Study On Deep Treatment And Disinfection Techniques Of City Dual Water Supply

Most of the drinking water sources in our country are heavy polluted. These types of source water are hard to reach high standards after they are treated by current water plant techniques. Dual water supply is a newly-developed field to supply drinking water with high quality. However, there are many problems both in theory and techniques for dual water supply, which have limited its development. In this study, tap water taken from Guangzhou City as an example to investigate micro-pollutants and evaluation. On the base of this, the study on dual supply water system is conducted, including deep treatment and disinfection technique, tube quality evaluation and safety evaluation. The following main results have been achieved:(1). The big problem of the tap water from Guangzhou City is the organic micro-pollutants, with TOC ranging from 1.5 to 4.5 mg/L, and positive behaves of the Ames' mutagenic test. According to this micro-pollution characteristics, a new combination technique of RO + NF was investigated and suggested as the deep treatment technique for dual water supply. This combination technique has a high removal proportion of micro-pollutants with more than 90% for the organic micro-pollutants and more than 60-80% for other micro-pollutants, and a high recovery of purified water, up to 85 %.(2) A disinfection combination technique of UV + TCCA was suggested to be applied to dual tube drinking water supply engineering based on a comparison of different common used disinfection methods. The results have shown that, this combination technique, in the case of 0.1 mg/L of TCCA dose in supplying water and more than 0.03 mg/L of effective chlorine in tap water, can control effectively microorganism parameters in a dual tube drinking water supply system.This technique has a lower running cost, a stable disinfection effect, and is worth popularizing in the dual tube drinking water supply engineering.(3). Micro-solution of different types of drinking water dual distribution tubes acted by different types of disinfects was conducted. The results have shown that although the micro-solution compounds from the tubes cannot lead to a significant change of related water parameters, they have a deep influence on the drinking water taste and odor, and that a tube which is suitable for drinking water dual distribution should be, besides meeting other quality requirements, TOC <0.08 mg/L, VOCs<5 ug/L and taste rank in the range of 1-2 under the experiment conditionsIVsuggested in this paper.(4). A dual water supply engineering of Guangzhou Baiyun Golf Garden was demonstrated by the studied and developed combination techniques, including deep treatment techniques and disinfection techniques. This demonstration engineering has been running for two year and it is quite stable.(5). It is suggested that three aspects should be considered to evaluate dual supply water safety. They are microorganisms, disinfected by-products and mutagenic effects. A 0.03 mg/L of effective chlorine in tap water, with the combination of water recycle, can guarantee microorganism risk in a dual tube drinking water supply system. The mutagenic effects of the disinfected by-products from the dual supply water is about 1/10 of the source tap water. TOC is suggested as a water quality parameter with a limited amount of 0.5 mg/L for dual supply water.These results have a great significance to improve the current technique of dual water supply and promote the development of this field.