anaerobic digestion Articles
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Extracellular polymeric substances and dewaterability of waste activated sludge during anaerobic digestion
Anaerobic digestion of waste activated sludge was conducted to gain insight into the mechanisms underlying change in sludge dewaterability during its anaerobic digestion. Unexpectedly, the results indicated that sludge dewatering properties measured by capillary suction time only deteriorated after 10 days of anaerobic digestion, after which dewaterability recovered and remained stable. The ...
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Methods of ammonia removal in anaerobic digestion: a review
The anaerobic digestion of substrates with high ammonia content has always been a bottleneck in the methanisation process of biomasses. Since microbial communities in anaerobic digesters are sensitive to free ammonia at certain conditions, the digestion of nitrogen-rich substrates such as livestock wastes may result in inhibition/toxicity eventually leading to process failures, unless ...
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Hygienization of sludge through anaerobic digestion at 35, 55 and 60 °C
Legislation in Sweden and the European Union concerning the use of sewage sludge in agriculture is under revision and future concentration limits for pathogens in treated sludge are likely to be expected. The aim of this study was to evaluate the hygienization of Salmonella, Escherichia coli, Enterococcus and Clostridium perfringens through continuous anaerobic digestion at 35, 55 or 60 ...
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Combination of extremum-seeking algorithms with effective hydraulic handling of equalization tanks to control anaerobic digesters
The benefits of upgrading extremum-seeking controllers with an effective exploitation of the buffer capacity of equalization tanks have been investigated and applied to anaerobic digesters. In this respect, a Fuzzy-based supervisory module that monitors the state of the equalization tank has been designed and built on top of an extremum-seeking algorithm in charge of automatically regulating the ...
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Anaerobic Digesters
Anaerobic digesters/Biogas storage tanks are widely utilized at fields of industry, agriculture or municipality. Amongst of them using anaerobic digestion to generate biogas from organic wastes is increasingly becoming one of the most important and popular utilization. The process of anaerobic digestion is used for industrial or domestic purposes to manage waste or to produce bio-energy. ...
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Microwave and its combined processes: an effective way for enhancing anaerobic digestion and dewaterability of sewage sludge?
The enhancement for sludge anaerobic digestion and dewaterability were investigated in sludge pretreated by microwave (MW) and its combined processes. The results showed that microwave and its combined processes can efficiently release soluble organic matter and thus enhance anaerobic digestion of sludge. The cumulative methane production in the test of the MW-H2O2-OH (0.2) process was ...
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Sequencing Batch Reactors - Case study
H2flow supplied the SAM SBR for treating this high strength wastewater. The wastewater is generated from dewatering wasted anaerobic digestion solids. In addition it supplied the glass fused to steel tanks as an integrated package. The tanks are covered with roofs and are 12m diameter by 7.4m tall. There is one equalization tank and two reactor tanks. There were a total of eight tanks ...
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Comparison of microbial activity in anaerobic and microaerobic digesters
Microaerobic alternative of anaerobic digestion offers many advantages especially when sulfide concentration in the digester is high. For better understanding of the microaerobic technology more detailed characterization of biomass activity is needed. Two equal digesters were operated under the same condition except of microaeration in one of them. During long term operation of anaerobic and ...
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The Anaerobic Digestion of Bio-Waste in Developing Countries
The anaerobic digestion process is typically used as a means of waste disposal or energy production. Anaerobic digestion of bio-waste in developing countries is extremely beneficial as it doesn’t just generate clean and safe energy, it also contributes towards other economic development issues and has considerable environmental benefits. In this article we will explore the many benefits of the ...
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Mathematical models and bacterial communities for ammonia toxicity in mesophilic anaerobes not acclimated to high concentrations of ammonia
In this study, we evaluated ammonia toxicity in mesophilic anaerobic digestion at various pH values and total ammonia nitrogen (TAN) concentrations. We performed anaerobic toxicity assays (ATAs) to evaluate the toxicity effects of TAN and pH on mesophilic anaerobic digestion. Modeling based on the results of the ATAs indicated that the specific methanogenic activity (SMA) decreased by 30% at ...
