Biosolids Research Articles

Reevaluating biostimulation strategies: the impact of humic acid on ofloxacin bioadsorption

The exogenous addition of humic acid (HA) is often seen as a biostimulation strategy to expedite the bioremediation of various pharmaceutical pollutants. Nevertheless, the impact of HA on the bioadsorption of ofloxacin (OFL), the main pathway for OFL removal in activated sludge, remains unknown. In this study, the presence of 10 mg/L HA notably decreased the theoretical OFL adsorption capacity from 8.94 to 7.95 mg/g. The inhibitory effect persisted across varying pH and ionic strengths and became more pronounced with increasing HA concentration. The morphological changes on biosolid (BIO) induced by HA indicated that HA was bioadsorbed, which in turn competed with OFL for metal binding sites like Ca and Mg on BIO. Further analysis of the OFL-HA interaction reveals the involvement of hydrogen bonding and electrostatic attraction. The study also demonstrates the bridging role of HA between OFL and BIO through consecutive desorption and re-absorption processes of OFL in the presence of HA. To quantify the direct and indirect adsorption ratios, a new approach was proposed, which determined the mass ratios of direct (OFL:BIO) and indirect bioadsorption (OFL:HA:BIO) as 1:192 and 1:21:854, respectively. These findings suggest that the indirect OFL adsorption through the HA bridge could not compensate for the adverse effects caused by the reduction of metal binding sites. Overall, this study calls for a reassessment of the addition of HA in the bioremediation process of OFL. Considering that HA widely coexists with antibiotics in wastewater, the study also provides valuable insights into OFL removal mechanisms in WWTPs.

Bio-based resources: systemic & circular solutions for (agro)environmental services.

The global promotion of decarbonisation through the circular solutions and (re)use of bio-based resources (BBR), i.e. waste streams, notably from the agricultural, forest and municipal sectors has steadily increased in recent decades. Among the transformative solutions offered by BBR, biosolids (BS), biochars (BC), and bioashes (BA) specifically attract scientific attention due to their highly complex organo-mineral matrices, which present significant potential for recovery in the agro-/forest-ecosystems. These materials enhance various soil (i) chemical (pH, macro/micro nutrient concentrations, organic matter content), (ii) physical (porosity, water-air relations, compaction) or (iii) microbial (diversity, activity) properties. Furthermore, some of transformed BBR contribute to a multitude of environmental services such as the remediation of contaminated sites and wastewater treatment, employing cost-effective and eco-friendly approaches that align with circular economy/waste management principles, ultimately contributing to climate change mitigation. However, several challenges impede the widespread utilization/transformation of BBR, including technological limitations in processing and application, concerns about contamination (e.g., PAHs, PCBs, micro/nano plastics present in BS), toxicity issues (e.g., heavy metals in BA or nanoparticles in BC), and regulatory constraints (e.g., non-uniform regulations governing the reuse of BA and BS). Addressing these challenges demands an interdisciplinary and intersectoral approach to fully unlock the potential of BBR in sustainable decarbonisation efforts.

Effects of mild acid pre-treatment on the co-pyrolysis behaviour of biosolids and wheat straw

Co-pyrolysis of biosolids (BS) and wheat straw (WS), as well as their treated variants, was performed in a fluidised bed reactor at 500 ℃. Under mild acid pre-treatment conditions (3% H2SO4 and 25 ℃), demineralisation was the dominating effect of pre-treatment on BS, while it was hemicellulose hydrolysis for WS. Consequently, the co-pyrolysis of raw biosolids (RBS) or treated biosolids (TBS) with raw wheat straw (RWS) or treated wheat straw (TWS) had varying effects on product distribution and product compositions. The co-pyrolysis of RBS+RWS gave the lowest bio-oil yield (36.3 wt%) and highest gas yield (23.1 wt%). In contrast, the highest bio-oil yield (45.8 wt%) and lowest gas yield (14.4 wt%) occurred during the co-pyrolysis of TBS+TWS. The degree of synergy in product distribution was strongest in TBS+RWS followed by RBS+RWS and was weakest in TBS+TWS, demonstrating the catalytic effect of inherent minerals on organic matter devolatilisation and char cracking reactions during co-pyrolysis. Biosolids pre-treatment alone performed competitively with BS co-pyrolysis alone with respect to enhancement in biochar properties producing biochar having 15–18 MJ/kg calorific value, 43–51 wt% carbon content, 0.7–1.0 fuel ratio, ⁓30% organic matter retention, and 27–41 wt% ash content. However, combining BS co-pyrolysis and pre-treatment gave the lowest reduction in biochar total heavy metal concentration. Furthermore, bio-oil compositions were influenced by pre-treatment and/or co-pyrolysis, increasing the yield (area%) of phenols to 25.4%, furans to 24.8%, anhydrosugars to 7.8%, and aromatic hydrocarbons to 20.6%. Lastly, pre-treatment alone weakened gas production while co-pyrolysis combined with pre-treatment impacted the pyrolysis gas profile, switching between light hydrocarbons and carbon oxides (CO and CO2). Overall, co-pyrolysis and pre-treatment can each be a standalone strategy for enhancing BS pyrolysis; however, their combination produced greater synergy for generating high value products.

