The Hygienic Quality Analysis And Investigation Of Urban Drinking Water From The Four River System Basin In Hunan Province

Objective: To investigate hygienic quality of raw and product water of centralized urban water supply in Xiangjiang river, Zishui river, Yuanjiang river and Lishui river basin (hereinafter referred to as the four river basins), and to provide scientific basis for recent planning of health supervision and the application of "Standard testing methods for drinking water" (GB5750-2006) on urban drinking water of Hunan.Methods: According to geographic distribution of river basins, 23 water plants were chosen randomly, where raw and product water samples were collected in rainy and dry seasons. Water quality monitoring was carried out according to "Surface water environmental quality standards" (GB 3838-2002), "Standard testing methods for drinking water" (GB5749-2006) and "Standard testing methods for drinking water" (GB5750-2006).Results: among 46 raw water samples, 23.9% up to class II standard and above, qualified rates of Xiangjiang river, Zishui river, Yuanjiang river and Lishui river were 28.6%, 0.0%, 35.7% and 50.0%, the lowest was Zijiang rive(p<0.05). Main contaminants in the four river basins were mercury, arsenic, iron, antimony and thallium. Mercury was common in four rivers, and antimony was the main contaminant of Zijiang river. Sodium, chromium, arsenic, thallium in Xiangjiang river were higher (p<0.05). Antimony and ammonia nitrogen in Zijiang river were the highest (p<0.05). Barium in Yuanjiang river was more (p<0.05). Iron concentration and total hardness in raw water of Lishui river were significantly higher than other rivers (p<0.05). In addition, mercury and iron concentration of Xiangjiang river, Yuanjiang river and Lishui river were significantly higher in rainy season than in dry season (p<0.05).Qualified rates of the conventional projects of Xiangjiang river, Zishui river, Yuanjiang river and Lishui river were 78.6%, 62.5%, 100.0% and 87.5%, qualified rates of different river basins showed no significant difference(p> 0.05). Aluminium, arsenic in conventional index and antimony, thallium in non-conventional index affected drinking water Hygienic quality. Arsenic and antimony were the main contaminants in product water of the four river basins, arsenic in Xiangjiang river had a higher concentration than the other rivers (p<0.05), the concentration of antimony in Zijiang river was the highest (p<0.05). Chromium, ammonia nitrogen, barium, total hardness, chloride, oxygen consumption, sodium did not exceed the limits, but showed significant differences in product water of different rivers (p<0.05). Levels of antimony, thallium, aluminium, arsenic showed no significant difference in product water and raw Water (p>0.05). Trichloromethane, trichloroacetaldehyde in product were higher than that in raw water (p<0.05). Turbidity, naked-eye visible residues, iron, manganese in raw water were than product water (p<0.05).Conclusion: The hygienic quality of urban drinking water in the four river basins was mainly affected by heavy metal contamination, it closely related with the industrial wastes emission. Conventional water-production technology (mix- precipitation- filtration- sterilization) can only improve on sensory traits, general chemical and bacteriology items, but showed limited effect on heavy metals. Therefore, to improve urban drinking water quality, we must think highly of water source area environment protection, and reduce environmental pollution. Water-production technique should be advanced in order to ensure hygienic quality of product water. In regular health supervision, index and frequency of non-conventional item could be adjusted according to local condition, to ensure maneuverability and efficiency of drinking water Hygienic Standard.