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Anaerobic co-digestion of sludge from recycled pulp and paper industry (RPPS) with vinasse effluent from alcohol distilleries (VW) was performed under mesophilic conditions (37 °C) at laboratory scale, using one-liter continuous stirred tank reactors (CSTRs). The physicochemical parameters were monitored during the process. The average pH and alkalinity were 7.7 and 1000 mg CaCO3 Kg−1, respectively, indicating that the process is working well without the risk of acidification. The methane yield and biodegradability of this mixture were determined. The methane yield was about 112 (NmL CH4 g−1 VS added) and biodegradability reached 73%. Nevertheless, in monodigestion of RPPS, the methane yield was 94 (NmL CH4 g−1 VS added) and biodegradability 65%. The anaerobic co-digestion of (RPPS) with (VW) at a proportion of (70:30) improved methane production by 16% and biodegradability by 11%. Bioenergy recovery from industrial (RPPS) is promoted by co-digestion with (VW), and the removal efficiency of 73% indicates the performance of the process adopted. A kinetic study was performed using five models Richards, modified Gompertz, Logistic, Cone, and first order. The results show that Richards' was the most appropriate model for adjusting methane production from (RPPS) and (VW) co-digestion. [ABSTRACT FROM AUTHOR]

The increasing energy and water demands by the Arab Gulf states highlight the importance of sustainable use of energy resources. Wastewater sludge management for energy recovery creates an opportunity for sector integration for both wastewater treatment plants and renewable energy production. The objective of this study was to theoretically estimate the biomethane potential of wastewater sludge, together with identification of the role of biomethane in the region. The prediction of biomethane potential was based on the theoretical stoichiometry of biomethanation reactions, using the R-based package 'Process Biogas Data and Predict Biogas Production'. The biomethane potential of sludge ranges between 232–334 × 106 m3, with a total heat-value up to 10.7 trillion BTUs annually. The produced biomethane can generate up to 1665 GWh of electric energy, an equivalent amount to the current levels of electricity generation from wind and solar power combined. The findings from the case study on Kuwait's indicate that biomethane could displace 13 × 106 m3 of natural gas, or approximately 86,000 barrels of crude oil, while simultaneously reducing greenhouse gas emissions by 86% when compared to the base-scenario. Despite its potential, biomethane recovery in the region is hindered by technical-, economic-, and policy-based barriers. [ABSTRACT FROM AUTHOR]

This study examines whether vapothermal pre-treatment is technically feasible and brings economic advantages for a subsequent anaerobic co-fermentation of reeds together with sewage sludge. This is illustrated by the example of remote sites located close to constructed wetlands in the Persian Gulf states. Thus, eight different biogas plant configurations with an installed electric power between 75 and 450 kW, each with and without vapothermal pre-treatment, are investigated in detail related to technical and economic figures. Within the technical assessment, suitable plant components are chosen and overall plant layouts are designed and dimensioned. Furthermore, the requirements on the substrate by means of quantity, pre-treatment and storage capacities are investigated. Based on this, an economic evaluation following the annuity method is performed in order to calculate the respective electricity production costs. The results show that the thermal energy required for vapothermal pre-treatment can be obtained completely from the residual heat of the combined heat and power unit used in each case. Additionally, the specific electricity production costs can be reduced by a vapothermal pre-treatment up to 7 % related to the systems without pre-treatment. Furthermore, a comparison shows that vapothermal pre-treatment can compete with other pre-treatment methods such as steam explosion and hydrothermal pre-treatment for plants with higher installed electric capacity. In addition, it is shown that the considered cases can compete with the production of electricity using diesel as a fuel at a fuel equivalent price of 1.00 € [ABSTRACT FROM AUTHOR]

The inhibition effect of limonene on the organisms involved in anaerobic reactors may affect obtaining H2 in this process. Rapid and precise limonene quantification is desirable to characterize wastewaters. The objective of this research was to develop a Gas Chromatography Coupled to Mass Spectrometry (GC-MS) method to determine limonene concentration in liquid samples from batch reactors applied to H2 production at 30 ºC. Method validation was carried out through calibration curves (3 to 20 mg L-1of limonene), in addition to evaluating its precision (CV =0.1%), linearity (R2=0.979), limits of detection (1.7 mg L-1) and quantification (4.2 mg L-1). Its inhibitory effect was evaluated with increasing concentrations of limonene (without addition to 2000 mg L-1). Limonene affected the starting time of H2 production (λ), since λ was 8.7 h in control assays and 15 h with 2000 mg L-1 of limonene. The same was observed for obtaining H2, since 19.5 mmol H2 L-1 was obtained in control assays and 8.7 mmol H2 L-1 was obtained in assays with 2000 mg L-1 of limonene. This method was effective for limonene determination in liquid samples from batch reactors and could be used for characterization and control of anaerobic reactors.

The objective of this study was to determine the efficiency and theoretical stability of the anaerobic digestion of the wastewater sludge obtained from a municipal wastewater treatment plant, using co-digestion with cocoa pod husks. The chemical structure of sewage sludge, including its high carbon and nitrogen content in carbohydrates and fats, gives it vast potential for biomethane generation. In this study, the main agri-food residues in the geographical area where the study was conducted that could be used for co-digestion were determined, and cocoa pod husks were found to be the best option based on elemental chemical analysis. The results demonstrate that the co-digestion of sewage sludge with cocoa pod husks can produce up to 555.7 L CH_4/Kg SV. In this article, we also propose a method for estimating biochemical methane potential (theoretical BMP) based on chemical equations and a systematic review of the most relevant research in BMP.

Increasing requirements of wastewater treatments and the development of wastewater treatment and sewage sludge systems cause a significant increase in the demand for electricity and heat. An alternative way to obtain cheap energy is to use biogas produced in the anaerobic digestion process from sewage sludge. The paper presents an analysis of sewage sludge and biogas-energy management at the wastewater treatment plant in Opole in the aspect of obtaining biogas and its use for electricity production. The biogas-energy system was functioning properly in 2017-2019. A total of 7.26 GWh of electricity was produced from biogas in two power generators, which allowed to cover nearly 35% of the demand for electricity.

Abstract Background This study investigated the feasibility of enhancing anaerobic digestion of sewage sludge with triple, dual, and individual pretreatment of waste activated sludge with heat, alkalinity, and hydrogen peroxide. These pretreatments disrupt sludge flocs, organisms’ cell walls, extracellular polymeric substance, and intracellular organic matter, which increase biodegradability and hydrolysis rate of activate sludge. In addition, the influence of various variables on methane production was analyzed using the response surface methodology with the quadratic model. Eventually, an optimized temperature and chemical concentration for the highest methane production and lowest chemical usage is suggested. Results The highest amount of methane production was obtained from the sludge pretreated with triple pretreatment (heat (90 °C), alkaline (pH = 12), and hydrogen peroxide (30 mg H2O2/g TS)), which had better performance with 96% higher methane production than that of the control sample with temperature of 25 °C approximately and a pH = 8. Response surface methodology with a quadratic model was also used for analyzing the influence of temperature, pH, and hydrogen peroxide concentration on anaerobic digestion efficiency. It was revealed that the optimized temperature, pH, and hydrogen peroxide concentration for maximizing methane production and solubilization of sludge and minimizing thermal energy and chemical additives of the pretreatments are 83.2 °C, pH = 10.6 and 34.8 mg H2O2/g TS, respectively, has the desirability of 0.67. Conclusion This study reveals that triple pretreatment of waste activated sludge performed better than dual and individual pretreatment, respectively, in all desirable output parameters including increasing methane production as the most important output, increasing in COD solubilization, protein and polysaccharide, and decreasing in VSS solubilization.