Structural analysis and characterization of biosolids. A case study of biosolids from wastewater treatment plants in Western Greece

The great interest of modern societies in the reuse of wastes opens up new horizons in the field of wastewater, as well. In particular, the treated sludge resulting from a Wastewater Treatment Plant (WWTP) is dealed with a new perspective in the context of circular economy. The aim of this study is the characterization of its complex matrix, and the evaluation for reuse. Biosolids (BS) collected from four urban WWTPs in the Western region of Greece i.e. Agrinio (AG), Amaliada (AM), Aegio (AE) and Itea (IT). Analytical and spectroscopical methods namely TGA, ICP-OES, Fluorescence, SEM/EDS, XRD, FT-IR and NMR were the means that served this purpose. SEM along with XRD proved the amorphous nature of BS. The dominant metals detected in the samples are: Fe, Zn, Mn, with concentrations which meet the guidelines included in 86/278/EEC Directive. The inorganic load is of great importance, along with their humic acid content, adding value at the samples as fertilizers. BS appeared to be rich in organic matter with long aliphatic chains and numerous functional groups, as capturedin FT-IR spectra. The applied methods form an analytical protocol of the BS mapping, highlighting its potential as a material to be utilized in agriculture.

The Impact of the Elemental Interactions on Soil Fertility and Toxicity in the Presence of Wastewater and Biosolids: A Quantitative Evaluation

A field experiment was conducted in Mesologgi, Greece, for the study of the elemental contribution to the soil under the following treatments in four replications i.e.,: a—Wastewater (TMWW), b—Biosolid (BSD), c—(TMWW + BSD) and d—CONTROL (fresh irrigation water). Similarly, the data of a greenhouse experiment conducted in four replications in Agrinion, under the effect of wastewater and biosolids was also taken into account for reasons of comparison. The soil analytical data of these two experiments were chosen to study the elemental interactions under two different experimental conditions The actual scope was the use of the elemental interactions as a tool for the evaluation of their contribution in terms of plant nutrients, and heavy metals to soil fertility and of heavy metals to soil toxicity. Based on the results of elemental contributions obtained for both of the above experimental soils, the key role of elemental interactions as a tool in evaluating the contributed heavy metals, and essential nutrients, as well as in producing quantitative changes in the physical and chemical properties of soil (pH, organic matter, calcium carbonate, and electrical conductivity), was also, studied. According to the obtained results, it was shown that the elemental interactions have shown approximately the same quantitative trend between some of the results obtained, differing in some others, showing higher concentrations. In other words, it was shown that the elemental interactions could be used as an effective tool for the quantitative evaluation of the elemental interactions’ contribution in terms of nutrients to soil fertility, and of heavy metals to soil toxicity, under the reuse of wastewater and biosolids, as well as in terms of changes of the soil physical and chemical properties. However, due to the complex nature of this subject, more detailed research must be conducted on the elemental contributions, so that the plant nutrients, or the heavy metals, eventually be managed effectively to the benefit of the agricultural economy and environmental quality.

