Tertiary treatment methods were tested on secondary effluent from an abattoir biological wastewater treatment plant with the purpose of renovating it for re-use in the abattoir. The colour and dissolved organic matter could be removed to such an extent that the water would comply with water of insignificant health risk (Department of Health). The treatment process sequence proven to be effective in upgrading this water so insignificant health risk standard were coagulation with a polymer blend, separation, ozonation, filtration and activated carbon filtration. The development of biologically activated carbon in practice was accepted as inevitable and desirable for optimum water quality, but not tested. A deciding factor in the selection of an appropriate treatment was that the final water would also have acceptable corrosion properties.