Effects of solids retention time on methanogenesis in anaerobic digestion of thickened mixed sludge

Lee, Il-Su; Parameswaran, Prathap; Rittmann, Bruce E.

doi:10.1016/j.biortech.2011.08.079

Cited by 105 publications

(38 citation statements)

References 32 publications

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“…The bacterial and archaeal community structures are highly diverse and affected by substrate composition (6,(12)(13)(14), HRT (12), and operating temperature (6, 15). Two methanogenic pathways from acetate have been reported, including (i) direct acetate cleavage in acetoclastic methanogenic archaea, such as Methanosarcina and Methanosaeta, and (ii) nonacetoclastic oxidation, i.e., the syntrophic association of acetateoxidizing organisms and hydrogenotrophic methanogens, including Methanobacteriales (5, 16).…”

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confidence: 99%

“…The main risk with a short HRT is washout of methanogens as well as other functional groups, causing a build-up of organic acids and a decreased pH (12). A key concern regarding elevated temperatures is the decrease in pK a of the ammonium/ammonia (NH 4 ϩ /NH 3 ) acid-base pair, which means that the NH 3 concentration will be 2 to 3 times higher for a given pH, potentially causing ammonia inhibition (1 to 2 mM) (2).…”

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Methanosarcinaceae and Acetate-Oxidizing Pathways Dominate in High-Rate Thermophilic Anaerobic Digestion of Waste-Activated Sludge

Jensen

Batstone

2013

Appl Environ Microbiol

132

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This study investigated the process of high-rate, high-temperature methanogenesis to enable very-high-volume loading during anaerobic digestion of waste-activated sludge. Reducing the hydraulic retention time (HRT) from 15 to 20 days in mesophilic digestion down to 3 days was achievable at a thermophilic temperature (55°C) with stable digester performance and methanogenic activity. A volatile solids (VS) destruction efficiency of 33 to 35% was achieved on waste-activated sludge, comparable to that obtained via mesophilic processes with low organic acid levels (<200 mg/liter chemical oxygen demand [COD]). Methane yield (VS basis) was 150 to 180 liters of CH 4 /kg of VS added . According to 16S rRNA pyrotag sequencing and fluorescence in situ hybridization (FISH), the methanogenic community was dominated by members of the Methanosarcinaceae, which have a high level of metabolic capability, including acetoclastic and hydrogenotrophic methanogenesis. Loss of function at an HRT of 2 days was accompanied by a loss of the methanogens, according to pyrotag sequencing. The two acetate conversion pathways, namely, acetoclastic methanogenesis and syntrophic acetate oxidation, were quantified by stable carbon isotope ratio mass spectrometry. The results showed that the majority of methane was generated by nonacetoclastic pathways, both in the reactors and in off-line batch tests, confirming that syntrophic acetate oxidation is a key pathway at elevated temperatures. The proportion of methane due to acetate cleavage increased later in the batch, and it is likely that stable oxidation in the continuous reactor was maintained by application of the consistently low retention time.A naerobic digestion (AD) is a biological process which has been widely used for waste-activated sludge and primary sludge stabilization. It offers substantial advantages over alternative stabilization techniques, including low energy requirements, good-quality biosolids product, energy recovery in the form of methane (CH 4 ) gas, and the possibility of nutrient recovery (1, 2). Conventional anaerobic digesters are operated at a mesophilic temperature (35°C) with long hydraulic retention times (HRTs) of 15 to 20 days on waste-activated sludge (WAS), which is excess bacterial material and residual organics from combined aerobic treatment of wastewater, and more than 20 days on primary sludge (PS), which is the settled fraction from raw wastewater (1, 3, 4). Long treatment times are a key disadvantage of anaerobic digestion, requiring large tank volumes and, consequently, high capital cost, as well as increased mixing and maintenance costs. Therefore, reducing digester volume would strongly enhance the competitiveness of anaerobic technologies.Thermophilic anaerobic digestion (55°C to 70°C) is an alternative to conventional mesophilic anaerobic digestion (35°C). The majority of systems are operated at 55°C (5, 6), as higher temperatures can result in instability due to ammonia inhibition and reduced operability (2). Thermophilic anaerobic digestion offer...

