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 anb only slowly bio degradable, and the remainder as collidal anb soluble metter. this varies considerably from domes tic wastewater.in which the COD is present mainly in the colloidal form.