| This dissertation is a component of the key project 'Study on the recycling and reuse of water resources for the arid and water-deficient area in China' funded by National Natural Science Foundation of China (NSFC). Based on the characteristics of typical municipal wastewater in China, theoretical and experimental studies were carried out to identify and quantify the health risks associated with the chemical and microbial contaminants in reclaimed water. This paper first investigated the distribution of the contaminants in reclaimed water; and then analyzed the exposure pathway and dosage involved in different reuse applications, using clinical and epidemiological data, the author studied the dose-response model in regard with the main health risk factors. Mathematical model for microbial and chemical risk assessment was proposed for wastewater reuse in our country. By using an advanced virological trace technique, the removal of pathogen by several water treatment methods was investigated. The main results of the study are as follows:1. The author monitored and analyzed the concentration of chemical pollutants and microbial pathogens in the secondary effluent from a typical municipal wastewater treatment plant and that in the reclaimed water by coagidation-sedimentation-filtration, ultrafiltration and ozonation-biologjcal activated carbon adsorption treatment techniques. The monitoring data were analyzed with nonparametric hypothesis testing method and it was found that the concentration of all pollutants fit with lognormal distribution well. Thus, the lognormal distribution was used in this study as the statistical model for the pollutants concentration and variability in reclaimed water.2. Based on the current water reuse standard and water quality for different reuse purposes, the author calculated the safety of water quality to meet the standards or guidelines. The concentration of chemical constituents and microbial pathogens in secondary effluent was too high to meet the quality for reuse, while the safety of reclaimed water by three advanced treatment techniques increases notably. For microbial pollutants, the disinfection process should be employed to guaranty the high safety of reuse water.3. Taking Coxsackie B3 virus as virologjcal tracer, the characteristics of pathogen removal by chlorine disinfection, ozone disinfection, coagulation-sedimentation-filtration and ultrafiltration were studied, hi order to compare the difference between the removal efficiency of bacteria and that of virus, total coliform and fecal coliform densities were also analyzed using membrane filtration method. The coagulation-filtration process and UF can remove approximately 21ogs CoxB3 virus; the chlorination almost has no effect of CoxB3 virus inactivation at the residual chlorine dose range l-6mg/L at pH 6 and pH 7.5; ozone disinfection remove approximately 41ogs of seeded CoxB3 virus when the ozone dose was 2.1mg/L with a contact time of 15min. However, the UF, chlorination and ozonation can almost achieve a complete removal of the total coliform and fecal coliform, while the coliform removal by coagulation-filtration process is about 31ogs. Experiments results indicated that the virus has a greater resistance to disinfection than bacteria4. Three common reuse applications-landscape irrigation (Irrigation of public access areas, parks, etc), agricultural irrigation, and recreational impoundment (swimming, full body contact) were taken into consideration for evaluation of the health risks. The exposure pathways include inhalation of aerosols, ingestion of water or food, absorption through the skin via dermal contact. For landscape irrigation, the exposure was estimated as 1mL per day for 104 days; for agricultural irrigation, the exposure was judged asl0mL on each of the 365 days in a year; and for recreational impoundment, a swimmer is exposed to 100mL of reclaimed water on each of 40 days during summer season.5. For chemicals that are potentially carcinogenic or have known health ef...
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