Microalgae-based wastewater treatment can support sustainable crop production. This study evaluated whether ethanol supplementation improves swine wastewater (SW) treatment by Dictyosphaerium sp. and enhances algal biofertilizer production. Across the ethanol levels tested, 500 mg/L ethanol significantly promoted algal growth and enhanced liquid-phase net removal of total salts, carbonate/bicarbonate, ammonium, phosphate, and calcium. Ethanol supplementation also reduced apparent nitrogen loss, and no residual ethanol was detected at the end of the culture. In the biofertilizer production experiment, peak algal biomass, algal nitrogen, and algal phosphorus increased by 320.0–407.4%, 122.7–158.1%, and 100.0–170.0%, respectively. Metatranscriptomic analysis showed active transcription of adh, aldh/aldB, and acs in Dictyosphaerium sp. and some bacterial taxa, mainly Flavobacterium, Chryseobacterium, Comamonas, and Brevundimonas. Community and transcriptomic results indicate enhanced photosynthetic activity and taxon-specific N- and P-related transcriptional responses, consistent with altered nitrate/nitrite transformation potential and increased nitrogen retention in the algal–bacterial system. Under the tested conditions, ethanol supplementation shows promise for SW treatment and algal biofertilizer production.
Zhang et al. (Wed,) studied this question.
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