ClO_(x)^(-)产物对电氧化去除COD性能评价及水体毒性影响

The adverse impacts of produced ClO_(x)^(-)on assessing electrochemical oxidation performance for COD removal and biotoxicity

电化学氧化处理真实含氯废水产生的氯氧根离子(ClO_(x)^(-))对COD去除性能评价以及水体毒性的影响鲜有报道。构建以Ti/RuO_(2)-IrO_(2)-SnO_(2)-Sb2O5为阳极的电催化氧化体系,处理某污水处理厂的气浮出水和水厂末端出水。结果表明,增加电流密度促进了ClO_(x)^(-)的产生,加剧了电化学氧化处理两种水体时COD去除效果的过高评价,主要原因是利用重铬酸盐法测定COD时产物ClO_(3)^(-)起到了掩蔽作用。处理气浮出水时,水中的NH_(4)^(+)和有机物会消耗HClO/ClO^(-),阻断了HClO/ClO^(-)向ClO_(3)^(-)转化,抑制了ClO_(x)^(-)的产生,COD去除率过高评价程度也较低。通过循环伏安法进一步分析得知,NH_(4)^(+)在间接氧化过程中能够快速捕获活性氯并与之反应,导致ClO_(x)^(-)的形成受到抑制。小球藻生物测定实验表明,电解含氯废水过程中会形成有毒副产物,ClO_(x)^(-)是造成生物毒性的主要原因。

The effects of oxychlorides(ClO_(x)^(-))produced by electrochemical oxidation of real wastewater on evaluation of COD removal performance and biotoxicity are rarely reported.In this study,an electrolytic reaction system with Ti/RuO_(2)-IrO_(2)-SnO_(2)-Sb_(2)O_(5)as anode was constructed to treat the air floatation produced water and effluent water.The experimental results showed that increasing the current density promoted the production of ClO_(x)^(-)and exacerbated the overestimation of the COD removal efficiency in electrochemical oxidation when treating the two types of water,mainly due to the produced ClO_(3)^(-)acted as a mask for the determination of COD by the dichromate method.When treating the air floatation produced water,ammonia nitrogen and organic matter in the water consumed HClO/ClO^(-)and inhibited the production of ClO_(x)^(-)by blocking the conversion of HClO/ClO^(-)to ClO_(3)^(-).As a result,the degree of over-evaluation of COD removal was relatively low in this case.Further analysis by cyclic voltammetry revealed that the indirect oxidation of ammonia nitrogen could rapidly capture and react with active chlorine,thus inhibiting the formation of ClO_(x)^(-).The Chlorella bioassay experiments showed that toxic by-products were formed during electrolysis of chlorinated wastewater,and ClO_(x)^(-)was the main substance for the increase of biotoxicity.