Application of a Pilot-Scale Pulsed Elecrocoagulation System to Pulp Mill OE Stage Beaching Effluent

Pulp mill is water use intensive, requiring substantial amount of water to produce a ton of product. The hindrances toward fuller reuse of the post-treatment effluents are mostly related to residual ionic species and coloration from ligneous fragments and dissolved organic solids. A pilot-scale study was conducted using pulsed electrocoagulation technology to treat the wastewater of an OE bleaching effluent, with the purpose of evaluating its treatment performance. The operating variables were a current density of 0-233.7 A/m2, a hydraulic retention time (HRT) of 6.5-16.25 min. Water quality indicators investigated were electrical conductivity, suspended solids (SS), chemical oxygen demand (COD), true color and hardness. The results obtained during pilot-scale studies were encouraging. Under the operating conditions studied, the removals of all water quality indicators always increased with an increase either in current density or HRT. The highest removals obtained at 266.7 A/m2 and an HRT of 16.25 min for conductivity, SS, COD, true color and hardness were 63.2%, 92.9%, 75.7%, 86.4% and 89.5% for aluminum electrode and 70.1%, 96.4%, 81.1%, 86.6% and 79.6% for iron electrode, respectively. Evaluation of the economy efficiency suggested that the OE bleaching effluent could be effectively treated using a current density of 266.7 A/m2 and HRT of 16.25 min at operational costs of US$ 0.1109 and 0.094/ton for the aluminum and iron electrode sets, respectively. The study showed that electrocoagulation technology can be used to treat effluent of an OE bleaching stage for water reuse.

制浆厂属于用水密集型产业，生产每吨产品需消耗大量水资源。制约后处理废水深度回用的障碍主要源于木质碎屑与溶解性有机固体所残留的离子类物质及色度污染。本研究采用脉冲电凝技术（pulsed electrocoagulation technology）处理某OE漂白（OE bleaching）工段废水，以评估其处理效能。实验操作变量设置为：电流密度（current density）0~233.7 A/m²，水力停留时间（hydraulic retention time, HRT）6.5~16.25 min。本次研究考察的水质指标包括电导率（electrical conductivity）、悬浮物（suspended solids, SS）、化学需氧量（chemical oxygen demand, COD）、真色与硬度。中试实验结果令人满意。在所考察的操作工况下，各项水质指标的去除率均随电流密度或水力停留时间的提升而升高。当采用电流密度266.7 A/m²、水力停留时间16.25 min的工况时，铝电极体系对电导率、悬浮物、化学需氧量、真色及硬度的最高去除率分别为63.2%、92.9%、75.7%、86.4%与89.5%；铁电极体系的对应最高去除率则分别为70.1%、96.4%、81.1%、86.6%与79.6%。经济性评估结果显示，采用电流密度266.7 A/m²、水力停留时间16.25 min的工况处理OE漂白废水时，铝电极组与铁电极组的运行成本分别为0.1109美元/吨与0.094美元/吨。本研究证实，脉冲电凝技术可用于处理OE漂白工段废水以实现水资源回用。