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An integrated process of anaerobic membrane bioreactor, microalgae cultivation, and hydrothermal carbonization for treatment of food industry wastewater and resource recovery
 
 
 
 

An integrated process of anaerobic membrane bioreactor, microalgae cultivation, and hydrothermal carbonization for treatment of food industry wastewater and resource recovery

 
Roy Bernstein
 
The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Israel
 
 

Anaerobic membrane bioreactor (AnMBR) is a promising sustainable alternative to common wastewater treatment technologies (WWT) for producing high-quality effluent while recovering most of the energy stored in wastewater as biogas. In addition, the nutrient-rich AnMBR effluent provides a unique opportunity to recover both NH 4 + and PO 4 3- as a sustainable alternative to energy-intensive production of inorganic fertilizers. A promising technology for nutrients recovery is microalgae cultivation. Moreover, sustainable WWT should include waste management. Lately, there has been a growing interest in converting low-cost wastewater sludge into hydrochar. The goal of this research was to develop, investigate, and analyze a near-zero waste treatment of food-processing wastewater consisting of AnMBR with outdoor PBR microalgae cultivation and hydrothermal carbonization under realistic arid- desert climate conditions for the production of high-quality effluent, recovery of nutrients, carbon, and energy.

The wastewater contained average values of 1.5 gr/L total organic carbon, 160 mg/L total nitrogen, and 9 mg/L total phosphate. The AnMBR process reduced total organic carbon by 97%, which was partially recovered as biogas and hydrochar. The AnMBR operated under constant sub-critical flux and therefore, the fouling was kept relatively low throughout the study. The AnMBR effluent was used as a growth medium for the cultivation of microalgae under outdoor conditions during one year (four seasons). The TN and TP were efficiently recovered and their concentration in the effluent reached the required standards for discharge within 2-5 days in summer in winter, respectively. Mass balance analysis demonstrated near-complete carbon and nutrient recovery and high-water recovery.

Overall, we present an integrated process with a near-zero waste discharge producing high-quality effluent, nutrient recovery into microalgae biomass, and energy production as biogas and hydrochar.