A study of the treatment of high-salt chromium-containing wastewater by the photocatalysis-constructed wetland combination method

Abstract

Abstract In this study, iron ore slag as the photocatalyst was introduced into a constructed wetland simulation system. A comparative experiment of the constructed wetland method and photocatalysis-constructed wetland combination method that treats the high-salt chromium-containing wastewater was carried out. The best hydraulic retention time (HRT) of the photocatalysis-constructed wetland combination system was studied. The effects of these two methods on biochemical oxygen demand (BOD5), chemical oxygen demand (COD) removal and Cr(VI) reduction rate of the high-salt chromium-containing wastewater were analysed after 14 periods. The results showed that under the optimal HRT of 4 hours, the COD and BOD5 of the wastewater reduced by 47% and 31%, and the reduction rate of Cr(VI) was 83% separately in the constructed wetland system. The COD and BOD5 of the wastewater reduced by 83% and 42%, and the reduction rate of Cr(VI) was 96% separately in the photocatalysis-constructed wetland combination method system. At the same time, the changes in plant parameters under these two systems were studied, and the results showed that the addition of photocatalyst and hydrogen peroxide to constructed wetlands did not affect the normal indicators of plant growth. The results showed that the photocatalysis-constructed wetland combination method not only reduced the treatment time greatly, but also improved the quality of the treated wastewater significantly.