•Accumulation of volatile fatty acids because of pH value.•Sugar beet pulp lixiviation (SBPL) improves cumulative net methane generation with initial pH control.•Different SS/SBPL ratios have been ...tested in biochemical methane potential tests.•Initial pH in batch test affects the biodegradability of anaerobic co-digestion.•A pH out of range for methanogenic microorganism, inhibits their growth.
In this study, biochemical methane potential (BMP) tests were conducted to investigate the effect of pH control on the co-digestion of sewage sludge (SS) and sugar beet pulp lixiviation (SBPL) at mesophilic range (35°C). Microbial concentrations (Eubacteria and methanogenic Archaea) are linked to traditional parameters, biogas production and total volatile solids (TVS) removal. Also, the relationship between Eubacteria and Archaea has been analysed. Organic matter being equal, higher net methane generation was reported for the assay with pH adjustment at the beginning of the biochemical methane potential (BMP) test. This showed that there was inhibition of methane generation as measured by the BMP test in the absence of pH adjustment. Evidence of this inhibition was also supported by the methane yield and TVS removal data. Microbial populations in the reactor at the end of both assays were composed of Eubacteria and Archaea, with a higher proportion of Eubacteria in all cases. It is noteworthy that in test 1, when inhibition occurred due to a system pH that was not optimal for the activity of methanogenic Archaea, the analysis showed the largest number of Archaea present. In terms of productivity, it can be said that methanogenic Archaea were inactive.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
High-rate activated sludge (HRAS) is wastewater treatment focusing on reducing greenhouse gas emissions via energy recovery from sludge. However, the effect of hydraulic retention time (HRT) on HRAS ...performance and redirection pathways has seldom been investigated. Also, the fractionation of extracellular polymeric substance (EPS) as loosely-bound (LB) and tightly-bound (TB) in HRAS sludge have not reported yet. This study aimed to comprehensively investigate the carbon redirection pathways and biogas recovery potential of the HRAS system, examining the separate effects of HRT and SRT. An HRT of 1.5 h and an SRT of 2 d, HRAS achieved the highest COD recovery, with 64.8 % removed and 60.5 % redirected as waste activated sludge (WAS) as the pseudo-steady average values. And WAS exhibited notably high LB-EPS, reaching 366.2 mg/g volatile suspended solids (VSS). Furthermore, the metabolism pathway for redirection resulted in biosorption 54.9 %, LB-EPS 34.0 %, TB-EPS 7.2 %, and cell growth 3.9 % based VSS. The biochemical methane potential of WAS was measured at 234.0 mL CH4/g COD, equivalent to 40.5 % of influent at HRT 1.5 h and SRT 2 d as optimal conditions. Notably, Family Carnobacteriaceae and Genus Trichococcus were emerged dominantly in HRAS. This study would be useful in the design and operation of HRAS for sustainable wastewater treatment and climate change mitigation.
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•HRT 1.5 h and SRT 2 d showed the maximum pollution removal and biogas recovery.•64.8 % of influent COD was removed, of which 62.5 % were recovered as biogas.•Redirected sludge had high LB-EPS, which is related to the high biodegradability.•Carnobacteriaceae was dominant bacterial family in HRAS.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Anaerobic digestion (AD) is a well-known biological conversion process to obtain a gaseous biofuel from organic matter: in fact, upgrading biogas to biomethane is a mean to substitute conventional ...natural gas. It is also known that biochar can improve the biogas production in AD processes. In this work, different biochars have been produced from various feedstocks at different process conditions. Biochars obtained from the carbonization of wheat straw (WS) and poplar (P) were produced in a Thermo Gravimetric Analyser at lab scale, at a temperature of 400 °C and 2 h of retention time at the maximum temperature, with a heating rate of 20 °C min
−1
. Another biochar from poplar (Pc) was also produced in a pilot plant (CarbOn, RE-CORD) working in oxidative pyrolysis conditions, at a temperature range between 500 and 600 °C. Biochars were oxidized with Oxone® using two different methods (ball-milling and simple aqueous solution mixing) to increase the amount of functional groups on their surface. Oxidized biochars (Ws_Ox and P_Ox) were characterized by FTIR, BET, and CEC, and their impact on biogas production was investigated through a lab scale biochemical methane potential (BMP) test using maize silage as substrate. 0.33 g of biochar was used for each treatment. BMP test shows that all batches containing biochar as additive produced more biogas than control (C). WS_Ox and P_Ox produced respectively a + 7.7% and + 11.3% of biogas than C, obtaining the higher productivities with respect to not oxidized biochars. The addition of P and Pc biochars were similar performances in AD, thus highlighting that no significant differences are due to different biochar production scales and process parameters from the same feedstock. This study highlights how in addition to the various examined parameters (nature of the feedstock, pyrolysis parameters, size of biochar and its concentration in AD), also the presence of specific functional groups on the biochar surface influences the AD performance.