ABSTRACT
This chapter discusses the Biothane-Aminodan (B-A) process which was developed for protein and fat recovery from slaughterhouse process water where the recovered product is used as animal feed. The basic principles and techniques involved in protein and fat coagulation and flocculation are discussed in relation to their removal with the dissolved air concentration system. Operating data of a full-scale protein, fat, and oil recovery installation at a poultry slaughterhouse is also presented.
The B-A process uses FDA edible food approved additives for soluble protein and emulsified fat coagulation and flocculation, as compared to metal salt coagulants and acrylamide based flocculants that are used in many dissolved air flotation systems for slaughterhouse wastewater treatment. The product recovered in the B-A system does not contain any toxic metal salts or cancer-causing acrylamide and can safely be rendered into animal feed.
The B-A system uses dissolved air concentration (DAC©) water for protein and fat removal from process water. During DAC© water addition, many small, homogeneously sized air bubbles (≈30 μm in diameter) are formed in the process water which attach to the flocs. The air-floc particles have enough buoyancy to float to the surface of the concentrator. Only part of the recycled water stream is used as DAC© water, which results in substantial savings in system operating (energy) cost.
Typically, the overall BOD removal efficiency of the B-A system varies between 70 and 85%. BOD removal efficiency is highest when process water soluble BOD consists mostly of proteins and fats. More than 95% total FOG and suspended solids are removed from process water.
