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The present study investigated the acidification treatment of an agrowaste digestate and a food waste digestate, which is necessary before the addition of the wood ashes to attain the pH of zero point of charge in the blend intended to behave as a slow-release fertilizer. The 336-h acidification treatments of the 2.39 ± 0.35 g of digestates were performed with high and low doses of four commercial acids (sulfuric, hydrochloric, nitric, and lactic acids) in 50-mL capped Corning® tubes. For analytical purposes, after the incubation, ultrapure milli-Q® water was added at a rate of 10 mL for each gram of digestate to create a water-soluble phase that allowed the measurement of the pH and the electric conductivity. The results showed that the optimum dose and type of acid were very dependent on the nature of the anaerobic digestate. The maximum buffer capacity of the agrowaste digestate was 0.07 mmol H+-H2SO4/g, but this increased by adding the food waste digestate with a greater content of ammoniacal nitrogen. The agrowaste digestate with a greater content of undigested fiber was more easily oxidized by nitric acid. On the other hand, sulfuric acid oxidized the food waste digestate to a greater extent than the other acids did. Since a high dose of acid was required to achieve a greater efficiency in the solid–liquid separation, which would ease any subsequent handling of the digestates, hydrochloric acid was considered to be the most suitable acid. Lactic acid promoted the growth of filamentous microbes in the agrowaste digestate and microbial colonies in the food waste digestate, which is an indication of the poor preservation of the organic matter under these conditions.

The use of the commercial simulator Aspen Plus® could bring an amelioration in the accuracy of the predictions of the chemical species composition in the output streams of the anaerobic digestion process. Compared to the traditionally employed lumped models, which are elaborated from scratch, the models implemented in Aspen Plus® have access to a broad library of thermodynamic and phenomena transport properties. In the present investigation, a process simulation model for anaerobic digestion has been prepared by including a stoichiometric-equilibria reactor to calculate the extent of the ionization of the molecules present in the anaerobic digestate. The model characterizes the technical feasibility of anaerobic digestate stabilization, by means of biomass ash-based treatment, for the production of an organic fertilizer and potential biogas upgradation with the synthesis of ammonium carbonate. First of all, the titration of the manure digestate with the hydrochloric acid showed that a dose of 3.18 mEq/g would be required to attain the targeted pH of zero-point charge, upon addition of the sewage sludge ash in a ratio to the manure digestate of 0.6 ± 0.2%. Secondly, the profiles of ammonia, carbon dioxide, and methane found in the biogas agree with the pH of the treated digestate and enable the upgrading of the biogas with the production of NH4HCO3. The model needs to be further developed to ensure the standards are attained in all output streams of stabilized anaerobic digestate, biomethane, and isolated added-value chemical fertilizers.

The antibacterial effects of a selection of volatile fatty acids (acetic, propionic, butyric, valeric, and caproic acids) relevant to anaerobic digestion were investigated at 1, 2 and 4 g/L. The antibacterial effects were characterised by the dynamics of Enterococcus faecalis NCTC 00775, Escherichia coli JCM 1649 and Klebsiella pneumoniae A17. Mesophilic anaerobic incubation to determine the minimum bactericidal concentration (MBC) and median lethal concentration of the VFAs was carried out in Luria Bertani broth at 37 °C for 48 h. Samples collected at times 0, 3, 6, 24 and 48 h were used to monitor bacterial kinetics and pH. VFAs at 4 g/L demonstrated the highest bactericidal effect (p < 0.05), while 1 g/L supported bacterial growth. The VFA cocktail was the most effective, while propionic acid was the least effective. Enterococcus faecalis NCTC 00775 was the most resistant strain with the VFAs MBC of 4 g/L, while Klebsiella pneumoniae A17 was the least resistant with the VFAs MBC of 2 g/L. Allowing a 48 h incubation period led to more log decline in the bacterial numbers compared to earlier times. The VFA cocktail, valeric, and caproic acids at 4 g/L achieved elimination of the three bacteria strains, with over 7 log10 decrease within 48 h.

