Dissolved air flotation technology

The disposal of industrial wastes has become an environmental concern and the public regulatory bodies are increasingly becoming involved with the establishment of water quality criteria. The Dairy Industry is one where major emphasis is put on the treatment of wastewater. A large challenge facing the dairy industry is effluent wastewater treatment for trade waste or environmental discharge compliance.

The main components of dairy waste are milk and milk products including: whey, casein, washings, cheese, butter and anhydrous milk fat. The appropriate treatment of wastewater depends on the products manufactured and the waste generated from them. Milk and its products are organic materials, which are characterized by BOD, COD & TOC. Dairy wastes do not contain significant quantities of toxic compounds. The wastes of these products are of relatively low pH.

Krofta Dissolved Air Flotation (DAF) units have played a key role in many applications in wastewater treatment in the dairy industry. The range of applications in the dairy industry is very wide. DAFs play an important role as a pre-treatment step (clarification), before the discharge by substantially reducing fats, oils and grease (FOG), total suspected solids (TSS), insoluble BOD and COD. This would be for milk processes, butter, ice cream and dairy plants that have added new products such as ice cream mixes, flavoured creamers and some cultured products.

Pre-treatment Krofta DAFs can also be used as a pre-treatment step ahead of Krofta aerobic or anaerobic treatment processes to reduce FOG’s, TSS or BOD/COD to reduce the size of the aerobic/anaerobic systems. Many high rate aerobic and anaerobic systems benefit substantially if much of FOG’s, TSS and BOD is reduced before treatment. Certain high rate aerobic systems may experience difficulties in start-up or operation with higher levels of fats, oils and grease.

DAF process introduces micro bubbles into the wastewater and with the aid of chemicals, removes suspended matter, reducing the pollutant levels in the wastewater. The bubbles released by the DAF process carry the suspended matter to the surface of the flotation cell, where the matter is removed by a rotating scoop or surface skimmer.

The recycle of waste water from dairy industry can be supplied for utilization of adsorption and membrane segregation along with other processes in the DAF unit. The odour and colour in the waste water can be eradicated with the help of activated carbon treatment. The pre-treated water can then be distributed through cross flow osmosis membrane system and the pre-treated water will be available for further use.