Effect Of Anaerobic Digestion Research Articles

Effect of anaerobic digestion on odor and ammonia emission from land-applied cattle manure

High ammonia (NH3) and odor emission can occur after land application of liquid animal manure. This study was aimed at evaluating NH3 loss and odor nuisance after field application of cattle manure and how it is affected by two anaerobic digestion strategies: i) digestion of cattle manure alone and ii) digestion with catch crops and dilution by water. A system of dynamic chambers with online measurements of NH3 and odorous compounds (summarized as odor activity value, OAV) was used. Two experiments were conducted under different temperature conditions. The results demonstrated that anaerobic digestion did not affect NH3 loss but did decrease OAV. Addition of catch crops and water to the digestion process reduced both NH3 loss and OAV. Cool temperature in one of the experiments had a large effect on both NH3 and odor emissions, and at high temperature the differences between treatments increased.

Characterizing molecular transformation of dissolved organic matter during high-solid anaerobic digestion of dewatered sludge using ESI FT-ICR MS

In this study, the effects of anaerobic digestion (AD) on molecular characteristics of dissolved organic matter (DOM) in the dewatered sludge has been described by advanced electrospray ionization combined with Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) technology. With the progress of AD, molecular amounts in DOM samples increased with the lowering in the carbon atom number of average molecular formula and average double bond equivalent (DBE). CHON and CHONS groups are the two main organic substances in sludge with their relative DOM proportions of 29.64% and 32.56%, respectively. The resistants (i.e., refractory organic matter) mainly consist of the proteins regions of CHO groups as well as the proteins/lignin regions of CHON groups. The contrasting temporal trends in protein contents (e.g., decrease (CHO and CHON) vs. increase (CHONS)) may imply differences in their degradation characteristics. Likewise, the multi-N (N3, N4) and S2 organic groups in the sludge are converted to N2 and S1 molecules, while the relative abundance of O atoms (in Ox molecules) tends to increase. In addition, the resistants in sludge DOM contain high oxidizing C and low unsaturation. The overall results of this research are expected to provide the theoretical basis for further optimization of the sludge AD process.

Enhanced Phosphorus Recovery as Vivianite from Anaerobically Digested Sewage Sludge with Magnetic Biochar Addition

Sustainable phosphorus (P) recovery from sewage sludge is crucial to reconciling the simultaneous shortage and excess of P. In this study, magnetic biochar (MBC) was synthesized and innovatively applied to enhance P recovery as vivianite. The effects of anaerobic digestion (AD) time, hydrothermal (HT) pretreatment temperature and MBC dose on vivianite formation were investigated using batch experiments and a modified sequential P extraction protocol. The P fractionation results showed that the concentration of pure vivianite-bound P (Fe(II)-P) reached a maximum on the 10th day of AD treatment, and then declined sharply due to vivianite oxidation and P limitation. HT pretreatment operated at relatively high temperatures (135 and 185 °C) reduced vivianite formation; this negative effect of HT pretreatment was partially compensated by MBC supplementation. The proportion of Fe(II)-P in the solid phase of sludge was substantially raised up to 57.1% from 8.3~17.4% with an increasing dose of MBC from 0 to 12.5 g/L, indicating that MBC had a markedly enhanced effect on vivianite formation; this could be attributed to the MBC-improved Fe(II) production, as evidenced by the elevated proportion of Fe(II) in Fe2p XPS spectra and the increased ratio of Fe(II)-P to oxidized vivianite-bound P (Fe(III)-P) in the sludge after MBC supplementation. MBC addition also decreased the proportion of water-extractable P by sorption and promoted organic P decomposition, which further facilitated vivianite production. These findings reveal a new strategy for enhancing P recovery from HT-pretreated AD sludge.