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Ammonia accumulation in biogas plants reactors is becoming more frequently encountered, resulting in reduced methane (CH4) production. Ammonia toxicity occurs when N-rich substrates represent a ...significant part of the biogas plant’s feedstock. The aim of this study was to develop an estimation method for the effect of ammonia toxicity on the CH4 production of biogas plants. Two periods where a biogas plant operated at 3200 mg·L−1 (1st period) and 4400 mg·L−1 (2nd period) of ammonium nitrogen (NH4+–N) were examined. Biomethane potentials (BMPs) of the individual substrates collected during these periods and of the mixture of substrates with the weight ratio used by the biogas plant under different ammonia levels (2000–5200 mg·L−1 NH4+–N) were determined. CH4 production calculated from the substrates’ BMPs and the quantities used of each substrate by the biogas plant was compared with actual CH4 production on-site. Biogas plant’s CH4 production was 9.9% lower in the 1st and 20.3% in the 2nd period in comparison with the BMP calculated CH4 production, of which 3% and 14% was due to ammonia toxicity, respectively. BMPs of the mixtures showed that the actual CH4 reduction rate of the biogas plant could be approximately estimated by the ammonia concentrations levels.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
•Influence of headspace pressure on the methane production was studied.•Cocoa shell, waste coffee grounds and dairy manure were the substrates studied.•Two headspace pressure conditions were tested ...for each substrate.•Only waste coffee grounds methane production was affected by high headspace pressures.•It has not been possible to determine why pressure affected waste coffee grounds BMP.
The biochemical methane potential test is the most commonly applied method to determine methane production from organic wastes. One of the parameters measured is the volume of biogas produced which can be determined manometrically by keeping the volume constant and measuring increases in pressure. In the present study, the effect of pressure accumulation in the headspace of the reactors has been studied. Triplicate batch trials employing cocoa shell, waste coffee grounds and dairy manure as substrates have been performed under two headspace pressure conditions. The results obtained in the study showed that headspace overpressures higher than 600mbar affected methane production for waste coffee grounds. On the contrary, headspace overpressures within a range of 600–1000mbar did not affect methane production for cocoa shell and dairy manure. With the analyses performed in the present work it has not been possible to determine the reasons for the lower methane yield value obtained for the waste coffee grounds under high headspace pressures.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Water hyacinth is capable of miraculously concealing an entire freshwater body within two weeks by forming thick mats. These thick mats of water hyacinth causes nuisance to both aquatic organisms and ...human beings. As it intimidates the existence of aquatic organisms and bothers the livelihood and recreational activities of human beings. Therefore this weed is used for biochemical methane potential test in order to check it's prospective for producing biogas. Biochemical methane potential (BMP) was examined for both untreated as well as hot air oven pretreated water hyacinth whole plant (i.e., leaves, stem and roots) to determine the ideal food to microorganism (F/M) ratio. A comparative study conducted between untreated and hot air oven pretreated water hyacinth revealed that the F/M ratio 2 of the untreated water hyacinth, showed the highest methane yield of 143 ± 14 mL CH4/g VS on the 32nd day whereas for hot air oven pretreated water hyacinth F/M ratio 1.5 showed the highest methane yield of 193 ± 22 mL CH4/g VS on the 14th day itself. It was observed that the hot air oven pretreated water hyacinth showed enhanced biogas production within a very short duration. Also, the ideal F/M ratio was determined for both untreated and pretreated water hyacinth through BMP study.
•Water hyacinth hampers underwater life and day to day human activities.•Physical or mechanical removal of this pest is not advantageous.•Anaerobic digestion is proficient for conversion of the waste into biogas.•BMP of untreated and hot air oven pretreated water hyacinth was studied.•Hot air oven pretreatment showed enhanced biogas production within a short period.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•Influence of headspace flushing on the specific methane production was studied.•Nitrogen gas (N2), a mixture of N2 and CO2 (80/20v/v) and no flushing was applied.•Results revealed that removing the ...oxygen is crucial to avoid aerobic respiration.•CO2 in the flush gas increased significantly the methane production by over 20%.•Flushing with gas similar to the expected biogas is suggested.
