the physical nature of slaughterhouse wastewater has been studies by Sayed (1987), who have shown that of COD in screened (1 mm mesh) effluent, 40-50% was present as coarse, suspended matter, which was insoluble and only slowly bio degradable, and the remainder as collidal anb soluble matter. this varies considerably from domestic wastewater, in which the COD is present mainly in the colloidal form.