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confidence: 99%

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confidence: 99%

Methanosarcinaceae and Acetate-Oxidizing Pathways Dominate in High-Rate Thermophilic Anaerobic Digestion of Waste-Activated Sludge

Jensen

Batstone

2013

Appl Environ Microbiol

132

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“…Lee et al, 2011;Chen et al, 2012). However limited knowledge exists pertaining to the performance of semi-continuous and/or unmixed systems.…”

Section: Introductionmentioning

confidence: 99%

“…However limited knowledge exists pertaining to the performance of semi-continuous and/or unmixed systems. Lee et al (2011) showed that removal efficiencies for chemical oxygen demand (COD) and VS in bench-scale CMFR mesophilic anaerobic digesters decreased with a reduction in solids retention time (SRT) from 20 to 4 days. That study also reported that a reduction in SRT caused significant shifts in the microbial population as bacteria and archaea present became less diverse.…”

Section: Introductionmentioning

confidence: 99%

“…Further investigation is needed to find operational strategies for household scale anaerobic systems that enhance pathogen removal because the biosolids are typically promoted for immediate land application. Recalling that changes to the SRT of continuous anaerobic systems may cause shifts in the microbial populations (Lee et al, 2011) through different methane production values, it is important to investigate if this finding holds true for other microorganisms, such as Escherichia coli or Salmonella, in semi-continuous systems because of the threat to public health that mesophilic sludge can present. Furthermore, the yet undefined influence of varying feeding frequencies on the semi-continuous system could be used to enhance pathogen removal and warrants investigation.…”

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confidence: 99%

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Semi-continuous mesophilic anaerobic digester performance under variations in solids retention time and feeding frequency

Manser

Mihelcic

Ergas

2015

Bioresource Technology

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The goal of this research was to understand the effect of solids retention time (SRT) and feeding frequency on the performance of anaerobic digesters used to recover bioenergy from swine waste. Semi-continuous mesophilic anaerobic digesters were operated at varying SRTs and feeding frequencies. Performance metrics included biogas and methane production rates, biomass robustness and functionality and removals of volatile solids, soluble chemical oxygen demand, the fecal-indicator bacteria Escherichia coli, and the human pathogen Salmonella. Biochemical methane formation potential and specific methanogenic activity assays were used to demonstrate biomass robustness and functionality. Results indicated that anaerobic digesters fed weekly had higher average methane yields (0.20 vs. 0.18m(3)CH4/kg-VSadded), specific methanogenic activities (40 vs. 35ml/day), and fecal indicator bacteria destruction (99.9% vs. 99.4%) than those fed every-other day. Salmonella, soluble COD, and VS destruction did not change with varied feeding frequency; however, higher removals were observed with longer SRT.

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Bacterial community analysis in upflow multilayer anaerobic reactor treating high‐solids organic wastes

Cho

Jung

Kim

et al. 2017

Biotechnology Progress

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A novel anaerobic digestion configuration, the upflow multi-layer anaerobic reactor (UMAR), was developed to treat high-solids organic wastes. The UMAR was hypothesized to form multi-layer along depth due to the upflow plug flow; use of a recirculation system and a rotating distributor and baffles aimed to assist treating high-solids influent. The chemical oxygen demand (COD) removal efficiency and methane (CH 4 ) production rate were 89% and 2.10 L CH 4 /L/d, respectively, at the peak influent COD concentration (110.4 g/L) and organic loading rate (7.5 g COD/L/d). The 454 pyrosequencing results clearly indicated heterogeneous distribution of bacterial communities at different vertical locations (upper, middle, and bottom) of the UMAR. Firmicutes was the dominant (>70%) phylum at the middle and bottom parts, while Deltaproteobacteria and Chloroflexi were only found in the upper part. Potential functions of the bacteria were discussed to speculate on their roles in the anaerobic performance of the UMAR system.

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Effects of solids retention time on methanogenesis in anaerobic digestion of thickened mixed sludge

Cited by 105 publications

References 32 publications

Methanosarcinaceae and Acetate-Oxidizing Pathways Dominate in High-Rate Thermophilic Anaerobic Digestion of Waste-Activated Sludge

Methanosarcinaceae and Acetate-Oxidizing Pathways Dominate in High-Rate Thermophilic Anaerobic Digestion of Waste-Activated Sludge

Semi-continuous mesophilic anaerobic digester performance under variations in solids retention time and feeding frequency

Bacterial community analysis in upflow multilayer anaerobic reactor treating high‐solids organic wastes

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