Biofilters--the influence of different filter materials and different operating conditions on the reduction efficiency.

A series of biofilter materials were tested for performance efficiency in treating ventilation air from pig sheds. Two different phases were conducted. In phase A five different biofilter materials were tested with the aim of selecting the best material regarding the odor reduction and over all efficiency. In conclusion of phase A, biochips, a new filter material, was selected due to its high average odor reduction (81%) in combination with a very low flow resistance (less than 30 Pa for filter volume loads of 600 m3 h(-1) m(-3)). In phase B, biochips and coconut fiber peat were tested under different operating conditions. Biofilters number 3 and 4 each with down-flow air supply could realize a higher average odor reduction than biofilter 5 with up-flow air supply. All three filter materials had the same moisture, however the two biofilters with down-flow air supply showed a more homogenous moisture distribution but they also used approximately three times more water than biofilter 5. Like in phase A the specific odor cleaning efficiency was mainly influenced by the specific odor loading rate and showed only slight differences between the five biofilters differing in bulk layer height (0.5 m and 1.0 m) and air supply mode. All in all the investigation showed that the efficiency of biofilters can be optimized by using an new filter material and a appropiate operating mode.