The anaerobic-anoxic sequence batch reactor (A2SBR) was applied to achieve nitrogen and phosphorus removal in an energy-saving sewage treatment system involving an up-flow anaerobic sludge blanket combined with a down-flow hanging sponge reactor to treat municipal sewage. After sludge acclimation, the A2SBR showed satisfactory denitrification and phosphorus removal performance with total phosphate and nitrate concentrations of the effluent of 8.4 ± 3.4 mg-N L⁻¹ and 0.9 ± 0.6 mg-P L⁻¹, respectively. 16S rRNA gene sequence and fluorescence in situ hybridization analyses revealed that 'Candidatus Accumulibacter phosphatis' was the dominant phosphate-accumulating micro-organism. Although a competitive bacterium for polyphosphate-accumulating organisms, 'Ca. Competibacter phosphatis', was not detected, Dechloromonas spp. were abundant. The ppk1 gene sequence analysis showed that the type II lineage of 'Ca. Accumulibacter' was dominant. The results suggest that denitrification and phosphorus removal in the A2SBR could be achieved by cooperative activity of 'Ca. Accumulibacter' and nitrate-reducing bacteria.

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.

A sulfur-redox-reaction-activated up-flow anaerobic sludge blanket (UASB) and down-flow hanging sponge (DHS) system, combined with an anaerobic/anoxic sequencing batch reactor (A2SBR), has been used for municipal sewage treatment for over 2 years. The present system achieved a removal rate of 95±14% for BOD, 74±22% for total nitrogen, and 78±25% for total phosphorus, including low water temperature conditions. Sludge conversion rates during the operational period were 0.016 and 0.218 g-VSS g-COD-removed(-1) for the UASB, and DHS, respectively, which are similar to a conventional UASB-DHS system, which is not used of sulfur-redox-reaction, for sewage treatment. Using the sulfur-redox reaction made advanced treatment of municipal wastewater with minimal sludge generation possible, even in winter. Furthermore, the occurrence of a unique phenomenon, known as the anaerobic sulfur oxidation reaction, was confirmed in the UASB reactor under the winter season.

In order to fulfill the imperative need of proper organic matter and nutrient removal technology, an integrated system of up-flow anaerobic sludge blanket (UASB), down-flow hanging sponge (DHS) and anaerobic/anoxic sequencing batch reactor (A 2 SBR) is developed in this study. An aerobic reactor called DHS has porous sponge material for oxygen supply and microbes retention. Likewise, A 2 SBR is reported to remove nutrients, like phosphorus and nitrogen, effectively using denitrifying phosphorus accumulating organisms (DNPAOs) with less sludge production. The findings of this study demonstrated that the average SS, COD and BOD removal efficiencies by UASB-DHS were 86%, 87% and 97%, respectively, in summer and were 69%, 78% and 88%, respectively, in winter. Moreover, upon adjusting the pH to 7.4 ± 0.2 and with COD/P of 20, phosphate removals as low as 1 mg-P/L and nitrate concentration as low as 5 mg-N/L were achieved. Therefore, this proposed system could be an innovative solution for the present prevalent municipal wastewater treatment problems due to its effective organic and nutrient removal capabilities.

The Slanted-Soil-Chamber-Method (SSCM) is an energy-saving aerobic purification method. We performed an experiment to elucidate this purifi cation mechanism using a SSC reactor fi lled with a sponge carrier. This experiment demonstrated concurrent purification of organic pollutants, total nitrogen (T-N) and total phosphorus (T-P) for a hydraulic retention time of 20-50 min. Water and organic pollutants are separated as the gravity-fed wastewater passes through the reactor chamber. Treatment of the dissolved organic pollutants relies upon biological adsorption, which takes approximately 20-50 min. Since biological purifi cation activity within the SSC reactor is high except the winter season, the organic matter that is trapped in the chamber is effi ciently decomposed by organisms that are typically found in soil. The SSC reactor weight increased in the winter season and decreased in spring. The extent of T-N and T-P purifi cation was dependent upon heterotrophic microbial utilization. Furthermore, T-N is purifi ed by nitrifi cation/ denitrifi cation, and T-P is purifi ed by trapping the phosphorus-containing soil in the SSC reactor. The advantages of the SSC reactor are that it separates pollutants from water, degrades organic matter, reduces sludge, and simultaneously removes T-N and T-P in the same reactor chamber.