Dolomite limits acidification of a biofilter degrading dimethyl sulphide

The applicability of dolomite particlesto control acidificationin a Hyphomicrobium MS3inoculated biofilter removingdimethyl sulphide (Me₂S) wasstudied. While direct inoculationof the dolomite particles with theliquid microbial culture was notsuccessful, start-up ofMe₂S-degradation in thebiofilter was observed when thedolomite particles were mixed with33% (wt/wt) of Hyphomicrobium MS3-inoculatedcompost or wood bark material.Under optimal conditions, anelimination capacity (EC) of 1680~g Me₂S m^-3 d^-1 wasobtained for the compost/dolomitebiofilter. Contrary to a wood barkor compost biofilter, no reductionin activity due to acidificationwas observed in these biofiltersover a 235 day period because ofthe micro environmentneutralisation of the microbialmetabolite H₂SO₄ with thecarbonate in the dolomite material.However, performance of thebiofilter decreased when themoisture content of the mixedcompost/dolomite material droppedbelow 15%. Next to this, nutrientlimitation resulted in a gradualdecrease of the EC andsupplementation of a nitrogensource was a prerequisite to obtaina long-term high EC (> 250 gMe₂S m^-3 d^-1) forMe₂S. In relation to thisnitrogen supplementation, it wasobserved that stable ECs forMe₂S were obtained when thisnutrient was dosed to the biofilterat a Me₂S-C/NH₄Cl-Nratio of about 10.Abbreviations:DW – dry weight,EC – elimination capacity,Me₂S – dimethyl sulphide,OL – organic loading rate,VS - volatile solids