A novel textile wastewater treatment using ligninolytic co-culture and photocatalysis with TiO₂

Textile industries produce effluent waste water that, if discharged, exerts a negative impact on the environment. Thus, it is necessary to design and implement novel waste water treatment solutions. A sequential treatment consisting of ligninolytic co-culture with the fungi Pleurotus ostreatus and Phanerochaete crhysosporium (secondary treatment) coupled to TiO₂/UV photocatalysis (tertiary treatment) was evaluated in the laboratory in order to discolor, detoxify, and reuse textile effluent waste water in subsequent textile dyeing cycles. After 48 h of secondary treatment, upto 80 % of the color in the waste water was removed and its chemical and biochemical oxygen demands (COD, and BOD₅) were abated in 92 % and 76 %, respectively. Laccase and MnP activities were central to color removal and COD and BOD₅ abatement, exhibiting activity values of 410 U.L-1 and 1 428 U.L-1, respectively. Subjecting waste water samples to 12h of tertiary treatment led to an 86 % color removal and 73 % and 86 % COD and BOD₅ abatement, respectively. The application of a sequential treatment for 18 h improved the effectiveness of the waste water treatment, resultingin 89 % of color removal, along with 81 % and 89 % COD and BOD₅ abatement, respectively. With this sequential treatment a bacterial inactivation of 55 % was observed. TiO₂ films were reused continuously during two consecutive treatment cycles without thermic reactivation. Removal percentages greater than 50 % were attained. Acute toxicity tests performed with untreated waste water led to a lethality level of 100 % at 50 % in Hydra attenuata and to a growth inhibition of 54 % at 50 % in Lactuca sativa. Whereas sequentially treated waste water excreted a 13 % lethality at 6.25 % and aninhibition of 12 % at 75 % for H. attenuata and L. sativa, respectively. Finally, sequentially treated waste water was reused on dyeing experiments in which 0.86 mg.g^-1 adsorbed dye per g of fabric, that is equivalent to 80 % of dye adsorption.