Investigating the methane production efficiency of single- and two-phase anaerobic digestion and population dynamics of a second-phase anaerobic digestion

Download
2015
Koç, Engin
The aim of this thesis study was to investigate the methane production efficiency of single-phase and two-phase anaerobic digestion (AD) in batch reactors and anaerobic sequencing batch reactor (ASBR). It was also aimed to monitor the population dynamics and change in the quantity of aceticlastic methane-producers of the second-phase of a two-phase ASBR. Two sets of batch reactors were conducted, namely, Batch Reactor Set-1 and Batch Reactor Set-2. The aim of Batch Reactor Set-1 was to investigate the effect of initial substrate concentration to initial microorganism concentration ratio (S/X0) on methane yield. To this purpose, batch reactors were conducted at different initial S/X0 ratios of 0.5, 1, 2, 3 and 4 g sCOD/g VSS. Results revealed that the highest methane yield (267±5 mL CH4/g CODadded) and anaerobic treatability were observed at S/X0 ratio of 1 g COD/g VSS. The results also indicated the applicability of the anaerobic seed sludge and 1 g COD/g VSS as the optimum S/X0 ratio for the following experiments. Batch Reactor Set-2 was conducted to investigate and compare the methane production efficiency of a single-phase AD and the second phase of a two-phase AD system. To this purpose, sucrose and effluent of a dark fermentative sequencing batch reactor (DF-SBR) operated with sucrose (Tunçay, 2015) were used as substrates. The highest vi methane yield and content in biogas were observed as 344±20 mL CH4/g CODadded and 83%, respectively, in the second phase of the two-phase AD. Two-phase AD resulted in 39% increase in methane yield compared to its single-phase counterpart. ASBR study was conducted to investigate the effect of hydraulic retention time (HRT) and solid retention time (SRT) on methane production, and archaeal and bacterial population dynamics, the latter performed with denaturating gradient gel electrophoresis (DGGE). The change in the quantity of aceticlastic methane-producers, namely, Methanosaeta and Methanosarcina sp. with respect to the changing SRT and HRT conditions was also investigated with quantitative polymerase chain reaction (qPCR) analysis. Thus, an ASBR fed with the effluent of the DF-SBR was operated. Results showed that the highest average methane yield was achieved at 20 days of SRT and 6 days of HRT as 343±17 mL CH4/g CODadded. The highest average methane productivity was observed as 1794±279 mL CH4/L/day at SRT and HRT values of 10 and 0.7 days, respectively. Methanosaeta sp. was found to be the dominant specie among the archaeal group during all HRT and SRT combinations (10-20 days of SRT and 0.7 to 6 days of HRT). Although Methanosarcina species was not found in sequence analysis, qPCR results revealed the existence of Methanosarcina species through the whole operation period. Yet, Methanosaeta dominated the ASBR for all HRT and SRT combinations studied. Gradual decrease in HRT from 6 days to 0.7 days resulted in three fold decrease in Methanosaeta (9.5×1014 to 3.1×1014 gene copy/g VSS) and nearly five fold increase in Methanosarcina concentration (9.4×1012 to 5.1×1013 gene copy/g VSS) at 20 days of SRT. On the other hand, decrease in SRT from 20 days to 10 days did not lead any significant change in the concentration of Methanosaeta and Methanosarcina species in the ASBR.

Suggestions

Investigation of the use of aerobic granules for the treatment of sugar beet processing wastewater
KOCATURK, İREM; Bayramoğlu, Tuba Hande (2015-10-18)
The treatment of sugar beet processing wastewater in aerobic granular sequencing batch reactor (SBR) was examined in terms of chemical oxygen demand (COD) and nitrogen removal efficiency. The effect of sugar beet processing wastewater of high solid content, namely 2255 +/- 250mg/L total suspended solids (TSS), on granular sludge was also investigated. Aerobic granular SBR initially operated with the effluent of anaerobic digester treating sugar beet processing wastewater (Part I) achieved average removal ef...
Investigating the operational conditions for enhancement of dark fermentative hydrogen production in batch and sequencing batch reactors
Tunçay, Ekin Güneş; Bayramoğlu, Tuba Hande; Department of Environmental Engineering (2015)
The aim of this master thesis study was to investigate the dark fermentative hydrogen production in batch and sequencing batch reactors (SBRs), and to investigate operational conditions leading to its maximization. Batch reactor studies were conducted to determine the initial operational conditions for the subsequent SBR operation. Two batch reactor sets, conducted with either sucrose or molasses as substrate, were operated to investigate the effect of initial pH, chemical oxygen demand (COD) and volatile s...
Understanding carbon metabolism in hydrogen production by PNS bacteria
Doğan, Ezgi Melis; Koku, Harun; Department of Chemical Engineering (2016)
In biological hydrogen production systems using purple non-sulfur bacteria (PNS bacteria), a thorough understanding of the metabolism of these microorganisms plays a vital role in assessing and improving efficiency and productivity. This metabolism is very complex, and the result of the interplay of several systems and components such as the photosystems, carbon flow and enzymatic reactions. Mathematical models are sought to represent the complex metabolism of these bacteria, which in turn can be used to in...
Investigating the effects of operational parameters on photofermentation in batch and semi-batch reactors and the applications of photofermentation in multi-stage energy systems
Akman, Melih Can; Bayramoğlu, Tuba Hande; Gündüz, Ufuk; Department of Environmental Engineering (2018)
The aim of this thesis study was to investigate the effects of operational parameters on photofermentation in batch and semi-batch reactors, and the application of photofermentation in multi-stage energy systems. Firstly, three operational conditions of the substrate concentration, Volatile Suspended Solids (VSS) concentration and the light intensity leading to the maximization of hydrogen production in a single stage were optimized. The highest hydrogen production rate (HPR) of 1.04 mmol H2/L.h was achieve...
EFFECT OF PRETREATMENTS ON THE SEMICONTINUOUS ANAEROBIC-DIGESTION OF SUNFLOWER HEADS
POLAT, H; Selçuk, Nevin; SOYUPAK, S (1992-10-01)
The effects of hydraulic retention time and alkali treatment on methane production rate from the semicontinuous anaerobic digestion of 2 % sunflower-head/water mixtures were investigated. The experiments were carried out in laboratory-scale fermenters, fed with 1 liter of untreated, 2 g NaOH/100 g total solids (TS), and 5 g NaOH/100 g TS alkali-treated sunflower-head/water mixtures, respectively, and maintained at 55-degrees-C Digestion experiments were performed for hydraulic retention times of 8, 10, and ...
Citation Formats
E. Koç, “Investigating the methane production efficiency of single- and two-phase anaerobic digestion and population dynamics of a second-phase anaerobic digestion,” M.S. - Master of Science, Middle East Technical University, 2015.