Development of a Decentralized Drinking Water Treatment Plant Based on Membrane Technology for Rural Areas in Vietnam
Membrane technology with effective removal of microbial contaminants has been applied widely in drinking water treatment (DWT), but its sustainable and efficient application in rural areas still needs practical research. Backflushing and chemical cleaning are well investigated for membrane-based systems. However, these methods are not always followed properly and in full, especially in cases of applications for remote areas in developing countries. Important key challenges in real world applications are how the system would actually sustain with unskilled personnel, with no electric power for backflushing or with no chemical cleaning on the long run. These challenges were addressed within the framework of this dissertation. A dead-end Ultrafiltration (UF) with flat-sheet membranes was configured to a stationary DWT system working with low pressure and simplest maintenance, in combination with a suitable chlorination solution without energy demand.
In the literature review of this dissertation, an overview of many up-to-date membrane based systems in different categories of use is given in detail, covering different aspects of technology, service efficiency and economics.
Hydraulic performance of membrane-based systems is normally studied in lab-scale in limited periods from hours to days. Thus, highlight of this research is the investigation of a full-scale demonstration plant based on UF flat-sheet membrane with pore size of 40 nm, conducted in the Hydraulic Workshop at the University of Kassel, operated continuously day and night for long-term tests. The long-term examination focused on many aspects, from hydraulic performance including flux, permeability, transmembrane pressure, efficiency of the simple membrane cleaning methods, to biological quality of treated water and also efficiency of chlorination by using a mechanical chlorine dosing device. During long-term examination, the phenomenon of gas generation from the water in the plant was recognized. The influence of this phenomenon on the permeate flow rate was evaluated and solution for this problem by the gas trapping device was investigated in this research.
The experimental results from long-term examination of the Pilot Plant at the University of Kassel served for the materialization of the system into life. Two DWT plants were implemented in a rural village in southern Vietnam. It could be proved that the product of this research is realistically an economic relief of the long lasted insufficient supply to the crucial demand for safe water in the rural communities of developing countries.