Heavy metals interact with the microbial community and affect biogas production in anaerobic digestion: A review (original) (raw)
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THE INFLUENCE OF HEAVY METALS ON BIOGAS PRODUCTION DURING THE ANAEROBIC DIGESTION PROCESS
Availability of heavy metals plays a very significant role in the performance and stability of biogas digesters, which are operated with energy crops, organic fraction of municipal solid wastes or any other type of organic waste. Heavy metals are present in significant concentrations in animal manure and in some industrial wastewaters. Heavy metals can be stimulatory, inhibitory, or even toxic in biochemical reactions, depending on their concentrations. A trace level of many metals is required for activation or functioning of many enzymes and co-enzymes. Excessive amounts, however, can lead to inhibition or toxicity, .
Occurrence, Fate, and Implications of Heavy Metals during Anaerobic Digestion: A Review
Energies
Over the years, anaerobic digestion (AD) has evolved as a competent technology to retrieve energy potential from various organic substrates, including wastewater. However, the energy metabolisms of anaerobic microorganisms, biochemical reactions, and biogas production are affected by various parameters, including heavy metals. It is important to understand the interaction of heavy metals with anaerobes and their potential influence on the process to enhance energy potential. This review methodically outlines the occurrence and role of heavy metals in the AD process. Additionally, the repercussions of the most common heavy metals (i.e., Cu, Zn, Cd, Fe, and Ni) on each stage of AD (i.e., hydrolysis, acidogenesis, and methanogenesis) have been discussed. We found that traces of heavy metals can endorse anaerobic digestion, but inhibition increases with increasing concentration. Methanogenic archaea are more susceptible to heavy metal inhibition than hydrolytic and acidogenic archaea. A...
The Role of Trace Elements on Anaerobic Co-digestion in Biogas Production
In this study, we investigated the concentration of trace elements in the digestates in a laboratory batch anaerobic digester. Many of these trace elements are important macro and micro nutrients. The availability of these nutrients for microbes responsible for anaerobic digestion and substrate toxicity have to be controlled in biogas production. The analyzed substrates were characterized at various concentrations in the following trace elements; potassium, phosphorus, manganese, copper, calcium, molybdenum, zinc, cobalt, iron, aluminum, silver, nickel and cadmium. Trace elements like copper, silver, nickel, cadmium, zinc have been reported to be inhibitory and toxic under certain conditions in biochemical reaction depending on their concentrations. These trace elements lower biogas production above threshold concentration due to accumulation of organic acid as a result of methanogenic bacterial inhibition. There was no deficit of nutrients detected in the anaerobic digesters analysis.
Journal of Cleaner Production, 2019
The use of trace metals as additives to the biogas production process to increase the biogas yield has been identified as a very common approach. Such additives can biostimulate the methanogenic bacteria to increase the biogas and methane production from the anaerobic digestion (AD) of livestock manure. The environmental impact of using the trace elements as manure additives still not evaluated. The objective of this paper is to conduct a comparative environmental impact evaluation of manure treatment with different trace elements for biogas production. The trace metals under evaluation were in the form of the chlorides of nickel (Ni), cobalt (Co) and iron (Fe) which were used as additives to the anaerobic digestion of livestock manure. The results were shown in the form of the specific impacts on global warming and greenhouse gas (GHG) emissions mitigation of producing and utilizing biogas as a bioenergy source. The results of this investigation show that the use of 1 g/m 3 cobalt chloride (CoCl 2) causes the lowest greenhouse gas emissions among all other evaluated trace metals which were calculated on the basis of CO 2-equivalent. An important observation is that the greenhouse gas emissions from the electricity generated using biogas produced without any additives, i.e. without trace metals, were the highest among all other variants/scenarios.
Bioavailability and Toxicity of Metal Nutrients during Anaerobic Digestion
Journal of Environmental Engineering, 2007
This paper investigates the effect of chelating agents on the bioavailability of Fe and Cu during anaerobic digestion. The results on metal speciation and methane production in anaerobic serum bottles showed that biomass was able to grow in the presence of citrate 1 mM and nitrilotriacetic acid ͑NTA͒ 1 mM, suggesting that the binding sites at the cell surface competed efficiently for the metals with the chelating agents added. The presence of free ethylenediaminetetraacetic acid 1 mM inhibited methanogenesis, and this seemed to be related to a loss in metal uptake capacity. Although the addition of soluble microbial products ͑SMP͒ did not change metal distribution in anaerobic systems, it caused an increase in the rate of methane production, and it is believed that direct uptake of Cu-SMP complexes was responsible for this increase. The best protection against Cu toxicity occurred when stoichiometric amounts of NTA, which should complex and solubilize most of the Cu, was added, and it is likely that NTA prevented lethal concentrations of Cu from being adsorbed onto the cell and hence internalized.
