Abstract
Sulfides and volatile organic sulfur compounds (VOSc) in water are not only malodorous but also toxic to humans and aquatic organisms. They cause serious deterioration in the ecological environment and pollute drinking water sources. In the present study, a source water reservoir—Zhoucun Reservoir in East China—was selected as the study site. Through a combination of field monitoring and in situ release experiments of sulfides, the characteristics of seasonal variation and distribution of sulfides and VOSc in the reservoir were studied, and the cause of the sulfide pollution was explained. The results show that sulfide pollution was quite severe in August and September 2014 in the Zhoucun Reservoir, with up to 1.59 mg·L−1 of sulfides in the lower layer water. The main source of sulfides is endogenous pollution. VOSc concentration correlates very well with that of sulfides during the summer, with a peak VOSc concentration of 44.37 μg·L−1. An installed water-lifting aeration system was shown to directly oxygenate the lower layer water, as well as mix water from the lower and the upper layers. Finally, the principle and results of controlling sulfides and VOSc in reservoirs using water-lifting aerators are clarified. Information about sulfides and VOSc fluctuation and control gained in this study may be applicable to similar reservoirs, and useful in practical water quality improvement and pollution prevention.
Highlights
Reservoirs have gained increasing importance as sources of drinking water for urban areas.In reservoirs, a three-layer temperature distribution tends to form in the summer due to the long hydraulic retention time and poor water convection [1]
The seasonal variation of sulfides in different water layers in the Zhoucun Reservoir during 2014 is shown in Figure 4a, with the sulfides concentration starting to increase in the middle of June, and reaching the highest concentration of 1.59 mg L1 in the bottom layer in August
The volatile organic sulfur compounds (VOSc) concentration decreased rapidly when the water-lifting aerator (WLA) started to operate, becoming undetectable at the end of the oxygenation operation. These results show that sulfides and VOSc in the water were effectively removed by the WLA operation, with a reduction rate up to 98%
Summary
A three-layer temperature distribution tends to form in the summer due to the long hydraulic retention time and poor water convection [1]. Such thermal stratification of reservoir water blocks the re-aeration pathway of the bottom-most water. Many researchers have studied the formation of thermal stratification and problems caused by hypolimnetic hypoxia [5,6,7,8,9]. Their studies mainly concentrated on the prediction of water
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