Nutrient and heavy metal removal from piggery wastewater and CH_4 enrichment in biogas based on microalgae cultivation technology under different initial inoculum concentration

摘要

Three microalgae‐based treatment technologies were applied for removing nutrients in piggery wastewater and CO_(2)in biogas simultaneously.iChlorella vulgaris (iC. vulgaris ),iScenedesmus obliquus (iS. obliquus ), andiNeochloris oleoabundans (iN. oleoabundans ) were selected for mono‐cultivation or co‐cultivation with fungi or activated sludge. The effects of initial inoculum concentration (low of 62.06 ± 6.23 mg/L, medium of 121 ± 9.34 mg/L, and high of 180 ± 12.78 mg/L) of microalgae/algal symbiont on the pollutant removal efficiency were evaluated. The results showed that cultivation ofiS. obliquus with activated sludge had a relatively high CO_(2)and nutrients removal efficiency at a medium concentration of initial inoculum. The highest removal efficiency of total organic carbon, total nitrogen, and total phosphorus in piggery wastewater was 87.29%, 87.26%, and 90.17% by co‐cultivation ofiS. obliquus with activated sludge. The highest CO_(2)removal of 64.28% could be achieved under co‐cultivation ofiS. obliquus and fungi at medium initial inoculum concentrations. This work will be helpful to promote the study of microalgae‐based biogas upgrading and piggery wastewater purification. Practitioner points Nutrient and CO_(2)were efficiently removed in moderate microalgal initial inoculum. iScenedesmus obliquus ‐activated sludge cultivation achieved the highest nutrient removal. Co‐cultivation ofiS. obliquus and fungi showed the highest CO_(2)removal. Zinc was removed efficiently in high microalgal initial inoculum. iChlorella vulgaris /iS. obliquus ‐activated sludge performed economically. The biogas and biogas slurry can be purified efficiently under different microalgae cultivation technologies at the optimal initial inoculum concentration.