人工湿地-电活性菌藻膜技术处理养猪废水的中试

    Pilot-scale study on the treatment of swine wastewater by constructed wetland consisted with exoelectrogens-microalgae biofilm

    • 摘要: 人工湿地由于具有运行成本低、维护简单等优点而被广泛应用于养殖废水处理。然而,人工湿地技术普遍存在污染物去除效率受温度影响大等问题。在该研究中,通过构建电活性菌藻生物膜来强化人工湿地系统,对养猪废水进行了自然温度下的处理效能与微生物群落研究,在室外开展了18个月试验,结果表明:电活性菌藻生物膜强化组在夏季化学需氧量、氨氮、硝态氮、总氮、总磷、亚硝态氮的去除率分别达到98.26%、97.96%、85.45%、95.07%、94.64%和85.45%。在冬季化学需氧量、氨氮、硝态氮、总氮、总磷、亚硝态氮的去除率分别达到96.10%、91.56%、75.29%、89.94%、92.12%和83.15%。具有良好低温适应性。强化组冬季化学需氧量、氨氮、硝态氮、总氮、总磷、亚硝态氮的出水浓度均满足《禽畜养殖业污染物排放标准》(GB18596-2001)。相比未构建电活性菌藻生物膜的对照组,以上污染物去除率均分别提高。电活性菌藻膜在冬夏季节的优势微生物均为Cyanobium、Shewanella、Azoarcus,群落结构稳定性高,有利于促进冬季污染物去除率,为提高系统污水处理可靠性提供了保障。

       

      Abstract: Abstract: Constructed wetland (CW) is widely used in the treatment of swine wastewater, due to the operation cost-saving and simple maintenance. However, the pollutant removal efficiency is greatly affected by temperature in CW technology. Fortunately, the exoelectrogens-microalgae biofilm is composed of extracellular respiratory bacteria and microalgae, particularly with the high efficiency, energy saving, and low cost in wastewater treatment. Therefore, the stability of CW can be enhanced by the exoelectrogens-microalgae biofilm at low temperatures. It is a high demand to evaluate the technical reliability of long-term outdoor operations. This study aims to improve the treatment efficiency and microbial community of swine wastewater under natural temperatures, in order to explore the effect of temperature on exoelectrogens-microalgae biofilm in the enhanced CW system. Extracellular respiratory bacteria were achieved in the direct interspecific electron transfer process through direct contact or conductive substance mediation. As such, the hydrogen partial pressure and the concentration of metabolite greatly improved the electron transport efficiency and metabolic rate. Extracellular respiratory bacteria mainly included electroactive bacteria, such as Shewanella. The extracellular respiratory bacteria produced carbon dioxide by metabolizing organic matter, which was used as a carbon source for the microalgae. The oxygen produced by microalgae was used as an electron acceptor for the extracellular respiratory bacteria, thus realizing the material and energy mutual camping between them. Therefore, the construction of exoelectrogens-microalgae biofilm was a feasible way to improve the efficiency of CW wastewater treatment. There were high concentrations of carbon, nitrogen, and phosphorus in the swine wastewater. The treatment efficiency of swine wastewater and microbial community of the system under natural temperature was determined in the coupling exoelectrogens-microalgae biofilms (EMB) with the CW system. The outdoor experiment then lasted for 18 months. The results showed that the removal rates of chemical oxygen demand (COD), ammonia nitrogen, nitrate nitrogen, total nitrogen, total phosphorus, and nitrite nitrogen in the EMB-CW group in summer and winter reached 98.26/96.10%, 97.96/91.56%, 85.45/65.29%, 95.07/89.94%, 91.44/92.12%, and 85.45%/83.15%, respectively, with the strong adaptability at low temperature. The effluent concentrations of COD, ammonia nitrogen, nitrate nitrogen, total nitrogen, total phosphorus, and nitrous nitrogen were 97.50, 12.70, 1.24, 24.44, 1.97, and 0.17 mg/L, respectively, which fully met the Emission Standard for Livestock and Poultry Industry (GB18596-2001) in China. Compared with the CW group, the removal rates of the above pollutants in the EMB-CW group increased by 5.75, 6.95, 8.00, 13.75, 2.38, and 20.93 percentage points, respectively. Cyanobium, Shewanella and Azoarcus were the dominant microorganisms of the EMB-CW group in both winter and summer, and the stability of community structure was high, which was conducive to the removal rate of pollutants in winter for the reliability of the EMB-CW system. Consequently, the exoelectrogens-microalgae biofilm significantly improved the pollutant treatment efficiency and stability of the CW system under low-temperature conditions. The finding can provide an idea for the treatment of rural livestock and poultry farming wastewater. Therefore, better social benefits and technically feasible can be expected to gain for the application of exoelectrogens-microalgae biofilm in practice.

       

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