This study focused on determining the effect of the inoculum to substrate ratio (ISR) on biogas production efficiency from the anaerobic co-digestion of two substrates: synthetic food waste and common reeds (Phragmites australis) that were ground and pre-treated using sodium hydroxide at a concentration of 2% to increase access to their cellulose. It also studied the role of different mixing ratios of the two substrates in improving the stability of the digestion process and increasing biogas production. A series of batch tests were carried out under mesophilic conditions using three ratios of ISR: 1:4, 1:2, and 1:1, and five substrate mixing ratios (synthetic food waste: pre-treated P. australis): 25:75, 50:50, 75:25, 100:0, and 0:100. The results showed low biogas production at the ISR 1:4 (21.58±0.00–44.46±0.01 mL/g volatile solid (VS) added), and the reactors suffered from acidification at the different substrates mixing ratios, while the biogas production increased at an ISR of 1:2, where the reactors with the substrate mixing ratio of 25:75 presented the highest biogas production (82.17±0.62 mL/g VS added), and the digestion process was stable. However, the reactors with substrate mixing ratios of 50:50, 75:25, and 100:0 suffered from acidification effects at this ISR. In contrast, at ISR of 1:1, the reactors did not expose to acidification inhibition at all the substrates mixing ratios, and the highest biogas production was found at synthetic food waste: pre-treated P. australis mixing ratios of 75:25 and 100:0 (76.15±1.85 and 82.47±1.85 mL/g VS added, respectively).

Trace-level plutonium in the environment often comprises local and global contributions, and is usually anthropogenic in origin. Here, we report estimates of local and global contributions to trace-level plutonium in soil from a former, fast-breeder reactor site. The measured 240 Pu/ 239 Pu ratio is anomalously low, as per the reduced 240 Pu yield expected in plutonium bred with fast neutrons. Anomalies in plutonium concentration and isotopic ratio suggest forensic insight into specific activities on site, such as clean-up or structural change. Local and global 239 Pu contributions on-site are estimated at (34 ± 1)% and (66 ± 3)%, respectively, with mass concentrations of (183 ± 6) fg g −1 and (362 ± 13) fg g −1 . The latter is consistent with levels at undisturbed and distant sites, (384 ± 44) fg g −1 , where no local contribution is expected. The 240 Pu/ 239 Pu ratio for site-derived material is estimated at 0.05 ± 0.04. Our study demonstrates the multi-faceted potential of trace plutonium assay to inform clean-up strategies of fast breeder legacies. This study proposes a method to differentiate between local plutonium-based contamination in soils versus trace plutonium stemming from global dispersion in the past, such as fallout from detonation and atmospheric testing of nuclear weapons.

Polycyclic aromatic hydrocarbons (PAHs), the nitrogen-containing analogues (N-PAHs) and lead 210 (210Pb) were measured in 2-cm interval core segments from Bodo Creek to evaluate impact of oil pollution in the waterbody. PAHs and N-PAHs were measured by gas chromatography analysis with mass spectrometry detection, and 210Pb activity concentration was determined by alpha spectrometry measurement. Data shows that ƩPAHs and ƩN-PAHs ranged from 12,774.3–18,470.2 µg/kg and 524.0–672.2 µg/kg, respectively. Concentrations were found to increase with increase in depth (cm). Petrogenic PAHs predominated the surface sediment (with elevated levels of 2,3,6-trimethyl-naphthalene, phenanthrene and 1-methyl-phenanthrene), while pyrogenic-PAHs dominated the deeper segments (with high levels of pyrene, benzo[a]anthracene, chrysene and benzo[k]fluoranthene). For N-PAHs, benzo[h]quinoline, 4,7-phenanthroline and benzo[a]acridine recorded high values. Chemicals comparison with values measured from Bonny Estuary revealed greater PAHs contamination in the estuary, while N-PAHs recorded elevated values in the creek. 210Pb activity concentration in the creek showed relatively low activity compared to the estuary, and similar distribution with the aromatic hydrocarbons. The measured hydrocarbons were high and exceeded the Canadian sediment quality guidelines. However, there are concerns over toxic ratios > 70% and radioactivity (EPR-D-values) > 3 – 4.E ± 01 Bq measured in the polluted creek. This gives insight on the level of radioactivity, PAHs, N-PAHs and PAHs toxic ratios in Bodo creek which would be useful in future remediation studies and/or monitoring the ability of sediments to recover under natural conditions.