Pyrolysis of food waste and food waste solid digestate: A comparative investigation

The effects of anaerobic digestion (AD) on pyrolysis were elaborated by comparing the pyrolysis performance of food waste (FW) and food waste solid digestate (FWSD). The pyrolysis mechanisms of FW and FWSD were revealed by experimental and kinetic analysis. The properties and potential applications of pyrolytic products from FW and FWSD were discussed. The results showed that part of organic matters of FW were consumed during AD, which altered the pyrolysis performance of FWSD. The pyrolytic gas from FW had better quality due to its higher lower heating value (LHV) (20.52 kJ/Nm3). The pyrolytic oil and biochar derived from FWSD showed better qualities as oil fuel and carbon-based absorbent. Pyrolysis of FWSD produced less nitrogen-containing pollutants (NCPs) indicated that AD coupled with pyrolysis is more environmental-friendly to treat FW. This study provides potential approach and theoretical guidance for the treatment and resource utilization of FW and FWSD.

Anaerobic digestion of sewage sludge has no effect on glucocorticoid and anti-progestagenic activity but increases estrogenicity three-fold

Although the recovery and beneficial reuse of organic matter and nutrients from sludge represents an important move towards environmental sustainability, the accumulation of chemicals in biosolid-amended soils could pose serious environmental and human health risks. However, (eco)toxicological profiling of complex chemical mixtures in biosolids is currently limited. In particular, the effect of anaerobic digestion (AD), the most common stabilization process for sewage sludge, on the (eco)toxicity of those complex mixtures is poorly studied. In this work, we fill this research gap by applying an effect-based monitoring approach to screen sludge samples (n = 4) from a full-scale sewage treatment plant before and after conventional mesophilic (37 °C) AD using a battery of cell-based in vitro bioassays for four types of hormonal activity: estrogenic, androgenic, progestagenic and glucocorticoid activity, both in agonist and antagonist modes. We detected estrogenic, glucocorticoid and anti-progestagenic activity in all sludge samples. The glucocorticoid and anti-progestagenic activity remained mostly unchanged after AD treatment, but estrogenicity increased three-fold, likely as a result of bioactivation processes in the digestor. This study presents the first report on the concentration and fate of glucocorticoid and anti-progestagenic activity in AD. Future research should apply bioanalytical tools to a wider range of sludge samples to get a better understanding of the typical hormonal activity in sludge and develop effect-based trigger (EBT) values for biosolids to help interpret the risk posed by the hormonal activity detected in sludge.

Comparism Analysis of Energy Content of Biogas and Its Physiochemical Properties

The correlations of energy content of biogas and physicochemical properties from cow manure and co-digestible as single and double substrates were investigated in this study. The blend that gives the highest energy, effect of anaerobic digestion on fertilizer values of the input slurry and relationship between the biogas yields were investigated. The experiment was performed at a constant temperature of 400C with a retention period of 16 days. The physicochemical properties of the slurries before and after digestion showed that the percentages of potassium, phosphorus, nitrogen and crude protein contents for all the samples batches increased. The blend of cow dung and plantain wastes in the 1:3 yielded the highest energy content and volume of biogas. This ratio can be effective for biogas production, mitigate the problems of energy shortage, fertilizer and uncontrolled waste disposal.

Effects of Anaerobic Digestion on Antibiotic Resistance Genes in Sludge

Sludge treatment and reuse in municipal sewage treatment plants is beneficial to improve economic effect and reduce environmental pollution. Sludge is an important source of contamination of antibiotic resistance genes. Anaerobic fermentation is an important way to treat activated sludge. Effective treatment of municipal sludge can avoid the release of pathogenic microorganisms and resistance genes (ARGs) into the environment and cause secondary pollution. The research results will be of certain guiding significance to the resource utilization of sludge.

