Combined natural/chemical coagulation and membrane filtration for wood processing wastewater treatment

Abstract

In this study, a wide range of inorganic and organic coagulants such as alum (Al2(SO4)3), iron(III) chloride (FeCl3), polyaluminium chloride (PAC), and processed Moringa Oleifera powder (PMOP) supported with membrane process were applied for wood processing wastewater treatment. Several parameters were investigated in the first stage of wastewater treatment, in terms of turbidity, chemical oxygen demand (COD), and colour removal, as coagulant dosage and pH variation. The optimum results for chemical coagulation were obtained for the use of alum at 500 mg/L dosage at pH = 7, where turbidity was removed by 99.5 %, COD reduced by 89.8 %, and colour declined to 51.1 % of their initial values. Besides, the natural coagulant results were as good as chemical ones and turbidity, COD, and colour were reduced to 98.9 %, 84.7 % and 73.7 %, respectively, for 2000 mg/L of PMOP concentration. The final water quality was assessed after membrane filtration. A series of different membranes such as UP150, UP005, NF270, and NF90 were tested for different operating pressures. An operating pressure of 20 bar for NF90 membrane filtration supplied the best water quality for both chemical and natural coagulation pre-treatments. Combined process with chemical coagulation and nanofiltration removed turbidity to 99.9 %, COD to 99.5 %, and colour to 99.4 % when alum was used for the pre-treatment. Moreover, for PMOP usage combined with NF90 at 20 bar of pressure, the final obtained water characteristics in terms of turbidity, COD, and colour were decreased to 99.6 %, 93.0 %, and 99.5 %, respectively.