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Beijing, China

Wang G.,CAS Research Center for Eco Environmental Sciences | Wang G.,North China University of Water Conservancy and Electric Power | Lu Z.,North China University of Water Conservancy and Electric Power | Shi B.,CAS Research Center for Eco Environmental Sciences | And 5 more authors.
Research of Environmental Sciences | Year: 2015

Making use of alternative sources of water (e.g. desalinated water, reclaimed water) and long distance water diversion are possible methods to solve water shortage problems. However, source water switching might cause undesirable water quality changes at consumer taps resulted from destabilization of corrosion scales in existing drinking water distribution systems (DWDS). In the present study, cast iron pipes historically transporting groundwater were harvested from three sites of an existing distribution system of a northern city in China, and pipe-loop simulation distribution systems were established to investigate the effects of different alkaline chemicals on iron release inhibition performance. For better comparison, the sulfate concentration of feed water was manipulated to obtain relatively high iron release. The results showed that: 1) The iron release decreased significantly with alkalinity supplementation (through NaHCO3 addition) in the range of 94-251 mg/L (as CaCO3) and could ensure the total iron concentration met the GB 5749-2006 Standards for Drinking Water Quality (<0.30 mg/L). 2) When water pH was elevated by addition of NaOH in the range of 7.83-9.01, the iron release was promoted to some extent instead of inhibition; while when the pH was elevated by adding Ca(OH)2, the iron release decreased obviously, but the total iron concentration was always higher than 0.30 mg/L. 3) Under the condition of low sulfate concentration of feed water, the iron release did not increase when NaHCO3 and Ca(OH)2 addition discontinued, but under high sulfate condition, iron release could increase again with the termination of alkalinity and pH adjustments. ©, 2015, Editorial department of Molecular Catalysis. All right reserved. Source

Mi Z.,Tsinghua University | Zhang X.,Tsinghua University | Lu P.,Tsinghua University | Chen C.,Tsinghua University | And 2 more authors.
Qinghua Daxue Xuebao/Journal of Tsinghua University | Year: 2013

This study investigated the effect of sulphate concentration changes on the iron release in a drinking water distribution system caused frequently switching of the water source. The rates of iron release from corrosion scale for different water sources were analyzed with pipe section reactors designed to simulate the distribution system flow mode. The results showed that the sulphate concentration was the dominant factor that led to red water. The iron release rate from the corrosion scale correlated well with the sulphate concentration with a sulphate concentration increase from 25 mg/L to 180 mg/L accompanied by a Larson ratio increase from about 0.35 to 1.40. The turbidity in the pipe section reactors increased 6 NTU after 8 h, the color increased 50 degrees and the iron release rate increased 2.00 mg/(m2·h). These results indicate that the sulphate concentration should be lower than 75 mg/L and the Larson Ratio should be controlled to less than 0.70 for the water quality in the distribution system to meet the Chinese drinking water quality standard. Based on these results, t was suggested to be and controlled less than 0.70 in order that in meet the standard of drinking in China. Source

Zhang X.,Tsinghua University | Mi Z.,Tsinghua University | Wang Y.,Tsinghua University | Wang Y.,Beijing General Municipal Engineering Design and Research Institute | And 6 more authors.
Frontiers of Environmental Science and Engineering | Year: 2014

A red water phenomenon occurred in several communities few days after the change of water source in Beijing, China in 2008. In this study, the origin of this problem, the mechanism of iron release and various control measures were investigated. The results indicated that a significant increase in sulphate concentration as a result of the new water source was the cause of the red water phenomenon. The mechanism of iron release was found that the high-concentration sulphate in the new water source disrupted the stable shell of scale on the inner pipe and led to the release of iron compounds. Experiments showed that the iron release rate in the new source water within pipe section was over 11-fold higher than that occurring within the local source water. The recovery of tap water quality lasted several months despite ameliorative measures being implemented, including adding phosphate, reducing the overall proportion of the new water source, elevating the pH and alkalinity, and utilizing free chlorine as a disinfectant instead of chloramine. Adding phosphate was more effective and more practical than the other measures. The iron release rate was decreased after the addition of 1.5 mg·L-1 orthophosphate-P, tripolyphosphate-P and hexametaphosphate-P by 68%, 83% and 87%, respectively. Elevating the pH and alkalinity also reduced the iron release rate by 50%. However, the iron release rate did not decreased after replacing chloramine by 0.5-0.8 mg·L-1 of free chlorine as disinfectant. © 2013 Higher Education Press and Springer-Verlag Berlin Heidelberg. Source

Lu Z.,North China University of Water Conservancy and Electric Power | Wang G.,North China University of Water Conservancy and Electric Power | Wang G.,CAS Research Center for Eco Environmental Sciences | Shi B.,CAS Research Center for Eco Environmental Sciences | And 6 more authors.
Chinese Journal of Environmental Engineering | Year: 2014

Water source switch to Danjiangkou reservoir (the middle route source area of the South-to-North Water Diversion Project in China) water might cause increased iron release in distribution systems of water receiving areas. Cast iron pipes transporting groundwater were harvested from three sites of existing distribution system of a northern city, and pipe-loop distribution systems were established in Danjiangkou. Pilot study was conducted to observe the outcomes of source water switch, and the effects of different disinfectants and dissolved oxygen concentration on iron release behaviors were investigated. Results show that the corrosion scales on the test pipes are relatively thin and less stable; at the early stage of water source switch, apparent "red water" occurs. The effluent iron concentration and turbidity increase accordingly with the increase of sulfate concentration. The change of iron release with free chlorine concentration change in the range of 0.3~3.6 mg/L has no clear trend. While iron release of YS system increases significantly as chloramine concentration is raised from 1.3 to 2.0 mg/L. When dissolved oxygen increases from 8 mg/L to 15 mg/L, iron release decreases significantly, but further increase of dissolved oxygen to 20 mg/L results in iron release increase. Source

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