Improving Anaerobic Digester Performance: Lessons Learnt from Digester Clean-out Operations

2010 ◽  
Vol 5 (2) ◽  
Author(s):  
D.-G. Ohandja ◽  
L. Gove ◽  
M. Edwards ◽  
J. Callan ◽  
N. Voulvoulis
Keyword(s):  
Anaerobic Digestion ◽  
Solid Material ◽  
Anaerobic Digester ◽  
Effective Capacity ◽  
Anaerobic Digesters ◽  
Incomplete Mixing ◽  
Large Size ◽  
Iron Salts ◽  
Water Companies ◽  
Alternative Sources

The increasingly higher costs of fossil fuel are pushing water companies to seek alternative sources of energy such as methane from anaerobic digestion of sludges. Anaerobic digestion can be hindered by several factors including accumulation of grit and rag inside the digester. Periodical clean-out of anaerobic digesters is a common practice in the Water Industry, but very little is known on the nature of the solid material in digester contents. This paper presents the composition of grit removed from a mesophilic anaerobic digester during clean-out operations. Grit and rag accounted for 40% of digester effective capacity but it was impossible to determine the nature of the constituents in the rag due to the large size of debris. However, grit analysis showed that 64% was of inorganic nature while 36 % was organic. It was found that fine grit particles (size between 425 and 1180 μm) represented the largest proportion, accounting for 67% of the total weight of grit. Accumulation of fine grit material could be attributed to inefficient degritting of digester feed, incomplete mixing of the digester content, as well as precipitation of heavy metals inside the digester. Fe3O4 was the main inorganic compound in the grit accounting for 66% of the inorganic fraction of the grit, unsurprisingly as this site uses iron salts for phosphorus removal. These results suggest that optimistaion of chemical dosage in secondary treatment and adequate screening of the digester feed could substantially improve the performance of mesophilic anaerobic digesters.

scholarly journals Anaerobic Digestion of Slaughterhouse Wastewater: CO2 Capture of Biogas Using Chlorella vulgaris

2019 ◽  
Vol 19 (1) ◽  
pp. 1 ◽  
Author(s):  
Nur Indradewi Oktavitri ◽  
Wahyu Budi Pratiwi ◽  
Indah Purnamasari ◽  
Mufrihatul Hayati ◽  
Mega Rosita Fitrianingtyas ◽  
...  
Keyword(s):  
Anaerobic Digestion ◽  
Chlorella Vulgaris ◽  
Observation Time ◽  
Anaerobic Digester ◽  
Co2 Removal ◽  
Anaerobic Digesters ◽  
Slaughterhouse Wastewater

Biogas quality from anaerobic digester influenced the combustion of biogas. A high percentage of CO2 in biogas indicates the low quality of biogas. Abatement of CO2 using microalgae, such as Chlorella vulgaris could enhance the quality of biogas. The aim of this research was to observe the ability of C. vulgaris on CO2 removal from slaughterhouse wastewater biogas. In this research, two anaerobic digesters were provided with the different condition of biogas collector bag. The first digester was combined with only biogas collector bag, while another digester was combined with C. Vulgaris. Slaughterhouse wastewater volume in each digester was 3.5 L. Observation time was 15 days and the samples were collected for every 5 days. The result showed that anaerobic digester was able to remove 63% of COD. Biogas composition of slaughterhouse wastewater after incubation for 15 days was 52.70% of air, 46.85% of CH4and 0.45% of CO2. C. Vulgaris enhanced CO2 removal from biogas up to 7%. The density of C. vulgaris decreased to 51 cell/mL. The biogas composition was probably influenced by the density of C. vulgaris.

Influence of the digested cod concentration on the alkalinity requirement in anaerobic digesters

1994 ◽  
Vol 30 (8) ◽  
pp. 23-34 ◽  
Author(s):  
Adrianus C. van Haandel
Keyword(s):  
Waste Water ◽  
Experimental Data ◽  
Anaerobic Digestion ◽  
Organic Nitrogen ◽  
Ph Value ◽  
Nitrogen Concentration ◽  
Anaerobic Digester ◽  
Anaerobic Digesters ◽  
Operational Conditions

pH value and stability in anaerobic digesters are governed by the carbonic system. An expression is derived to determine the alkalinity requirement for maintaining a desired pH value in an anaerobic digester. The requirement is calculated from stoichiometric relationships and depends on measurable parameters of the influent (notably concentration of digestible material, influent VFA, alkalinity, acidity and organic nitrogen concentration) and operational conditions (temperature, recycle of effluent and/or biogas). The derived expression is applied to three cases of anaerobic digestion: dilute waste water (sewage), concentrated waste water (vinasse) and sludge. In each case it was calculated if the influent alkalinity was sufficient to maintain an adequate pH for digestion and when it was not, what was the alkalinity requirement to maintain the desired pH value. The calculated values of pH and alkalinity demand compared well with experimental data.

