Temperature-phased Anaerobic Digestion Research Articles

Effect of organic loading on the microbiota in a temperature-phased anaerobic digestion (TPAD) system co-digesting dairy manure and waste whey.

Temperature-phased anaerobic digestion (TPAD) has gained increasing attention because it provides the flexibility to operate digesters under conditions that enhance overall digester performance. However, research on impact of organic overloading rate (OLR) to microbiota of TPAD systems was limited. In this study, we investigated the composition and successions of the microbiota in both the thermophilic and the mesophilic digesters of a laboratory-scale TPAD system co-digesting dairy manure and waste whey before and during organic overloading. The thermophilic and the mesophilic digesters were operated at 50 and 35 °C, respectively, with a hydraulic retention time (HRT) of 10 days for each digester. High OLR (dairy manure with 5 % total solid and waste whey of ≥60.4 g chemical oxygen demand (COD)/l/day) resulted in decrease in pH and in biogas production and accumulation of volatile fatty acids (VFAs) in the thermophilic digester, while the mesophilic digester remained unchanged except a transient increase in biogas production. Both denaturant gradient gel electrophoresis (DGGE) and Illumina sequencing of 16S ribosomal RNA (rRNA) gene amplicons showed dramatic change in microbiota composition and profound successions of both bacterial and methanogenic communities. During the overloading, Thermotogae was replaced by Proteobacteria, while Methanobrevibacter and archaeon classified as WCHD3-02 grew in predominance at the expense of Methanoculleus in the thermophilic digester, whereas Methanosarcina dominated the methanogenic community, while Methanobacterium and Methanobrevibacter became less predominant in the mesophilic digester. Canonical correspondence analysis (CCA) revealed that digester temperature and pH were the most influential environmental factors that explained much of the variations of the microbiota in this TPAD system when it was overloaded.

Upgrading of anaerobic digestion of waste activated sludge by temperature-phased process with recycle

Thermophilic (55 °C)-mesophilic(35 °C) and hyper-thermophilic(70 °C)-mesophilic TPAD-R (temperature-phased anaerobic digestion with recycle) were conducted to compare and evaluate the operation performance to treat WAS (waste activated sludge) with the MD (conventional mesophilic anaerobic digestion). TPAD-R was based on the TPAD (temperature-phased anaerobic digestion), and introduced a recycle system from the end mesophilic stage to the front stage. Thermophilic-mesophilic TPAD-R produced more biogas 0.99 L/g VS (volatile solids) reduced/d than MD 0.83 L/g VS reduced/d. In thermophilic-mesophilic TPAD-R 35.7% and 18.7% of WAS was converted to methane in the thermophilic stage and in the mesophilic stage, respectively, according to a COD balance. Solids reduction was improved to a similar extent in thermophilic-mesophilic TPAD-R and hyper-thermophilic-mesophilic TPAD-R, which was 10% higher than that in MD (approximately 40% of VS reduction). Hydrolysis, acidogenesis and methanogenesis analysis indicated that thermophilic and hyper-thermophilic stage accelerated the hydrolysis rate of TPAD-R, 0.053 gCOD/gVS/d and 0.040 gCOD/gVS/d, respectively, compared to about 0.025 gCOD/gVS/d in MD. In addition, thermophilic-mesophilic TPAD-R achieved more surplus energy than hyper-thermophilic-mesophilic TPAD-R and MD.

Temperature-phased anaerobic digestion of Industrial Organic Fraction of Municipal Solid Waste: A batch study

Anaerobic digestion of the Organic Fraction of Municipal Solid Wastes from non-selective collection systems is widely implemented at industrial scale. Classically, single-temperature anaerobic digestion systems (mesophilic or thermophilic) have been used although some limitations were found in the processes performance. However, the specific advantages of the two processes could be exploited by using a temperature-phased anaerobic digestion (TPAD). Thus, in this paper, the application of a TPAD process without microbiological separation (thermophilic 55°C–mesophilic 35°C) to the biomethanation of OFMSW has been studied.The TPAD assays were carried out in batch reactors. The processing times for the thermophilic (55°C) stage have been located in the range from 12 to 3days. After the first stage, the waste treatment was continued in a second mesophilic reactor (35°C) until completing the degradation process.The higher values for the organic matter removal (VS removal 82–85%) and the maximum specific growth rates of microorganisms (0.31–0.43days-1), were obtained for thermophilic phase operation at 5 and 4days, respectively. Lower operation times, namely 3-days, for thermophilic first-phase are viable and the methane productivity obtained was comparable with respect to that obtained in the above mentioned conditions (0.6L/gVSremoved). However, in this conditions, a decrease in the maximum specific growth rate of microorganisms (0.26days−1), a lower SV removal (75%), and a higher final amount of non-biodegradable substrate (1231mg/L) were obtained, working at 3days, despite of using higher operational times (29days). According to these results, it can be concluded than the optimum time for the thermophilic first-phase in TPAD would be between 5-days and 4-days.

