The drinking water quality closely correlates with the life and health of the public, therefore, the tap water pollution and drinking water safety has become a concerned issue by the whole world, which is led by the pollutants in the water sources, and the produced toxic and harmful substances during the water purification processes.

Based on the system method of safety assurance and users’ health risk assessment during the water supply, for three important phases of safe water supply: source water, process water, and pipe network water, multiple methods with the combination of chemical analysis, multi-endpoint biossays, biological on-line monitoring, health risk assessment and etc. are used to estimate the safety of drinking water and the process. For the water quality change during the water treatment processes, automatic and on-line monitoring technology is established. Different health risk analytical methods are established according to the drinking habits of habitants in different regions in order to provide established and technical support for the drinking water with high safety in China. Main progress includes:

(1) Development of relatively complete chemical analysis/quanlity assurance method system and the screening method of preferably controlled substances
By far, the quantifiable water quality indices and chemical pollutant indices include: volatile organic substances (54 categories), organochlorine pesticides (20 categories), PAHs (16 categories), polychlorinated biphenyl (12 categories), algal toxin (2 categories), methyl phthalate (8 categories), nonyl phenol and bisphenol A, organic P and carbamate pesticides (32 categories), substituted phenol (10 categories), substituted benzene (13 categories), disinfection by-products (6 categories) and acrylamide and etc.

In the case study in Shenzhen WaterWorks, the above mentioned over 280 indices are monitored for the source water and waters during the treatment processes. The pollutant concentration scope of different seasons is obtained, and the screening of preferably controlled substances is carried out according to related standards/rules in China. The control list is proposed for Shenzhen WaterWorks:

Preferably controlled: chroma, turbidity, pathogenic micoorganisms, polonium, boron, aluminium, benzo(a)pyrene.
General detection: taste, solid substances, hardness, NO3-, SO42-, fluoride, total cyanide, Cr, NH4+-N, Fe, Ba chloroform, α-HCH, β-HCH, γ-HCH, γ-Chlorane, α-chlorane, chrysene, benzo[b]fluorathene, benzo[k]fluorathene, chrysene, benzo[b]fluorathene, benzo[k]-fluo- rathene, ∑PCBs, algal toxin (LR, RR).

(2) Development of in-vitro-bioassays and total toxicity level assessment method for drinking and surface water
in-vitro-bioassay is introduced into the safety assessment of drinking water, and thus new water quality assessment indices are constructed based on the conventional water quality ones, to develop and perfect the group organism test method, and develop a set of water quality assessment system in the molecular and cell level. The system includes: 1. Acute toxicity test of organic substances with photobacteria; 2. Cytotoxicity determined by the neutral red test; 3. Mutagenicity determined by Ames, umu, COMET and V. faba root micronucleus test; 4. Dioxin like-substance-effect detected by EROD test; 5. Endocrine disruption effect detected by Yeast assay and human mammary cancer (MCF-7) cell proliferation test; 6. Neurotoxicity of organic P and carbamates detected by acetylcholine esterase test. Investigations on the variation of the endocrine disruption effect during the water treatment process of waterworks show that the removal effect is not obvious for estrogenic substances through the conventional water treatment process.

(3) Water quality on-line organism monitoring
The multispecies freshwater biomonitor (MFB) manufactured by Germany LIMCO Corporation is used. The objectives of water quality on-line monitoring include: 1. Preventing serious water quality pollution accidents such as toxic substance addition; 2. Preventing the large-scale water quality change of source water, and subsequent decrease of water supply quality; 3. Preventing the excess of used preparations during the process; 4. Controlling the water quality out of the waterworks relatively stable. At present the key work is to investigate the rules between the mobility, shift, respiratory change under the roles of water quality change and less toxic substances and subsequent physical quantity variation (field disturbance effect) for protozoan, Daphnia magna, fishes and etc.Finally they will be applied to water quality safety control for drinking water during the process.

(4) Pipe network water (users end) water quality health risk assessment
The average exposure model (Drinking/Sample, D/S), consumption habit exposure model (Water Consumption Habit Survey, WCHS), and risk assessment model are used to discuss the health risks caused by the heavy metal exposure for the population in Beijing and Shanghai. The drinking water quality, pipe network materials, management ways, consumption habits, life styles, and season variation are investigated to find out the impacts of heavy metals in water on human exposure, and assess possible health risks. Simultaneously, the differences between WCHS and D/S method are compared, and the risk levels and causes for potential exposure and instantaneous exposure are elucidated.