Rising efficiency of wastewater purification systems causes an increase in the amounts of sewage sludge. Its land application is economically attractive because of low cost and high efficiency. Using sewage sludge in agriculture is one of the most preferred ways of its disposal. Only stabilized sludge and containing permissible concentrations of heavy metals can be used for this purpose. The heavy metals introduction into the environment may cause a potential problem for public health, especially when they percolate from soil to plants or groundwater. Therefore, the concentrations of heavy metals in sludge intended for agriculture are regulated. Determination of total content of heavy metals in digested sludge is not sufficient for the evaluation of a potential risk to the environment. The mobility and toxicity of heavy metals depend strongly on their specific chemical forms. The concentrations of particular heavy metal fractions are the most important parameters, which should be examined in order to estimate the influence of sludge on the environment. The aim of an article was to evaluate the influence of anaerobic digestion on the concentration and variability of chemical forms of selected heavy metals (Cr, Cu, Ni, Pb, Zn) in the sewage sludge coming from a municipal wastewater treatment plant in Pulawy (Poland). The content of particular forms of heavy metals in raw and digested sewage sludge was determined by means of the BCR (Community Bureau of Reference) method. The BCR method enables separating four fractions of heavy metals: exchangeable, reducible, oxidizable and residual. The results obtained after analyzing raw sludge showed that the majority of the analyzed heavy metals were predominantly associated with the oxidizable and residual fractions. Only in the case of Zn, the reducible form constituted a greater part. In the case of digested sludge, all studied heavy metals exhibited the most dominant oxidizable and residual fractions; however, the percentages of particular fractions were different than in raw sludge. It was noticed that all heavy metals concentrations were higher in digested sludge in comparison to sludge before anaerobic digestion. The content of heavy metals in the analyzed materials did not exceed the admissible Polish levels for the sludge intended for the agricultural use.

Appropriate management is necessary to mitigate the environmental impacts of wastewater sludge. One lesser-known technology concerns the use of solidified CO2 for dewatering, sanitization, and digestion improvement. Solidified CO2 is a normal byproduct of natural gas treatment processes and can also be produced by dedicated biogas upgrading technologies. The way solidified CO2 is sourced is fully in line with the principles of the circular economy and carbon dioxide mitigation. The aim of this review is to summarize the current state of knowledge on the production and application of solid CO2 in the pretreatment and management of sewage sludge. Using solidified CO2 for sludge conditioning causes effective lysis of microbial cells, which destroys activated sludge flocs, promotes biomass fragmentation, facilitates efficient dispersion of molecular associations, modifies cell morphology, and denatures macromolecules. Solidified CO2 can be used as an attractive tool to sanitize and dewater sludge and as a pretreatment technology to improve methane digestion and fermentative hydrogen production. Furthermore, it can also be incorporated into a closed CO2 cycle of biogas production–biogas upgrading–solidified CO2 production–sludge disintegration–digestion–biogas production. This feature not only bolsters the technology’s capacity to improve the performance and cost-effectiveness of digestion processes, but can also help reduce atmospheric CO2 emissions, a crucial advantage in terms of environment protection. This new approach to solidified CO2 generation and application largely counteracts previous limitations, which are mainly related to the low cost-effectiveness of the production process.

The present study evaluated different sludge-reduction mechanisms in the oxic-settling-anaerobic (OSA) process in terms of their effects on methane productivity by anaerobic digestion of sewage sludge. Two different layouts were investigated for the sludge return from an anaerobic side-stream reactor (ASSR) to the anoxic (scheme A) or the aerobic (scheme B) reactor of a pre-denitrification plant. Biochemical methane-potential (BMP) assays performed on the excess sludge revealed that scheme A promoted an overall increase of methane production in the OSA (20 mLCH4 gVSS−1d−1, +19%), although compared with a control CAS plant a significant decrease in the excess sludge production (31%) was obtained. Operating conditions in scheme A caused the occurrence of cell lysis and EPS hydrolysis, thereby increasing the biodegradability of sludge. In contrast, scheme B favoured the occurrence of uncoupling and a maintenance metabolism that did not involve sludge hydrolysis. Consequently, despite a higher reduction of excess sludge (82%), a significant decrease in methane productivity in the OSA (4 mLCH4 gVSS−1d−1, −41%) was observed. Based on the results, implementing the OSA process may allow high levels of methane production by anaerobic digestion to be maintained if specific sludge-reduction mechanisms are triggered in the waterline, also raising the possibility of co-digestion with other feedstocks.

Arıtma çamurlarının stabilizasyonunda kullanılan ve net enerji üretimi ile ön plana çıkan anaerobik çürütme proseslerinin modellenmesi konusunda literatürdeki mevcut çalışmalar proses ve model kompleksliği nedeniyle oldukça sınırlı sayıdadır. Güvenilir dinamik modellenme yaklaşımları; prosesin izlenmesi, proses dinamiğindeki temel mekanizmaların daha iyi anlaşılması ve tanımlaması ile proses davranışının tahmin edilmesine, kontrol algoritmalarının geliştirilmesine ve dizaynın kolaylıkla yapılmasına yönelik önemli bilgiler sunmaktadır. Bu çalışmada; arıtma çamurlarının anaerobik çürütülmesi ile stabilizasyonu ve anaerobik çürütme prosesinin modellenmesinde kullanılan basit substrat karakterizasyon modelleri, ara substrat karakterizasyon modelleri ve ileri düzey substrat karakterizasyon modelleri tanıtılmıştır. Son olarak, Anaerobik Çürütme Modeli (ADM1), ADM1 uygulamaları ve modifikasyonları ve arıtma çamurlarının ADM1 ile modellenmesi konusunda literatürde mevcut çalışmalar detaylı olarak incelenmiştir.

This study examined the effectiveness of thermophilic sewage sludge co-digestion of and milled/non-milled brewery spent grain. In order to evaluate both the biogas potential and the biogas production rate, the experiments were conducted in batch-mode. Five runs were carried out, one of them concerned the anaerobic sewage sludge digestion (as control), whereas the others referred to the co-digestion of sewage sludge with addition of milled and non-milled brewery spent grain at doses of 5 and 10 g. The runs were conducted under thermophilic conditions (temperature 55±1°C) and lasted for 21 days. The effectiveness of the process was assessed on the basis of the volatile solids removal, biogas potential and the rate of biogas production. The physiochemical composition of reactor feed and digestate were characterized. The addition of the brewery spent grain resulted in increase of the biogas potential, but a decrease in the removal of volatile solids. In the case of biogas production rate, the highest value was recorded in the run with the addition of 10 g of milled and non-milled brewery spent grain (0.69 Ndm3dm-3d-1). There was no observed influence of milling on the thermophilic co-digestion effectiveness since the parameters specified revealed comparable values.

Arıtma çamurlarının stabilizasyonunda kullanılan ve net enerji üretimi ile ön plana çıkan anaerobik çürütme proseslerinin modellenmesi konusunda literatürdeki mevcut çalışmalar proses ve model kompleksliği nedeniyle oldukça sınırlı sayıdadır. Güvenilir dinamik modellenme yaklaşımları; prosesin izlenmesi, proses dinamiğindeki temel mekanizmaların daha iyi anlaşılması ve tanımlaması ile proses davranışının tahmin edilmesine, kontrol algoritmalarının geliştirilmesine ve dizaynın kolaylıkla yapılmasına yönelik önemli bilgiler sunmaktadır. Bu çalışmada; arıtma çamurlarının anaerobik çürütülmesi ile stabilizasyonu ve anaerobik çürütme prosesinin modellenmesinde kullanılan basit substrat karakterizasyon modelleri, ara substrat karakterizasyon modelleri ve ileri düzey substrat karakterizasyon modelleri tanıtılmıştır. Son olarak, Anaerobik Çürütme Modeli (ADM1), ADM1 uygulamaları ve modifikasyonları ve arıtma çamurlarının ADM1 ile modellenmesi konusunda literatürde mevcut çalışmalar detaylı olarak incelenmiştir.

