Two-Phase Thermophilic Acidification and Mesophilic Methanogenesis Anaerobic Digestion of Waste-Activated Sludge

Demirer, Göksel Niyazi
Othman, Maazuza
Biological pretreatment methods of waste-activated sludge (WAS) have recently received attention because of their efficiency and relatively low investment. The application of hydrolysis/acidification step before methanization in anaerobic digestion or the two-phase anaerobic digestion process constitutes one of these methods. Two phase (thermophilic acidification and mesophilic methanogenesis) anaerobic digestion of WAS was investigated and reported to perform better in terms of chemical oxygen demand (COD) solubilization, volatile solids destruction, gas production, and pathogen indicator reduction. The solids loading rates (SLR) used in these studies were significantly high (6.5-28.9 g volatile solids (VS)/L . day). It is well-known that high SLRs along with low retention times lead to higher acidification in two-phase systems. However, WAS from different wastewater treatment plants is likely to have different concentrations due to different process configurations and operational practices that lead to lower solids loading rates. Therefore, this study investigated the performance of thermophilic anaerobic preacidification of WAS prior to conventional mesophilic (methanogenic) anaerobic digestion at low SLRs (0.98-3.93 g VS/L . day). To this purpose, continuous anaerobic acidogenic reactors with no recycle were operated at two different HRT (or SRT) values of 2 and 4 days, and three different SLR values of 0.98, 1.97, and 3.93 g VS/L . day. After the acidification reactors reached to steady-state conditions, the preacidified WAS samples (or the effluents of thermophilic acidogenic anaerobic reactors) and raw WAS samples (or the feeds to the thermophilic acidogenic anaerobic reactors) were subjected to biochemical methane potential (BMP) assay. Results indicated that thermophilic preacidification led to a 20.9-34.8% increase in dissolved (soluble) COD concentration and 18.2-33.3% CODt reduction in acidogenic reactors. When the CODt removals observed for preacidification and BMP were both considered, preacidification (or phase separation) has led to 26.2-49.4% additional CODt removal. It is apparent from these results that beneficial effect of preacidification on CODt removal is sustained for low SLRs (0.98-3.93 g VS/L . day).


A Laboratory Column Investigation for the Treatment of Cr(VI) with Zero-Valent Iron
Uyusur, Burcu; Ünlü, Kahraman (Mary Ann Liebert Inc, 2009-02-01)
Permeable reactive barrier (PRB) technology is commonly placed in the list of options for groundwater remediation at hazardous waste sites, where Cr(VI) treatment in groundwater has been a concern more than any other inorganic contaminants. The objective of this study was to investigate the effectiveness and longevity of Cr(VI) removal with zero-valent iron based PRBs. The main focus was on two parameters affecting the performance of Cr(VI) removal with PRBs: (1) amount of reactive media and (2) groundwater...
Kinetic modeling of enzymatic hydrolysis of pretreated kitchen wastes for enhancing bioethanol production
Çekmecelioğlu, Deniz (Elsevier BV, 2013-03-01)
It is well known that use of low cost and abundant waste materials in microbial fermentations can reduce product costs. Kitchen wastes disposed of in large amounts from cafeterias, restaurants, dining halls, food processing plants, and household kitchens contain high amounts of carbohydrate components such as glucose, starch, and cellulose. Efficient utilization of these sugars is another opportunity to reduce ethanol costs. In this study, the effect of pretreatment methods (hot water, acid solutions, and a...
Assessment of PCB contamination, the potential for in situ microbial dechlorination and natural attenuation in an urban watershed at the East Coast of the United States
Kaya, Devrim; Sowers, Kevin R.; Demirtepe, Hale; Stiell, Brian; Baker, Joel E.; İmamoğlu, İpek; Kjellerup, Birthe (Elsevier BV, 2019-09-15)
Sediment contamination is a major environmental issue in many urban watersheds and coastal areas due to the potential toxic effects of contaminants on biota and human health. Characterizing and delineating areas of sediment contamination and toxicity are important goals of coastal resource management in terms of ecological and economical perspectives. Core and surficial sediment samples were collected from an industrialized urban watershed at the East Coast of the United Stated and analyzed to evaluate the ...
Managing aquatic ecosystems and water resources under multiple stress - An introduction to the MARS project
Hering, Daniel; Carvalho, Laurence; Argillier, Christine; Beklioğlu, Meryem; Borja, Angel; Cardoso, Ana Cristina; Duel, Harm; Ferreira, Teresa; Globevnik, Lidija; Hanganu, Jenica; Hellsten, Seppo; Jeppesen, Erik; Kodes, Vit; Solheim, Anne Lyche; Noges, Tiina; Ormerod, Steve; Panagopoulos, Yiannis; Schmutz, Stefan; Venohr, Markus; Birk, Sebastian (Elsevier BV, 2015-01-15)
Water resources globally are affected by a complex mixture of stressors resulting from a range of drivers, including urban and agricultural land use, hydropower generation and climate change. Understanding how stressors interfere and impact upon ecological status and ecosystem services is essential for developing effective River Basin Management Plans and shaping future environmental policy. This paper details the nature of these problems for Europe's water resources and the need to find solutions at a rang...
Two-phase anaerobic digestion of semi-solid organic wastes
Doğan, Eylem; Demirer, Göksel Niyazi; Department of Environmental Engineering (2008)
The objective of this study is to illustrate that phase separation improves the efficiency of an anaerobic system which digests semi-solid organic wastes. Organic fraction of municipal solid waste (OFMSW) was the semi-solid organic waste investigated. In the first part of the study, the optimum operational conditions for acidified reactor were determined by considering the volatile solid (VS) reductions and average acidification percentages at the end of two experimental sets conducted. Organic loading rate...
Citation Formats
G. N. Demirer and M. Othman, “Two-Phase Thermophilic Acidification and Mesophilic Methanogenesis Anaerobic Digestion of Waste-Activated Sludge,” ENVIRONMENTAL ENGINEERING SCIENCE, pp. 1291–1300, 2008, Accessed: 00, 2020. [Online]. Available: