Effect of Fly ash amendment on compost bacterial community and functional gene enrichment with heavy metal contamination

Fly ash (FA) addition affect compost bacterial diversity and their adaptability in metal stressed composting system that remains largely underexplored. This study aims to evaluate the fly ash amendment in composting and specifically focus on the changes in bioavailability of heavy metals (HMs), bacterial diversity and their functional gene enrichment pattern under metal intoxicated mesophilic composting. Composting system were developed in lab-scale reactors with 0%, 5% and 10% FA addition, also bioavailable content transformation results were ascertained by analyzing fractional shifts in heavy metal speciation during composting period. Results indicates that bioavailable content (F1) was effectively reduced for measured HMs in FA containing compost reactors. Moreover, bacterial community analysis confirms that Phylum diversity does not significantly change up to 10% FA addition in composting whereas, the Genus diversity differed between the compost. Significant similarity were observed in a relationship between bioavailable metal content and metal-regulatory gene enrichment pattern in compost containing 0% and 5% FA. Gene related to efflux system were dominated in FA containing compost samples. Moreover, Cu was the most influential metal followed by Zn showing dominance in a group associated with gene regulation mechanisms. This study provides the detailed experimental findings and significant comparisons statistically proven to understand the functional potential of bacterial community which could be used to understand bacterial response to metal contamination in composting.