The effects of two total solids contents (TS) and two inocula were studied for the semi-continuous high-solids anaerobic digestion (HS-AD) of cassava pulp under mesophilic conditions (35 ± 2 °C). In the 1.0-L bioreactors, two TS of 15% and 20% with digestate as a sole inoculum were chosen to run the HS-AD, and two inocula (the digestate from the AD of cassava pulp and sewage sludge) were used separately under TS 20%. All treatments were carried out at the organic matter loading rates (OLRs) of from 3.0 to 10.0 kg volatile solids (VS)/(m³·d), with each phase of 6 days followed by two 3-days phases of no feeding and then low OLR of 6.5 kg VS/(m³·d). Compared with TS 15%, the bioreactors of TS 20% with the digestate had a higher buffering capability to alleviate the rapid acidification and a higher level of the specific methane yields (SMYs) of from 0.212 to 0.233 m³/(kgVSadded) at the OLRs of 4.0 to 6.5 kgVS/(m³·d), while TS 15% obtained the highest SMY of from 0.152 to 0.182 m³/(kgVSadded) at the OLR of 4.0, 6.5, and 8.0 kgVS/(m³·d). In contrast, sewage sludge did not restrain the rapid acidification and only yielded quite small SMYs under TS 20%. [ABSTRACT FROM AUTHOR]

Anaerobic digestion (AD) is a biological treatment process to stabilize organic solids and produce biogas. If present, sulfate is reduced to sulfide by anaerobic sulfate‐reducing bacteria and the sulfide can be toxic to anaerobic microorganisms. Here, the effect of high initial sulfate concentration on AD of wastewater sludge was investigated using lab‐scale batch experiments. Additionally, a systematic mathematical modeling approach was applied for insight into the experimental results. Cumulative biogas and methane production decreased with increasing initial sulfate doses (0–3.300 mg S L−1). The correlation between the sulfate dose and methane production was consistent with theoretical predictions and model results, indicating no toxic effect of sulfide on methane production. The carbon dioxide content in the biogas decreased linearly with the increasing sulfate dose, which is consistent with the model‐predicted behavior of the bicarbonate and hydrogen sulfide buffering system. The examined high sulfate concentrations resulted in no clear negative effects on the COD removal or VSS destruction of the wastewater sludge, indicating negligible inhibition by sulfide toxicity. Even considering the possibility of ferrous sulfide precipitation and the low model estimates of residual sulfide concentration the residual sulfide concentration was higher than reported concentrations that trigger process inhibition. Practitioner points: The effect of sulfate loading on anaerobic digestion of waste activated sludge was characterized.The stoichiometry of sulfate reduction allows accurate prediction of CH4 loss.High sulfate levels (up to 3300 mg/L as S) did not affect COD/VSS removal.Sulfide formation increases effluent COD; often misinterpreted as sulfide toxicity.Correcting COD for sulfide's contributions is crucial for results interpretation. [ABSTRACT FROM AUTHOR]

Excess sewage sludge in wastewater treatment plants (WWTPs) is regarded the key energy source for achieving energy neutral WWTPs. The anaerobic digestion process transforms sludge-organic matter into methane, which subsequently can be used for heat and electricity production. Conventional anaerobic digesters (ADs) have been used for sludge treatment for many decades, requiring high energy and providing poor effluent quality. Anaerobic membrane bioreactor (AnMBR) technology exhibits a promising option for treatment of high solids concentration streams including sludge. AnMBRs result in an increase in digestion efficiency and enhancement in effluent quality at small footprints. AnMBRs have the potential to reduce capital and operational costs, and produce more energy in comparison to conventional ADs. Thus, energy neutral or positive operation can be achieved with AnMBRs. Besides, nutrient recovery or direct use of permeate will become more feasible in AnMBRs compared to use of sludge supernatant in ADs. However, membrane fouling can limit the feasibility of AnMBRs for sludge treatment, which requires further research. This review paper critically evaluates the current status of AnMBR technology for municipal sludge treatment discussing the effect of different factors on treatment and membrane filtration performances. Furthermore, future research opportunities to enhance applicability of this technology are addressed. [ABSTRACT FROM AUTHOR]

Anaerobic digestion is among the essential biological techniques used for stabilization of organic sludge from sewage and highly concentrated effluents from food processing industries. It also recycles the municipal solid wastes into compost with simultaneous production of methane. The current study was performed to estimate the biomethanation potential of various agro- and industrial wastes like Jatropha de-oil cake, prawn shells, chicken feathers, bagasse, rice straw and wheat husk by mimicking the conditions in the biphasic Nisargruna biogas plant. A small volume of samples was chemically characterized and allowed to decompose under aerobic and anaerobic conditions to determine the effect of aerobic predigestion (i.e. phase 1 of Nisargruna plant) on final methane production. The biogas produced was quantified by downward displacement of water. The observations indicated that approximately 60-80% methane was produced when Jatropha de-oil cake, prawn shells and rice straw was used. Conversely, the wheat straw and sugarcane wastes showed less methane formation, which may be due to the presence of complex polymers like lignocellulose and silica that considerably reduces the metabolic potential of microorganisms. [ABSTRACT FROM AUTHOR]

The study was aimed at evaluating the influence of bioaugmentation on the limitation of the toxic impact of mature landfill leachate (MLL) in the co-digestion with sewage sludge (SS). The bioaugmenting mixture (BA) comprised wild-living microorganisms at the concentrations of 0.07 and 0.19 g kg-1VS. The study was conducted in semi-flow mesophilic digesters, using different SS:MLL:BA ratios of 90:5:5 and 87:4.3:8.7% v/v at related HRTs of 18.2 and 17.4 d, respectively. The control runs included the sole SS anaerobic digestion, and co-digestion of SS and MLL in a volumetric ratio of 95:5%. Using a sufficiently high BA dose and an adequate inoculum size, bioaugmentation improved the co-digestion efficiency. The methane yields were higher as compared to a non-bioaugmented co-digestion system, reaching 0.24 m³ kg-1VSadded and 0.17 m³ kg-1TSadded, and the difference was of statistical significance. The same tendency occurred regarding the VS removal. Bioaugmentation seemed to accelerate the metabolic transformations, which was confirmed by the enhanced values representing the rate constant of biogas production. Thus, a beneficial effect of overcoming the toxic impact of MLL on the efficiency of its co-digestion with SS was revealed using bioaugmentation. [ABSTRACT FROM AUTHOR]

The treatment of municipal wastewater is considered a cornerstone for the protection of public health and environment. However, a major issue derived from this process is the large quantities of produced sewage sludge. Although anaerobic digestion is a widely applied method in Wastewater Treatment Plants (WWTPs) aiming to stabilize the sludge and to recover energy in the form of methane, it is usually limited due to the reduced decomposition efficiency and slow biodegradation rate of this recalcitrant substrate. For this reason, various pretreatment methods have been proposed aiming to modify the sludge structure, solubilize the organic matter, and decrease the crystallinity of sludge so as to accelerate hydrolysis and consequently enhance methane production. The current research is a comprehensive collection of recent advances in pretreatment technologies that can be potentially applied in wastewater treatment facilities. The critical review analysis presented herein reveals the several advantages and drawbacks, as well as the technical opportunities of the pretreatment methods and provides an assessment of their feasibility/applicability from an energetic, environmental, and economic point of view.

