Reuse of Sludge as Organic Soil Amendment: Insights into the Current Situation and Potential Challenges

Sludge generation as an organic by-product of wastewater treatment has seen a consistent increase worldwide due to population growth and industrial activities. This poses a chronic challenge regarding management options and environmental concerns. The agricultural valorization of unconventional organic materials has become inevitable, especially in semi-arid and arid countries that suffer from depleted soils and shortages in farm manure supply. High-income countries have also been interested in this recycling practice to mitigate landfilling or incineration issues. Sewage and some industrial sludges contain a complex mixture of beneficial and harmful substances, which varies with the origin of effluents. Therefore, sludge land application should be well managed in order to achieve sustainable agro-environmental goals. This review paper focuses on different aspects related to sludge reuse in agriculture, starting by investigating the diversity of sludge types and composition. In addition to the preponderant urban sewage sludge, the less-studied industrial sludges, such as those generated from pulp and paper mills or gas-to-liquid industries, are hereby addressed as well. Then, post-land application effects are discussed in relation to sludge quality, dose, and reuse conditions. The present paper also examines the disparities between guidelines that determine sludge conformity for land application in various countries or regions. Accordingly, special attention is given to increasing risks related to emerging pollutants in sludge such as pharmaceuticals, which have been overused since the outbreak of COVID-19 pandemic. This exhaustive investigation will assist the establishment of sustainable strategies for the safe agricultural reuse of biosolids.This review paper is an outcome of the research project M-QJRC-2020-9 funded in the framework of collaboration between Qatar University and Marubeni Corporation.Scopu

Identification, characterization, production and application of biosurfactant lipopeptides of Pseudomonas spp.

Des souches de Pseudomonas ont été isolées à partir d’échantillons de sol contaminés par les hydrocarbures ou par de l’huile végétale et d’effluent industriel en vue d’en sélectionner les bactéries ayant un potentielle de production des molécules biosurfactantes. Le criblage a été réalisé en s’appuyant essentiellement sur la mesure de la tension de surface et l’activité émulsifiante. Trois souches ont été choisies pour leurs intéressantes activités biosurfactantes et émulsifiantes. Une identification phénotypique et moléculaire des souches sélectionnées a été réalisée en se basant essentiellement sur le séquençage de leurs ARNr 16S et dont l’arbre phylogénétique a révélé qu’il s’agit de souches qui sont génétiquement très proches et appartiennent au groupe des Pseudomonas putida avec une grande similarité au Pseudomonas alkylphenolica KL28 (99%). L’étude de l’applicabilité des biosurfactants produits a été évaluée en testant leur stabilité à des conditions extrêmes de pH, Température et salinité. Les résultats ont révélés que ces biosurfactants ont maintenu leurs activités à un intervalle de pH compris entre 6 et 12, à une température allant jusqu’à 80°C et à une forte salinité (10%). L’étude du potentiel des souches productrices des biosurfactants dans la dégradation du diesel dans les sols contaminés a été réalisée pour une durée de 1 mois. Les résultats ont montré que les 3 souches possèdent une capacité de dégradation du diesel sur sable avec des débits d’élimination considérables. Une identification de la nature chimique des biosurfactants produits en utilisant une chromatographie sur couche mince (CCM) et la spectrométrie de masse MALDI-ToF sur des surnageants semi-purifiés par une précipitation acide a révélés que ces molécules sont de nature lipopeptidique et ayant des masses comprises dans l’intervalle de masse des syringafactines. L’identification structurale de ces molécules a été effectuée en spectrométrie de masse faite sur les biosurfactants purifiés par des techniques chromatographiques et membranaires et par l’étude bioinformatique du génome bactérien séquencé. Les résultats de cette identification ont été obtenus en combinant les révélations issus de ces 2 dernières techniques et ont montré qu’il s’agit de 2 lipopeptides ayant des structures inconnus et qui sont ~89% similaires aux Syringafactines et aux cichofactines. Une optimisation des conditions de culture a été ensuite réalisée en utilisant des plans d’expériences qualitatifs et quantitatifs. La fermentation Batch réalisée dans les conditions optimisées a montré une augmentation de la production des lipopeptides d’un facteur de 2,6.Pseudomonas strains have been isolated from hydrocarbon-contaminated soil, industrial effluent and vegetable oil samples for the purpose of selecting bacteria having the potential of biosurfactant molecules production. The screening was carried out based essentially on the measurement of the surface tension and the emulsifying activity. Three strains have been chosen for their interesting biosurfactant and emulsifying activities. A phenotypic and molecular identification of the selected strains was carried out based essentially on 16S rRNA sequencing and whose phylogenetic tree revealed that the 3 selected strains are genetically very close and belong to the group Pseudomonas putida with great similarity to Pseudomonas alkylphenolia KL28 (99%). The study of the produced biosurfactants applicability, was evaluated by testing their stability under extreme conditions of pH, temperature and salinity. Results revealed that these biosurfactants maintained their activities at a pH range of 6 to 12, at a temperature of up to 80°C and high salinity (10%). The study of the biosurfactant-producing strains potential in diesel degradation in contaminated soils was carried out for duration of 1 month. Results showed that the 3 strains possess a capacity of diesel degradation on sand with considerable disposal rates. An identification of the produced biosurfactants chemical nature using thin layer chromatography (TLC) and MALDI-ToF mass spectrometry on semi purified supernatants by acid precipitation revealed that these molecules have lipopeptidic nature and having masses within syringafactins mass range. The structural identification of these molecules was carried out using purified biosurfactants on chromatographic and membrane techniques by mass spectrometry and bioinformatic studies of the bacterial genome sequenced. Identification results were obtained by combining the revelations resulting from these two techniques and showed that the produced molecules are 2 new octalipopeptides and are ~ 89% similar to Syringafactins and cichofactines. Optimization of the culture conditions of the produced lipopeptides was then carried out using qualitative and quantitative experimental designs. Batch fermentation carried out under the optimized conditions showed an increase in the production of the lipopeptides by a factor of 2.6

