DAF system delivers on water quality

Salad manufacturer Sunfresh Salads discharges about 55,000 litres of wastewater from its Adelaide production facility each day. The wastewater contains suspended solids (SS) concentrations of up to 1500 mg/L and fats, oils and grease (FOG) concentrations up to 800 mg/L and is highly variable in pollutant concentration, pH and flowrate. 

SA Water has set a discharge specification of 500 mg/L for SS and 100 mg/L for FOG. Sunfresh’s wastewater is discharged to the sewerage system and the wastewater quality was regularly exceeding SA Water’s discharge specifications for a number of parameters.

The company contracted Aerofloat Australia to install a Model 3500 Aerofloat to treat the wastewater and ensure it meets SA Water discharge requirements.

The Aerofloat unit is a miniature dissolved air floatation (DAF) system and was originally developed in 2009 to treat greywater produced on houseboats. Today, there are five different models of the patented product that treat a variety of wastewaters with varying flows.

Able to process up to 3500 L/h of wastewater, the Aerofloat 3500 was developed specifically to treat industrial wastewaters and greywater from larger residential complexes.

The project included a number of components: conversion of the existing grease trap to a combined primary treatment tank and pumping chamber; provision of screens for removal of large solids; a mixed blending tank for strength balancing and pH correction; installation of a complete Model 3500 Aerofloat system including coagulant and polymer dosing systems; pH monitoring of the effluent; continuous flow recording prior to discharge to sewer; and a float collection tank for thickening and storage of waste float material from the 3500 DAF.

The Sunfresh project was the first installation of the Aerofloat 3500. The company says it has been highly successful, with the effluent exceeding SA Water specification limits. The Aerofloat 3500 is removing up to 97% of both suspended solids and fats, oils and grease.