Antibiotics are widely used in human and veterinary medicine, and they are accumulated in various types of waste, including sewage sludge (SS) and cattle slurry (CS), processed by anaerobic digestion (AD). Anaerobic treatment is a method enabling the stabilization of these substrates before transferring to the environment. The presence of contaminants, such as antimicrobials, in organic substrates processed by AD is not regulated by law. The accumulation of antimicrobials in SS and CS is a crucial issue because it may reduce the effectiveness of their stabilization. This study aimed to evaluate the long-term impact of growing concentrations of a mixture of antibiotics on the AD of SS and CS. Methane (CH4) yield, which is the main indicator of the efficiency of AD, was determined. Antibiotic exposure significantly decreased CH4 production only in SS (by 5–8% relative to control; p < 0.05). The copy numbers of the mcrA gene, a functional marker of methanogenesis, were not reliable indicators of CH4 yields in either substrate. During long-term AD, the average concentrations of the mcrA gene were determined at 108 in 1 g of SS digestate and from 108 to 109 in 1 g of CS digestate samples. At the end of long-term AD, methanogens belonging to the family Methanosarcinaceae were more prevalent than methanogens of the family Methanosaetaceae both in SS and CS samples (107 and 108–109 gene copies in 1 g of digestate, respectively).

The starting point for the research discussed in this study was the assumption that sewage sludge generated by wastewater treatment plants (WWTP) should be treated as a valuable raw material in the Circular Economy. Hence, the results of the research are part of the search for the best technological solutions aimed at achieving the maximum possible efficiency of sludge management in WWTP. The research was carried out on the example of a sewage treatment plant in Minsk (the capital of Belarus), where the dominant technology is still the storage of sewage sludge, and annually more than 5 million tons of sludge accumulates, which represents a significant hazard to the environment. The research takes into account the real economic, environmental, economic and social conditions in this country. As an alternative to the current technology, which is no longer recommended in EU countries, the effectiveness of three technological solutions was analyzed: (1) thermophilic digestion option with the production of biogas and subsequent combustion of the fermented sludge in the territory of treatment facilities, (2) high-temperature drying followed by the use of sludge in cement production and (3) production of fertilizers (soil-improving additives). A comparative analysis of these technologies was performed by the ranking method using weighting indicators (significance factors). The methodology takes into account technical, economic, environmental and social criteria. As a result of the evaluation, it was found that the most effective technology for the management of sewage sludge of the WWTP in Minsk is the technology of drying and then using the sludge as an alternative fuel in cement production. This technology provides, among others waste-free utilization of the entire volume of sewage sludge generated in Minsk, and also gives opportunities to create new jobs in the area of production of alternative fuel from sewage sludge. [ABSTRACT FROM AUTHOR]

The hyperthermophilic anaerobic bacterium, Caldicellulosiruptor bescii, is effective in degrading and solubilizing lignocellulosic materials. Laboratory studies have characterized the chemistry of the process for crystalline cellulose and switchgrass, but the data are insufficient for engineering commercial plants to use C. bescii for pre-digestion of waste streams. The purpose of this study is three-fold: 1) to identify any potential toxicities in C. bescii pre-digestion and biogas production from several wastes; 2) to determine the potential enhancement of biogas production by anaerobic digestion of pre-digested dairy manure and waste activated sludge; and 3) to identify variables that must be quantified and controlled for engineering commercial, continuous-flow systems for waste disposal and biogas production incorporating C. bescii pre-digestion. Tests were run at lab-, bench- and pilot plant-scale with C.bescii pre-digestion and controls run at 75°C and pH 7-8 followed by mesophilic anaerobic digestion at 37-41°C. The lab- and bench-scale tests demonstrate that C. bescii is capable of growing on several organic wastes and pre-digestion with C. bescii increases conversion of waste into biogas, typically by a factor of 2 or more. Incorporation of C. bescii pre-digestion in an optimized commercial system is predicted to provide 75-85% volatile solids conversion to biogas with 75% methane when digesting dairy manure and sewage sludge. Achieving these results at a commercial scale requires further work to quantify C. bescii growth and enzyme production rates, as well as rates of base- and enzyme-catalyzed hydrolysis of the polymeric materials, e.g., lignocellulose, in the waste in order to optimize retention times. [ABSTRACT FROM AUTHOR]

The effects of nanoparticles on performance and stability of anaerobic digestion of sewage sludge were investigated in four reactors. One reactor was fed with only sewage sludge(control reactor) while the remaining ones were fed with sewage sludge with the addition of the following additives:1) silver nanoparticles(NPs reactor); 2) ionic silver(AgNO3 reactor); 3) diluent used for nanoparticles(DIS reactor). The results indicated that: 1) the form of silver had significantly affected the methane yield as well as the share of hydrogen sulphide in the biogas, however this was not the case for VS removal; 2) the tested additives did not significantly affect methane content; 3) the addition of nanoparticles had a positive effect on the kinetic parameters of anaerobic digestion; for the aforementioned sample, the maximum rate of methane production was significantly higher in comparison to other trials executed in this experiment. Additionally, a shorter lag time phase was observed for the feed with the additive in the form of silver NPs; 4) control and Ag reactors harboured similar microbial diversities, in the reactors submitted to Ag-NPs or DIS microbial communities were very different from the other ones; in Ag-NPs reactor, with a 5-fold increase in the number of Methanosarcina genus compared to the control reactor. • Addition of silver into feedstock does not negatively impact on the process stability. • The nanoparticles affect in a significant reduction of hydrogen sulfide in biogas. • Silver nanoparticles addition significantly increase methane yield. • Nanoparticles has positive impact on kinetic parameter of anaerobic digestion process. [ABSTRACT FROM AUTHOR]

Treatment and recycling of organic waste play important roles in an integrated waste management system by producing a stabilized material that can be utilized as a source of nutrients and as a soil conditioner. In this study, the viability of composting for the recycling of sewage sludge and also the possible effects of pretreatment under various conditions on the quality of the end-product were examined. Waste sewage sludge was obtained from a wastewater treatment plant in Hamedan, Iran, and was subjected to aerobic and anaerobic digestions. After analyzing the physicochemical properties of the digest, both treated sludges were composted. A third reactor was also set as control by direct composting of sewage sludge without pretreatment. The composting process was controlled by the measurement of the physicochemical properties of the substrate during and at the end of the process. The results of the analyses showed a substantial decrease in the C/N ratio, pH, volatile solids (VSS), total organic carbon, as well as pathogenic populations; however, a significant increase was observed in the ash and nitrogen contents in the compost obtained after anaerobic digestion. Accordingly, it was decided that the compost obtained, especially after anaerobic digestion, showed adequate degrees of maturity and stability and reflected characteristics, which based on national and international standards made it suitable for agricultural use. [ABSTRACT FROM AUTHOR]

Anaerobic co-digestion (AcoD) of grease trap waste (GTW) and sewage sludge (SS) is an attractive management option for GTW valorisation and the transition to energy-neutral wastewater treatment plants (WWTPs). The main constraints that limit the direct use of GTW as a co-substrate in WWTP anaerobic digesters are the high content of non-disabled materials (floating plastics and fibres) and the low anaerobic biodegradability rates. This study assessed a single-step alkali and sieving pre-treatment of GTW at a low temperature (<25 °C) to improve the bioavailability of GTW and facilitate its use as a co-substrate. The experimental results showed that the alkaline pre-treatment of GTW at NaOH doses of 20–30 g NaOH ·kg VS −1 allowed the recovery of approximately 55–62 % of organic matter (on a volatile solids basis) present in the GTW in the form of saponified fat and generated a small waste reject fraction. Full-scale anaerobic AcoD assays (SS and pre-treated GTW) did not show inhibitory or operational problems under the experimental conditions and tested concentrations. Finally, a preliminary economic assessment for a 160 000 population equivalent WWTP in a European scenario presented a payback period of 1.75 y. [ABSTRACT FROM AUTHOR]