Effect of autothermal treatment on anaerobic digestion in the dual digestion process

1998 ◽  
Vol 38 (8-9) ◽  
pp. 435-442 ◽  
Author(s):  
Amanda Ward ◽  
H. David Stensel ◽  
John F. Ferguson ◽  
Gregory Ma ◽  
Stan Hummel
Keyword(s):  
Anaerobic Digestion ◽  
Fecal Coliform ◽  
Detection Limits ◽  
Anaerobic Digester ◽  
Treatment Unit ◽  
Anaerobic Digesters ◽  
Digestion Process ◽  
Volatile Solids ◽  
Destruction Kinetics ◽  
Pre Treatment

The performance of two laboratory mesophilic anaerobic digesters was studied to determine if the claims for improved mesophilic anaerobic digestion following autothermal pre-treatment are valid and if the benefits claimed are affected by the mesophilic digester SRT. One digester was fed sludge taken after a full-scale autothermal reactor and the other was fed sludge from the same plant just before the autothermal treatment unit. Autothermal treatment did not significantly increase volatile solids destruction kinetics during subsequent anaerobic digestion. The VS destruction rate was 2.7 to 2.8% per day with or without autothermal treatment. Autothermal pre-treatment did not affect methane production per unit VS destroyed at anaerobic digester SRTs ranging from 6 to 12 days. In the digester fed autothermal sludge, higher alkalinity and lower VFA concentration produced a lower VFA to alkalinity ratio, indicating the autothermal pretreatment has the potential to make anaerobic digester operation more stable compared to anaerobic digestion only. Autothermal pretreatment consistently reduced fecal coliform to below detection limits and fecal coliform remained below detection limits during anaerobic digestion.

scholarly journals Anaerobic Digestion and Removal of Sulfamethoxazole, Enrofloxacin, Ciprofloxacin and Their Antibiotic Resistance Genes in a Full-Scale Biogas Plant

Antibiotics ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 502
Author(s):  
Andrea Visca ◽  
Anna Barra Caracciolo ◽  
Paola Grenni ◽  
Luisa Patrolecco ◽  
Jasmin Rauseo ◽  
...  
Keyword(s):  
Antibiotic Resistance ◽  
Anaerobic Digestion ◽  
Resistance Genes ◽  
Emerging Contaminants ◽  
Antibiotic Resistance Genes ◽  
Animal Manure ◽  
Full Scale ◽  
Antibiotic Residues ◽  
Anaerobic Digesters ◽  
One Year

Anaerobic digestion is one of the best ways to re-use animal manure and agricultural residues, through the production of combustible biogas and digestate. However, the use of antibiotics for preventing and treating animal diseases and, consequently, their residual concentrations in manure, could introduce them into anaerobic digesters. If the digestate is applied as a soil fertilizer, antibiotic residues and/or their corresponding antibiotic resistance genes (ARGs) could reach soil ecosystems. This work investigated three common soil emerging contaminants, i.e., sulfamethoxazole (SMX), ciprofloxacin (CIP), enrofloxacin (ENR), their ARGs sul1, sul2, qnrS, qepA, aac-(6′)-Ib-cr and the mobile genetic element intI1, for one year in a full scale anaerobic plant. Six samplings were performed in line with the 45-day hydraulic retention time (HRT) of the anaerobic plant, by collecting input and output samples. The overall results show both antibiotics and ARGs decreased during the anaerobic digestion process. In particular, SMX was degraded by up to 100%, ENR up to 84% and CIP up to 92%, depending on the sampling time. In a similar way, all ARGs declined significantly (up to 80%) in the digestate samples. This work shows how anaerobic digestion can be a promising practice for lowering antibiotic residues and ARGs in soil.

scholarly journals Life Cycle Assessment of Bioplastics and Food Waste Disposal Methods

2021 ◽  
Vol 13 (12) ◽  
pp. 6894
Author(s):  
Shakira R. Hobbs ◽  
Tyler M. Harris ◽  
William J. Barr ◽  
Amy E. Landis
Keyword(s):  
Life Cycle Assessment ◽  
Life Cycle ◽  
Anaerobic Digestion ◽  
Waste Management ◽  
Food Waste ◽  
Energy Demand ◽  
Anaerobic Digester ◽  
Management Scenarios ◽  
Cumulative Energy ◽  
Cumulative Energy Demand

