RESEARCH ON SAFETY TEST OF SLUDGE WATERREFLUX COAGULATION

摘要

Using lake water in the campus as the raw water, the pilot-scale test of sludge water reflux is con- ducted to determine the turbidity, chroma, CODMn, UV2s4, ammonia nitrogen content, total phosphorus content, metal content (Al, Fe, Mn, etc.), total bacte- rial count and the number of fecal coliform of the water firstly to evaluate the safety of the reflux: then Zeta potential and floc particle size change of the wa- ter is measured to indicate the effect of sludge waterreflux; finally, the effect for sludge water reflux to treat the low temperature and low turbidity water is investigated. The experiment demonstrates that: un der the test conditions, the lowest turbidity and chroma of the effluent appear at a dosage of 30 mg/L. and the reflux ratio is between 2% and 4%: CODMn and UV2s4 reach the lowest value at reflux ratios of 4% and 6% respectively, with the removal rate in- creased by 15%-20%, compared with that without reflux; the ammonia nitrogen content will increase along with the reflux ratio, with the reflux ratio con- trolled at about 2%: the total phosphorus content is controlled at about 0.4 ug/L under 2% reflux ratio; the content of Al. Fe. and Mn in the effluent has not accumulated: the total bacterial count and the num- ber of fecal coliforms may be prevented from over- growth with the reflux ratio controlled within 4%. To sum up, sludge water reflux with an appropriate re-flux ratio may guarantee both the enhanced coagula- tion and the safety of the effluent. Secondly. the FCD floc displaver shows that sludge water reflux can en- hance the compactness of the floc with the effect of enhanced coagulation. Finally, the comparison test of the low-temperature and low-turbidity water inthe presence or absence of reflux shows that com- pared with the case of no reflux, the sludge water re- flux can increase turbidity and promote CODMn, UV254, and removal rate by 13%, 11%, and 7% re- spectively.