The increasing demand for a Thermal Hydrolysis Process (THP) to pretreat municipal sludge upstream Anaerobic Digestion (AD) opens the opportunity to further develop and optimise this technology. The optimal THP temperature remains unclear due to the production of refractory compounds at high temperature. A compilation of literature data was conducted to investigate the existence of a temperature sweet spot for the THP applied to municipal sludge. All related reports (n = 43) were included. The THP temperature range impact was assessed in the range of 100 °C–200 °C on four AD and dewatering performance indicators (CH4 production, Volatile Solid Reduction (VSR), Dewaterability (DW) and filtrate quality). Other parameters potentially affecting the performance indicators were also considered. These parameters include the type of sewage sludge and operational conditions related to THP and AD. The impact of all parameters on performance indicators was evaluated with a Kruskal–Wallis statistical test. For THP temperature optimisation, a pairwise comparison, using a Wilcoxon test, was made. A temperature optimum in the [140–160] °C range was proposed. It seemed to minimize the production of refractory compounds, while maximising AD and dewatering performances. It is noteworthy that above 160 °C, the concentration in refractory compounds and soluble COD increases sharply, thus leading to a potential deterioration of WWTP effluent quality. Optimal THP temperature range for an optimal outcome on both sludge and wastewater treatment lines. [ABSTRACT FROM AUTHOR]

Biosolids, derived from wastewater treatment processes, have garnered increasing attention as a valuable resource due to their rich organic and inorganic constituents, which can be beneficially utilized in multiple sectors, including agriculture, civil engineering, and energy recovery. The present review article begins by providing an overview of biosolids, including their production methods and classification based on treatment processes. Subsequently, the chemical composition of biosolids is explored, highlighting the diverse array of organic and inorganic components present. The characterization techniques employed for analyzing biosolids, such as spectroscopy, chromatography, and microscopy, are thoroughly discussed, emphasizing their role in determining the quality and suitability of biosolids for different applications. Furthermore, the environmental impacts associated with biosolids disposal are extensively examined. This includes the potential risks posed by heavy metals, pathogens, and emerging contaminants, as well as strategies for mitigating these risks through proper treatment and management practices. In addition to environmental considerations, the article explores the various products that can be derived from biosolids. These include organic matter-rich soil amendments for agricultural applications, inorganic nutrient supplements for enhancing plant growth, and the potential for energy recovery through anaerobic digestion and thermal conversion technologies. The utilization of biosolids in civil engineering projects, such as landfill capping and construction materials, is promising. Land application of biosolids also can have economic and waste management benefits (e.g., conservation of landfill space; reduced demand on non-renewable resources like phosphorus; and a reduced demand for synthetic fertilizers). [Display omitted] • The utilization of biosolids and their environmental impacts and disposal was reviewed. • The nutrient content of biosolids provides insight into their agronomic utility. • Methane and biogas production is an emerging technique for recovering energy from biosolids. • The conversion of biosolids into useful materials is significant. [ABSTRACT FROM AUTHOR]

The biogas produced in a centralized digestion plant treating high-solid sewage sludge under thermophilic conditions was biologically desulfurized via in-situ headspace micro-oxygenation. The removal of hydrogen sulfide (H 2 S) from the produced biogas was evaluated for 84 days under decreasing injection flows of oxygen (O 2), resulting in O 2 doses from 0.96(±0.03) to 0.19(±0.01) NL/Nm3 biogas. A stable H 2 S removal efficiency of 98.2(±1.3)% was obtained with an O 2 dose of 0.96(±0.03) NL/Nm3 biogas, whereas removal efficiencies of 67.4(±0.7)% were observed at the lowest O 2 dose tested. The response time of the biological desulfurization system to transient oxygen conditions was evaluated through intermittent O 2 injection. Headspace micro-oxygenation did not negatively impact the digestion performance, and the optimization of O 2 dose allowed to reach a biogas quality complying with the specification for biomethane in terms of both O 2 and H 2 S contents. Lentimicrobiaceae, Caldicoprobacteraceae, DTU014, Syntrophomonadaceae, and Rhodobacteraceae were the main microbial families responsible for biological H 2 S oxidation in digester headspace. [Display omitted] • Stable H 2 S removal of 98% was obtained with an O 2 dose of 0.96(±0.03) NL/Nm3 biogas. • Biological desulfurization response time to transient O 2 flows occurred in 10 h. • Oxygen is recommended instead of air if biogas upgrading to biomethane is targeted. • Micro-oxygenation did not disrupt the anaerobic digestion of sewage sludge. • Sulfide-oxidizing bacteria were identified on digestate surface and internal walls. [ABSTRACT FROM AUTHOR]

• Dead sludge biomass skewed DNA-based functional predictions for anaerobic digestion. • PMA-seq is a promising approach for assessing the active biomass of anaerobic sludge. • Potential predictive value of dead-biomass DNA for process-relevant metabolites. • Two universal primer candidates for amplicon sequencing of anaerobic sludge. DNA-based monitoring of microbial communities that are responsible for the performance of anaerobic digestion of sewage wastes has the potential to improve resource recoveries for wastewater treatment facilities. By treating sludge with propidium monoazide (PMA) prior to amplicon sequencing, this study explored how the presence of DNA from dead microbial biomass carried over with feed sludge may mislead process-relevant biomarkers, and whether primer choice impacts such assessments. Four common primers were selected for amplicon preparation, also to determine if universal primers have sufficient taxonomic or functional coverage for monitoring ecological performance; or whether two domain-specific primers for Bacteria and Archaea are necessary. Anaerobic sludges of three municipal continuously stirred-tank reactors in Victoria, Australia, were sampled at one time-point. A total of 240 amplicon libraries were sequenced on a Miseq using two universal and two domain-specific primer pairs. Untargeted metabolomics was chosen to complement biological interpretation of amplicon gene-based functional predictions. Diversity, taxonomy, phylogeny and functional potentials were systematically assessed using PICRUSt2, which can predict community wide pathway abundance. The two chosen universal primers provided similar diversity profiles of abundant Bacteria and Archaea, compared to the domain-specific primers. About 16 % of all detected prokaryotic genera covering 30 % of total abundances and 6 % of PICRUSt2-estimated pathway abundances were affected by PMA. This showed that dead biomass in the anaerobic digesters impacted DNA-based assessments, with implications for predicting active processes, such as methanogenesis, denitrification or the identification of organisms associated with biological foams. Hence, instead of running two sequencing runs with two different domain-specific primers, we propose conducting PMA-seq with universal primer pairs for routine performance monitoring. However, dead sludge biomass may have some predictive value. In principal component analysis the compositional variation of 239 sludge metabolites resembled that of 'dead-plus-alive' biomass, suggesting that dead organisms contributed to the potentially process-relevant sludge metabolome. [Display omitted] [ABSTRACT FROM AUTHOR]

• State-of-art on anaerobic digestion for treatment of olive-oil industries residues. • EU policies set the goal to supply at least 32% of energy demand by renewable in 2030. • The goal is also to reduce net greenhouse gas emissions by at least 55%. • It is expected at least 25% bioenergy shall be obtained from anaerobic co-digestion. • Biogas is also expected to help reduce the cost of imports of natural gas. European Union policies focused on the acceleration of renewable energy systems take-up have recently set forward the minimum binding goal of contributing to the supply of at least 32% of the European energy demand in 2030, and by the hand reaching the task of reducing net greenhouse gas emissions by minimum 55%. Moreover, it is expected that at least 25% of the whole bioenergy shall be obtained from anaerobic digestion/co-digestion (AD/AcoD) of organic matter, comprising agro-food wastes, whole crop silages, and sewage sludge, among others. Within this review study, key state-of-the art of anaerobic digestion processes for the treatment of both liquid and solid residues of olive-oil industries, OMW and OMSW, with a focus on energy recovery and digestate valorization is reviewed and discussed, with a focus on proposed and most effective co-digestion co-substrates, bioreactor configurations and conditions (temperature, hydraulic retention time, organic loading rate), adopted sequences (comprising pretreatments, acidogenesis and methanogenesis stages), biogas upgrading (H 2 S purification, CO 2 removal) and success case. Energy experts highlight compressed biogas as the best positioned candidate to become the fuel of the future, as a result of its virtue of being a clean, renewable and indigenous source of energy. Moreover, biogas is also expected to help reduce the cost of imports of natural gas. In the current scenario, in which worldwide new Circular Economy adoption is pursued, modernization and up-grading of industry, in particular the agri-food sector, is a very relevant and necessary challenge. [ABSTRACT FROM AUTHOR]

The presence of micro/nanoplastics (MPs/NPs) in sewage sludge has sparked considerable apprehensions over their potential negative effects on anaerobic digestion (AD) performance. The occurrence of MPs/NPs can trigger oxidative stress on the anaerobic microbiome, leading to potential inhibition of the AD process. While the thermal hydrolysis process (THP) is an extensively utilized sludge pretreatment method for AD, its impact on stress induced by MPs/NPs during AD remains poorly understood. In this study, we assessed the impacts of low-temperature THP (90 °C, 90 min) on AD of sewage sludge in the presence of 150 μg/L of polystyrene nanoplastics (PsNPs) under different solid retention times (SRTs) of 20, 15, and 10 d. The presence of PsNPs resulted in a higher reactive oxygen species (ROS) production and a higher abundance of antibiotic resistance genes (ARGs). Additionally, their presence caused a significant inhibition of methane production by 28.2%, 29.3%, and 38.8% for SRTs of 20, 15, and 10 d, respectively. Introducing low-temperature THP prior to the AD could partially recover methane production by mitigating ROS-induced stress and curbing the propagation of ARGs during the AD process. These results shed light on the potential benefits of THP and further optimization opportunities in alleviating the adverse effects of MPs/NPs-induced stress during sewage sludge AD. [Display omitted] • PsNPs (150 μg/L) hindered methane production in AD under three different SRTs. • Low-temperature THP as a pre-treatment could partially recover methane production. • PsNPs caused a 41.3% increase in ROS levels under 10 d SRT. • Although PsNPs boosted ARGs propagation, THP showed an opposite pattern. • PsNPs and THP increased the abundance of hydrogenotrophic Methanobacterium. [ABSTRACT FROM AUTHOR]

Domestic organic waste resources have increased over the past decade and treatment of this waste via co-digested biogasification facilities is increasing annually. However, inspection standards for such facilities are not well-established. Herein, we aimed to derive calculation formulas and factors related to organic matter decomposition efficiency and methane production rate in accordance with waste treatment facility inspection standards. We also aimed to determine the optimum waste mixing ratio. Sample (field) surveys of 18 treatment facilities and complete enumeration of 110 facilities were conducted. Calculation formulas and factors were derived using the survey data and biochemical methane potential (BMP) test. The calculated coefficients derived through the BMP test were 0.512 m3 CH 4 /kgVS in for food waste, 0.601 m3 CH 4 /kgVS in for livestock manure, and 0.382 m3 CH 4 /kgVS in for sewage sludge. The final derived calculation factors were 65.0% for food waste, 36.0% for livestock manure, and 20.0% for sewage sludge for organic matter decomposition efficiency, and 0.380 m3 CH 4 /kgVS in for food waste, 0.27 m3 CH 4 /kgVS in for livestock manure, and 0.140 m3 CH 4 /kgVS in for sewage sludge for methane production rates. The derived effective capacity calculation factors can be utilized in future waste treatment facility inspection methods by aiding in the establishment of appropriate inspection standards for co-digested biogasification facilities other than single food waste treatment facilities. In addition, the optimum mixing ratio can be used as design data for co-digested biogasification facilities. • An inspection standard for organic waste co-digestion facilities was determined • Highest methane production food waste: livestock manure: sewage sludge ratio is 0.402:0.592:0.006 • Decomposition and methane production rates used to assess suitability of facility [ABSTRACT FROM AUTHOR]

As the typical quarternary ammonium compounds (QACs), benzalammonium bromide (BK) are frequently detected in sewage sludge. This study explored the responses of methane production from digestion sludge at present different BK addition. Experimental results indicated that BK stress seriously inhibited the methane production at the pre-anaerobic digestion stage, but the final cumulative methane production (∼ 1124.0 ± 40.2 mL/g VSS) was similar in these digesters. While BK obviously promoted the release and transformation of organic substances, but severely inhibited the rate of methane production. In addition, the relative abundances of hydrogenotrophic methanogens were significantly decreased from 69.38% to 38.57%, but the acetotrophic methanogens enhanced from 26.75% to 58.86% with BK exposure from 0 to 8.69 mg/g VSS. Correspondingly, BK addition could impact the key functional genes involved in the major methanogenic metabolic pathways and energy metabolism. This work shed light on the effect of BK on methane production under anaerobic sludge digestion system, and provide useful information to understand the relevant mechanism. [Display omitted] • Benzalammonium bromide stress significantly inhibited 17.2% methane production efficiency. • 8.69 mg BK/ kg VSS significantly enhanced 1.5 times soluble COD release than in the control. • Higher level of benzalammonium bromide reduced the H 2 -dependant methanogens. • Acetoclastic methanogenesis had an advantage over other methanogenesis with BK exposure. [ABSTRACT FROM AUTHOR]

• HTL aqueous from mixed sludge cake at ≤ 340 °C was readily biodegradable aerobically. • HTL aqueous was 50 % and 32 % biodegradable under mesophilic and thermophilic AD. • HTL aqueous obtained at 360 °C was highly inhibitory for mesophilic/thermophilic AD. • HTL aqueous from mixed sludge cake was found unsuitable for dark fermentation. • HTL aqueous aerobic treatment and mesophilic AD were identified as feasible options. Aerobic treatment, mesophilic anaerobic digestion, thermophilic anaerobic digestion, and dark fermentation were evaluated for on-site biological treatment of municipal sludge derived HTL aqueous. For all four described batch test scenarios, municipal sludge-derived HTL aqueous samples obtained under 290–360 °C and 0–30 min retention time were used. In the aerobic respirometric tests, HTL aqueous samples resulted in a five-day biochemical oxygen demand range of 40.75 g/L (350 °C-25.6 min) to 54 g/L (325 °C-0 min). The calculated aerobic biodegradability index showed that approximately 50 % of the organics in HTL aqueous were easily biodegradable. Mesophilic and thermophilic biochemical methane potential tests resulted in specific yields of 151–179 mL CH 4 /g chemical oxygen demand (COD) and 103–122 mL CH 4 /g COD, respectively. HTL aqueous obtained under 360 °C-15 min condition caused total inhibition in both mesophilic and thermophilic anaerobic digestion. Possible causes for this inhibition were pyridine, pyrrolidinone, piperidinone, pyridinol, and phenolic compounds, which were higher in abundance in the 360 °C-15 min sample. HTL aqueous was found unfit for hydrogen production in dark fermentation due to inhibitory composition. In summary, on-site biological treatment of HTL aqueous was found to be most suitable under aerobic and mesophilic anaerobic conditions. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Fermentation pH needs optimization based on specific inorganic P species. • Pre-treating sludge improves P release but its cost needs assessment. • Organic chelators boost metal-bound P release, but optimal dosage is essential. • Studies on effective P enrichment, release, recovery and utilization are required. Phosphorus recovery and recycling from waste streams is of great significance to achieve a sustainable phosphorus management. Daily discharged sewage contained a considerable content of phosphorus, which offers a promising phosphorus source for its recovery. Biological phosphorus removal technology is the most widely employed process for treating sewage and how to effectively extract and capture phosphorus from excess sludge becomes essential. In this review, the state-of-art progress on enhancing phosphorus release from sewage sludge via anaerobic digestion are systematically summarized and discussed. First, phosphorus species transformation during sewage treatment process and the corresponding extraction and analytical methods were summarized. Also, the different pretreatments methods and their economic costs for applying to sludge treatment was analyzed. Then, phosphorus release pathways and mechanisms from sludge under anaerobic conditions were summarized and the influence of key operation parameters on phosphorus release performance was discussed. Moreover, the current practices and achievements on enhancing phosphorus release via sludge anaerobic digestion were reviewed. Finally, the challenges associated with improving the phosphorus release efficiency from sludge and problems related to the current methods are analyzed, and major directions for future research are proposed. This review may provide valuable information for advancing the research and engineering application of phosphorus capture and recovery technology. [ABSTRACT FROM AUTHOR]

