Department of Civil and Environmental Engineering , Stanford University , 473 Via Ortega , Stanford , California 94305 , United States.
Environmental Simulation and Pollution Control State Key Joint Laboratory, State Environmental Protection Key Laboratory of Microorganism Application and Risk Control (SMARC), School of Environment , Tsinghua University , Beijing 100084 , P. R. China.
Environ Sci Technol. 2019 Apr 16;53(8):4416-4425. doi: 10.1021/acs.est.8b06894. Epub 2019 Apr 2.
Chloramines applied to control membrane biofouling in potable reuse trains pass through reverse osmosis membranes, such that downstream ultraviolet (UV)/HO advanced oxidation processes (AOPs) are de facto UV/HO-chloramine AOPs. Current models for UV/chloramine AOPs, which use inaccurate chloramine quantum yields and ignore the fate of NH, are unable to simultaneously predict the loss of chloramines and contaminants, such as 1,4-dioxane. This study determined quantum yields for NHCl (0.35) and NHCl (0.75). Incorporating these quantum yields and the formation from NH of the radical scavengers, NO and NO, was important for simultaneously modeling the loss of chloramines, HO, and 1,4-dioxane in the UV/HO-chloramine AOP. Although the level of radical production was higher for the UV/HO-chloramine AOP than for the UV/HO AOP, the UV/HO AOP was at least 2-fold more efficient with respect to 1,4-dioxane degradation, because chloramines efficiently scavenged radicals. At low chloramine concentrations, the UV/chloramine AOP efficiency increased with an increase in chloramine concentration, as the level of radical production increased relative to that of radical scavenging by the dissolved organic carbon in RO permeate. However, the efficiency leveled out at higher chloramine concentrations as radical scavenging by chloramines offset the increased level of radical production. The level of 1,4-dioxane degradation was ∼30-50% lower for the UV/chloramine AOP than for the UV/HO-chloramine AOP when the concentration of residual chloramines in RO permeate was ∼50 μM (3.3 mg/L as Cl). Initial cost estimates indicate that the UV/chloramine AOP using the residual chloramines in RO permeate could be a cost-effective alternative to the current UV/HO-chloramine AOP in some cases, because the savings in reagent costs offset the ∼30-50% reduction in 1,4-dioxane degradation efficiency.
应用于控制饮用水再利用系统中膜生物污染的氯胺会穿过反渗透膜，因此下游的紫外线 (UV)/HO 高级氧化工艺 (AOP) 实际上是 UV/HO-氯胺 AOP。目前的 UV/氯胺 AOP 模型使用不准确的氯胺量子产率且忽略 NH 的命运，因此无法同时预测氯胺和污染物（如 1,4-二恶烷）的损失。本研究确定了 NHCl（0.35）和 NHCl（0.75）的量子产率。同时，将 NH 形成的自由基清除剂，NO 和 NO 的形成纳入其中，对于同时模拟 UV/HO-氯胺 AOP 中氯胺、HO 和 1,4-二恶烷的损失非常重要。尽管 UV/HO-氯胺 AOP 中的自由基产生水平高于 UV/HO AOP，但由于氯胺有效地清除了自由基，UV/HO AOP 对 1,4-二恶烷降解的效率至少高 2 倍。在低氯胺浓度下，随着自由基产生水平相对于 RO 渗透物中溶解的有机碳的自由基清除而增加，UV/氯胺 AOP 的效率随着氯胺浓度的增加而增加。然而，随着氯胺的自由基清除作用抵消了自由基产生水平的增加，效率水平在较高的氯胺浓度下趋于平稳。当 RO 渗透物中残余氯胺的浓度约为 50 μM（3.3 mg/L 作为 Cl）时，UV/氯胺 AOP 中 1,4-二恶烷的降解水平比 UV/HO-氯胺 AOP 低约 30-50%。初步成本估算表明，在某些情况下，使用 RO 渗透物中残余氯胺的 UV/氯胺 AOP 可能是当前 UV/HO-氯胺 AOP 的一种具有成本效益的替代方案，因为试剂成本的节省抵消了 1,4-二恶烷降解效率降低约 30-50%的影响。
