In water-scarce South Africa there is pressure on water-intensive industries to conserve water, and at the same time to reduce the organic and salinity concentrations discharged in effluents back (indirectly) to the water resources.
These requirements are usually contradictory: effective water conservation will generally lead to more concentrated effluents, motivating the need, in some cases, for effluent pretreatment before discharge.
Wide-ranging effluent pretreatment trials have been carried out at a number of red meat abattoirs over the past few years, under funding from the Water Research Commission. Fat removal, screening and dissolved air flotation (DAF) trials have confirmed the usefulness of such processes, but results from treatment with membranes have been both exciting and promising.
These treatment techniques have now been lifted from the research phase into commercial application on small scale (25 m3/d) using full size modules. The South African Abattoir Corporation, as the major representative of the industry in South Africa, has undertaken to assess the value of membrane treatment processes as a part of a number of effluent treatment strategies. This paper describes the experiences and future potential for abattoir effluent treatment by membrane processes.
Ultrafiltration will consistently remove 90% COD, 85% phosphate from the effluent, and provide a relatively non-fouling feed for reverse osmosis which produces a high quality reusable water for abattoir use.
Indicative costing shows the costs of membrane treatment compare favourably with anaerobic digestion as an alternative, and even to municipal effluent tariffs.