**6. Conclusion**

From the retrospection of the state-of-art of DHS system, it has always been considered a sustainable system for developing countries. Even though, there are extensive researches being carried out for the performance improvement and application of DHS for other types of wastewater, few efforts have been made for testing and validating the sustainability of DHS system. This chapter introduced and analyzed the sustainability indicators of DHS system based on environment, economic and social indicators. By assessing the range of environmental performance indicators, including treatment performance, land requirement, carbon footprint along with economic costs and social factors, this review provides information on DHS system pursuing positively towards sustainability than UASB+TF. However, the availability of data is still an issue in this context for both the systems. It is recommended to conceptualize the sustainability assessment framework that will also encourage and support data collection for better and more quantitative analysis to ensure the applicability and usefulness of DHS technology. Considering the outcomes from sustainability assessment, regardless of data insufficiency, the DHS system fulfilled the criteria of self-sustaining WWTP to a greater extent. Nevertheless, more comprehensive studies are suggested for understanding the other aspects of self-sustainability which are not discussed in this chapter.
