Performance evaluation of a slow-release packing material-embedded functional microorganisms for biofiltration

International audienceA composite packing material (CM-5) was prepared in this study, mainly consisting of compost withfunctional microorganisms, calcium carbonate (CaCO3), perlite, cement and plant fiber. To getstronger compressive strength, mass ratios of these components were optimized based onsingle factor experiments, and finally adding amounts of perlite, cement, plant fiber, CaCO3,compost and binder at 18%, 18%, 7%, 13%, 17% and 27%, respectively. According to theoptimum proportion, CM-5 was extruded in cylindrical shape (12 mm in diameter and 20 mm inlength) with a bulk density of 470 kg m−3, a moisture retention capacity of 49% and themicrobial counts of × 105 CFU g−1 of packing material. The cumulative release rates of totalorganic carbon (TOC) and total nitrogen (TN) from CM-5 were 3.1% and 6.5%, respectively, after19 times extraction in distilled water. To evaluate the H2S removal capacity, CM-5 was comparedwith an organic (corncob) and an inorganic (ceramsite) packing material in three biofilters. Theresults showed that CM-5 had higher H2S removal capacity compared with corncob andceramsite. CM-5 could avoid the large fluctuation of pH value and pressure drop during theoperation. The maximum H2S removal capacity of CM-5 was 12.9 g m−3 h−1 and the removalefficiency could maintain over 95.4% when the inlet H2S loading rate was lower than11.3 g m−3 h−1 without any addition of nutrients and pH buffer substances. Besides, only 2–3days were needed for the recovery of biofiltration performance after about two weeks of idleperiod