Initial growth and quality of jussara palm seedlings cultivated in biosolid-based substrates

All palms present ornamental appeal and may be widely used in landscaping, especially the native ones because of their ecological importance, such as the jussara palm (Euterpe edulis Mart.). In this sense, aiming at maximum plant development in the urban environment, it is necessary to use high-quality seedlings; the substrate is one of the key factors that directly influence it. The objective of this study was to evaluate the initial growth of jussara palm seedlings cultivated in biosolid-based substrates, which is a material of good characteristics besides attending sustainability issues. The experimental design was entirely randomized with six treatments consisted of substrates composed by biosolid (BIO) and subsoil (SS) at different proportions (v:v): 100% SS - control; 20% BIO + 80% SS; 40% BIO + 60% SS; 60% BIO + 40% SS; 80% BIO + 20% SS; 100% BIO. Seedlings were cultivated in a greenhouse and evaluated according to the following variables: height of aerial part; root length; collar diameter; leaf number; dry mass of aerial part and of roots; total dry mass; chlorophyll content; height of aerial part/collar diameter rate; dry mass of aerial part/dry mass of roots rate; and Dickson Quality Index. There was a significant effect (p < 0.05) for all evaluated characteristics. The biosolid, combined with subsoil, may be used for 20% and 40% substrate composition, as it is potentially appropriate for jussara palm seedling production. Higher proportions were toxic to seedling growth.

Potential of Pseudomonas yamanorum for the valorization of municipal biosolids

Abstract It is generally accepted that some trace organic contaminants (TrOCs) pass through the wastewater treatment process without being properly treated and find their way into waterbodies. These molecules can also be concentrated within the biosolids (BS) through adsorption. The presence of TrOCs in BS, which are then commonly used as soil amendments in agriculture, may affect plant growth and viability. The potential risks posed by TrOCs are usually ignored because they are present in low concentrations and mostly have relatively short half-lives. However, the continuous addition of these substances in water sources and on farmlands makes them pseudo-persistent. To reduce the concentrations of selected TrOCs from these BS, Pseudomonas yamanorum LBUM636 (PY) was tested with and without a commercial bacterial blend of Bacillus spp. (BC). About 60% removal of atrazine was achieved using PY-amended BS. Bioslurries inoculated with PY had relatively high laccase activity at about 2,200 U/L. Laccase activity was seven times higher in samples where BC was also present, which suggests a synergistic effect between BC and PY. Concentrations of phenazine-1-carboxylic acid, an antibiotic with a biopesticide effect, were also relatively important in PY-inoculated bioslurries.

Co-pyrolysis of biosolids with lignocellulosic biomass: Effect of feedstock on product yield and composition

Co-pyrolysis technology is an effective method to reduce heavy metal concentration in biochar produced from biosolids. In the current study, the effect of co-pyrolysis feedstock on product yield and properties was studied by mixing Biosolids (BS) with Wheat Straw (WS) and Canola Straw (CS) in a 3:1 mass ratio and carrying out thermal decomposition at 700 °C in a fluid bed reactor. This study found that the feedstock ash content and the volatile matter had a significant effect on biochar, oil, and gas yields from co-pyrolysis. The results also indicated that the addition of WS and CS feedstock notably reduced As, Cd, Cr, Cu, Ni, Pb, Se, and Zn concentrations in the biochar, due to the net effect of dilution and synergistic effects. BS-WS and BS-CS co-pyrolysis reduced Cu concentration in biochar by 61.6% and 63.3%, respectively, and Zn concentration by 66.4% and 64.4%, respectively. Lignocellulosic biomass addition also reduced biochar yield and improved C, H, and N content, along with the calorific value and the thermal stability of biochar. C content was increased by 36.9% in BS: WS biochar and 43.3% in BS: CS biochar compared to solely biosolids’ biochar. The calorific value of biochar was increased by 43.5% and 52.9% in BS-WS biochar and BS-CS biochar compared to biosolids’ biochar. During co-pyrolysis, CS addition produced oil with the lowest mole percentage of nitrogenated compounds. However, the addition of WS and CS increased co-pyrolysis oil acidity. Biosolids co-pyrolysis with WS and CS also increased the gas yield and the heating value compared to biosolids pyrolysis. Furthermore, the synergistic effect between biosolids and co-feedstocks resulted in increased gas yields and decreased oil and biochar yields.

