Drinking water is scarce in the Indonesian region of Gunung Kidul. In this karst area, rainwater quickly drains away into the ground. It accumulates in an underground cave system and flows into the ocean unused. For several years now, KIT scientists in cooperation with German industry partners have developed simple technologies to extract and distribute this water under the "Integrated Water Resources Management" (IWRM) project. They also implemented solutions for water processing, quality assurance, and sewage treatment. The new technologies and concepts serve as models for other karst regions.
Under the IWRM Indonesia joint project funded by the Federal Ministry of Education and Research (BMBF), hydraulic engineering experts of KIT built an underground cave power station. For the first time, they succeeded in completely filling a karst cave with water. In 2010, they handed the cave power station over to the Indonesian authorities. The plant can supply 80,000 people with water. For the water to reach the households in a clean state via the distribution network, a team headed by microbiologist Ursula Obst, who directs the partial project for water processing and water quality assurance, developed methods for the central, semi-centralized, and local processing of water.
The water from the cave is first filtered with sand in order to prevent turbid substances from entering the distribution network. In the next step, bacteria in the tap water are reduced. For this purpose, the KIT scientists established a pilot plant at the hospital of Wonosari. There, bacteria in the water are reduced among others by UV radiation and the addition of chlorine or by filtration using ceramic membranes. However, these methods require high-voltage current and, hence, are suited mainly for urban facilities, such as schools and hospitals.
"In the villages, where power is lacking, we need much simpler technologies," Obst says. The inhabitants collect tap water and rainwater in a local open pool. "There, animals and plants can pollute the water. We therefore recommend to cover the pool when there is no rain," Obst points out. The scientists also installed a sand filter that retains dirt and turbid substances when tapping the water. Prior to use, the inhabitants filter the water again with the help of a clay pot that is provided with very small holes. The water released via these holes is potable. The pots are produced by Indonesian potters using local materials according to specifications made by the scientists.
For water quality control, the scientists apply a rather simple method: Users take a small water sample and mix it with an enzyme substrate, a nutrient that activates certain enterobacteria only. If these enterobacteria are contained in the water, they convert the substrate and a clearly visible yellow color develops. If the water is contaminated, the cleaning steps are checked and the filtration system is repaired, if necessary.