Biofilter material selection for odor removal

摘要

A possible way to arrange sanitation in developing countries and economize on sanitation in the industrialized countries is dry sanitation. In order to become general in industrial countries, the dry toilets should be pleasant to use. In dry toilets unpleasant odors are possible. The odors can be removed from the toilet with proper ventilation. However, when the odors are convoyed outside it is possible that the surroundings of the building have unpleasant odors. In that case the exhaust gases of dry toilet must be treated.Possible way to treat the exhaust gases is biofiltration. In biofiltration gas flows through porous bed and the contaminants of the gas transfer to water phase of the filter bed. In water phase the micro-organisms of the biofilter degrade the contaminants biologically.The aim of this study is to find a good material for biofilter treating exhaust gases of dry toilet. In two experiments five materials were tested in laboratory scale biofilters. Tested materials were Langfaserfiltergranulat (UGN Umwelttechnik GmbH), UgnCleanPellets © B (UGN Umwelttechnik GmbH), UgnCleanPellets © N (UGN Umwelttechnik GmbH), vermiculite (Nelson Garden PLC) and activated carbon (PICA).First experiment was done with dry air and in the second experiment the inlet gas was humidified. Real stored urine was used as a source of odorous compounds. Performance of the biofilters was determined by measuring ammonia and total organic carbon removal in the biofilters. Also water-holding capacity, pressure drop, nitrate concentration and microbial growth in the filter beds were determined. With data collected during the experiment it was also possible to calculate a mass transfer coefficient for ammonia from urine to air.All tested materials were able to remove ammonia and organic compounds from air. Because of drying none of them was able to perform efficiently through the whole experiment. Vermiculite and Langfaserfiltergranulat maintained best moisture conditions in the filter bed. Ammonia and organic compounds were significantly biodegraded only in UgnCleanPellets © B and UgnCleanPellets © N biofilters.According to results it was possible to recommend that combination of UgnCleanPellets © B and vermiculite would be good material for biofilter treating exhaust gases of dry toilet. It would be a good growth medium for microorganisms and it would have high water-holding capacity. Also its pressure drop would be relatively small. However, further laboratory experiments in slightly larger scale are recommended before the new material is used in full scale applications.