131 † To whom correspondence should be addressed. E-mail: yasar.abdullah@gmail.com Korean J. Chem. Eng., 30(1), 131-138 (2013) DOI: 10.1007/s11814-012-0110-4 INVITED REVIEW PAPER Comparison of cost and treatment efficiency of solar assisted advance oxidation processes for textile dye bath effluent Abdullah Yasar † , Sadia Khalil, Amtul Bari Tabinda, and Afifa Malik Sustainable Development Study Center, GC University, Lahore, Pakistan (Received 27 February 2012 • accepted 5 July 2012) Abstract -The study investigated the efficiency and cost effectiveness of solar-assisted photochemical processes in comparison with advance oxidation processes (AOPs) for the textile effluents treatment. Efficiency of UV irradiation alone for one hour in removing color was almost double in comparison to solar radiation alone for effluents of dif- ferent dye concentrations (E1>E2>E3). For coupled UV/H 2 O 2 process, there was higher color removal efficiency ob- tained for effluent E 3 (85%) as compared to E 2 (70%) and E 1 (57%), while E 1 showed higher COD removal efficiency (70%) as compared to E 2 (50%) and E 3 (62%). However, the efficiency of solar/H 2 O 2 for COD removal was comparable to UV/ H 2 O 2 , i.e., E 2 (57%) and E 3 (53%). In the case of UV and solar-assisted photo-Fenton processes, removal effi- ciency of the UV process was further increased as approached to almost 90% removal for E 1 ; on the other hand, the solar-assisted process efficiency remained the same. The relative efficiencies of AOPs were found to be in the order of UV assisted photo-Fenton process>UV/H 2 O 2 >UV alone. Although, solar-assisted Fenton treatments were rela- tively low and slow but without any energy consumption in comparison to high energy consumption of UV. Among the UV processes, UV assisted photo-Fenton treatment appeared to have better color removal efficiency with energy requirements of 5 kWh/m 3 , 8 kWh/m 3 and 3 kWh/m 3 for E 1 , E 2 and E 3 , respectively. Key words: Advance Oxidation Processes (AOPs), Removal Efficiency, Textile Effluent, Cost Efficiency, COD (Chemi- cal Oxygen Demand) INTRODUCTION Fresh water is essential for all activities of living organisms. In the recent century this natural source is being contaminated by dif- ferent anthropogenic activities. Water-pollution control, wastewater treatment and conservation of water bodies have become an area of major concern for scientific society. Discharging untreated sew- age and industrial wastewater and moreover excessive use of pesti- cides for agriculture has increased this pollution load into the major fresh water resources, which in turn has proved to be harmful for the health of living organisms and their surrounding environment [1]. The textile industry is the top ranked among the most water con- suming industries around the world. It produces 50-100 liter waste- water per Kg of finished goods [2]. A total of 15% of the world production of dyes has been wasted in dyeing units and has added the pollution load in wastewater. Various environmental hazards are associated particularly with the intense nature of chemicals used in textile dyeing process (dyestuffs, surfactants, dispersing agents and other additives which are normally complex organic substances etc.), which in turn produces effluent that contains toxic contents of dye bath auxiliaries and unfixed dye material [3]. These chemicals are of recalcitrant nature: resistant to biodegradation and most phys- iochemical remediation methods such as precipitation and adsorption, and causes variations in the wastewater characteristics like chemical oxygen demand (COD), biological oxygen demand (BOD), Color, total suspended solids (TSS), total dissolved solids (TDS), pH and heavy metals. Many studies have highlighted the mutagenic and carcinogenic nature of these dyes which are used in the textile indus- try. An understanding of the textile effluent is fundamental for the design of wastewater treatment plants and application of appropri- ate treatment technology. Textile effluent generally contains waste materials such as hard wastes, highly toxic waste with numerous pathogenic microorganisms, refractory organics, high volume wastes and dispersible wastes. The wastewater treatment process involves many steps such as primary, secondary and tertiary treatment steps. Several physio-chemical decolorizing techniques in combination with biological methods are used for treating textile effluent accord- ing to the pollution load, which includes physio-chemical flocculation combined with flotation, chemical coagulation, membrane tech- nologies, adsorption, photo catalytic degradation, ion-exchange, irradiation and ozonation [4]. Biological method is promising in reducing organic content and nutrient content of municipal wastewater, but in case of biologically resistant dyestuffs of textile dye baths, the biological treatment does not produce effective results . Advanced oxidation processes (AOPs) have been widely used in removing organic and inorganic contam- inants from textile wastewater, as various physiochemical technol- ogies such as membrane filtration or activated carbon adsorption and conventional chemical oxidation processes have some limita- tions [5-13]. Venkatadri et al. (2009) reported application of three chemical treatment methods such as UV/H 2 O 2 process, Fenton’s reagent treatment and titanium dioxide-assisted photo catalytic degra- dation [14]. Photo-assisted Fenton’s system is one of the best tech- nologies used for degrading water-soluble organic contaminants