Novel wedge structured rotating disk photocatalytic reactor for post-treatment of actual textile wastewater

• Actual textile wastewaters were post treated using a wedge rotating disk PC reactor.
• Wedge disk exhibited much higher COD removal efficiency than planar disk.
• Both the large surface area and multiple reflections played important role.
• The inhibition caused by inorganic anions could be weakened by wedge structure.
• PEC process could further improve COD removal without adding extra electrolyte.

A wedge structured rotating disk photocatalytic (PC) reactor was used for post-treatment of actual textile wastewater collected after activated sludge treatment. Compared with a conventional planar disk, the wedge structured disk had larger surface area and exhibited better light utilization efficiency. Treatment conditions such as pH and rotating speed were optimized. The COD content in effluent was reduced from 380 mgO2 L−1 to 109 and 56 mgO2 L−1 respectively after 3 h and 5 h treatment at pH 6.0 and rotating speed of 20 rpm. The effect of anions (NO3−, SO42− and Cl−) in actual textile wastewater on treatment was investigated. Benefit from high light utilization efficiency, the wedge rotating disk reactor could compensate COD removal inhibition caused by anions. A 1.5 V voltage was also applied to perform photoelectrocatalysis process to further improve the performance, and no additional electrolyte was needed. COD in effluent was reduced to as low as 75 mgO2 L−1 after 3 h treatment. In addition, this reactor was used to treat other water samples including the actual textile wastewaters collected before activated sludge treatment (initial COD of 880 mgO2 L−1) and after activated carbon adsorption post-treatment (initial COD of 108 mgO2 L−1). Experimental results suggested that wedge structured rotating disk photocatalysis process was stable, efficient and worth further scale-up investigation.

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