Evaluation of DEWATS in Java, Indonesia

Under the Indonesian PPSP (Accelerated Sanitation Development for Human Settlements Program) thousands of new DEWATS (Decentralized Wastewater Treatment Systems) may be realized in the coming five years. Taking the massive scale of planned implementation into consideration an evaluation of the technical and financial-economic aspects and users' involvement for three different types of DEWATS was performed. Evaluated systems included (1) Settler (Set)+Anaerobic Baffled Reactor (ABR)+Anaerobic Filter (AF), (2) Digester+Set+ABR+AF and (3) Settler, equalization, activated sludge, clarifier, filtration. All three systems complied with the current regulations. System 3 suggested the best overall performance on selected parameters in the monitored period. A clear reduction in specific investment costs per household was found with an increasing number of households per system. Only daily, regular operational costs were recovered from fees collected by the community, whereas costs for desludging, major repairs and capital and replacement costs were not. Surveys with users showed a different degree of involvement of local men and women in the planning stages of the project for the systems. Recommendations are provided to scale up the introduction of DEWATS in a more sustainable way in the framework of a city wide sanitation strategy.