Fate of antibiotic resistance genes during temperature-changed psychrophilic anaerobic digestion of municipal sludge

The effects of anaerobic digestion (AD) on the abundance of antibiotic resistance genes (ARGs) are highly related to operational temperature. However, the removal performance of ARGs in psychrophilic AD and changed temperatures simulating variable seasonal temperatures is poorly understood. Herein, we investigated the fate of ARGs, correlated bacterial communities and physicochemical properties of AD operation at psychrophilic (15 ℃), mesophilic (35 ℃), and temperature changed conditions (15 to 35 ℃ and 35 to 15 ℃). The results indicated that ammonia release was positively correlated with temperature. The mesophilic AD facilitated phosphorous intake and ARGs proliferation and selection with oxytetracycline (OTC), while psychrophilic AD was conducive to the removal and control of ARGs if no OTC existed. The diversity and composition of AD bacterial communities were influenced more by temperature than OTC. The dominant genera like Candidatus_Microthrix and Acinetobacter had dramatical abundance discrepancies at different temperatures and were obviously positively correlated with ARGs (tet39, tetC and mexD), mobile genetic elements (MGEs) intI, insert sequences (IS) and plasmid. The physicochemical properties of AD influenced the bacterial richness, which in turn significantly correlated with the ARGs abundances. Therefore, ARGs removal could be potentially optimized by eliminating bacterial hosts with deteriorated living conditions and decreased nutrients. This study clarified the response of antibiotic resistome to different temperature variation and highlighted the potential strategies for improved ARGs removal in AD.

Maximizing the energy potential of urban sludge treatment: An experimental study and a scenario-based energy analysis focusing on anaerobic digestion with ultrasound pretreatment and sludge combustion

With stricter regulations and concerns over sustainability, combustion can be a beneficial handling method as dried sludge can be used as an energy source. Anaerobic digestion of sludge also provides energy in the form of biogas without the need for sludge drying. Yet, anaerobic digestion reduces the calorific value (CV) of sludge. In this study, the effect of anaerobic digestion (with or without ultrasound pretreatment) on the fuel properties of sludge were examined through laboratory experiments. Additionally, a number of sludge management strategies were evaluated to maximize energy gain. Temporal changes in fuel properties of sludge were tracked during digestion. Results showed that sonication provided a 3.4-fold increase in soluble COD, 15% increase in biogas production and 32% increase in methane production, while the CV of sludge reduced from 14.7 kJ/g to 10 kJ/g. Energy balances for a number of sludge management process trains showed that the optimal method was the combination of thickening, dewatering, thermal drying and combustion. Addition of digestion and ultrasound pretreatment to this scenario reduced the energy gained from sludge. Yet, high ambient temperatures impacted results such that the net energy gain by the scenario including digestion and combustion was close to that of combustion only.

Comparative Analysis of the Amount of Biogas Produced by Different Cultures using the Modified Gompertz Model and Logistic Model

With the increase in population, the amount of food waste generated is increasing exponentially. Anaerobic digestion can serve the purpose of managing organic waste in an eco-friendly way. Microorganisms play a vital role in the process of anaerobic digestion. In this work, the effect of anaerobic digestion was analyzed using two organic cultures- Cow Dung and Horse waste which was in turn compared to an Industrial Culture with regards to the biogas produced over a cycle of 14 days. Between the two organic cultures, the volume of biogas produced by Horse waste was 35,366.03 cm3 which compared to the biogas produced by cow dung was considerably large. The use of Horse waste as potential biomass has the capacity to produce biogas which can be utilized as a biofuel. The experimental data were evaluated using mathematical models like the Modified Gompertz Model, Logistic Model, and First Order Kinetics Model. Of the three models used, Modified Gompertz Model and Logistic Model gave a good fit for the experimental data with 0.98 and 0.97 respectively as the Coefficient of Determination (R2). While the First Order Kinetics Model underperformed with an R2 value of 0.68. The Modified Gompertz gave accurate results which thus validated the experimental data.

Anaerobic Digestion and Dewatering of Biological Trickling Filter Sludge

AbstractThis study investigated digestibility of biological trickling filter (BTF) sludge (in terms of the mass and volume reduction of the sludge) and the effect of anaerobic digestion on sludge d...

