LAMIR Institute, Federal University of Paraná, Curitiba, Brazil.
Postgraduate Program in Pathophysiology and Toxicology, University of Sao Paulo, Sāo Paulo, Brazil.
Photochem Photobiol Sci. 2020 Aug 1;19(8):1078-1087. doi: 10.1039/d0pp00050g. Epub 2020 Jul 3.
Microcystins are a group of cyanotoxins with known hepatotoxic effects, and their presence in drinking water represents a public health concern all over the world. The main objective of this work was to evaluate the solar photo-Fenton process at near-neutral pH in the degradation of microcystin-LR (MC-LR) under conditions close to those found in bloom episodes, with a high concentration of cell debris and natural organic matter (NOM). The influence of experimental parameters such as Fe and HO concentrations, reaction matrix, and the presence of scavenger ions, as well as ecotoxicity before and after treatment, was also evaluated. The reaction matrix was obtained from Microcystis aeruginosa cultivated in ASM-1 medium (ACE1 and ACE2 extracts). HO and Fe concentrations were optimized by 2 factorial design with the central point in a bench-scale solar reactor, using ACE1 extract, and the improved condition was applied in a compound parabolic collector (CPC) reactor, for the ACE2, natural water (RVW) and natural water with M. aeruginosa crude extract (RVCE). Matrix effect assays indicated that radical scavengers present in the medium were responsible for the decrease in the mineralization rates. The solar photo-Fenton process in the CPC reactor achieved COD (75%) and MC-LR (70%) reduction after 120 min at pH = 7.8, [HO]/COD = 3.18 and [HO]/[Fe] = 10 for the ACE2 sample. When the same conditions were applied to the RVCE sample, the process removed 77% of DOC and up to 99% of MC-LR after 45 min of the reaction. Sinapis alba bioassays showed that there was no increase in ecotoxicity after the solar photo-Fenton treatment. These results demonstrate the potential of the solar photo-Fenton process at neutral pH as an additional step in the treatment of natural matrices contaminated with microcystins. In addition, the work reinforces the importance of bioassays in treatment process monitoring.
微囊藻毒素是一组具有已知肝毒性的蓝藻毒素，其在饮用水中的存在是全世界公共卫生关注的一个问题。本工作的主要目的是在接近水华爆发期间发现的条件下，在高浓度细胞碎片和天然有机物（NOM）存在的情况下，评估近中性 pH 下的太阳光芬顿工艺对微囊藻毒素-LR（MC-LR）的降解效果。还评估了实验参数的影响，如 Fe 和 HO 浓度、反应基质以及清除剂离子的存在，以及处理前后的生态毒性。反应基质是从在 ASM-1 培养基中培养的铜绿微囊藻中获得的（ACE1 和 ACE2 提取物）。HO 和 Fe 浓度通过中心点位于中试规模太阳反应器中的 2 因素设计进行优化，使用 ACE1 提取物，并将改进的条件应用于复合抛物面集热器（CPC）反应器，用于 ACE2、天然水（RVW）和含有铜绿微囊藻粗提取物的天然水（RVCE）。基质效应试验表明，介质中存在的自由基清除剂是导致矿化率降低的原因。在 CPC 反应器中的太阳光芬顿工艺在 pH = 7.8、[HO]/COD = 3.18 和 [HO]/[Fe] = 10 时，在 ACE2 样品中 120 分钟后实现 COD（75%）和 MC-LR（70%）的去除。当相同的条件应用于 RVCE 样品时，该过程在反应 45 分钟后去除了 77%的 DOC 和高达 99%的 MC-LR。白芥菜生物测定表明，太阳光芬顿处理后生态毒性没有增加。这些结果表明，在中性 pH 下的太阳光芬顿工艺作为处理受微囊藻毒素污染的天然基质的附加步骤具有潜力。此外，该工作强调了生物测定在处理过程监测中的重要性。