Investigating mixed biosolids and cardboard for methylene blue adsorption: Activation, adsorption modelling and thermodynamics

Ongoing global population boom has led to the rise in waste and related research on increasing its economic value. In such an attempt, this study aims to activate gas-to-liquids (GTL) derived biosolids (BS) and cardboard (CB) and mixed samples (50:50) using potassium carbonate to produce three activated carbons (ACs): KBS, KCB and KM respectively. The characterization of the samples revealed surface areas of 156, 515, and 527 m2/g for KBS, KCB, and KM, respectively based on Brunauer–Emmett–Teller (BET) analysis, with increased porosity and metal content after activation evident from the Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS) results, as well as the presence of magnetite in the KBS and KM samples apparent from the X-ray powder diffraction (XRD) results. Additionally, Fourier Transform Infrared Spectroscopy (FTIR) results indicate increased C–O–C stretches and O–H bonds after activation of the samples.The ACs were used for methylene blue (MB) removal process which is a rapid for all three samples, reaching equilibrium after 9 h, and optimal at neutral pH and maximum at the highest temperature, 40 °C. The MB adsorption capacity was highest for KM (191.07 mg/g), followed by the KCB and KBS samples. Isotherm modelling of the samples showed best fits for KBS, KCB and KM as Langmuir-Freundlich (LF), Langmuir and Toth models respectively. On the contrary, kinetic modelling using contact time study data for all samples exhibited best fits by the Diffusion-chemisorption (DC) model. Finally, the thermodynamic calculations of the mixed sample disclosed the adsorption process to be exothermic and spontaneous, with potential mechanisms being electrostatic attraction, ion exchange, π-π interactions, and hydrogen bonding. Multiple cycles of KM regeneration was also achieved with good adsorption capacities. Future work will explore other activation methods and examine the magnetic properties of KBS and KM for real water treatment.

Potential of GTL-Derived Biosolids for Water Treatment: Fractionization, Leachate, and Environmental Risk Analysis

This study aims to understand the potential of using biosolids produced from the world’s largest gas-to-liquid (GTL) plant for water treatment applications. The metal fractionization of the two samples: raw biosolid (BS) and the pyrolyzed biosolid-BS char (BSC) (temperature: 450 °C, heating rate: 5 °C/min, residence time: 30 min) into exchangeables (F1), reducible (F2), oxidizable (F3), and residual (F4) were carried out following the Community Bureau of Reference (BCR) procedure. Characterization showed an increased carbon content and reduced oxygen content in the biochar sample. Additionally, the presence of calcium, magnesium, and iron were detected in smaller quantities in both samples. Based on the extraction results for metals, the environmental risk analysis was determined based on RAC (Risk Assessment Code) and PERI (Potential Ecological Risk Index) indices. Furthermore, leaching studies following the TCLP (Toxicity Characteristic Leaching Procedure) were conducted. The results prove that pyrolyzing stabilizes the metals present in the raw material as BS sample had high F1 fractions, and the BS char had a greater F4 fraction. While the RAC and PERI indices show that the pyrolyzed BS has a ‘low risk’, much reduced compared to the original BS sample, this is confirmed by the leaching studies that displayed minimal leaching from the pyrolyzed sample. Overall, this study proves that the GTL biosolids can best be applied for water treatment after pyrolysis.

Compost Quality Indexes (CQIs) of Biosolids Using Physicochemical, Biological and Ecophysiological Indicators: C and N Mineralization Dynamics

The increasing production of biosolids (BS) as a result of urban wastewater treatment generates pollution problems in their management and final disposal, and a better management is needed for their disposal. The composting of BS is an alternative process for obtaining a product with potential application as an organic amendment in the recovery of agricultural soils. As a biotechnological contribution, this study analyzed a composting process with BS, bovine manure (BM) and rice husks using four treatments T1 (C/N = 24); T2 (C/N = 34); T3 (C/N = 44); T4 (C/N = 54) for 120 days, in order to develop compost quality indexes (CQIs) through the analysis of 18 physicochemical, biological and ecophysiological indicators. Subsequently, three methodologies—successfully used on soils—were implemented for the development of the CQIs called “unified”, “additive” and “nemoro”. The indicators that comprised the CQIs were nitrification index (NI) and synthetic enzymatic index (SEI). The CQIs made it possible to differentiate the quality of the compost according to the treatments applied. The treatments used resulted in composts considered phytonutritious whose average quality value depending on the CQI developed was considered high (CQIw = 0.62), moderate (CQIa = 0.56) and low (CQIn = 0.30). The developed CQIs can be applied to determine the quality of BS composting systems reducing the cost of monitoring.

