Performance evaluation of a slow-release packing material-embedded functional microorganisms for biofiltration
Résumé
A composite packing material (CM-5) was prepared in this study, mainly consisting of compost with
functional microorganisms, calcium carbonate (CaCO3), perlite, cement and plant fiber. To get
stronger compressive strength, mass ratios of these components were optimized based on
single 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 the
optimum proportion, CM-5 was extruded in cylindrical shape (12 mm in diameter and 20 mm in
length) with a bulk density of 470 kg m−3, a moisture retention capacity of 49% and the
microbial counts of × 105 CFU g−1 of packing material. The cumulative release rates of total
organic carbon (TOC) and total nitrogen (TN) from CM-5 were 3.1% and 6.5%, respectively, after
19 times extraction in distilled water. To evaluate the H2S removal capacity, CM-5 was compared
with an organic (corncob) and an inorganic (ceramsite) packing material in three biofilters. The
results showed that CM-5 had higher H2S removal capacity compared with corncob and
ceramsite. CM-5 could avoid the large fluctuation of pH value and pressure drop during the
operation. The maximum H2S removal capacity of CM-5 was 12.9 g m−3 h−1 and the removal
efficiency could maintain over 95.4% when the inlet H2S loading rate was lower than
11.3 g m−3 h−1 without any addition of nutrients and pH buffer substances. Besides, only 2–3
days were needed for the recovery of biofiltration performance after about two weeks of idle
period.