Monitoring N : P Ratio and Cd, Cu, Pb, and Zn Contents in Different Types of Anaerobic Digestates
2020
Depending on the quality of the input substrates, process parameters, and postfermentation treatments, digestates may contain a broad spectrum of potentially toxic elements. We suspected that these contents may vary on a broad scale even under seemingly stable process conditions at the biogas plant. Digestates from four biogas plants were therefore continuously analyzed for their contents of phosphorus, nitrogen, cadmium, copper, lead, and zinc over a period of six years. The input substrates varied between the plants (e.g., cattle and pig slurry and rye and maize silage), but were the same for each plant over the whole period. The N : P ratio of the digestates ranged from 2 to 24, with the digestate coming from cofermentation of pig slurry and energy crops ("DG Pig") having the widest range of N : P ratio over the years. Heavy metal loads of all digestates and during all evaluations did not exceed the limits set by European or German legislation, but as previously expecte...
International Journal of Agronomy
Depending on the quality of the input substrates, process parameters, and postfermentation treatments, digestates may contain a broad spectrum of potentially toxic elements. We suspected that these contents may vary on a broad scale even under seemingly stable process conditions at the biogas plant. Digestates from four biogas plants were therefore continuously analyzed for their contents of phosphorus, nitrogen, cadmium, copper, lead, and zinc over a period of six years. The input substrates varied between the plants (e.g., cattle and pig slurry and rye and maize silage), but were the same for each plant over the whole period. The N : P ratio of the digestates ranged from 2 to 24, with the digestate coming from cofermentation of pig slurry and energy crops (“DG Pig”) having the widest range of N : P ratio over the years. Heavy metal loads of all digestates and during all evaluations did not exceed the limits set by European or German legislation, but as previously expected, showed ...
Trace metals are essential for the growth of anaerobic microorganisms, however, in practice they are often added to anaerobic digesters in excessive amounts, which can lead to inhibition. The concept of bioavailability of metals in anaerobic digestion has been poorly understood in the past, and a lack of deep understanding of the relationship between trace metal speciation and bioavailability can result in ineffective metal dosing strategies for anaerobic digesters. Sequential extraction schemes are useful for fractionating trace metals into their different forms, and metal sulfides can serve as a store and source for trace metals during anaerobic digestion, while natural/synthetic chelating agents (soluble microbial products-SMPs, extracellular polysaccharides-EPS, and EDTA/NTA) are capable of controlling trace metal bioavailability. Nevertheless, more work is needed to: investigate the speciation and bioavailability of Ca, Mg, Mn, W, and Se; compare the bioavailability of different forms of trace metals e.g. carbonates, sulfides, phosphates to different anaerobic trophic groups; determine what factors influence metal sulfide dissolution; investigate whether chelating agents can increase trace metal bioavailability; develop and adapt specialized analytical techniques, and; determine how trace metal dynamics change in an anaerobic membrane bioreactor (AnMBR).
The Influence of Trace Elements on Anaerobic Digestion Process
Civil and Environmental Engineering Reports, 2018
The article is the literature review on the importance of trace elements supplementation in the methane fermentation process. The production of biogas, including methane, as well as the efficiency of the process depend on the substrates to be fermented. Substances supplied with the substrate as well as products generated in the decomposition phases can inhibit the process. The factor limiting fermentation is the rate of enzymatic hydrolysis of substrates. Certain compounds, such as alkanes, alkenes, biphenol, aromatic hydrocarbons, alcohols and ketones, are not directly susceptible to hydrolysis. They undergo this process in the presence of extracellular enzymes. The instability of the methane fermentation process described in the literature may be related to the lack of trace elements or micronutrients. Trace elements (Co, Ni, Cu, Mn, Fe, Zn, Se and Mo) are components of enzymes, some bacterial nucleic acids and essential for the synthesis of vitamins. The role of some trace elemen...