Clean freshwater is a resource indispensable to all life and it is needed in rather large quantities for most human activities. Climate, freshwater, biophysical and socio-economic systems are interconnected in complex ways, so a change in any one of these systems induces a change in another. Many studies have shown that climate change induces freshwater pollution and it will cause increases in salinity when sea level rise. Hence, activities to promote protection of water resources, sustainable use of freshwater including water re-use are very urgent. In addition to regulative measures to facilitate sustainable water use, research on adaptive technology, energy optimization in water treatment systems, water recycling and reuse of water are important aspects of future water handling and management.
The paradox during natural disasters is that although a large area is flooded and covered by water, there is no clean water available. During such periods many new diseases are likely to develop as diarrhea, typhoid, and skin problems due to lack of clean water. In Vietnam, many areas still do not have regular water supply systems but obtain drinking water from common water well. In other cases communities do have water supply systems, but these systems are disabled or destroyed during flood disasters. Unfortunately, it takes long time to re-launch these systems after a flooding, and also has substantially costs. Hence, the current solution to temporarily produce water for drinking a cooking during a flooding disaster is to add alum for coagulation and precipitation of pollutants followed by disinfection by chloramines. This is expensive, and the waters produced are not healthy and may contain pollutants even after treatment. Thus, supply with freshwater during flood and post-flood periods are of special importance.
In Vietnam, more than 80% of the population works in agriculture, comprising both crop and animal production as well as production in aquaculture. Use of fertilizers, insecticides, herbicides, and antibiotics are critical to production costs and to safeguard production; use of agrochemicals has been increasing over the last 20 years and it is still increasing. However, agrochemicals are also a major source of pollution to water resources. During periods of flash floods or inundation, flooding water brings nutrients and sediments to soils which in general can increase soil quality. Unfortunately, the flooding water causes dispersion of the contaminants present in soil, pesticides in plants, and antibiotics present in aquaculture ponds. The situation is aggravated as agrochemicals are often overdosed, and as soils and sediments still contain persistent pollutants such as dioxins originating from the war. In addition some soils have high natural contents of toxic trace elements, most seriously arsenic which is highly toxic to humans [2,3]. Pollutant release and spreading is highly variable depending on soil properties, pollutant chemical characteristics and loads, the hydrological regime and flow pathways. Hence, there is a strong need to investigate how toxic soil pollutants are released and spread during flooding disasters.
The main objective of the proposed project is to carry out research on water cleaning methods which can be used to treat polluted water rendering it available for human consumption. The research will be followed by method optimization and development of a pilot plant for water treatment. The pilot system will be applied to provide clean water for households during flooding disasters and to treat sewage water from agricultural production in order to reuse the water. The new water treatment technology should be robust, fast, and it should respond to many different types of pollutants present at variable concentrations. Also, the water treatment systems should be highly flexible, applicable at different scales, and be energy and cost efficient and producing low emissions. However, for construction of optimal water treatment systems the composition of the water to be treated should be characterized, and hence a second objective of the project is to obtain knowledge on flooding water quality, and in particular how the flooding water pick up contaminants from inundated soils and sediments. A third objective comprise the food safety aspects of the water treatment process.
Drinking water pilot system
Based on the data collected, the process studies and optimization parameters, a modularized water treatment pilot plant will be build. The pilot will involve three main modules: coagulation/flocculation, mineralization reactor and disinfection module. Coagulation/flocculation method is well known in water treatment for efficient removal the heavy metal as well as the suspended particles. Additional, trace of ferric ion or hydroxide ferric, which usually use as coagulation agent, can be serve as a homogeneous or heterogeneous catalyst in Photo-Fenton and Electro-Fenton process.
The mineralization reactor will be constructed based on Ozonation, photo-Fenton, Electro-Fenton or combined of these processes, which is heart of pilot plan. This module – reactor is responsible for degradation of organic compounds as well as disinfection. Other pilot operation parameters such as water flows, energy, optimal condition, etc will be test. To ensure the quality of produced water, the pilot will integrate a measurement online system to determinate some mainly parameters e.g. pH, redox, DO, TOC, etc…
At preliminary stage, the pilot plant will produce 1000 liter per 24 hours may be developed. After optimization in the laboratory and tested with real samples, all component will be build as a mobile system and transportable. An assessment on the validity of the method, technical parameters and economics factor will be realized. The built pilot plan will be applied for on-site drinking water production in flooding period and for treatment of effluent from agricultural or aquacultural activity. The user manual is also produce for facility of fieldworks application