School of Environmental and Municipal Engineering, Qingdao University of Technology, 11 Fushun Road, Qingdao, 266033, PR China; Sembcorp-NUS Corporate Laboratory, Faculty of Engineering, National University of Singapore, 1 Engineering Drive 2, 117576, Singapore.
Sembcorp-NUS Corporate Laboratory, Faculty of Engineering, National University of Singapore, 1 Engineering Drive 2, 117576, Singapore; Centre for Water Research, Department of Civil & Environmental Engineering, National University of Singapore, 1 Engineering Drive 2, 117576, Singapore.
Chemosphere. 2020 Feb;240:124804. doi: 10.1016/j.chemosphere.2019.124804. Epub 2019 Sep 7.
Chemical oxygen demand (COD) is one of the most important water quality parameters that quantifies the amount of oxygen needed to oxidize oxidizable pollutants (mainly organics) in water samples. However, erroneous COD results were commonly observed for bromide-rich industrial wastewater samples using standard COD test. Bromide in water sample is known to seriously interfere with COD test. However, there is no satisfactory approach to effectively eliminate bromide interference thus far. In this study, two strategies, namely masking and correction, were investigated for their effectiveness to suppress bromide interference. For the masking strategy, silver ion was assessed for its effectiveness to neutralize bromide in water samples through precipitation and complex formation reactions. Silver ion offered only partial masking effect on bromide, while the residue bromide can still cause significant interference on COD determination. For the correction strategy, an equivalent redox reaction reflecting bromide interference mechanism was proposed, and a theoretical correction factor of 0.1 g COD/g Br was found based on stoichiometry. The effectiveness of the proposed correction factor for bromide interference under different wastewater pollutant matrix was evaluated using different types of wastewater samples (synthetic wastewater, domestic wastewater and bromide-rich industrial wastewater) with varying amounts of bromide (from 0 to 2000 mg L) added to the samples. The findings showed that with bromide concentration up to 600 mg L, the correction factor of 0.1 g COD/g Br was applicable to all the tested wastewater samples, suggesting that this correction strategy could be practically used to eliminate bromide interference in standard COD test.
化学需氧量（COD）是衡量水样中可氧化污染物（主要是有机物）所需氧量的最重要水质参数之一。然而，对于富含溴化物的工业废水样品，使用标准 COD 测试通常会得到错误的 COD 结果。水中的溴化物已知会严重干扰 COD 测试。然而，迄今为止，还没有令人满意的方法来有效消除溴化物的干扰。在这项研究中，研究了掩蔽和校正两种策略，以评估它们抑制溴化物干扰的效果。对于掩蔽策略，评估了银离子通过沉淀和络合反应来中和水样中溴化物的有效性。银离子对溴化物仅提供部分掩蔽效果，而残留的溴化物仍会对 COD 测定造成显著干扰。对于校正策略，提出了一个反映溴化物干扰机制的等效氧化还原反应，并根据化学计量学发现了 0.1g COD/g Br 的理论校正因子。使用不同类型的废水样品（合成废水、生活污水和富含溴化物的工业废水），在样品中添加不同量的溴化物（从 0 到 2000mg/L），评估了该校正因子对不同废水污染物基质下溴化物干扰的有效性。研究结果表明，在溴化物浓度高达 600mg/L 的情况下，0.1g COD/g Br 的校正因子适用于所有测试的废水样品，这表明该校正策略可实际用于消除标准 COD 测试中的溴化物干扰。