Improved Biosolids Stabilization Utilizing Temperature Phased Anaerobic Digestion

Improved Biosolids Stabilization Utilizing Temperature Phased Anaerobic Digestion

Upgrading of anaerobic digestion of waste activated sludge by a hyper-thermophilic–mesophilic temperature-phased process with a recycle system

A hyper-thermophilic–mesophilic temperature-phased anaerobic digestion with a recycle system effectively upgraded the mesophilic digestion of waste activated sludge.

High pressure homogenization and temperature phased anaerobic digestion for enhanced biogas conversion from municipal waste sludge

High pressure homogenization and temperature phased anaerobic digestion for enhanced biogas conversion from municipal waste sludge

Upgrading the temperature-phased anaerobic digestion of waste activated sludge by ultrasonic pretreatment

Abstract Biochemical methane potential assays were performed to assess the influence of ultrasonic pretreatment on the temperature-phased anaerobic digestion (TPAD) of waste-activated sludge (WAS). Ultrasound (specific energy = 3380 kJ kg−1 TS) was applied to the WAS before the thermophilic stage or to the effluent after the thermophilic stage. In addition, a control system without pretreatment was also carried out. No significant differences were found in the overall performance of the TPAD process, but different behaviours were observed between the thermophilic and mesophilic stages. Total methane production was enhanced by more than 50% and the volatile solid removal increased by 13% in comparison to the TPAD control process. Finally, a previously defined kinetic model was applied successfully to the experimental data and showed an excellent fit.

Microbial diversity in innovative mesophilic/thermophilic temperature-phased anaerobic digestion of sludge.

Anaerobic digestion (AD) is one of the few sustainable technologies that both produce energy and treat waste streams. Driven by a complex and diverse community of microbes, AD may be affected by different factors, many of which also influence the composition and activity of the microbial community. In this study, the biodiversity of microbial populations in innovative mesophilic/thermophilic temperature-phased AD of sludge was evaluated by means of fluorescence in situ hybridization (FISH). The increase of digestion temperature drastically affected the microbial composition and selected specialized biomass. Hydrogenotrophic Methanobacteriales and the protein fermentative bacterium Coprothermobacter spp. were identified in the thermophilic anaerobic biomass. Shannon-Weaver diversity (H') and evenness (E) indices were calculated using FISH data. Species richness was lower under thermophilic conditions compared with the values estimated in mesophilic samples, and it was flanked by similar trend of the evenness indicating that thermophilic communities may be therefore more susceptible to sudden changes and less prompt to adapting to operative variations.

Fate of organic matter during moderate heat treatment of sludge: kinetics of biopolymer and hydrolytic activity release and impact on sludge reduction by anaerobic digestion

Temperature-phased anaerobic digestion with a 50-70 °C pre-treatment is widely proposed for sludge. Here, such a sludge pre-treatment (65 °C) was studied against the physical, enzymatic and biodegradation processes. The soluble and particulate fractions were analysed in terms of biochemical composition and hydrolytic enzymatic activities. Two kinetics of organic matter solubilisation were observed: a rapid transfer of the weak-linked biopolymers to the water phase, including sugars, proteins or humic acid-like substances, to the water phase, followed by a slow and long-term solubilisation of proteins and humic acid-like substances. In addition, during the heat treatment a significant pool of thermostable hydrolytic enzymes including proteases, lipases and glucosidases remains active. Consequently, a global impact on organic matter was the transfer of the biodegradable chemical oxygen demand (COD) from the particulate to the soluble fraction as evaluated by the biological methane potential test. However, the total biodegradable COD content of the treated sludge remained constant. The heat process improves the bio-accessibility of the biodegradable molecules but doesn't increase the inherent sludge biodegradability, suggesting that the chemistry of the refractory proteins and humic acids seems to be the real limit to sludge digestion.

Drivers of microbial community composition in mesophilic and thermophilic temperature-phased anaerobic digestion pre-treatment reactors

Temperature-phased anaerobic digestion (TPAD) is an emerging technology that facilitates improved performance and pathogen destruction in anaerobic sewage sludge digestion by optimising conditions for 1) hydrolytic and acidogenic organisms in a first-stage/pre-treatment reactor and then 2) methogenic populations in a second stage reactor. Pre-treatment reactors are typically operated at 55–65 °C and as such select for thermophilic bacterial communities. However, details of key microbial populations in hydrolytic communities and links to functionality are very limited. In this study, experimental thermophilic pre-treatment (TP) and control mesophilic pre-treatment (MP) reactors were operated as first-stages of TPAD systems treating activated sludge for 340 days. The TP system was operated sequentially at 50, 60 and 65 °C, while the MP rector was held at 35 °C for the entire period. The composition of microbial communities associated with the MP and TP pre-treatment reactors was characterised weekly using terminal-restriction fragment length polymorphism (T-RFLP) supported by clone library sequencing of 16S rRNA gene amplicons. The outcomes of this approach were confirmed using 454 pyrosequencing of gene amplicons and fluorescence in-situ hybridisation (FISH). TP associated bacterial communities were dominated by populations affiliated to the Firmicutes, Thermotogae, Proteobacteria and Chloroflexi. In particular there was a progression from Thermotogae to Lutispora and Coprothermobacter and diversity decreased as temperature and hydrolysis performance increased. While change in the composition of TP associated bacterial communities was attributable to temperature, that of MP associated bacterial communities was related to the composition of the incoming feed. This study determined processes driving the dynamics of key microbial populations that are correlated with an enhanced hydrolytic functionality of the TPAD system.

Occurrence and reactivation of viable but non-culturable E. coli in sewage sludge after mesophilic and thermophilic anaerobic digestion

The occurrence and reactivation of viable but non-culturable (VBNC) Escherichia coli after different anaerobic digestions and the subsequent dewatering and storage were evaluated and compared. Culturable E. coli in digested sludge increased by two to four orders of magnitudes immediately after dewatering. However, counts of both the total and viable E. coli indicated that the increase of E. coli was attributed to its reactivation from the VBNC state to the culturable state. The VBNC pathogen incidences of thermophilic digestion were two to three orders of magnitude higher than those of mesophilic digestion. Accordingly, culturable E. coli in thermophilic, digested sludge after storage were one order of magnitude higher than mesophilic digestion. Anaerobic digestion thus mainly alters the culturable state of pathogens rather than killing them; therefore the biological safety of digested sludge, especially temperature-phased anaerobic digestion, should be carefully assessed.

Evaluation of system performances and microbial communities of two temperature-phased anaerobic digestion systems treating dairy manure

Two temperature-phased anaerobic digestion (TPAD) systems, with the thermophilic digesters acidified by acidogenesis products (AT-TPAD) or operated at neutral pH and balanced hydrolysis/acidogenesis and methanogenesis (NT-TPAD), were evaluated to treat high-strength dairy cattle manure. Despite similar methane productions (about 0.22 L/g VS fed), the NT-TPAD system removed significantly more VS (36%) than the AT-TPAD system (31%) and needed no pH adjustments. The thermophilic digester of the NT-TPAD system dominated the system performance and performed significantly better than that of the AT-TPAD system. The opposite held true for the mesophilic digesters. Differences of the thermophilic digesters between two TPAD systems affected the microbial communities of both local and downstream digesters. Each digester harbored distinctive microbial populations, some of which were significantly correlated with system performance. Methanosarcina was the most important methanogenic genus in both TPAD systems, while Methanosaeta only in the NT-TPAD system. Their populations were inversely related to VFA concentrations.

Evaluation of system performance and microbial communities of a temperature-phased anaerobic digestion system treating dairy manure: Thermophilic digester operated at acidic pH

A temperature-phased anaerobic digestion system with the thermophilic digester acidified by acidogenesis products (referred to as AT-TPAD) was evaluated to treat high-strength dairy cattle manure at a 15-day retention time. Three temperatures (50, 55, and 60°C) were tested on the thermophilic digester, and 50°C was found to be the optimal temperature for overall performance of the AT-TPAD system, achieving 31% VS removal and 0.22 L methane/g VS fed. The mesophilic digester contributed significantly more to the overall system performance than the thermophilic digester. The thermophilic and the mesophilic digesters had different microbial communities under all conditions, and both microbial communities exhibited dynamic changes in response to different conditions. Certain microbial groups were found significantly correlated with the system performance. Methanosarcina was the most important methanogen genus of the AT-TPAD system and its population abundance was inversely correlated with high concentrations of volatile fatty acids (VFA).

