Abstract
The concept of water resources recovery facilities (WRRFs) has gained more attention as a more sustainable substitute for the conventional activated sludge-based wastewater treatment plant (CAS-WWTPs). Anaerobic treatment is advantageous due to its lower energy use, limited sludge production, and higher recovery of the soluble chemical oxygen demand (sCOD) from the received wastewater. In this article, a critical review of the proposed scheme for the anaerobic-based WRRF (An-WRRFs) is presented which is preceded with discussion of CAS-WWTPs limitations. In addition, the evolution of anaerobic treatment from being viewed as wastewater treatment plant (WWTP) to WRRF is demonstrated. It is attained that, even though anaerobic WWTPs (An-WWTPs) have simple and low energy mainline and very limited sludge handling process, its limited removal and recovery capacity have been widely reported, especially in cold weather. On the other hand, in the An-WRRF, higher energy expenditures are employed by using membranes, dissolved methane recovery unit, and primary treatment (extra sludge handling). Yet, energy recovery in the form of biogas is notably increased, as well as the removal efficiency under moderate residence times. The three key challenges to be overcome are the low value of biogas, reducing the energy use associated with membranes, and maintaining high performance in full-scale, especially in cold weather.
Highlights
For more than a century, conventional activated sludge (CAS) has been the most common treatment process adopted by wastewater treatment plants (WWTPs), especially in North America and Europe
The aim of this review is to provide a technological update and critical discussion about the configuration of the anaerobic-based water resources recovery facilities (An-WRRFs)
The anaerobic-based WRRF (An-WRRF) scheme was proposed based on a coherent rationale, argued in Section 4, in which primary treatment, membranes, and D-methane recovery units are added to the
Summary
For more than a century, conventional activated sludge (CAS) has been the most common treatment process adopted by wastewater treatment plants (WWTPs), especially in North America and Europe. SRT and primary treatment efficiency, the COD mineralized and COD captured in the sludge ranges from 30% to 50% and from 18% to 26% of the influent TCOD, respectively [3,12,17,18]. The rationale for An-WWTPs is to combine both removal and recovery in the liquid stream, cancel the solids stream, separate the carbon and nutrients removal/recovery (in some cases nutrients removal is not desired when effluent used for agricultural purposes [2]), and minimize the energy use On the upsides, it successfully achieves substantial energy savings (up to 90%) since no aeration and mechanical mixing is needed, while sludge production is minimal. Anaerobic microbial activity is notably declined, resulting in diminishing process stability, capacity to handle shock loads, removal efficiency, and methane recovery.
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