Abstract：
In this work, a one-stage dual internal circulation airlift anaerobic/anoxic/aerobic (DCAL-A2O) bioreactor was continuously operated for concurrent removal of nutrients and organics from milk processing wastewater (MPW). Special configuration of the airlift A2O bioreactor created possibility of the formation of desired anaerobic, anoxic and aerobic zones in a single unit. The process functionality of the bioreactor was examined under three influential operating variables i.e. hydraulic retention time (HRT; 7-15 h), air flow rate (AFR; 1-3 L/min) and aerobic volume ratio (AVR; 0.324-0.464). The optimum region was identified at HRT of 13h, AFR of 2L/min and AVR of 0.437, leading to TCOD, TN and TP removal efficiency of 94.5 %, 59.6 %, and 62.2 %, respectively, and effluent turbidity of 8 NTU. The impact of feed biodegradability on the process performance of the bioreactor treating the MPW, soft drink wastewater (SDW) and soybean oil plant wastewater (SOW) was also assessed. From the results, the feed characteristics affected significantly the nutrients removal. Moreover, the feeding location played an effective role in the nutrient removal while treating the MPW at optimum operating conditions. In this study, the change in residual organic matters as soluble microbial products (SMP) was monitored at various operating conditions. In addition, the impact of SMP extracted from sludge, extracellular polymeric substances (EPS) comprising of loosely bound EPS (LB-EPS) and tightly bound EPS (TB-EPS) was analyzed on sludge characteristics as bio-flocculation and settleability properties. According to the obtained data, the increase in operating variables led to the reduction in contents of effluent SMP, sludge SMP, LB-EPS, turbidity, and SVI, thereby, the enhancement in the sludge characteristics. Meanwhile, analysis of microbial communities verified the presence of various functional bacterial species. The cost operating evaluation confirmed the cost effectiveness of the airlift A2O bioreactor in reduction of energy consumption for the MPW treatment.
摘要：
在这项工作中,连续运行一级双内循环气升式厌氧/缺氧/好氧（DCAL-A2O）生物反应器，以同时去除牛奶加工废水（MPW）中的养分和有机物。气升式A2O生物反应器的特殊配置创造了形成所需厌氧的可能性，缺氧和好氧区在一个单元。在三个有影响的操作变量下检查生物反应器的工艺功能，即水力停留时间（HRT;7-15h），空气流量（AFR；1-3L/min）和有氧体积比（AVR；0.324-0.464）。在HRT为13h时确定了最佳区域，AFR为2L/min，AVR为0.437，导致TCOD，TN和TP去除率达94.5%，59.6%,和62.2%，分别,出水浊度为8NTU。饲料生物降解性对生物反应器处理MPW的工艺性能的影响,还评估了软饮料废水（SDW）和大豆油厂废水（SOW）。从结果来看,饲料特性对养分去除有显著影响。此外，在最佳操作条件下处理MPW时，进料位置在养分去除中发挥了有效作用。在这项研究中,在各种操作条件下监测作为可溶性微生物产物(SMP)的残余有机物的变化。此外,从污泥中提取SMP的影响，分析了由松散结合的EPS（LB-EPS）和紧密结合的EPS（TB-EPS）组成的胞外聚合物（EPS）的污泥特性，如生物絮凝和可沉降性。根据获得的数据，操作变量的增加导致废水SMP含量的减少，污泥SMP,LB-EPS,浊度,SVI,因此，污泥特性的增强。同时,对微生物群落的分析证实了各种功能性细菌的存在。成本运行评估证实了气升式A2O生物反应器在降低MPW处理能耗方面的成本效益。