The influence of headspace flushing on the specific methane (CH4) production of blank samples with just inoculum in Biochemical Methane Potential (BMP) tests was studied. The three most common ways were applied: flushing with nitrogen (N2) gas, flushing with a mixture of N2 and CO2 (80/20v/v), and no flushing. The results revealed that removing the oxygen is crucial to avoid aerobic respiration, which caused both hindered activity of methanogens and loss of methane potential. Furthermore it was demonstrated that 20% of CO2 in the flush gas increased significantly the methane production by over 20% compared to the flushing with pure N2. In order to mimic the same headspace conditions as in full-scale treatment plants, using a flush gas with a similar CO2 concentration as the expected biogas is suggested.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Methane production from wastes, like sewage sludge and fruit and vegetable wastes, has double benefits; first is minimizing these wastes and second is energy recovery. The goal of this research is to ...enhance methane yield from anaerobic co-digestion of primary sludge (PS) with fruit and vegetable wastes (FVW) in Egypt using different mixture and various inoculum types. Bio-chemical methane potential (BMP) tests were conducted in a 500-mL glass reactor under mesophilic conditions (35–37 °C). In the first BMP tests, six mixtures with PS to FVW ratios of 100:0, 70:30, 50:50, 30:70, 20:80, and 0:100 (based on volatile solids) were performed to obtain the best mixture for an optimal methane production. In the second BMP tests, three types of inoculum (fresh cow manure, activated sludge, and excess sludge) were used to identify the optimal inoculum for the greatest methane production. The highest methane yield was observed at PS to FVW ratio of 50:50 (141 mL/g VS), which was higher than the individual digestion of the other used feedstock. However, the minimum methane yield was recorded at PS to FVW ratio of 20:80. On the other hand, using the activated sludge as inoculum improved the methane yields from anaerobic co-digestion of PS with FVW compared with the other types of inoculum. Statistical analysis of the results was conducted using ANOVA test. The results conducted that the production of methane was improved by anaerobic co-digestion of PS with FVW and using the activated sludge as inoculum.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Hydrothermal treatment (HT) is a promising technology to enhance anaerobic digestion (AD) of municipal sludge. However, the capacity of pre‐ and inter‐stage HT (i.e., HT‐AD and AD‐HT‐AD, ...respectively) to enhance the digestibility of municipal sludge has not been sufficiently explored. This study compared the efficacy of pre‐ and inter‐stage HT performed from 90 to 185°C to enhance methane production from a mixture of primary sludge and waste activated sludge using mesophilic (35°C) biochemical methane potential tests. In both configurations, sludge solubilization increased with HT temperature. HT‐AD, and to a greater extent AD‐HT‐AD, increased the release of ammonium nitrogen. Even though HT at 185°C dramatically increased sludge solubilization, the overall specific methane yield with HT at 185°C was lower than or comparable to that at lower HT temperatures in the HT‐AD and AD‐HT‐AD configurations, respectively. Up to 155°C HT, the overall specific methane yield with the HT‐AD configuration was higher by 4.9%–8.3% compared to the AD‐HT‐AD configuration. However, when the HT energy was considered, compared to the control (i.e., AD of sludge without HT), the net energy gain (ΔE) decreased as the HT temperature increased, becoming negative at an HT of 185°C. The AD‐HT‐AD configuration resulted in a higher overall volatile solids destruction (by 8.1 to 20.1%). In conclusion, for municipal sludge with a relatively high ultimate digestibility, as was the case in this study, HT‐AD is preferable as it has a smaller footprint and is easier to operate than the AD‐HT‐AD configuration. However, given the significantly higher volatile solids destruction in the AD‐HT‐AD configuration, compared to the HT‐AD configuration, AD‐HT‐AD may be more beneficial considering post‐AD sludge handling processes.
Practitioner points
Hydrothermal treatment (HT) increased the rate and extent of methane production from municipal sludge mixture.
155°C was the optimal temperature for either pre‐ or inter‐stage HT to increase biogas production.
Pre‐ and inter‐stage HT resulted in comparable ultimate methane production.
Pre‐stage HT is preferable to inter‐stage HT (smaller footprint, easier to operate).
AD‐HT‐AD resulted in significantly higher volatile solids destruction compared to the HT‐AD configuration.
HT, hydrothermal treatment; AD, anaerobic digestion.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
•Methane productivity is higher under a mesophilic than thermophilic regimen.•Sugar beet pulp lixiviation (SBPL) improves cumulative net methane generation.•Several sludge/SBPL ratios were tested in ...biochemical methane potential assays.•Initial volatile fatty acid (VFA) content of inocula affects BMP test results.•High VFA content reduces microbial activity.
The feasibility of anaerobic co-digestion of sewage sludge (SS) and sugar beet pulp lixiviation (SBPL) was assessed. Mesophilic and thermophilic batch assays of five different SS/SBPL ratios were used to investigate the effect of temperature, providing basic data on methane yield and reduction in total volatiles. Microbe concentrations (Eubacteria and methanogenic Archaea) were linked to traditional parameters, namely biogas production and removal of total volatile solids (TVS). The relationship between Eubacteria and Archaea was analysed.
Given equal masses of organic matter, net methane generation was higher in the mesophilic range on the biochemical methane potential (BMP) test. Methane yield, TVS removal data and high levels of volatile fatty acids provided further evidence of the best behaviour of the mesophilic range. At the end of testing the microbial population under of the reactors consisted of Eubacteria and Archaea, with Eubacteria predominant in all cases.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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