolism of microbial and reduce sludge production. However, present researches hold that it need high DO concentration in sludge reduction system, and the wastewater disposal effect, especially the nitrogen and phosphorus removal effect will be severely affected. This paper carries out a synthetic analysis of present researches on uncouple sludge reduction system, it holds that the operation mode of high DO concentration increases energy consumption, also accelerates the oxidation of biological substance, the latter is just the main reason of bad wastewater disposal effect. On the premise of good wastewater disposal effect, including nitrogen and phosphorus removal effect, we studied the changing of DO, sludge reduction effect, process performance and sludge characteristics, expecting good sludge reduction and wastewater disposal effect in condition of low DO concentration. The results indicate that:①The consumption of dissolved oxygen (DO) increased when TCP was added, and the time of low DO concentration also increased.②When TCP concentration was lower than 5mg/L, nitrification and denitrfication was affected lightly; When TCP concentration was higher than 5mg/L, nitrification and denitrfication could not carry through normally, made the nitrogen removal effect worse. Under the condition of low DO concentration in TCP sludge reduction system, aerobic nitrogen removal effect was better than anoxic nitrogen removal effect.③TCP inhibited the anaerobic phosphorus release effect, When TCP concentration was lower than 2mg/L, the inhibitory effect could be ignored. The higher TCP concentration, the lower aerobic phosphorus accumulation effect, but in TCP sludge reduction system, when TCP concentration was 2mg/L, aerobic phosphorus accumulation effect only decreased 8.5% comparing with comparison system, it showed that we could get good aerobic phosphorus accumulation effect in the low DO condition of TCP sludge reduction system.④The results of continuous operation showed that TCP is good uncoupler in reducing sludge production, the higher TCP concentration, the lower sludge production. Because low DO condition lasted longer in TCP sludge reduction system, the simultaneous nitrification and denitrfication was promoted, to some extent, it could counteracte the inhibition of TCP on nitrogen removal effect. When TCP concentration was lower than 4mg/L, effluent phosphorus concentrations were not inversely influenced, but effluent PO43--P and TP concentrations increased as TCP concentration higher.⑤Population structure of microbial was changed in TCP sludge reduction system, the species and quantity of protozoa and metazoa were cut down, and the sludge flcos became looser. Sludge settlability was affected greatly, the higher TCP concentration, the worse sludge settlability. Sludge oxygen uptake rate (SOUR) was higher than that of comparison system; it showed that TCP could improve the respiration rate of microbial. When TCP concentration was higher, the toxicity of TCP is severe and some sensitive microbial died, it made the SOUR value lower.Considering the effect of sludge reduction, process performance and sludge characteristics, the optimal concentration of TCP is about 2mg/L. From the economic benefit accounting of comparison system and TCP sludge reduction system, the operation cost of wastewater (including sludge) could reduce 0.019 yuan/m3; it showed that applying TCP to reduce excess sludge production in activated sludge system is feasible, not only in technique, but also in economic.