George A. Serad

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

Abstract 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.

EFFECT OF MIXING CONDITIONS ON FLOCCULATION KINETICS OF WASTEWATERS CONTAINING PROTEINS AND OTHER BIOLOGICAL COMPOUNDS USING FIBROUS MATERIALS AND POLYELECTROLYTES

The application of a combined system of a polyelectrolyte, carboxymethyl cellulose (CMC), and highly fibrillated fibrous materials, cellulose triacetate fibrets (CTF), for the recovery of proteins and other biological compounds from model and actual biological systems has been demonstrated . In the present work, reaction batches were scaled-up to a one-liter agitated vessel, with a standard configuration. The effect of mixing conditions on the adsorption and flocculation process was studied. It was observed that flocculation time was very fast, occurring within the period of polymer addition. Long term shearing did not result in floc breakage and the values of percentage light transmission and protein concentration of the final filtrate remained the same during the incubation period. Increasing the shear rate resulted in improved process efficiency, up to an optimum value, above which performance was poorer. Perikinetic and orthokinetic rate parameters were calculated and results analyzed in view of these parameters.

Recovery of proteins and other biological compounds using fibrous materials: I. Adsorption by salt addition

An adsorption and filtration process for the recovery of proteins and other biological compounds from aqueous streams has been developed, using cellulose-based fibrous materials. Of the many cellulose derivatives studied, cellulose acetate fibrets (CAF) and cellulose triacetate fibrets (CTF) have been shown to be the most effective. In the presence of salts, they lead to protein adsorption by hydrophobic interactions. Model proteins, such as bovine serum albumin (BSA), have been recovered by incubating these solutions with CTF in the presence of ammonium sulfate, followed by filtration through a 20 µm pore size filter. The amount of salt necessary varies with the protein type, but decreases with increasing temperature and protein concentration. High protein recovery has been obtained from an actual wastewater system at low salt dosages. © 1999 Society of Chemical Industry

Recovery of proteins and other biological compounds using fibrous materials: II. Flocculation by polyelectrolyte addition

Polyelectrolytes have been used in wastewater treatment processes to destabilize colloidal suspensions of proteins, cells and other biological compounds, resulting in flocculation. When a solution containing a single model protein, bovine serum albumin (BSA), is treated with a polyelectrolyte, carboxymethyl cellulose (CMC), large and strong flocs are formed, which are easily retained by a 20 µm pore size filter. However, when a mixture of proteins, cells, and fats from an actual wastewater sample is treated in the same manner, smaller and weaker flocs are observed. An adsorption and filtration process for the recovery of valuable biological compounds using cellulose-based fibrous materials has been developed. When used simultaneously with CMC, cellulose acetate and triacetate fibrets (CAF and CTF) resulted in high recovery of biomolecules from solution at very low dosages of both polyelectrolyte and fibrets. CMC interacts with biomolecules by electrostatic interactions and polymer bridging, while CTF/CAF facilitate floc growth by adsorption and bridging of primary particles and by entrapment of small aggregates within their highly fibrillated microstructure. © 1999 Society of Chemical Industry

Protein Recovery Using Fibrous Materials

Tighter environmental regulations challenge industry to improve processes to minimize waste and conserve energy (Metzner, 1988). Traditionally, solid wastes resulting from effluent treatment systems have been disposed by incineration or by sending to landfills (Swinehart, 1990). These approaches are no longer appropriate, since incineration may lead to toxic gaseous emissions and air pollution, and landfills could result in contamination of water supplies.