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Enhancement of the conventional anaerobic digestion of sludge: comparison of four different strategies
Anaerobic digestion (AD) is the preferred option to stabilize sludge. However, the rate limiting step of solids hydrolysis makes it worth modifing the conventional mesophilic AD in order to increase the performance of the digester. The main strategies are to introduce a hydrolysis pre-treatment, or to modify the digestion temperature. Among the different pre-treatment alternatives, the thermal ...
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Use of an elemental balance over primary and secondary anaerobic digestion of sewage sludge to determine its carbon impact
This paper details how a mass balance, which was conducted for all of United Utilities’ anaerobic digestion plants, was used to calculate emission factors for various types of anaerobic digestion processes to enable calculation their carbon footprint. The mass balance showed average volatile solids destruction rates of 45% and 11% over primary and secondary digestion respectively. The calculated ...
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When Is It Best to Use Anaerobic Digestion?
The benefits can be compelling, but several factors must be considered Anaerobic digestion is a biological process that breaks down organic matter in the absence of oxygen, producing biogas and nutrient-rich sludge. Used in wastewater treatment, anaerobic digestion helps reduce the volume of sludge, stabilizes the solids, and produces valuable biogas. The solid matter that remains, called the ...
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Control of C/N ratio for butyric acid production from textile wastewater sludge by anaerobic digestion
Increasing textile wastewaters and their biotreatment byproduct–waste activated sludge are serious pollution problems. Butyric acid production from textile wastewater sludge by anaerobic digestion at different C/N ratios was investigated. Adding starch to textile wastewater sludge with a C/N ratio of 30 increased the butyric acid concentration and percentage accounting for total volatile fatty ...
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More Industries, Regions Discovering Power of Anaerobic Digestion
Anaerobic digestion can turn waste into a valuable resource Billions of tons of organic waste are generated every day by households, industries, and municipalities. It’s discarded into landfills or discharged as effluent, or both, at a huge cost to the environment. But what if that waste could be turned into energy? The good news is that it can, through anaerobic digestion. In anaerobic ...
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A novel technique for evaluating foam dynamics in anaerobic digesters
Foaming in anaerobic digesters has severe impacts on process efficiency and operational costs. In this study, we present an experimental method to determine foam behaviour and stability for various foaming solutions. This novel technique measured foam conductivity at different heights along a foam column allowing changes in foam composition to be monitored in time. We analysed foam stability ...
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Pretreatment followed by anaerobic digestion of secondary sludge for reduction of sewage sludge volume
The influence of two pretreatment methods, thermal treatment and low-pressure wet oxidation, on the sludge digestion efficiency was examined. Batch thermophilic anaerobic digestion was used to evaluate the effectiveness of the pretreatment methods in terms of volatile suspended solids (VSS) digestion efficiency and gas production. The results showed that the gas production was not proportional ...
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Methane conversion efficiency as a simple control parameter for an anaerobic digester at high loading rates
The anaerobic digestion process is globally applied to the treatment of highly concentrated wastes such as industrial and rural effluents, and sewage sludge. However, it is known to be relatively unstable. When loaded with high concentrations of organic material, unwanted volatile fatty acids (VFA) are often produced rather than methane (CH4) gas which can lead to digester acidification and ...
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Environmental efficiency of composting versus anaerobic digestion of separately collected, organic waste
Environmental policy in the Netherlands among others aims at closing material cycles and minimising the amount of waste requiring final disposal. In this policy the highest priority is given to the prevention of waste production followed by (in descending order of preference) reuse, incineration with energy recovery and sanitary landfilling. In the implementation of this solid waste policy also ...
By ORBIT e.V.
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Foaming during anaerobic digestion: Causes and Solutions
Foaming during sludge treatment has traditionally been associated with activated sludge systems which have been victim to this phenomenon for several decades. However, foaming has been documented in anaerobic digestion plants, leading, fundamentally, to a reduction in digester capacity and an increase in operational expenditure. The requirements for foaming of: surface active agents, gaseous ...
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