Study On Rainwater Harvesting And Utilization And Its Feasibility As The Drinking Water In The Island Environments

The drinking water crisis is one of the severe challenges facing the current and future human society.The situation in China is also not optimistic.Nansha Qundao,Xisha Qundao and some other islands which have a tropical monsoon climate in the South China Sea are far away from land and lack of drinking water,which restricts their further development.The Southeast Asia and South Asia countries along the belt and road initiative also face the drinking water safety problem.Rainfall is abundant on islands in tropical monsoon climate,so rainwater harvesting and utilization can be an significant method to solve this problem.In this study,Hainan Island and Sri Lanka under the tropical climate were used as experimental sites to analyze and compare the characteristics of water quality and quantity of runoff.Based on data obtained from rainfall runoff,domestic rainwater harvesting devices were designed and installed in Sri Lanka according to local conditions.Through the study and analysis of the rainwater quality in the storage tank of the domestic rainwater harvesting devices,the operation of the household rainwater harvesting and storage devices were evaluated,and the drinking water treatment process of rainwater in the storage tank was constructed.In this study,two sets of water catchment surfaces(cement road and cement roof)in Hainan Island were selected to analyze the water quality of rainwater runoff in rainy seasons and dry seasons.The results show that the runoff in Hainan island mainly polluted by color,turbidity,pH,ammonia nitrogen,total organic carbon,aluminum,lead,petroleum and microorganisms,and metal ions have the characteristics of seasonal changes.In the rainy season and dry season,the initial water quality of runoff is generally poor,and tends to be stable with the change of rainfall duration.The color maximum declined 75%on different catchments in rainy and dry seasons.The water quality in rainy season is better than that in dry season.The water quality of roof runoff is less influenced by the environment,and is better than the road surface.Rainwater harvesting was studied in Kandy,Anuradhapura and Puttalam in Sri Lanka.Runoff pollution in the three regions mainly comes from color,turbidity,pH,ammonia nitrogen,aluminum,manganese,organic matter and microorganism.Microbial contamination in rainfall runoff from different fields in Sri Lanka is random.CODcr and total organic carbon concentrations were higher in the early stage of rainfall runoff in Kandy,and the range of organic matter pollution was larger than that of Anuradhapura and Puttalam,and the maximum value was far greater than the other two regions.Color and turbidity are serious in the whole process of rainfall runoff,and the values of color and turbidity have a linear correlation.When color pollution is taken as a reference in the scheme of abandon flow,the rainfall of Sri Lanka roof abandonment ranges from 2.2 mm to 2.9 mm.Comparing the sources of rainwater runoff pollution in Sri Lanka and Hainan island,it was found that the indicators of pollution were similar,and the roof runoff in both islands faced coliform contamination.On the basis of in-depth study of rainwater runoff,the rainwater harvesting in Sri Lanka has formed a scheme with the domestic rainwater harvesting system as the core.The domestic rainwater harvesting system is composed of three parts:gutter,inlet pipe and water tank,and it works well.The collection system will not aggravate organic pollution in the process of scheme design,material selection and construction,but it cannot prevent microbial contamination.The water quality of rainwater in the water storage tank is significantly better than the water quality of rainfall runoff in terms of color,turbidity,pH,ammonia nitrogen and organic matter,etc.During long-term storage and operation,there are no contaminations release from the water storage tank itself,but the growth of thermotolerant coliform bacteria has been found.The preliminary rainwater treatment process can effectively reduce the concentration of ammonia nitrogen and the contamination of coliform bacteria,but it cannot completely remove the pollution of thermotolerant coliform bacteria.Further study is needed to improve the process according to this index.