Feedstocks Affect the Diversity and Distribution of Propionate CoA-Transferase Genes (pct) in Anaerobic Digesters

Anaerobic digestion (AD) is an attractive microbiological technology for both waste treatment and energy production. Syntrophic acetogenic bacteria are an important guild because they are essential for maintaining efficient and stable AD operation. However, this guild is poorly understood due to difficulties to culture them. In this study, we developed specific PCR assays targeting the propionate-CoA transferase genes (pct) to investigate their diversity and distribution in several mesophilic anaerobic digesters and a bench-scale temperature-phased AD (TPAD) system. Phylogenetic analysis of sequenced pct amplicons revealed the occurrence of Syntrophobacter fumaroxidans and six other clusters of putative pct genes. Principal coordinate analysis (PCoA) showed that pct diversity and abundance were largely correlated to the feedstocks of the digesters, while little difference was seen between the granular and the liquid fractions of each digester or between the two digesters of the TPAD system. Cluster-specific qPCR analysis revealed major impact of feedstocks and fractions on the abundance of pct genes. Readily fermentable substrates such as sugar- or starch-rich feedstocks selected for pct genes (Cluster I) related to Syntrophobacter, while manure feedstock selected for pct clusters related to pct of Clostridium spp. These results suggest that propionate metabolism can be affected by feedstocks and partition differently between solid and liquid phases in digesters. The PCR assays developed in this study may serve as a tool to investigate propionate-oxidizing bacteria in anaerobic digesters and other anaerobic environments.

San Francisco Sequencing Batch Reactor Temperature Phased Anaerobic Digestion: Efficient Adaptation to Class A Biosolids

San Francisco Sequencing Batch Reactor Temperature Phased Anaerobic Digestion: Efficient Adaptation to Class A BiosolidsSan Francisco Public Utilities Commission (SFPUC), in collaboration with CH2M HILL, evaluated and designed the conversion of its existing high-rate mesophilic anaerobic digestion process at OSP to a SBR TPAD process in order to produce Class A biosolids, per USEPA Title 40 Code of Federal Regulations Part 503 (40 CFR 503) Alternative 1 - Time and Temperature. Approximately 30 percent of San...Author(s)Drury D. WhitlockDavid W. GreenBonnie M. JonesAlexandre MiotTim L. BauerDouglas BarberSourceProceedings of the Water Environment FederationDocument typeConference PaperPublisherWater Environment FederationPrint publication date May, 2013ISSN1938-6478DOI10.2175/193864713813536714Volume / Issue2013 / 5Content sourceResiduals and Biosolids ConferenceCopyright2013Word count296

Anaerobic digestion technology in livestock manure treatment for biogas production: A review

This article reviews the potential of anaerobic digestion (AD) for biogas production from livestock manure wastes and compares the operating and performance data for various anaerobic process configurations. It examines different kinds of manure waste treatment techniques and the influence of several parameters on biogas and methane yield. The comparison indicates that a variety of different operational conditions, various reactor configurations such as batch reactors, continuously stirred tank reactor (CSTR), plug flow reactor (PFR), up‐flow anaerobic sludge blanket (UASB), anaerobic sequencing batch reactor (ASBR), temperature phased anaerobic digestion (TPAD), and continuous one‐ and two‐stage systems, present a suitable technology for the AD of livestock manure waste. Main performance indicators are biogas and methane yield, degradation of volatile solids (VS), higher loading, and process stability with a short retention time.

High rate mesophilic, thermophilic, and temperature phased anaerobic digestion of waste activated sludge: A pilot scale study