Identification, caractérisation, production et application des biosurfactants lipopeptidiques de Pseudomonas spp.

Pseudomonas strains have been isolated from hydrocarbon-contaminated soil, industrial effluent and vegetable oil samples for the purpose of selecting bacteria having the potential of biosurfactant molecules production. The screening was carried out based essentially on the measurement of the surface tension and the emulsifying activity. Three strains have been chosen for their interesting biosurfactant and emulsifying activities. A phenotypic and molecular identification of the selected strains was carried out based essentially on 16S rRNA sequencing and whose phylogenetic tree revealed that the 3 selected strains are genetically very close and belong to the group Pseudomonas putida with great similarity to Pseudomonas alkylphenolia KL28 (99%). The study of the produced biosurfactants applicability, was evaluated by testing their stability under extreme conditions of pH, temperature and salinity. Results revealed that these biosurfactants maintained their activities at a pH range of 6 to 12, at a temperature of up to 80°C and high salinity (10%). The study of the biosurfactant-producing strains potential in diesel degradation in contaminated soils was carried out for duration of 1 month. Results showed that the 3 strains possess a capacity of diesel degradation on sand with considerable disposal rates. An identification of the produced biosurfactants chemical nature using thin layer chromatography (TLC) and MALDI-ToF mass spectrometry on semi purified supernatants by acid precipitation revealed that these molecules have lipopeptidic nature and having masses within syringafactins mass range. The structural identification of these molecules was carried out using purified biosurfactants on chromatographic and membrane techniques by mass spectrometry and bioinformatic studies of the bacterial genome sequenced. Identification results were obtained by combining the revelations resulting from these two techniques and showed that the produced molecules are 2 new octalipopeptides and are ~ 89% similar to Syringafactins and cichofactines. Optimization of the culture conditions of the produced lipopeptides was then carried out using qualitative and quantitative experimental designs. Batch fermentation carried out under the optimized conditions showed an increase in the production of the lipopeptides by a factor of 2.6.Des souches de Pseudomonas ont été isolées à partir d’échantillons de sol contaminés par les hydrocarbures ou par de l’huile végétale et d’effluent industriel en vue d’en sélectionner les bactéries ayant un potentielle de production des molécules biosurfactantes. Le criblage a été réalisé en s’appuyant essentiellement sur la mesure de la tension de surface et l’activité émulsifiante. Trois souches ont été choisies pour leurs intéressantes activités biosurfactantes et émulsifiantes. Une identification phénotypique et moléculaire des souches sélectionnées a été réalisée en se basant essentiellement sur le séquençage de leurs ARNr 16S et dont l’arbre phylogénétique a révélé qu’il s’agit de souches qui sont génétiquement très proches et appartiennent au groupe des Pseudomonas putida avec une grande similarité au Pseudomonas alkylphenolica KL28 (99%). L’étude de l’applicabilité des biosurfactants produits a été évaluée en testant leur stabilité à des conditions extrêmes de pH, Température et salinité. Les résultats ont révélés que ces biosurfactants ont maintenu leurs activités à un intervalle de pH compris entre 6 et 12, à une température allant jusqu’à 80°C et à une forte salinité (10%). L’étude du potentiel des souches productrices des biosurfactants dans la dégradation du diesel dans les sols contaminés a été réalisée pour une durée de 1 mois. Les résultats ont montré que les 3 souches possèdent une capacité de dégradation du diesel sur sable avec des débits d’élimination considérables. Une identification de la nature chimique des biosurfactants produits en utilisant une chromatographie sur couche mince (CCM) et la spectrométrie de masse MALDI-ToF sur des surnageants semi-purifiés par une précipitation acide a révélés que ces molécules sont de nature lipopeptidique et ayant des masses comprises dans l’intervalle de masse des syringafactines. L’identification structurale de ces molécules a été effectuée en spectrométrie de masse faite sur les biosurfactants purifiés par des techniques chromatographiques et membranaires et par l’étude bioinformatique du génome bactérien séquencé. Les résultats de cette identification ont été obtenus en combinant les révélations issus de ces 2 dernières techniques et ont montré qu’il s’agit de 2 lipopeptides ayant des structures inconnus et qui sont ~89% similaires aux Syringafactines et aux cichofactines. Une optimisation des conditions de culture a été ensuite réalisée en utilisant des plans d’expériences qualitatifs et quantitatifs. La fermentation Batch réalisée dans les conditions optimisées a montré une augmentation de la production des lipopeptides d’un facteur de 2,6