Comparison study on pyrolysis characteristics and kinetics of corn stover and its digestate by TG-FTIR

The pyrolysis potential of corn stover digestate (CSD) was compared with corn stover (CS). The effects of anaerobic digestion (AD) on pyrolysis were investigated at different rates by a thermogravimetric analyzer coupled with Fourier transform infrared spectrometry (TG-FTIR). The distributed activation energy model (DAEM) was used to show the differences in the kinetics. The results indicated that the AD process improved the thermal stability with lower mean reactivity (RM), higher solid residue (S850), and decreased release of observed gaseous productions, except for CH4. The release of CH4 from CSD was higher than that of CS, especially in the temperature range of 430 °C to 520 °C. The activation energies (E) of CS and CSD were 184 kJ/mol to 293 kJ/mol (conversions were 0.1 to 0.8) and 99 kJ/mol to 331 kJ/mol (conversions were 0.1 to 0.9), respectively. The activation energies decreased after AD at the same conversion level. The calculated TG data of CS and CSD from the kinetic parameters were in good agreement with the experimental curves.

The effect of anaerobic digestion and storage on indicator microorganisms in swine and dairy manure.

The aim of this experimental study was to evaluate the influence of anaerobic digestion and storage on indicator microorganisms in swine and dairy excreta. Samples were collected every 90days for 15months at eight farms, four pig, and four dairy farms, four of them having a biogas plant. Moreover, to evaluate storage effects on samples, 20l of manure and slurry taken at each farm (digested manure only in farms with a biogas plant) were stored in a controlled climatic chamber at 18°C, for 6months. The bacterial load and the chemical-physical characteristics of excreta were evaluated at each sampling time, stored slurry, and manure were sampled and analyzed every 2months. A high variability of the concentration of bacteria in the different excreta types was observed during the experiment, mainly depending on the type and time of treatment. No sample revealed either the presence of Escherichia coli O157:H7 or of Salmonella, usually linked to the temporary rearing of infected animals in facilities. Anaerobic digestion and storage affected in a significant way the reduction of indicator bacteria like lactobacilli, coliforms, and streptococci. Anaerobic digestion lowered coliforms in pig slurry (-2.80 log, P<0.05), streptococci in dairy manure (-2.44 log, P<0.001) and in pig slurry (-1.43 log, P<0.05), and lactobacilli in pig slurry (-3.03 log, P<0.05). Storage lowered coliforms and the other indicators counts, in particular in fresh wastes, while clostridia did not show a reduction in concentration.

Environmental impact of municipal solid waste management using Life Cycle Assessment: The effect of anaerobic digestion, materials recovery and secondary fuels production

Material and energy recovery from waste is significantly growing its importance in the last decades aiming to reduce the primary resources exploitation and the excessive recourse to incineration and landfilling. Several processes, technologies and methods can be chosen to design a proper waste management system (WMS) so that an objective comparison between alternatives has to be made. To this end, Life Cycle Assessment (LCA) can be used to compare possible alternative scenarios and create an evaluation grid where different environmental parameters are reported. The aim of this work was to compare the environmental impacts of four different scenarios already analysed for technological and economic aspects in a previous work. The scenario taken as base case referred to a real waste management system applied in Caserta Province, an area of 924,614 inhabitants in the Campania region of Southern Italy. The base scenario considers the household separation of waste in five fractions addressed to material recovery (polyethylene, polyethylen-terephtalate, polypropylene, metals, cellulosic fibers, …), composting (biowaste) and incineration (residual waste). The results of the LCA demonstrated that the best scenario is that one including the highest separate collection rate technically and economically feasible to be carried out i.e. 60%, the recourse to anaerobic digestion and biogas production to treat the biowaste separately collected and the maximization of the re-processing of recyclable materials such as PET, HDPE, glass, metals, … In particular, the Global Warming Potential decrease of 166% and the Eutrophication Potential decrease of 646%, when the alternative scenario, including the recalled features is compared to the base-case one. The most important result is that the raised separate collection of recyclable materials utilized as substitutes of raw materials and of biowaste utilized for production of renewable energy helps to mitigate the direct and indirect burdens connected to the overall life cycle of goods production.

