The hydrothermal solution for decentralized drinking water purification

Decentralized drinking water purification complements water supply in areas with unreliable or absent infrastructure. The exacerbating consequences of climate change in form of droughts and floods force remote households to tap various water sources. Hence, household-based processes must be versatile to cope with e.g. contaminated ground water and turbid surface waters. Therefrom derived major pollutants are pathogens, suspended matter and micropollutants, the latter mostly originating from agricultural runoff. Moreover, purification at household level must ensure easy operation; minimum and easy maintenance; and minimum dependency on supply of spare parts, consumables and most notably 24/7 power supply. The main objective of this thesis was to develop a water treatment process that fulfills the above-mentioned requirements, and to demonstrate its technical feasibility in order to assure self-sustaining operation at household level.The developed process consisted of two steps: water purification and process regeneration. In the first step, water was purified by state-of-the-art gravity-driven ultrafiltration and activated carbon adsorption. However, the process regeneration represents the crucial step in fulfilling the above-mentioned requirements. Therefore, the second step, the process regeneration was conceived of employing a simple pressure cooker to yield a hydrothermal solution, that is liquid water under elevated pressure and temperature. Consequently, the elevated pressure was exploited to backwash the ultrafiltration membrane (so-called Temperature Enhanced Backwash); and the elevated temperature was exploited to desorb organics from the adsorbent (Temperature Swing Adsorption). With the final process design, stable operation over more than 40 days was demonstrated by a sustained flowrate and a consistent product quality (high removal of turbidity, micropollutants and organics) for all relevant raw waters. In particular, no adsorbent exhaustion was observed. Hence, the in-situ regeneration promises long-term, self-sufficient operation that remains to be verified in forthcoming field tests. This process can potentially contribute to safeguarding the access to improved and safe drinking water for more than 785 million people around the world that are currently lacking this fundamental human right