Polybrominated diphenyl ethers (PBDE) are priority contaminants historically used as flame retardants. PBDEs are known to occur in wastewater biosolids posing potential concerns with the beneficial land application of the biosolids. This study evaluated the removal of 21 congeners in nine full-scale sludge treatment systems including pelletization (P), alkaline stabilization (AS), and aerobic (AE) and anaerobic (AN) digestion. It is the first study to conduct a mass balance analysis of a broad spectrum of PBDEs during physical, chemical, and biological sludge treatment. The PBDE congener pattern in raw sludge and biosolids samples was consistent with commercial formulations. The fully brominated congener BDE-209 dominated biosolids from all sites with an average concentration of 620 ng/g dry weight (dw), followed by BDE-99 (173 ng/g dw) and BDE-47 (162 ng/g dw). Mass balance analysis on the P and AS processes showed no change in PBDE mass flows with treatment. However, aerobic and anaerobic digestion processes reported significant levels of removal and formation of individual congeners, though the results were not consistent between facilities. One aerobic digestion process (AE2) reported an overall average removal of 48%, whereas the other (AE1) reported very high levels of accumulation of tri- and tetraBDE congeners. Similarly, there were significant variations in PBDE behavior across the five anaerobic digestion plants studied. The plant with the longest solids retention time (SRT) (AN1) reported a moderate removal (50%) of overall PBDE loading and lower congeners, whereas other plants (AN2-AN5) showed significant low (−19%) to high (−166%) levels of formation of lower congeners. The results suggest that reduced SRTs result in formation of lower congeners while extended SRTs can lead to moderate removal of some PBDEs. Conventional sludge treatment result in low to moderate PBDE removal and advanced thermal conversion technologies may be needed to improve the contaminant removal during sludge treatment. [Display omitted] • Alkaline stabilization and pelletization processes did not change PBDE mass flows significantly. • Aerobic and anaerobic digestion result in PBDE removal and accumulation of lower congeners. • Operational SRT could impact PBDE removal in anaerobic digestion processes. • Conventional sludge treatment technologies result in only low to moderate PBDE removal. [ABSTRACT FROM AUTHOR]

• Effects of different recycled magnetic additives on the AD was investigated. • Methane production increased by 79.81% with addition of recycled Fe 3 O 4. • The predominant aceticlastic pathway was consolidated with recycled Fe 3 O 4. • Recycled Fe 3 O 4 enriched more Methanosarcina that broadened the methanogenic pathway. The addition of magnetic additives has been found to enhance the anaerobic co-digestion of sludge and straw. Due to strong magnetic properties, these additives can be easily separated from the digestate, allowing for recycling during the continuous anaerobic digestion process. This study aimed to investigate the impact of different recycled magnetic additives (specifically, magnetic biochar and Fe 3 O 4) on the anaerobic co-digestion of sewage sludge with corn straw. The results showed that the addition of recycled Fe 3 O 4 with an initial amount of 10 g/kg resulted in the highest cumulative methane yield of 295.70 mL/g VS added , which increased by 79.81% as compared to the control. The results suggest that magnetic biochar with higher carbon content exerts a more noticeable impact on shortening the digestion lag phase time, as indicated by kinetic analysis. With the addition of recycled Fe 3 O 4 , the Methanosaeta and Methanosarcina enhanced significantly. Especially Methanosarcina , which was increased from 3.85% to 6.28%, resulting in a 2.43% increase. Furthermore, the predominant aceticlastic pathway of digestion process was consolidated, and the enriched Methanosarcina broadened the pathways of methanogenesis. This research provides a potential utilization strategy of recycling Fe 3 O 4 for accelerating the anaerobic degradation of urban and rural areas solid waste. [ABSTRACT FROM AUTHOR]

[Display omitted] • Comparison of three digestion scenarios using plant-wide modeling and LCA. • Mono-digestion of WAS showed the least desirable environmental outcomes. • WAS-FOG/FW co-digestions have consistent results but for freshwater eutrophication. • WAS-FOG co-digestion stands out due to substantial energy content of the sludge. • WAS-FW co-digestion has lower scores due to the prevention of FW landfilling. Anaerobic co-digestion of fat-oil-grease (FOG) and food waste (FW) with sewage sludge (SS) in wastewater treatment plants is a method used to increase biogas production. In this study, digestion scenarios were compared using plant-wide modeling and life cycle assessment: Scenario-0 (mono-digestion of waste-activated sludge (WAS)), Scenario-1 (co-digestion of WAS with FOG), and Scenario-2 (co-digestion of WAS with FW). Scenario-0, with the highest energy use and landfilling of FOG/FW, has the worst environmental impact. Scenario-1 and Scenario-2 minimize the environmental load by energy recovery and avoiding landfilling of organic waste. Scenario-wise, the change in greenhouse gas (GHG) emissions from treatment was negligible. However, due to the impact of landfilling, GHG emissions in Scenario-0 were 21% and 30% higher than in Scenario-1 and 2, respectively. The environmental benefit of anaerobic co-digestion of FOG/FW with SS is not only in the contribution to energy production but also in the recycling of organic waste. [ABSTRACT FROM AUTHOR]

This paper presents the energy potential of biogas obtained from the anaerobic digestion (AD) of sewage sludge (SS) preceded by thermal hydrolysis (THP) using Cambi THP® technology. The presented data are for the Tarnów (Poland) wastewater treatment plant for the year 2020. A detailed energy balance of biogas and its use in the cogeneration process and in the production of heat in the water boiler and the steam boiler is presented. The article contains data on the amount of processed SS and the content of dry matter and dry organic matter at different stages of the technological process. The annual plant operation resulted in the production of 3,276,497 Nm3 of biogas as a result of processing 8684 tonnes of dry solids (tDS) of municipal SS from the Tarnów wastewater treatment plant (WWTP) and regional WWTPs. The energy potential of the produced biogas was 75,347.06 GJ. The average calorific value of biogas was 23,021 kJ/Nm3.. The obtained biogas production allowed us to cover the thermal energy demand of the THP 100%. The annual average specific biogas conversion rate during the study period was 0.761 Nm3/kg of dry organic matter reduced and the average organic matter content reduction in the sludge was 64.60%.

