Simultaneous removal of nitrogen and organic carbon from swine wastewater using the pre-denitrification/nitrification process

Abstract Wastewater from confined animal feeding operations (CAFOs) can interfere significantly with the natural nitrogen and phosphorus balance in the environment if not treated adequately prior to disposal. In this work, a modified Lutzak-Ettinger (MLE) consisting of sequential pre-denitrification/ nitrification was used to determine the effects of nutrient loading rates and hydraulic retention times (HRT) on total nitrogen (TN) and organic carbon (TOC) removal from swine wastewater. MLE reactor was continuously fed swine wastewater for over 205 days using different recycle ratios (Rr) and HRT. Higher TN and TOC removal efficiencies (90.7% and 96.1%, respectively) were obtained when recycling effluent from the nitrification tank (4.5:1) combined with effluent from the final clarifier (1:1). Removal efficiencies of 96% for TOC and 90% for TN were obtained for the maximum loading rates of 0.56 gTN L-1 d-1 and 2.15 g TOC L-1 d-1, respectively. TN and TOC removal rates were achieved with HRT in as little as 3.5 days. Overall, MLE was a robust bioprocess withstanding variations in wastewater physical-chemical composition and/or changes in operational conditions without significant impairment of N and TOC removal efficiencies.

集约化畜禽养殖场（confined animal feeding operations, CAFOs）产生的废水若在排放前未得到妥善处理，将对环境自然氮、磷平衡造成显著干扰。本研究采用由顺序前置反硝化/硝化工艺组成的改良型Lutzak-Ettinger（modified Lutzak-Ettinger, MLE）工艺，探究了营养负荷率与水力停留时间（hydraulic retention times, HRT）对猪粪废水中总氮（total nitrogen, TN）与总有机碳（total organic carbon, TOC）去除效果的影响。本研究通过设置不同回流比（recycle ratios, Rr）与HRT，使该MLE反应器连续进料猪粪废水并稳定运行超过205天。当以4.5:1的比例回流硝化池出水、并以1:1的比例回流最终沉淀池出水时，TN与TOC的去除效率分别达到90.7%与96.1%。当营养负荷分别达到最大限值0.56 gTN·L⁻¹·d⁻¹与2.15 gTOC·L⁻¹·d⁻¹时，TOC与TN的去除效率分别可达96%与90%。仅需3.5天的水力停留时间即可实现稳定的TN与TOC去除速率。整体而言，MLE工艺是一种性能稳定的生物处理工艺，可耐受废水理化组成的波动与运行条件的变化，且不会对氮与TOC的去除效率造成显著负面影响。