Effect of alkaline treatment pattern on anaerobic fermentation of swine manure

• Fermentation by initial pH 10 adjustment took less days to reach the same VFAs concentration.
• Initial pH 10 adjustment had lower hydrolysis rate but higher acidification rate.
• Lachnospiraceae and Porphyromonadaceae were inhibited at continued pH 10 condition.
• Phosphorus release was accelerated by continued pH 10 adjustment.

Swine manure contains large amount of organic resource, turning to be a favorable substrate for volatile fatty acids (VFAs) production. Alkaline treatment has demonstrated an effective way to enhance VFAs production. To optimize the alkaline treatment pattern, swine manure fermentation under initial pH 10.0 and continued pH 10.0 conditions was carried out in batch experiments, to evaluate their efficiency on hydrolysis and acidogenesis. The results showed that compared with continued pH 10.0 adjustment, initial pH 10.0 pretreatment achieved similar VFAs production at 11939 mg-COD/l within shorter period. Kinetic analysis demonstrated the rate-limiting step for fermentation under alkaline adjustment was acidogenesis not hydrolysis. High throughput sequencing was applied to investigate microbial community, showing that new non-spore-forming Lachnospiraceae and Porphyromonadaceae enriched during initial pH 10.0 fermentation, while spore-forming Bacillaceae and Sporolactobacillaceae dominated at constant pH 10.0 condition. With lower chemical dosage and higher acidogenesis rate, initial pH 10.0 pretreatment is more favorable than continued pH 10.0 adjustment for swine manure fermentation.

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