High Added-Value Co-Product: the Porcine Cruor is an Attractive Source of Active Peptides

International audienc

Recycling of gas-to-liquid sludge as a potential organic amendment: effect on soil and cotton properties under hyperarid conditions

Gas-to-liquid (GTL) sludge is a specific wastewater treatment by-product, which is generated during the industrial process of natural gas conversion to transportation fuels. This least studied sludge is pathogen-free and rich in organic carbon and plant nutrients. Therefore, it can be reused for soil enhancement as a sustainable management strategy to mitigate landfill gas emissions. In this field study, we compared the performance of soil treatments with GTL sludge to the more conventional chemical fertilizers and cow manure compost for the cultivation of cotton under hyperarid conditions. After a complete growing season, GTL sludge application resulted in the enhancement of soil properties and plant growth compared to conventional inputs. As such, there was a significant dose-dependent increase of soil organic matter (4.01% and 4.54%), phosphorus (534 and 1090 mg kg−1), and cumulative lint yield (4.68 and 5.67 t ha−1) for GTL sludge application rates of 1.5% and 3%, respectively. The produced fiber quality was adequate for an upland cotton variety (Gossypium hirsutum var. MAY 344) and appeared more dependent on the prevailing climate conditions than soil treatments. On the other hand, the adverse effects generally related to industrial sludge reuse were not significant and did not affect the designed agro-environmental system. Accordingly, plants grown on GTL sludge-amended soils showed lower antioxidant activity despite significant salinity increase. In addition, the concentrations of detected heavy metals in soil were within the standards’ limits, which did not pose environmental issues under the described experimental conditions. Leachate analysis revealed no risks for groundwater contamination with phytotoxic metals, which were mostly retained by the soil matrix. Therefore, recycling GTL sludge as an organic amendment can be a sustainable solution to improve soil quality and lower carbon footprint. To reduce any environmental concerns, an application rate of 1.5% could be provisionally recommended since a two-fold increase in sludge dose did not result in a significant yield improvement

Valorization of Gas-To-Liquid Sludge as a Sustainable Soil Organic Amendment for Cotton Cultivation

Gas-to-liquid (GTL) sludge is a specific wastewater treatment by-product generated during the industrial process of natural gas conversion into liquid fuels. This least studied sludge is pathogen?free and rich in organic matter and plant nutrients. Therefore, it can be recycled in agricultural soils as an organic amendment and reduce therefore the potential risks of landfilling. In this open field study, we compared the performance of soil treatments with GTL sludge to the more conventional chemical fertilizers and cow manure compost for the cultivation of cotton under the natural conditions of Qatar. After a complete growing season, GTL sludge application resulted in the enhancement of soil properties and plant growth compared to conventional inputs. As such, there was a significant dose-dependent increase of soil organic matter (4.01% and 4.54%), phosphorus (534 and 1090 mg kg-1 ), and cumulative fiber yield (4.68 and 5.67 t ha-1 ) for GTL sludge application rates of 1.5% and 3%, respectively. The produced fiber quality was adequate for an upland cotton variety and appeared more dependent on the prevailing climate conditions than soil treatments. On the other hand, the adverse effects generally related to industrial sludge reuse were not significant and did not affect the designed agro-environmental system. Accordingly, plants grown on GTL sludge-amended soils showed lower antioxidant activity despite a significant salinity increase. In addition, the concentrations of detected heavy metals in soil were within the standards’ limits, which did not pose environmental issues under the described experimental conditions. Leachate analysis revealed no risks for groundwater contamination with phytotoxic metals, which were mostly retained by the soil matrix. Therefore, the agricultural reuse of GTL sludge can be a sustainable solution to improve soil quality, lower carbon footprint, and mitigate environmental contamination.</p