The environmental impacts of five waste management scenarios for polylactic acid (PLA)-based bioplastics and food waste were quantified using life cycle assessment. Laboratory experiments have demonstrated the potential for a pretreatment process to accelerate the degradation of bioplastics and were modeled in two of the five scenarios assessed. The five scenarios analyzed in this study were: (1a) Anaerobic digestion (1b) Anaerobic digestion with pretreatment; (2a) Compost; (2a) Compost with pretreatment; (3) Landfill. Results suggested that food waste and pretreated bioplastics disposed of with an anaerobic digester offers life cycle and environmental net total benefits (environmental advantages/offsets) in several areas: ecotoxicity (−81.38 CTUe), eutrophication (0 kg N eq), cumulative energy demand (−1.79 MJ), global warming potential (0.19 kg CO2), and human health non-carcinogenic (−2.52 CTuh). Normalized results across all impact categories show that anaerobically digesting food waste and bioplastics offer the most offsets for ecotoxicity, eutrophication, cumulative energy demand and non-carcinogenic. Implications from this study can lead to nutrient and energy recovery from an anaerobic digester that can diversify the types of fertilizers and decrease landfill waste while decreasing dependency on non-renewable technologies. Thus, using anaerobic digestion to manage bioplastics and food waste should be further explored as a viable and sustainable solution for waste management.

Biological nutrient removal wastewater treatments and sewage sludge anaerobic mesophilic digestion performances

2002 ◽  
Vol 46 (10) ◽  
pp. 199-208 ◽  
Author(s):  
D. Bolzonella ◽  
L. Innocenti ◽  
F. Cecchi
Keyword(s):  
Anaerobic Digestion ◽  
Sewage Sludge ◽  
Economic Assessment ◽  
Gas Production ◽  
Anaerobic Digester ◽  
Biological Nutrient Removal ◽  
Energetic Balance ◽  
Mesophilic Digestion ◽  
The Difference ◽  
Energy Balances

The paper deals with the performances of the mesophilic anaerobic digestion treatment of sewage sludge from a full scale BNR process without primary settling (nominally 300,000 PE). A relation between the activated sludge observed yields, Yobs, and the anaerobic digester performance was preliminarily found: for values of Yobs of 0.25 kgVSS/kgCOD the anaerobic digester specific gas production showed the best performances (0.22 m3/kgVSfed). This has to be confirmed with wider future studies. It was also shown the level of sludge pre-thickening to be reached for the self-sustaining warming of the digester also in wintertime. According to the energetic balance and to a comparison with an aerobic stabilisation process, it was pointed out as when a co-generation unit for heat and energy production was introduced about 3.4 kWh/PE y of energy were produced in the anaerobic digestion process. On the other hand, 4.3 kWh/PE y were spent if an aerobic stabilisation process was applied. The economic assessment, carried out on the basis of the energy balances, showed that the anaerobic digestion is always economically advantageous if compared to aerobic stabilisation processes, also for small WWTPs. According to the energetic evaluations an environmental balance was assessed, in terms of CO2 emissions. The difference between anaerobic and aerobic processes was about 5.3 kgCO2/PE y in favour of anaerobic processes application.

Patterns of Hydrogen in Biogas from the Anaerobic Digestion of Milk-Sugars

1989 ◽  
Vol 21 (4-5) ◽  
pp. 187-196 ◽  
Author(s):  
F. E. Mosey ◽  
X. A. Fernandes
Keyword(s):  
Anaerobic Digestion ◽  
Anaerobic Digester ◽  
Laboratory Scale ◽  
Feed Pump ◽  
Anaerobic Digestion Process ◽  
Digestion Process ◽  
Skimmed Milk

Concentrations of hydrogen (1-1000 vpm) in the biogas from a laboratory-scale anaerobic digester, fed with (70 g/l) reconstituted skimmed milk as substrate, were intensively monitored to determine whether hydrogen could provide a useful new alarm/loading indicator for the anaerobic digestion process. With fast-fermenting substrates such as milk-sugars it proved to be a very sensitive event-marker, producing small ripples in time with operation of the digester feed pump as well as larger pulses caused by chloroform toxicity. Scavenging of hydrogen by lithotropic methanogens appeared to promote the fermentation of sugars directly to acetate, bypassing both the formation and subsequent breakdown of higher acids, a feature that is likely to prove peculiar to methanogenic and sulphate-reducing fermentations.

