Yiqi Jiang1, Hong Wang1, Wannan Wang2, Liangwei Deng1, Wenguo Wang3. 1. Key Laboratory of Development and Application of Rural Renewable Energy, Biogas Institute of Ministry of Agriculture, Chengdu, 610041, China. 2. State Key Laboratory of Remote Sensing Science, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing, 100101, China. 3. Key Laboratory of Development and Application of Rural Renewable Energy, Biogas Institute of Ministry of Agriculture, Chengdu, 610041, China. wangwenguo@caas.cn.
Abstract
Liquid digestate (LD) is highly turbid and contains ammonium (NH4+-N), which negatively influences microalgal growth. Therefore, a method of reducing LD turbidity and NH4+-N content is proposed, using struvite precipitation. To obtain struvite precipitation supernatant with an ideal UV transmittance, NH4+-N concentration, and N/P ratio for microalgal growth, the effects of pH and the molar ratio of NH4+/Mg2+/PO43- were studied. Results show that the optimal NH4+/Mg2+/PO43- molar ratio was 1:1.5:1.5, with a pH value of 8.5, following NaOH addition. Gray relational analysis (GRA) was applied to obtain a relative gray scale for the evaluation of multiple outputs. Results show that Chlorella regularis FACHB-1068 was the optimal microalgae species to support growth in the struvite precipitation supernatant. Using struvite precipitation and treatment with cultured C. regularis FACHB-1068 for 7 days, the removal efficiencies of NH4+-N, PO43--P, and COD in LD were 96.52, 99.33, and 35.30%, respectively.
Liquid digestate (LD) is highly turbid and contains ammonium (NH4+-N), which negatively influences microalgal growth. Therefore, a method of reducing LD turbidity and n>an class="Chemical">NH4+-N content is proposed, using struvite precipitation. To obtain struvite precipitation supernatant with an ideal UV transmittance, NH4+-N concentration, and N/P ratio for microalgal growth, the effects of pH and the molar ratio of NH4+/Mg2+/PO43- were studied. Results show that the optimal NH4+/Mg2+/PO43- molar ratio was 1:1.5:1.5, with a pH value of 8.5, following NaOH addition. Gray relational analysis (GRA) was applied to obtain a relative gray scale for the evaluation of multiple outputs. Results show that Chlorella regularis FACHB-1068 was the optimal microalgae species to support growth in the struvite precipitation supernatant. Using struvite precipitation and treatment with cultured C. regularis FACHB-1068 for 7 days, the removal efficiencies of NH4+-N, PO43--P, and COD in LD were 96.52, 99.33, and 35.30%, respectively.