A series of batch assays have been conducted to investigate the optimal factors that can be adopted to improve the anaerobic digestion (AD) performance of Phragmites australis and increase biogas production. The assays were carried out using 125 mL microcosm reactors with a working volume of 80 mL and incubated at mesophilic conditions (37 ± 1ºC). The effect of particle size (10, 5, 2, and < 1 mm) and alkaline pre-treatment of P. australis using various concentrations of sodium hydroxide (0.5, 1, 2, and 4%) on biogas production was examined. Furthermore, the best pre-treatment incubation time (12, 24, 48, 72, 96, and 120 h) and the optimal inoculum to substrate ratio (ISR: 4:1, 2:1, 1:1, 1:2 and 1:4) were also assessed. The results revealed that the highest biogas production from P. australis was achieved at particle size < 1 mm (27.97 ± 0.07 and 16.67 ± 0.09 mL/g VS added, for pre-treated and untreated P. australis respectively); 2% and 4% NaOH concentration for pre-treatment (70.01 ± 3.75 and 76.14 ± 2.62 mL/g VS added, respectively); pre-treatment incubation time of 72, 96, and 120 h (71.18 ± 1.79, 72.46 ± 1.08, and 73.78 ± 1.87 mL/g VS added, respectively); and ISR of 1:2 for pre-treated P. australis (78.21 ± 0.36 mL/g VS added) and ISR 1:4 for untreated P. australis (28.93 ± 1.55 mL/g VS added). Determining optimal parameters in this work would guide further development of process configurations, such as continuous AD systems.

Nitrogen- heterocyclic polycyclic aromatic hydrocarbons (N-PAHs) are ubiquitous constituents of contaminated sites in which their high water solubility and lower k ow values imply greater mobility and impacts. Biodegradation is a major route of loss for organic contaminants in soil. In this study, microbial degradation was investigated in soil artificially contaminated with N-PAHs and monitored for over 200 days. The results showed that all the aromatic chemicals exhibited loss with increasing incubation time; however, only 0.05 ± 0.04 mg kg day −1 loss was observed for N-PAHs at 10 mg kg −1 amendments over the first 30 days incubation, with the exception of 4,7-phenanthroline which recorded 0.19 ± 0.03 mg kg day −1 . The study showed that soil microflora have the potential to degrade N-PAHs since all of the aromatics recorded chemical losses under aerobic condition. However, degradation rates varied between chemicals and this was attributed to N -atom position and/or number of N -substituents. Further, relatively little or no biodegradation was observed in B[h]Q amended soils with increasing concentration; indicating that B[h]Q is more resistance to biodegradation in soil.

This transdisciplinary literature review paper aims at addressing the literature lacuna in community engagement and water, sanitation and hygiene (WASH) in sub-Saharan countries. By responding to a set of identified WASH-related questions to community engagement, it explores through different disciplinary lenses the challenges and opportunities in this significant area that impacts human health. This transdisciplinary review brought together the disciplines of water engineering, environmental microbiology, public health and infectious disease, design research, women and gender studies, and developmental studies. It examined over 430 papers with 29 papers included in the final review. The main findings suggest integrating women into leadership roles in community water management and water and sanitation programmes can lead to more sustainability and can make water projects more effective. Second, cultural preferences should be a key factor when planning and implementing WASH technologies and interventions. Third, for community engagement to be effective, it should be done with intentionality and over a longer period; and employ existing culturally embedded leadership structures, such as schoolteachers, religious leaders and train change agents.

Anaerobic digestion (AD) is a waste management method worldwide, that results in biogas and digestate production. The digestate remains is a potential biofertilizer but may fall short of vital nutrients required for optimal plant growth, hence, requires amendment with other biomass residues. This study was aimed at investigating the microbial quality of digestate amended with wood ash and vegetable matter during treatment. Digestate from cattle rumen content (CR), food waste (FW), fruit waste (FRW) and their combinations were amended with wood ash, vegetable (green) matter and a blend of both. Amendment was carried out for 5 weeks, and samples were analyzed weekly. Enumeration and identification of bacteria and fungi were carried out on culture media. The rhizobacterial potential of the identified bacterial isolates was also investigated using standard microbiological procedures. The results showed high bacterial and fungal load in vegetable amended digestate from the first to the fourth week. Comparatively, cattle rumen content and food waste digestate amended with vegetables were highly significant, with mean values of 0.8 and 0.6, respectively. The identified bacterial isolates namely, Bacillus subtilis, Salmonella sp, Pseudomonas sp, Proteus sp, Enterobacter sp, Chromobacterium sp Bacillus spp. and Escherichia coli were found to be involved in the solubilization of phosphate, nitrogen fixation, ammonia production and induction of indole acetic acid. Specifically, feedstocks amended with vegetable (green) waste was found to have a significant influence on microbial growth (bacterial and fungal loads) between week 1 and 4. This suggests that digestate amendment is a crucial recipe for microbial growth which has considerable benefits in nutrient enhancement and increase in carbon levels. Graphical Abstract Digestate amendment and nutrient enhancement for plant growth