The paper reports the findings of a two-year pilot scale experimental trial for the mesophilic (35°C), thermophilic (55°C) and temperature phased (65+55°C) anaerobic digestion of waste activated sludge. During the mesophilic and thermophilic runs, the reactor operated at an organic loading rate of 2.2kgVS/m3d and a hydraulic retention time of 20days. In the temperature phased run, the first reactor operated at an organic loading rate of 15kgVS/m3d and a hydraulic retention time of 2days while the second reactor operated at an organic loading rate of 2.2kgVS/m3d and a hydraulic retention time of 18days (20days for the whole temperature phased system).The performance of the reactor improved with increases in temperature. The COD removal increased from 35% in mesophilic conditions, to 45% in thermophilic conditions, and 55% in the two stage temperature phased system. As a consequence, the specific biogas production increased from 0.33 to 0.45 and to 0.49m3/kgVSfed at 35, 55, and 65+55°C, respectively. The extreme thermophilic reactor working at 65°C showed a high hydrolytic capability and a specific yield of 0.33gCOD (soluble) per gVSfed. The effluent of the extreme thermophilic reactor showed an average concentration of soluble COD and volatile fatty acids of 20 and 9g/l, respectively. Acetic and propionic acids were the main compounds found in the acids mixture. Because of the improved digestion efficiency, organic nitrogen and phosphorus were solubilised in the bulk. Their concentration, however, did not increase as expected because of the formation of salts of hydroxyapatite and struvite inside the reactor.

Modelling of the temperature-phased batch anaerobic digestion of raw sludge from an urban wastewater treatment plant

The disposal of excess sludge from wastewater treatment plants is a serious problem that needs to be addressed. Temperature-phased anaerobic digestion (TPAD) which combines thermophilic and mesophilic processes in one, brings together the advantages of both systems. The aim of the present work was to develop a simple kinetic model to describe the TPAD of sewage sludge in batch completely stirred tank reactors (CSTRs) and to determine the kinetic parameters of both thermophilic and mesophilic stages. A zero-order kinetic equation described the thermophilic step after 2, 4 and 6 days of digestion time (experiment 1, 2 and 3, respectively), yet a first-order equation was found to be adequate to correlate the methane gas accumulated with time in the mesophilic step, the kinetic constant being 0.21 days−1. The methane yield coefficient obtained was found to be almost proportional to the digestion time used in the thermophilic step with values of 0.067, 0.132 and 0.193 L CH4 STP/g VSadded for experiments 1, 2 and 3, respectively. By contrast, the kinetic constant of the mesophilic stage was not influenced by the digestion time used in the thermophilic phase.

Assessment of solid retention time of a temperature phased anaerobic digestion system on performance and final sludge characteristics

AbstractBACKGROUND: This paper describes the results obtained during the thermophilic/mesophilic temperature phased anaerobic digestion (TPAD) of sewage sludge on a pilot scale. The aim of this research study was not only to optimize the anaerobic digestion process, but also to obtain a digested sludge suitable for agricultural applications according to the legal requirements.RESULTS: Four TPAD assays were carried out: 5/15, 3/15, 3/12 and 3/9 (days/days of solid retention time) with a specific methane production (expressed as LCH4 g−1 VSdestroyed) of 0.77, 0.83, 0.66 and 0.20, respectively. TPAD 3/15 and 3/12 reached pathogen concentrations of less than 1000 MPN g−1 TS (faecal colifoms) and 3 MPN per 4 g TS (Salmonella spp.); therefore, these digested sludges can be considered Class A biosolids, according to the US Environmental Protection Agency. Concentrations of heavy metals rose after the anaerobic digestion of mixed sludge, but the final values were always below the limits required by legal regulations.CONCLUSION: TPAD 3/15 is the best option in terms of organic matter removal, CH4 generation, and process stability. TPAD 3/12 obtained the best final dewaterability and pathogen reduction and in general, showed much better results than those obtained by anaerobic mesophilic control (15 days of SRT). Copyright © 2012 Society of Chemical Industry

Drivers and Solutions to Develop a Low-Cost Class A Solution: San Francisco Sequencing Batch Reactor Temperature Phased Anaerobic Digestion

Drivers and Solutions to Develop a Low-Cost Class A Solution: San Francisco Sequencing Batch Reactor Temperature Phased Anaerobic DigestionSan Francisco Public Utilities Commission (SFPUC), in collaboration with CH2M HILL, evaluated and designed the conversion of its existing high-rate mesophilic anaerobic digestion process at OSP to a SBR TPAD process in order to produce Class A biosolids, per USEPA Title 40 Code of Federal Regulations Part 503 (40 CFR 503) Alternative 1 - Time and Temperature. Approximately 30 percent of San...Author(s)Drury D. WhitlockDavid W. GreenBonnie M. JonesAlexandre MiotTim L. BauerDouglas BarberSourceProceedings of the Water Environment FederationDocument typeConference PaperPublisherWater Environment FederationPrint publication date Sep, 2012ISSN1938-6478DOI10.2175/193864712811726419Volume / Issue2012 / 14Content sourceWEFTECCopyright2012Word count300