Disinfection of greywater by heterogeneous photocatalysis

ABSTRACT Proper disinfection of greywater is needed to ensure the safety of its reuse, especially in applications with potential for human exposure. Various advanced oxidation processes have been used in recent years for the degradation of organic contaminants, as well as for disinfection of water and wastewater. The purpose of this study was to test TiO2 supported in microtubes to disinfect greywater by photocatalysis in order to reuse it in sanitary bowl. The greywater used in the experiments was collected after passing through a treatment system consisting of an evapotranspiration tank followed by constructed wetland with horizontal flow. Batch tests were conducted using a cylindrical photochemical reactor of 1.0 L (total volume of the reactor), filled with small glass Pyrex cylinders with supported TiO2. For disinfection tests, the processes UV, H2O2, UV/TiO2, UV/H2O2 and UV/TiO2/H2O2 were used. It was possible to obtain a homogeneous layer of TiO2 deposited in small Pyrex glass tubes with an average thickness of 35.3 µm; this layer was able to promote an increase in the greywater disinfection. However, even with a greater disinfection power of TiO2 compared with photolysis (UV), the processes with hydrogen peroxide was much more efficient in disinfection (total inactivation of total coliforms, enterococci and Pseudomonas aeruginosa) and in the removal of organic matter in terms of chemical oxygen demand (around 60%). Samples stored at a room temperature and wrapped in plastic dark showed no bacterial regrowth after 24 hours of storage after the experiments, thus showing the viability of treated greywater for domestic reuse.

摘要：为保障灰水（greywater）回用安全，尤其在存在人类暴露风险的应用场景中，需对其进行妥善消毒。近年来，各类高级氧化工艺（advanced oxidation processes）已被应用于有机污染物降解以及水体与废水消毒领域。本研究旨在测试负载于微管内的二氧化钛（TiO₂）通过光催化作用对灰水进行消毒的效果，以实现处理后灰水在坐便器中的回用。本实验所用灰水经蒸发塘-水平流人工湿地组成的处理系统处理后收集获得。实验采用总容积为1.0 L的圆柱形光化学反应器，反应器内装填有负载二氧化钛的小型派热克斯（Pyrex）玻璃圆柱管。消毒实验分别采用了紫外线（UV）、过氧化氢（H₂O₂）、UV/二氧化钛、UV/过氧化氢以及UV/二氧化钛/过氧化氢五种工艺。研究成功在小型派热克斯玻璃管上制备出平均厚度为35.3 μm的均匀二氧化钛涂层，该涂层可有效提升灰水的消毒效果。尽管二氧化钛的消毒性能优于光解（UV）工艺，但添加过氧化氢的工艺在消毒效果与有机物去除能力上表现更优：可完全灭活总大肠菌群、肠球菌与铜绿假单胞菌，且以化学需氧量（chemical oxygen demand, COD）计的有机物去除率约为60%。实验结束后，将样品置于室温环境下用避光塑料包装储存24小时，未观察到细菌再生现象，证实了处理后灰水用于家居回用的可行性。