Design of Dual Water Supply System Using Rainwater and Groundwater at Arsenic Contaminated Area in Vietnam

Abstract

In Cukhe, a village located in the outskirts of Hanoi, the capital of Vietnam, people suffer from a shortage of high-quality water due to arsenic contaminated supply water resource. We found that a dual water supply of rainwater and groundwater is a suitable method to provide sustainable water to the local residents. Rainwater is supplied for potable purposes. Groundwater is supplied for non-potable purposes. In this paper, a novel model is developed based on rainfall variance. An Rainwater Harvesting (RWH) system can get optimal performance by changing demand of water use due to rainfall. This model is then used to assess the reliability and water savings of an RWH system for Cukhe village. Using rainwater for portable purposes in dry days and for all purposes in rainy days is recommended. The cost of RWH systems was analyzed. In order to get 100% reliability, an RWH system has a roof area of 100m2 and a tank size of 2m3 is recommended in terms of cost efficiency. From the water supply chart in a year, it is recommended that rainwater should be supplied for only potable purposes in January-April and October-December

and should be supplied for all purposes in May-September. The research also investigated arsenic removal from groundwater. A novel adsorbent Fe-Mn-Si oxide was prepared by coprecipitation from environmentally friendly and low-cost materials for effective arsenic removal and evaluated its arsenic adsorption capacities. Batch and column adsorption experiments were conducted to study efficiency adsorption of arsenic on Fe-Mn-Si oxide. Results from this study demonstrate the potential usability of Fe-Mn-Si oxide as a good arsenic-selective adsorbent. Eventually, this research suggested water supply system options. There are three water supply system options namely: (1) rainwater supply system

(2) groundwater supply system and (3) Dual system which rainwater is used for drinking purposes and groundwater is used for non-drinking purposes. The triple bottom line considerations, the environmental, economical, and social impacts of the systems are examined. From the results it is clear that rainwater harvesting is a sustainable method to obtain good-quality drinking water at low cost and with little energy expenditure. A dual system, rainwater is supplied for drinking purposes and groundwater is supplied for non-drinking purposes, is recommended in terms of engineering, social and economic benefits.