Heterotrophic and mixotrophic cultivation of microalgae to simultaneously achieve furfural wastewater treatment and lipid production

Furfural wastewater (FWW) treatment is important in modern chemical production. However, traditional wastewater treatment methods are inappropriate for the treatment of FWW. In this work, Chlorella pyrenoidosa was employed to study the growth and pollutants removal with both heterotrophic and mixotrophic cultures. The results show that the biomass and removal efficiency for COD and TN were the highest under 10-fold dilution. However, TP removal were inconsistent when the algae were cultivated in both mixotrophic and heterotrophic modes. Compared to high nitrogen (0.75 g/L NaNO₃), the algal cells grew faster when adding 0.25 g/L NaNO₃ to the FWW, whether in mixotrophic or heterotrophic conditions. The total lipid content in heterotrophic conditions was 18.53%, which was higher than the values in mixotrophy when the concentration of NaNO₃ was 0.75 g/L. Different carbon assimilation mechanisms of the algal cells result in a discrepancy in cell growth and pollutant removal, under different culture modes.

Furfural wastewater pretreatment of corn stalk for whole slurry anaerobic co-digestion to improve methane production

Previous studies showed that excellent anaerobic digestion performance could be achieved using acid pretreatment, whereas the development of acid pretreatment was limited by high cost of acid consumption and severe operation. The aim of this study consisted in expanding the possibilities of low-cost acid pretreatment method for anaerobic digestion. For this, the feasibility of substituting conventional acid pretreatment with furfural wastewater was verified, and the whole slurry anaerobic digestion was performed to improve the production of methane. The furfural wastewater was used to pretreat crop stalk at different ambient temperatures (20, 35, 50°C) for different time periods (0, 3, 6, 9days). Subsequently, all treated and untreated crop stalk were digested at 35°C for 25days. According to experimental data showed that the dissimilar degradability of compositions for crop stalk was due to furfural wastewater pretreatment, and the reducing sugar content, volatile fatty acid content, pH during pretreatment phase, and their initial maximum & minimum values in anaerobic digestion phase were changed, which made a significant difference in methane production. The highest total methane production of anaerobic digestion (196.68mL/g VS) was achieved by the treatment at 35°C for 6days, which was 59.28% higher than untreated crop stalk (123.48mL/g VS). On the whole, the results showed that furfural wastewater pretreatment followed by the whole slurry anaerobic co-digestion was feasible and could contribute to application value for anaerobic digestion industry while providing an effective way for the treatment of furfural wastewater.