This paper assesses the technical and economic sustainability of a combined system of an up-flow anaerobic sludge blanket (UASB)-down-flow hanging sponge (DHS) for sewage treatment. Additionally, this study compares UASB-DHS with current technologies in India like trickling filters (TF), sequencing batch reactor (SBR), moving bed biofilm reactor (MBBR), and other combinations of UASB with post-treatment systems such as final polishing ponds (FPU) and extended aeration sludge process (EASP). The sustainability of the sewage treatment plants (STPs) was evaluated using a composite indicator, which incorporated environmental, societal, and economic dimensions. In case of the individual sustainability indicator study, the results showed that UASB-FPU was the most economically sustainable system with a score of 0.512 and aeration systems such as MBBR, EASP, and SBR were environmentally sustainable, whereas UASB-DHS system was socially sustainable. However, the overall comparative analysis indicated that the UASB-DHS system scored the highest value of 2.619 on the global sustainability indicator followed by EASP and MBBR with scores of 2.322 and 2.279, respectively. The highlight of this study was that the most environmentally sustainable treatment plants were not economically and socially sustainable. Moreover, sensitivity analysis showed that five out of the seven scenarios tested, the UASB-DHS system showed good results amongst the treatment system.

No abstract

In this study, conventional slow sand filter (SSF) and modified slow sponge sand filter (SpSF) were investigated for the post-treatment of up-flow anaerobic sludge blanket (UASB)-down-flow hanging sponge (DHS) reactor effluent. The seasonal variation did not show significant differences in removal efficiencies of both filters. However in summer, both filters were able to achieve high total suspended solids and total biochemical oxygen demand removal averaging 97% and 99%, respectively. Contrary to organic removal, total nitrogen removal efficiency was satisfactory, showing increased removal efficiencies averaging 58% and 62% for SSF and SpSF in summer. On the other hand, average total coliform removal of SSF and SpSF was 4.2 logs and 4.4 logs and corresponding Escherichia coli removal was 4.0 logs and 4.1 logs, respectively. From our observation, it could be concluded that the relative performance of SpSF for nutrients and coliforms was better than SSF due to the effectiveness of sponge media over fine sands. Moreover, microbial community analysis revealed that the members of phylum Proteobacteria were predominant in the biofilms of both filters, which could have contributed to pollutant removal. Therefore, SpSF could be concluded to be a suitable post-treatment of UASB-DHS system in warmer conditions.

No abstract

Need of self-sustaining wastewater treatment plants (WWTPs) has become critical to cope up with dynamics of the environmental regulations and rapid advancements in the contemporary technologies. At present there are limited number of self-sustaining WWTPs around the world. The aim of this chapter is to present state -of- art of Downflow Hanging Sponge (DHS) system which was developed as a post treatment unit of Upflow Anaerobic Sludge Blanket (UASB) from sustainability perspective. DHS system is a non-submerged fixed bed trickling filter (TF) that employs a core technology of polyurethane sponges as a media where the microorganisms thrive and major treatment processes take place. This chapter reviews the introduction of DHS system (UASB+DHS) summarizes the quantitative analysis of environmental, economic and social sustainability using indicators. Furthermore, self-sustaining prospects of DHS system are assessed and discussed by comparing with conventional TF (UASB+TF).