scholarly journals Historical Perspective of the Addition of Magnetic Nanoparticles Into Anaerobic Digesters (2014-2021)

2021 ◽  
Vol 3 ◽  
Author(s):  
Eudald Casals ◽  
Raquel Barrena ◽  
Edgar Gonzalez ◽  
Xavier Font ◽  
Antoni Sánchez ◽  
...  
Keyword(s):  
Organic Matter ◽  
Magnetic Nanoparticles ◽  
Anaerobic Digestion ◽  
Historical Perspective ◽  
Research Field ◽  
Organic Wastes ◽  
Anaerobic Digesters ◽  
Anaerobic Digestion Process ◽  
Digestion Process ◽  
Iron Based

The addition of magnetic nanoparticles to batch anaerobic digestion was first reported in 2014. Afterwards, the number of works dealing with this subject has been increasing year by year. The discovery of the enhancement of anaerobic digestion by adding iron-based nanoparticles has created a multidisciplinary emerging research field. As a consequence, in the last years, great efforts have been made to understand the enhancement mechanisms by which magnetic nanoparticles (NPs) addition enhances the anaerobic digestion process of numerous organic wastes. Some hypotheses point to the dissolution of iron as essential iron for anaerobic digestion development, and the state of oxidation of iron NPs that can reduce organic matter to methane. The evolution and trends of this novel topic are discussed in this manuscript. Perspectives on the needed works on this topic are also presented.

Application of Methanobrevibacter acididurans in anaerobic digestion

2004 ◽  
Vol 50 (6) ◽  
pp. 109-114 ◽  
Author(s):  
D.V. Savant ◽  
D.R. Ranade
Keyword(s):  
Fatty Acids ◽  
Anaerobic Digestion ◽  
Methane Production ◽  
Volatile Fatty Acids ◽  
Low Ph ◽  
Anaerobic Digesters ◽  
Hydrogenotrophic Methanogen ◽  
Distillery Wastewater ◽  
Acid Tolerant ◽  
Acidic Conditions

To operate anaerobic digesters successfully under acidic conditions, hydrogen utilizing methanogens which can grow efficiently at low pH and tolerate high volatile fatty acids (VFA) are desirable. An acid tolerant hydrogenotrophic methanogen viz. Methanobrevibacter acididurans isolated from slurry of an anaerobic digester running on alcohol distillery wastewater has been described earlier by this lab. This organism could grow optimally at pH 6.0. In the experiments reported herein, M. acididurans showed better methanogenesis under acidic conditions with high VFA, particularly acetate, than Methanobacterium bryantii, a common hydrogenotrophic inhabitant of anaerobic digesters. Addition of M. acididurans culture to digesting slurry of acidogenic as well as methanogenic digesters running on distillery wastewater showed increase in methane production and decrease in accumulation of volatile fatty acids. The results proved the feasibility of application of M. acididurans in anaerobic digesters.

Thermochemical pretreatment in the anaerobic digestion of waste activated sludge

2002 ◽  
Vol 46 (10) ◽  
pp. 173-179 ◽  
Author(s):  
S. Tanaka ◽  
K. Kamiyama
Keyword(s):  
Anaerobic Digestion ◽  
Activated Sludge ◽  
Sewage Treatment ◽  
Sewage Treatment Plant ◽  
Treatment Plant ◽  
Municipal Sewage ◽  
Waste Activated Sludge ◽  
Anaerobic Digesters ◽  
Thermochemical Pretreatment ◽  
Methane Production Rate

Effects of a thermochemical pretreatment on the anaerobic digestion of waste activated sludge (WAS) was investigated by semicontinuously-fed digesters operated at 37¡C. WAS from a return sludge line of a municipal sewage treatment plant was pretreated by autoclaving at 130°C for 5 minutes after adding 0.3g NaOH/g VSS. Solids of WAS were thermochemically solubilized to one half and then 60% or more were in totality solubilized in anaerobic digesters fed with pretreated WAS at 2-8 days of hydraulic retention times (HRT), while only 16-36% were solubilized in digesters fed with raw WAS. The adverse effect of the set temperature (130°C) on the biodegradability of protein was not found. As a result, removal rates of COD in digestion was increased from 38% to 57% at 8 days HRT by the pretreatment. A specific methane production rate in the pretreated process was three times as high as the normal process. The thermochemical pretreatment was found to be very effective to enhance biodegradability as well as solubilization of WAS in anaerobic digestion.

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