Membrane distillation for concentration of protein-rich waste water from meat processing

This work studies a promising waste valorization approach involving recovery of fresh water from protein-rich waste water from the meat processing and rendering industry via membrane distillation (MD). Blood stick water samples from an industrial plant have been treated in batch and continuous tests with two different PTFE membranes (native hydrophobic and hydrophilic coated). Treated water coming from MD permeate was evaluated using various parameters including sodium (for salinity), total organic carbon (TOC) and total nitrogen (TN). Overall, MD was shown to yield concentrated high strength stick water up to a concentration factor of 20 for potential re-use and recover clean water rejecting >99% salinity and TOC, and >95% of TN. Compared to conventional native hydrophobic PTFE, the hydrophilic coated membrane showed higher constant rejection in continuous experiments, but performed with less total flux. Uniquely for the first time in MD studies, the transfer of volatile fatty acids through the membrane into the permeate was explored, showing concentrations of 30-160 mg/L in the permeate appearing more related to hydrophobic surface diffusion than volatile diffusion. While MD for valorization of meat industry wastewater appears viable with correct conditions and membranes, the value of recovered water due to fatty acid presence and other practical considerations, such as membrane cleaning, need to be considered.