Fat recovery from dissolved air flotation sludge

Industrial wastewaters containing oil and grease are often treated by dissolved air flotation (DAF). This treatment gives a sludge with a high fat content. While currently often disposed, this fat can also be recovered as a valuable product. This laboratory and pilot-scale research investigates a novel treatment for fat recovery from chemical-free DAF sludge. At pilot scale 94% of the fat present in DAF sludge was recovered as a fat fraction containing 1.9%w/w water and 0.01%w/w insoluble impurities using the i-FAT system which uses a special prepared three-phase decanter centrifuge to separate heated sludge from a chemical-free DAF unit into three fractions. Application of this i-Fat system on a scale of 2500 m3/d wastewater, gives a reduction of 21% on total yearly costs and therefore a return on investment of 1.7 - 2.0 years.