Wastewater treatment in an anaerobic filter using small lava stones as filter media without temperature control

摘要

For their simplicity and using cheap support materials, biological filtration of municipal wastewaterncan be adequate for developing countries where the legislation is not as strict as in otherncountries, like the members of the European Union. Biological filters are fixed biomass reactorsnwhere the suspended pollutants can easily be retained and the dissolved substances can bentransformed by microbial activity. A pilot anaerobic filter was built and filled with lava stonesnsieved to obtain particles with an average size of 6 mm. The filter was fed with municipalnwastewater during 220 days under hydraulic retention times (HRT) of 4.3 and 9.8 hours (averagenorganic loading rates of 0.48 and 1.23 kgCOD/m3 d). The results show that the pH did not changensignificantly during the process. Lower organic loading rates (higher HRT) resulted in better CODnand TSS removal rates. Average biogas composition showed methane to be 67% for the lowernorganic loading rate and 63% for the higher one. Backwashing with air for 5 minutes everyn72 hours did not negatively affect the overall anaerobic process. Average TSS removal wasn79 and 73% for the higher and lower HRT (lower and higher organic loading rates), respectively.nThe overall performance of the anaerobic filter is comparable with the reported values innthe literature. The COD and TSS removal rates are slightly inferior to the ones reported innthe literature for UASB reactors treating municipal wastewater.