Effects of anaerobic digestion on chlortetracycline and oxytetracycline degradation efficiency for swine manure

Manure containing antibiotics is considered a hazardous substance that poses a serious health risk to the environment and to human health. Anaerobic digestion (AD) could not only treatment animal waste but also generate valuable biogas. However, the interaction between antibiotics in manure and the AD process has not been clearly understood. In this study, experiments on biochemical methane potential (BMP) were conducted to determine the inhibition of the AD process from antibiotics and the threshold of complete antibiotic removal. The thresholds of the complete antibiotic removal were 60 and 40mg/kg·TS for CTC and OTC, respectively. CTC and OTC with concentrations below thresholds could increase the BMP of manure. When the CTC and OTC concentrations exceeded the thresholds, they inhibited manure fermentation, and the CTC removal rate declined exponentially with concentration (60–500mg/kg·TS). The relationship between OTC antibiotic concentration and its removal rate in AD treatment was described with exponential (40–100mg/kg·TS) and linear equations (100–500mg/kg·TS).

Effect of Anaerobic Digestion on Rheological Parameters and Dewaterability of Aerobic Sludges from MBR and Conventional Activated Sludge Plants

The paper investigates and compares the characteristics of sludges produced by membrane Bio-Reactor (MBR) and Conventional Activated Sludge (CAS) systems. Stability and dewaterability of full-scale MBR and CAS treatment plants are measured and compared. Obtained results show that specific methane production is higher in CAS sludge compared to MBR sludge because of the higher solid retention time of the MBR. Nonetheless MBR sludge results to be characterized by a non-negligible biometanation potential (BMP). Methane production measured during BMP tests is around 250 NmL/gVS for MBR sludge, equaling 2/3 of methane production obtained, in similar condition, for CAS sludge. Dewaterability is evaluated by Specific Resistance to Filtration (SRF), Capillary Suction Time (CST) and Time To Filter (TTF) tests. Data obtained before and after the anaerobic digestion of the sludges show that the stabilization process affects much more the resistance to filtration of CAS sludge than the resistance to filtration of MBR sludge. The same trend is observed, for the other measured parameters. This is attributed to the variation of the rheological characteristics of the two sludges during the stabilization process, and to the different initial rheological properties of them due to the different selection process of the biomass deriving from the different biomass retention methods of MBR and CAS systems.

Physicochemical changes of rice straw after lime pretreatment and mesophilic dry digestion

A better understanding of the physicochemical properties of the material, its changes and the effects of anaerobic digestion, will help to improve methane production efficiency. The physicochemical changes of rice straw after solid-state lime pretreatment and dry digestion were investigated. Those changes were revealed by the composition of the substrate before any treatment, from samples of the material during the process and by the final product. Such compositions were studied with X-ray, Fourier transform infrared spectroscopy and thermogravimetric analyzes. The obtained results showed that low mass transfer limited the lignin modification and polysaccharide decomposition, resulted in a low biogas yield; and that after pretreatment and 60 days of mesophilic dry digestion, the concentration of cellulose decreased (23.4%) as well as hemicellulose (13.1%). In the opposite case, the concentration of lignin increased (59%) as well as ash (108%). The crystallinity index increased by 5.4% after pretreatment and decreased by 4.8% after digestion. The FTIR spectrogram of the raw sample included a peak reflecting absorption of ester linkages. This peak was absent from FTIR spectra of pretreated and digested samples, indicating that such linkages are broken during pretreatment and then digested by the microorganisms during the anaerobic fermentation. Furthermore, lime pretreatment and dry digestion significantly changed the decomposed profiles and rate, the distribution of pyrolysis product. The obtained data showed that polysaccharides and lignin were decomposed during pretreatment and digestion phases, leading to changes in structural and thermal properties.

