van Gijn K, van Dam M R H P, de Wilt H A, de Wilde V, Rijnaarts H H M, Langenhoff A A M
Department of Environmental Technology, Wageningen University & Research, 6700 AA Wageningen, the Netherlands.
Royal HaskoningDHV, 3800 BC Amersfoort, the Netherlands.
Water Res. 2023 Aug 15;242:120179. doi: 10.1016/j.watres.2023.120179. Epub 2023 Jun 6.
Ozonation is a viable option to improve the removal of micropollutants (MPs) in wastewater treatment plants (WWTPs). Nevertheless, the application of ozonation is hindered by its high energy requirements and by the uncertainties regarding the formation of toxic transformation products in the process. Energy requirements of ozonation can be reduced with a pre-ozone treatment, such as a biological activated carbon (BAC) filter, that removes part of the effluent organic matter before ozonation. This study investigated a combination of BAC filtration followed by ozonation (the BO process) to remove MPs at low ozone doses and low energy input, and focused on the formation of toxic organic and inorganic products during ozonation. Effluent from a WWTP was collected, spiked with MPs (approximately 1 µg/L) and treated with the BO process. Different flowrates (0.25-4 L/h) and specific ozone doses (0.2-0.6 g O/g TOC) were tested and MPs, ecotoxicity and bromate were analyzed. For ecotoxicity assessment, three in vivo (daphnia, algae and bacteria) and six in vitro CALUX assays (Era, GR, PAH, P53, PR, andNrf2 CALUX) were used. Results show that the combination of BAC filtration and ozonation has higher MP removal and higher ecotoxicity removal than only BAC filtration and only ozonation. The in vivo assays show a low ecotoxicity in the initial WWTP effluent samples and no clear trend with increasing ozone doses, while most of the in vitro assays show a decrease in ecotoxicity with increasing ozone dose. This suggests that for the tested bioassays, feed water and ozone doses, the overall ecotoxicity of the formed transformation products during ozonation was lower than the overall ecotoxicity of the parent compounds. In the experiments with bromide spiking, relevant formation of bromate was observed above specific ozone doses of approximately 0.4 O/g TOC and more bromate was formed for the samples with BAC pre-treatment. This indirectly indicates the effectivity of the pre-treatment in removing organic matter and making ozone more available to react with other compounds (such as MPs, but also bromide), but also underlines the importance of controlling the ozone dose to be below the threshold to avoid formation of bromate. It was concluded that treatment of the tested WWTP effluent in the BO process at a specific ozone dose of 0.2 g O/g TOC, results in high MP removal at limited energy input while no increase in ecotoxicity, nor formation of bromate was observed under this condition. This indicates that the hybrid BO process can be implemented to remove MPs and improve the ecological quality of this WWTP effluent with a lower energy demand than conventional MP removal processes such as standalone ozonation.
臭氧化是改善污水处理厂（WWTPs）中微污染物（MPs）去除效果的可行选择。然而，臭氧化的应用受到其高能量需求以及该过程中有毒转化产物形成的不确定性的阻碍。可以通过预臭氧化处理（如生物活性炭（BAC）过滤器）来降低臭氧化的能量需求，该过滤器在臭氧化之前去除部分出水有机物。本研究调查了BAC过滤后接臭氧化（BO工艺）的组合，以在低臭氧剂量和低能量输入下去除MPs，并重点关注臭氧化过程中有毒有机和无机产物的形成。收集了一个WWTP的出水，加入MPs（约1μg/L）并用BO工艺进行处理。测试了不同的流速（0.25 - 4L/h）和特定臭氧剂量（0.2 - 0.6g O/g TOC），并分析了MPs、生态毒性和溴酸盐。对于生态毒性评估，使用了三种体内（水蚤、藻类和细菌）和六种体外CALUX测定法（Era、GR、PAH、P53、PR和Nrf2 CALUX）。结果表明，与仅进行BAC过滤和仅进行臭氧化相比，BAC过滤和臭氧化的组合具有更高的MP去除率和更高的生态毒性去除率。体内测定法显示初始WWTP出水样品中的生态毒性较低，且随着臭氧剂量增加没有明显趋势，而大多数体外测定法显示随着臭氧剂量增加生态毒性降低。这表明对于所测试的生物测定法、进水和臭氧剂量，臭氧化过程中形成的转化产物的总体生态毒性低于母体化合物的总体生态毒性。在添加溴化物的实验中，在特定臭氧剂量约0.4 O/g TOC以上观察到了溴酸盐的相关形成，并且对于经过BAC预处理的样品形成了更多的溴酸盐。这间接表明了预处理在去除有机物以及使臭氧更易于与其他化合物（如MPs，还有溴化物）反应方面的有效性，但也强调了将臭氧剂量控制在阈值以下以避免形成溴酸盐的重要性。得出的结论是，在特定臭氧剂量为0.2g O/g TOC的情况下，采用BO工艺处理所测试的WWTP出水，在有限的能量输入下可实现高MP去除率，且在此条件下未观察到生态毒性增加或溴酸盐形成。这表明可以实施混合BO工艺来去除MPs，并以比传统MP去除工艺（如单独臭氧化）更低的能量需求提高该WWTP出水的生态质量。
