Daisuke TAKAYAMA
Evaluation of the operation and maintenance of DHS reactor in combination with UASB pretreatment in INDIA
Akiyoshi OHASHI
UASB-DHS (Down-flow Hanging Sponge) system has been proposed as a cost-effective sewage treatment system in developing countries. Now 1 MLD (million liter per day) DHS has been installed in INDIA since 2002. It has demonstrated an excellent performance for 4 years, so that the operation and maintenance (O/M) of the DHS in terms of effect of low temperature, organic shock load and long-term halt, calculation of DHS excess sludge and comparison the O/M cost of DHS with conventional UASB post-treatment system was evaluated.
DHS performance of organic removal was not affected by low temperature. Nitrification on the DHS slightly decreased during under 20¡î. DHS has a capability to withstand high fluctuations in 5.7kgCODt.m-3.day-1 of organic loading and 0.68kgNH4-N.m-3.day-1 of ammonia loading and can establish a normal state rapidly once the shock load had ended. Although DHS was exposed to starvation for 10 days, DHS could produce an excellent effluent as soon as it restarted. This might be due to its high ability to retain water as well was sludge inside the sponge media. Sludge yield of the DHS was 0.02 kgSS.kgCOD removed-1 which is extremely less than that of other UASB post-treatment. As compared to the O/M cost of conventional UASB post-treatment, DHS cost was much less than conventional ones and also performance was excellent. Thus DHS is applicable system as novel UASB post-treatment in developing countries
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