Effect of Manure Treatment on Ammonia Emission during Storage under Ambient Environment

The effect of anaerobic digestion (AD), coarse solids removal, and a manure additive More Than ManureTM (MTMTM) on ammonia (NH3) emission from raw (Non AD) dairy manure and AD manure was studied during 110 days of storage. The study consisted of eight treatments in duplicate: AD manure and non AD manure, with and without coarse solids, and with and without MTMTM additive. These studies were conducted in a naturally ventilated barn. The nitrogen content of manure, especially the ammoniacal nitrogen, played an important role in NH3 emission. During the first 11 weeks of the storage, AD manure had significantly greater peak (33 to 38 ppm) concentrations of NH3, and NH3 fluxes (94 to 130 μg min−1 m−2) compared to raw manure (14 to 25 ppm and 55 to 81 μg min−1 m−2, respectively). From the 11th week until the end of storage, there was no significant difference in NH3 emissions across the manure treatments. The presence of course solids resulted in significanlty less peak NH3 for non AD manure when data were evaluated for the whole storage period. The manure additive MTMTM did not have a significant effect on NH3 emissions during storage, however, temperature was positively related to NH3 emissions. Total ammoniacal nitrogen and solids concentration in manure was the most important factors affecting NH3 emissions during storage.

Effect of anaerobic digestion at 35, 55 and 60 °C on pharmaceuticals and organic contaminants

The application of treated sewage sludge on farmland is a suggested method for recycling nutrients and reducing demand for commercial fertilizer. However, sludge needs to be safe from possible contaminants which can cause acute and long-term health and environmental problems. Residual pharmaceuticals and organic contaminants are mentioned as emerging threats since wastewater treatment plants are not designed to degrade these substances. The aim of this study was to screen and evaluate the presence, and reduction, of pharmaceuticals and polycyclic aromatic hydrocarbons (PAHs) during anaerobic digestion of mixed primary and waste-activated sludge at 35, 55 and 60 °C and during pasteurization at 70 °C. The study showed the difficulty of analysing pharmaceutical compounds in low concentrations in the sludge matrix. No general reduction of these compounds was seen during treatment, but for individual substances some reduction occurred. The PAHs were generally not reduced during digestion or pasteurization, but for three substances (indeno[1,2,3-cd]pyrene and dibenzo[a,h]anthracene (analysed together) and benzo[g,h,i]perylene) reduction (up to 60%) during digestion was seen. Digestion at 35 and 55 °C resulted in about the same order of reduction of the three individual PAHs, which was higher than for digestion at 60 °C.

Effects of anaerobic digestion on digestate nutrient availability and crop growth: A review

Anaerobic digestion (AD) for biogas production leads to several changes in the composition of the resulting digestates compared to the original feedstock (ammonia content, pH, carbon to nitrogen ratio, etc.), which are relevant for the plant availability of macro‐ and micronutrients after field application. Increased NH4+‐N content in digested slurries compared to undigested slurries does not guarantee improved uptake efficiency of slurry nitrogen and increased savings in fertilizer nitrogen. AD of crop residues and cover crops leads to an increase in the total amounts of mobile organic manures within the farming system, resulting in a higher nitrogen use efficiency and an increased scope for target‐oriented nitrogen application in time and space, when needed by the crop, as an alternative to the site‐bound soil incorporation as green manures. AD of dairy manure appears to reduce the fraction of immediate plant available phosphorus and micronutrients. This does, however, not affect short‐term crop availability under field conditions. More studies are needed to improve current knowledge on sulfur losses during AD and fertilizer value of digestates.