Conventional anaerobic digestion is currently challenged by limited degradability and low methane production. Herein, it is proposed that magnetic nanoparticles (Fe3O4-NPs) and bioelectrochemical systems can be employed for the improvement of organic content degradation. In this study, the effect of electrode configuration was examined through the application of a bioelectrochemical system and Fe3O4-NPs in anaerobic digestion (AD). A microbial electrolysis cell with cylindrical electrodes (MECC) and a microbial electrolysis cell (MEC) with rectangular electrodes were compared against the traditional AD process. Biochemical methane potential (BMP) tests were carried out using digesters with a working volume of 800 mL charged with 300 mL inoculum, 500 mL substrate, and 1 g Fe3O4-NPs. The electrodes (zinc and copper) of both digesters were inserted inside the BMPs and were powered with 0.4 V for 30 days at 40 °C. The MECC performed better, improving degradability, with enhanced methane percentage (by 49% > 39.1% of the control), and reduced water pollutants (chemical-oxygen demand, total organic carbon, total suspended solids, turbidity, and color) by more than 88.6%. The maximum current density was 33.3 mA/m2, and the coulombic efficiency was 54.4%. The MECC showed a remarkable potential to maximize methane enhancement and pollution removal by adjusting the electrode configuration.

As the amount of sewage sludge (SS) is increasing worldwide, anaerobic digesters (ADP) are being distributed to reduce it and treat it in an environmentally friendly way. In Korea, 20 years have passed since the introduction of ADP, but the number of sewage treatment plants (STP) installed with ADP is only about 10% of the total STP. Accordingly, problems and improvements were examined through material flow analysis targeting STP, and the effect of introducing anaerobic digestion (AD) was analyzed as a way to solve them. As a result of the analysis, the amount of SS generated by the STP (SS-ADP + Co-ADP) installed and operated by an AD was 0.54 kg/m3, and the facility without it was 0.77 kg/m3, showing a reduction effect of about 31%. The SS reduction effect of the facility that only used SS-AD was found to be reduced by 21–24% TOE (Ton Of Equivalent))/day, which has the effect of reducing 794,867 kg-CO2/day of greenhouse gas. In terms of energy efficiency, Co-AD was 86% higher than SS-AD, and biogas production yield was 90% higher than that of SS-AD. Therefore, it is necessary to introduce Co-AD into STP in terms of reducing SS, energy production, and greenhouse gas reduction.

The management and disposal of sewage sludge is becoming a growing concern at the global level. In the past, the main goal was to completely eliminate sewage sludge since it was deemed a threat to humans and the environment, but recently different possibilities for energy generation and material recovery are emerging. Existing technologies such as incineration or direct application in agriculture contribute to quantity reduction and nutrient recovery but are unable to fully exploit the potential of sewage sludge within the frameworks of circular economy and bioeconomy. This paper developed a model within the PROMETHEE method, which analyses technologies for the sustainable management of sewage sludge, which could make the most from it. For the empirical part of the study, the Republic of Croatia was used as a country in which sewage sludge is increasing in quantity as a result of recent upgrades and expansions in the wastewater system. Incineration, gasification, anaerobic digestion, and nutrient recovery were analyzed as treatment concepts for the increased amounts of sewage sludge. The model reveals that the best solution is the material recovery of sewage sludge, using the struvite production pathway through analysis of selected criteria.

• 71 OCs mass balances were performed in full-scale sludge treatment facilities. • Screw decanter was selected as reference as its action is only physical. • Several OCs mass balances are frequently not correct in screw decanter. • The frequency of correct mass balances is significantly correlated to logKow. • Removal of the 71 OCs are reported in full-scale sludge digestion process. This paper analyzes the fate of 71 priority and emerging organic contaminants all along the treatment trains of sewage sludge treatment facilities in Paris including dewatering by centrifugation, thermal drying and anaerobic digestion. It aimed at proposing and applying a mass balances calculation methodology to each process and pollutant. This data validation strategy demonstrated the complexity to perform representative inlet/outlet sampling and analysis campaigns at industrial scales regarding organic compounds and to propose options to overcome this issue. Centrifugation and drying processes only implied physical mechanisms as phase separation and water elimination. Hence, correct mass balance were expected observed for organic contaminants if sampling and analysis campaigns were representative. This was the case for hydrophobic and neutral compounds. For the other more hydrophilic and charged compounds, the mass balances were scarcely correct. Thus, the conventional sampling and analytical practices used with sludge should be questioned and adapted to better take into account the high heterogeneity of sludge and the evolution of matrix effect within sludge treatment processes on micropollutant determination. For the biological anaerobic digestion process where degradations can occur and removals can be observed, the mass balances were deeply interpreted for 60 contaminants. This process contributed to the elimination above 70% of 21 detected compounds including 16 pharmaceuticals, 2 phthalates, 2 hormones and 1 perfluorinated compound. Removals of domperidone, propranolol, escitalopram, lidocaine, verapamil and cefoperazone under this condition were reported for the first time. [ABSTRACT FROM AUTHOR]

Anaerobic Digestion is the most common process used for energy generation from sewage sludge but only one half of the sewage sludge is susceptible to biodegradation. Hydrothermal Carbonization is considered an option for harness all the energy embedded in sewage sludge because of its high-value products (Hydrochar and Process waters). The integration AD followed by HTC is a recent approach that is still under development. The challenge is to provide evidence for coupling HTC with the existing infrastructure at wastewater treatment works. In this work, a mass and energy integration study of the potential of coupling HTC with AD for sewage sludge treatment was evaluated. Six proposed process configurations were built using primary sludge, secondary sludge and a mix, in order to evaluate net waste generation, fate of nutrients, net energy production and potential economic benefits. The proposed scenarios showed an overall total solid and COD reduction up to 68 and 66% respectively. The inclusion of hydrochar as a fuel source increased the net energy production 10 times compared when only biogas is considered as an energy source. The potential struvite production ranged from 0.02 to 0.06 kg per tonne of sludge treated. Scenarios with 250 °C thermal treatment temperature provided better economic benefits when struvite and hydrochar are considered. Image 1 • Mass and Energy balance of the HTC-AD integration are presented. • Six HTC-AD scenarios with different process temperature and sewage sludge were evaluated. • Scenarios assessed with 250 °C process temperature showed higher energy and economic benefits. • Scenarios with MIX sludge stream showed to be the most suitable option for HTC-AD integration. [ABSTRACT FROM AUTHOR]

[Display omitted] • Sewage sludge is used as infeed for anaerobic digestion in a full-scale plant. • The plant produces a soil improver (digestate) and a fertilizer (ammonium sulphate). • Ammonium sulphate has high ammonium concentration, i.e. 74 ± 2 g kg−1 wet weight. • The digestate produced has both high carbon content and biological stability. • Digestate and ammonium sulphate present low pollutant and pathogen contents. This work reports a full-scale study in which organic wastes were transformed by high-solid thermophilic anaerobic digestion (HSAD), into N fertilizers and organic fertilizers, i.e. digestate. The produced fertilizers were characterized over 42 months and their properties were discussed in comparisons with literature data. HSAD coupled with N stripping technology led to ammonia sulphate production having high N concentration (74 ± 2 g kg−1 wet weight), neutral pH (6.8 ± 1.3) and low traces of other elements. Digestate showed both higher carbon (C) content (314 ± 30 g kg−1 on dry matter (DM) and biological stability than green composts, indicating good amendment properties. Digestate was also interesting for its N (77 ± 3.7 g kg−1 dry matter – DM) content, half of it in the ammonia form, and P content (28 ± 4.1 g kg−1 DM) that was 43% readily available as soluble P-orthophosphate. K content was low (6.5 ± 1.3 g kg−1 DM), indicating poor fertilizing ability of digestate for this element. All organic pollutants investigated were much lower than the limits required for agricultural use and levels of some of them were lower than the content revealed for other organic matrices such as agricultural and energy crop digestates and compost. Emerging pollutants (i.e., pharmaceuticals) were tested as markers and they were found to be below the detection limit (<0.01 mg kg−1 DM) indicating very low content. The results obtained showed that HSAD coupled with N stripping allowed transforming sewage sludge into fertilizers and soil improvers exploitable in agriculture. [ABSTRACT FROM AUTHOR]