Degradation of recalcitrant organic polluants in seafood wastewater by modified TiO2 photocatalysts

Abstract

In seafood processing plants, industrial waste water discharge reached virtually the level B (QCVN 11-MT:2015/BTNMT) after using mechanical, physicochemical and biological wastewater treatment methods. However, their COD values (COD = 20-120 mg/L) were not qualified for allowable concentration of discharge requirement - level A (COD £ 75 mg/L) in many cases. In this paper, bio-treated seafood waster water was continually treated by TiO₂ photocatalyst modified by doping Fe and N to degrade recalcitrant organic pollutants to obtain the A level water which can be resused. TiO₂ modified by doping Fe and N were prepared and investigated the physico-chemicalproperties. The results showed that modified TiO₂ had a lower band gap and more photoactivity than pure TiO₂. Beside that, at the reaction conditions: reaction temperature 25 ^oC, dissolved oxygen concentration 7.6 mg/L and pH = 7, the optimal concentration of catalysts was determined (1.25 g/L). After 12 hours of treatment, COD removal efficiency on TiO₂-Fe and TiO₂-N catalysts attained 41.1 % and 64.3 %, respectively, and their COD values reached 49.3 and 29.9 mg/L, correspondingly. After treatment, the quality of waste water discharge met the level A (QCVN 11-MT:2015/BTNMT) and became a safety source for reusing (QCVN 08-MT:2015/BTNMT). In addition, the relationship between the characterization of modifed TiO₂ and their activity was characterized.