Abatement of high concentrated ammonia loaded waste gases in compost biofilters

The performance of lab-scale compost biofilters for the purification of was te gases containing high (> 70 mg m(-3)) ammonia concentrations was studied . When using fresh compost material, no effect of inoculating the compost m aterial with a nitrifying culture was observed since high elimination capac ities (up to 350 g NH3 m(-3) d(-1)) were obtained in both the inoculated an d the non-inoculated biofilter. Due to the physico-chemical interaction of NH3 with the compost material at the start of the experiment, no microbiolo gical start-up period was observed and high removal efficiencies were obtai ned from the first day on. Next to this, no NH3-toxicity was observed even at concentrations up to 550 mg NH3 m(-3). About 50% of the NH3-removal was found to be nitrified, while the other 50% remained in the biofilter as NH4 +. As a result of this, no acidification of the carrier material was observ ed and NH4NO3 accumulated in the biofilter. Due to osmotic effects, however , a complete inhibition in nitrification and NH3-removal was obtained at a measured NH4NO3-concentration in the compost material of 6-7 g N kg(-1), co rresponding to a cumulative NH3-removal in the biofilter of +/- 6000 g m(-3 ). Finally, it was illustrated that the removal of the odorant dimethyl sul fide (Me2S) in a Hyphomicrobium MS3-inoculated compost biofilter is complet ely inhibited due to NH3-toxicity at a waste gas concentration of 100 mg NH 3 m(-3). Next to this, the NH4+- and NO3--concentrations in the compost mat erial that were shown to inhibit the nitrification, also strongly affected the Me2S-degrading activity of Hyphomicrobium MS3.