Madan Tandukar

Development of Self-sustainable Municipal Sewage Treatment System consisting of UASB and DHS (Down-flow Hanging Sponge) Reactors for Developing Countries

Prof. Harada Hideki, Assc. Prof. Ohashi Akiyoshi

Pollution of water bodies due to the discharge of untreated or partially treated municipal sewage in most of the developing countries does not need any further explanation. Practical scale UASB has been installed in many developing countries (tropical and sub-tropical regions) like; Brazil, India, Colombia, etc. But treatment of municipal sewage by UASB alone cannot meet the discharge standards of those countries. There must be a post treatment unit to further polish up UASB effluent. Post treatment along with UASB can only be applied beneficially if it is simple, inexpensive and at the same time, efficient. gDown-Flow Hanging Spongeh (DHS) reactor has been proposed as a novel post treatment unit for UASB treating municipal sewage.
This study aims at the evaluation of process performance of sewage treatment system consisting of UASB and the gFourth Generationh DHS named as G4. Efficiency of the new generation DHS was evaluated as a post treatment unit.
Grab sampling of the influents and effluents were done thrice a week. Parameters analyzed were Filtered and unfiltered BOD, COD, nitrogen species, SS, VSS, gas production from UASB and composition, etc.
Presently, a 1.15 m3 UASB reactor and 0.375 m3 DHS (G4) have been installed and are in operation in municipal sewage treatment site, Nagaoka. At present HRT of UASB is 6h and that of DHS is 2h.
Results obtained from the treatment system is satisfactory with 95% unfiltered BOD removal, 91% unfiltered COD removal and 94% SS removal. Total nitrogen removal was 33% only which is expected to rise after the full sludge development in the reactor.
At HRT of 2h in DHS pathogen removal was impressive. Fecal coliform removal was 99.96% with its count decreased to 103 in the final effluent from 106 in raw sewage.
The system can be recommended as one of the possible solutions for wastewater problem in the developing countries.