Study On O₃/UV-BAC Combined Process For Rural Micro-polluted Source Water

As the dual challenges of Water shortage and worsening water pollution, and the unbalanced economic and social development, the rural drinking water of our country has faced with a widespread water shortage and water safety issues. The traditional water purification process in rural areas can not meet the demand for drinking water safety requirements. In this paper, an O₃/UV-BAC combined process was studied to treat rural micro-organic pollution of surface drinking water sources. Through the model selection of the unit of combined technology and by investigating the impact of water quality when changing the operating parameters, the best operating conditions of the process was selected. Finally we studied the purification of combined process for raw water.The study of O₃/UV process for treating raw water was carried out in laboratory and the effect of ozone dosage, HRT for oxidation section, the UV lamp power on the remove of contaminant by O₃/UV process was investigated through orthogonal test. The experiment focus on the removal of CODMn and TOC as a basis to determine the optimum conditions for oxidation unit as follows: ozone dosage is 7mg/L, HRT for oxidation unit is 15min and UV lamp power is 23W.By comparising the pollutant adsorption and removal of rate water by different carbon fillers, we choose the activated carbon B which has the best adsorption effect as a filler of BAC unit. And by examining the removal of CODMn, NH3-N, UV254 and NTU, the empty bed residence time (EBCT) of 30min is the economical and reasonable choice choice for BAC unit.The purification effect of O₃/UV-BAC overall combined process for the raw water was investigated, and the average removal rate of the four water quality indicators CODMn, NH3-N, UV254 and NTU, are 58.12%, 86.50%, 70.05% and 84.86%, respectively, when the operating conditions of the combined process is: ozone dosage=7mg/L, HRT of oxidation unit = 15min, UV lamp power=23W, EBCT of BAC unit = 30min. O₃/UV-BAC combined process can effectively purify the contaminated raw water, the effluent can fully meet the requirement of the latest national water quality "drinking water health standards" (GB5749-2006) s. In addition, it showed that, the BAC unit of the combined process of BAC process has higher purifying ability than the single BAC process under the same conditions, whose removal rate of the CODMn, UV254 is 16.15% and 19.32% higher than a single BAC, respectively. By analyzing the SUVI and BDOC/DOC of the raw water, it is found that the after the treatment process by O₃/UV, the molecular composition and structure of organic compounds in water changes, and a number of difficult- biochemical- degradation organic macromolecules is oxidative decomposited into small molecules, which increased biodegradability of water and strengthen microbial adsorption degradation of the follow-up BAC unit.