Recovery of proteins and other biological compounds from food processing wastewaters using fibrous materials and polyelectrolytes

A combined system of cellulose-based fibrous materials and polyelectrolytes has been studied for the recovery of proteins and other biological compounds from wastewaters from a typical food processing plant. Carboxymethyl cellulose (CMC) interacts with biomolecules by electrostatic and polymer bridging, while cellulose triacetate fibrets (CTF) facilitate floc growth by adsorption and bridging of primary particles and by entrapment of small aggregates within their highly fibrillated microstructure. Final slurries have good filtration properties, resulting in a dry and easy to handle filter cake, which could be recovered as animal feed. The final filtrate has high water clarity and low protein concentration. This recovery system exhibits high reductions in total suspended solids (TSS), total Kjeldahl nitrogen (TKN), ammonia, oils and greases, biochemical oxygen demand (BOD) and total fecal coliforms. The final levels of TSS, oils and greases and ammonia are below regulatory limits. Reduction of BOD reached 90%, although final concentrations are slightly higher than the regulatory levels.