Abstract
The performance of a sludge blanket anaerobic baffled reactor was tested as an integrated treatment system for source-separated blackwater. The system consists of a stirred equalization tank, a buffer inlet tank, and two identical reactors, each with a working volume of 16.4 L, operated in parallel. Both reactors run at 3-days hydraulic retention time with different intermittent pulse feeding. Pulse lengths of 12 and 24 seconds per feed were set with respective rates of 114 L h-1 and 52 L h-1 for the short-pulse fed reactor (RI) and the long-pulse fed reactor (RII). Stable performance of the reactors was attained after 120 and 90 days, for RI and RII, respectively. After stable conditions attained, total chemical oxygen demand (COD) removal efficiency stabilized above 78%. Biogas production ranged from 0.52 to 1.16 L d-1 L-1 reactor volume, with 67-82% methane concentration and an average conversion of 0.69 ± 0.2 and 0.73 ± 0.2 g CH4-COD g-1CODin for RI and RII, respectively. The results imply that source-separated blackwater can be treated effectively in an anaerobic sludge blanket process on average loading rate of 2.3 ± 0.5 g COD d-1 L-1 reactor volume with high methane production potential and more than 80% removal of organic and particulate matter.
Highlights
Considering the increasing concerns of water scarcity and environmental pollution, a new trend has emerged for decentralized and source-separated approaches to processing wastewater as a resource
The raw blackwater (BW) composition used in this research is presented in Table 1 and is characterized by organic matter concentration measured as CODt, chemical oxygen demand (COD), total suspended solids (TSS), total solids (TS), volatile solids (VS), pH, volatile fatty acid, ammonium nitrogen and phosphorus
Source-separated blackwater was anaerobically treated with a sludge bed anaerobic reactor at controlled temperature (i.e. 25 to 28 C) for several months, going from variable efficiency to steady-state in less than half a year
Summary
Considering the increasing concerns of water scarcity and environmental pollution, a new trend has emerged for decentralized and source-separated approaches to processing wastewater as a resource. Recent studies on separate collection and treatment of blackwater (BW) fraction show that anaerobic upflow reactors have the potential for energy and nutrient recovery The key feature of anaerobic upflow reactors is the formation of sludge blankets in which biomass and particulate organic matter are retained in the reactor. The feasibility of sludge bed anaerobic processes for blackwater, depends primarily on: (i) the nature of the organic components in the blackwater, (ii) the operational conditions, the organic loading rate (OLR), hydraulic loading rate (HLR), pH and temperature, and (iii) the reactor configuration, especially its capacity to retain biomass in the sludge bed
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