Using modified coir pith–glucose syrup beads inoculated with Bacillus thuringiensis as a packing material in trimethylamine (fishy odor) biofilter

Abstract

Trimethylamine (TMA) is an odorous, toxic compound generated in several manufacturing processes. Coir pith is an effective material for adsorbing gaseous TMA, and it presents good water-retention properties. A combination of coir pith and glucose syrup can maintain high humidity and serve as a nutrient source for microorganisms in a biofilter without external nutrient support. Preliminary studies on TMA removal efficiency using Bacillus thuringiensis, Bacillus megaterium and mixed culture inoculated on coir pith powder showed that B. thuringiensis exhibited the highest TMA removal in a batch experiment (96.0% within 12 h). Therefore, B. thuringiensis-inoculated coir pith–glucose syrup beads were used to treat gaseous TMA (100 ppm) in a 15.6-L glass chamber. TMA degradation metabolites, including ammonium, nitrite, nitrate, nitric oxide, nitrous oxide and carbon dioxide, were also measured to predict the TMA degradation pathway. The results showed that TMA (30 ppm) could be removed by inoculated microorganisms on coir pith–glucose syrup beads (89.1% up to 100% within 16 h). A pilot-scale biofilter containing B. thuringiensis-inoculated coir pith–glucose syrup beads was established in a 24-m3 testing room. The system could remove 72.52 mg m−3 of gaseous TMA (100%) within 1 h and can continuously maintain TMA removal efficiency for greater than 5 cycles. During biofilter operations, gaseous ammonia was detected. The result confirmed TMA biodegradation process in the biofilter. Therefore, the developed biofilter packed with B. thuringiensis-inoculated coir pith–glucose syrup beads exhibits high potential to remove TMA and intermediate products.