The control of red water occurrence and opportunistic pathogens risks in drinking water distribution systems: A review

Many problems in drinking water distribution systems (DWDSs) are caused by microbe, such as biofilm formation, biocorrosion and opportunistic pathogens growth. More iron release from corrosion scales may induce red water. Biofilm played great roles on the corrosion. The iron-oxidizing bacteria (IOB) promoted corrosion. However, when iron-reducing bacteria (IRB) and nitrate-reducing bacteria (NRB) became the main bacteria in biofilm, they could induce iron redox cycling in corrosion process. This process enhanced the precipitation of iron oxides and formation of more Fe₃O₄ in corrosion scales, which inhibited corrosion effectively. Therefore, the IRB and NRB in the biofilm can reduce iron release and red water occurrence. Moreover, there are many opportunistic pathogens in biofilm of DWDSs. The opportunistic pathogens growth in DWDSs related to the bacterial community changes due to the effects of micropollutants. Micropollutants increased the number of bacteria with antibiotic resistance genes (ARGs). Furthermore, extracellular polymeric substances (EPS) production was increased by the antibiotic resistant bacteria, leading to greater bacterial aggregation and adsorption, increasing the chlorine-resistance capability, which was responsible for the enhancement of the particle-associated opportunistic pathogens in DWDSs. Moreover, O₃-biological activated carbon filtration-UV-Cl₂ treatment could be used to control the iron release, red water occurrence and opportunistic pathogens growth in DWDSs.     

光-Fenton/TiO2催化氧化法降解酸性红B的研究

以钛酸丁酯为前驱体,采用溶胶-凝胶法制备TiO2,将TiO2与Fenton试剂联合用来处理酸性红B模拟废水,研究了在紫外光条件下的降解效果,确定最佳反应条件.实验结果表明,采用TiO2与Fenton试剂联合的方式对酸性红B染料废水进行处理,其降解效果明显优于单一使用TiO2和Fenton法的处理方式.对于初始浓度为100 mg/L的酸性红B模拟染料废水,在TiO2投加量为1 g/L,pH为3,Fe2+为0.15 mmol/L,H2O2为1mmol/L,UV光照时间为60 min时,脱色率可达最佳.     

耐盐菌GTY对偶氮染料活性艳红X-3B的脱色研究

为了选择耐盐菌GTY对偶氮染料活性艳红X-3B的最佳脱色条件,研究了不同环境条件对脱色效果的影响,结果表明耐盐菌GTY对偶氮染料活性艳红X-3B有较好的脱色效果,能够适应较宽范围的pH值以及污染物负荷,当pH值在7～9之间,活性艳红X-3B初始浓度在600mg/L以下,GTY菌液生长期在对数末期时脱色效果达到最佳状态,24h脱色率能达到90%左右。同时考察了GTY的不同初始接菌量对活性艳红X-3B脱色的影响,结果发现高的初始接菌量可以提高脱色速率,但是一定时间后,初始接菌量对最终脱色效果并无太大影响,兼顾节约成本和脱色效果选择最佳初始接菌量为5%。     

我国环境空间规划制度的研究进展

建立严格的环境空间管控制度,可以破解现阶段城市出现的一系列复合型、区域性和格局性环境问题,对从源头促进"人-城市-自然"和谐发展具有重要意义。为全面梳理环境空间规划制度和弥补其研究发展中的不足,对以环境功能区划、城市环境总体规划和生态保护红线制度为代表的环境空间规划制度的理论、技术与实践进行了较为全面的分析,对现有研究和未来探索提出展望,以期为以环境质量改善和风险防范为指导的环境空间规划制度提供理论依据和实践管理经验,从而全面引导城市的健康可持续发展。     

Precise regulation of acid pretreatment for red mud SCR catalyst: Targeting on optimizing the acidity and reducibility

• The optimum SCR activity was realized by tuning the acid pretreatment. • Optimized catalysts showed NO_x conversion above 90%. • The NH₃ and NO adsorption capacity of Al-O₃-Fe is stronger than Fe-O₃-Fe. • The formation of almandine consumes Fe³⁺ and Al³⁺ and weakens their interaction. Red mud (RM), as an alkaline waste, was recently proved to be a promising substitute for the SCR catalyst. Dealkalization could improve the acidity and reducibility of red mud, which were critical for SCR reaction. However, the dealkalization effect depended on the reaction between acid solution and red mud. In this study, we realized the directional control of the chemical state of active sites through tuning the acid pretreatment (dealkalization) process. The pretreatment endpoint was controlled at pH values of 3–5 with diluted nitric acid. When the pH values of red mud were 3 and 5 (CRM-3 and CRM-5), activated catalysts showed NO_x conversion above 90% at 275°C–475°C. The high initial reaction rate, Ce³⁺/(Ce³⁺ + Ce⁴⁺) ratio, and surface acidity accounted for the excellent SCR performance of CRM-5 catalyst. Meanwhile, more Fe³⁺ on the CRM-3 surface improved the NH₃ adsorption. There was a strong interaction between Al and Fe in both CRM-5 and CRM-3 catalysts. DFT results showed that the adsorption capacity of the Al-O₃-Fe for NH₃ and NO is stronger than that of Fe-O₃-Fe, which enhanced the NO_x conversion of the catalyst. However, the almandine was formed in CRM-4, consumed part of Fe³⁺ and Al³⁺, and the interaction between Al and Fe was weakened. Also, deposited almandine on the catalyst surface covered the active sites, thus leading to lower NH₃-SCR activity.