Department of Environment, Land and Infrastructure Engineering, Politecnico di Torino, corso Duca degli Abruzzi, 24, 10129 Torino, Italy; CleanWaterCenter@PoliTo, Politecnico di Torino, corso Duca degli Abruzzi 24, 10129 Torino, Italy.
Department of Environment, Land and Infrastructure Engineering, Politecnico di Torino, corso Duca degli Abruzzi, 24, 10129 Torino, Italy.
Sci Total Environ. 2019 Nov 20;692:1191-1200. doi: 10.1016/j.scitotenv.2019.07.251. Epub 2019 Jul 17.
Bromide-enhanced ozonation (BEO) process can be a fast and effective solution for the complete removal of total nitrogen (TN) from wastewaters containing from moderate to high concentrations of ammonia nitrogen (AN). Like the traditional biological process of AN oxidation, even BEO requires the presence of buffering agents, in order to oppose the progressive acidification induced by the reaction. This study compares the effect of two buffering substances (namely bicarbonate and mixtures of orthophosphates) in hindering the acidification caused by AN oxidation and, consequently, optimizing the overall efficiency of the process. Tests were carried out with on-purpose made solutions containing concentrations of AN of 5-10 mM. The range of [Br]/[O] ratio values was from 12 to 18, so as to make ozone the limiting factor in HOBr generation. The results of this study proved that, in the absence of natural buffering agents, mixtures of orthophosphates must be preferred to the more traditionally employed bicarbonate to control the pH evolution of BEO process. In fact, orthophosphates proved to be capable to guarantee an initial pH of the wastewater in the order of 7.5, thus making the zero-order AN removal rates 15% faster than those observed in the presence of bicarbonate. Furthermore, in the presence of mixtures of orthophosphates, the generation of ozonation byproducts in the oxidized form (nitrate, bromate) was reduced by over 70%. Finally, the fine control of pH obtained with orthophosphates in the BEO of AN makes that process an attractive solution for the treatment of effluents containing AN, thus preventing the discharge of residual nitrogen into aquatic environments and avoiding eutrophication of receiving water bodies.
溴酸盐增强臭氧化（BEO）工艺可以快速有效地去除废水中总氮（TN），这些废水含有中等至高浓度的氨氮（AN）。与传统的 AN 氧化生物工艺一样，即使是 BEO 也需要缓冲剂的存在，以抵抗反应引起的渐进酸化。本研究比较了两种缓冲物质（即碳酸氢盐和混合正磷酸盐）在阻止 AN 氧化引起的酸化以及优化整个过程效率方面的效果。测试是在含有 5-10 mM AN 的专用溶液中进行的。[Br]/[O] 比值范围为 12 至 18，以使臭氧成为 HOBr 生成的限制因素。本研究的结果证明，在没有天然缓冲剂的情况下，混合正磷酸盐必须优先于传统使用的碳酸氢盐，以控制 BEO 过程的 pH 值演变。事实上，正磷酸盐被证明能够保证废水的初始 pH 值在 7.5 左右，从而使零级 AN 去除率比在碳酸氢盐存在下的去除率快 15%。此外，在混合正磷酸盐存在的情况下，氧化形式（硝酸盐、溴酸盐）的臭氧化副产物生成减少了 70%以上。最后，正磷酸盐在 BEO 中对 AN 的精细 pH 值控制使得该工艺成为处理含有 AN 的废水的一种有吸引力的解决方案，从而防止残余氮排入水生环境并避免受纳水体富营养化。