Phytomanagement of Pb/Zn/Cu tailings using biosolids-biochar or -humus combinations: Enhancement of bioenergy crop production, substrate functionality, and ecosystem services.

The extreme characteristics of mine tailings generally prohibit microbial processes and natural plant growth. Consequently, vast and numerous tailings sites remain barren for decades and highly susceptible to windblown dust and water erosion. Amendment-assisted phytostabilization is a cost-effective and ecologically productive approach to mitigate the potential transport of residual metals. Due to the contrasting and complementary characteristics of biosolids (BS) and biochar (BC), co-application might be more efficient than individually applied. Studies considering BS and BC co-application for multi-metal tailings revegetation are scarce. As tailings revegetation is a multidimensional issue, clearly notable demand exists for a study that provides a comprehensive understanding on the co-application impact on interrelated properties of physicochemical, biological, mineral nitrogen availability, metal immobilization, water-soil interactions, and impacts on plant cultivation and biomass production. This 8-month greenhouse study aimed at investigating the efficacy of co-application strategies targeting BS and carbon-rich amendments (BC or humic substances (HS)) to phytomanage a slightly alkaline Pb/Zn/Cu tailings with bioenergy crops (poplar, willow, and miscanthus). A complementary assessment linking revegetation effectiveness to ecosystem services (ES) provision was also included. Owing to their rich nutrient and organic matter contents, BS had the most pronounced influence on most of the measured properties including physicochemical, enzyme activities, NH4+-N and NO3--N availability, immobilization of Zn, Cu, and Cd, and biomass production. Co-applying with BC exhibited efficient nutrient release and was more effective than BS alone in reducing metal bioavailability and uptake particularly Pb. Poplar and willow exhibited more superior phytostabilization efficiency compared to miscanthus which caused acidification-induced metal mobilization, yet BC and BS co-application was effective in ameliorating this effect. Enhancement of ES and substrate quality index mirrored the positive effect of amendment co-application and plant cultivation. Co-applying HS with BS resulted in improved nutrient cycling while BC enhanced water purification and contamination control services.

Biosolids-based activated carbon for enhanced copper removal from citric-acid-rich aqueous media.

In this study, we employed batch experiments to assess the effects of citric acid on the Cu(II) removal efficiencies of seven biosolids-based adsorbents. The adsorbents used were dried biosolids (BS), biosolids biochar (BSBC), biosolids-based activated carbon (SBAC), nitric-acid-modified BSBC (BSBC-HNO3) and SBAC (SBAC-HNO3), and amine-modified BSBC (BSBC-NH2) and SBAC (SBAC-NH2). However, with 100mM citric acid in 1mM Cu(II) solution, only SBAC showed an increase in Cu(II) removal efficiency (64.0-93.5%). Therefore, we used SBAC for further optimisation of the adsorption process. The kinetics data, optimally described by the pseudo-second-order model, indicated that bulk Cu(II) adsorption occurred within 10min. The highest Cu(II) removal was at pH 3, with the estimated maximum Cu(II) adsorption capacity of SBAC increasing from 0.14 to 0.30mmol/g, with 100mM citric acid present. This result clearly indicated the positive effect of citric acid on Cu(II) adsorption. With citric acid present, the Freundlich model optimally fitted the adsorption isotherm data, suggesting adsorption of Cu(II) in multilayers. Further investigation of Cu(II) adsorption in a sequential setup proved that SBAC could lower the residual Cu(II) in the solution to below the discharge limit (0.05mM) in 1h. Overall, the production of activated carbon from BS has been proven an efficient Cu(II) adsorbent for Cu-citric-acid-rich aqueous media as a simulation of real wastewaters/leachates, as well as achieving waste-to-resources goals. This is the first study to identify an adsorbent (SBAC) with increased Cu(II) adsorption capacity in the presence of excess citric acid.

Estimation of Higher heating Value of Biomass from Proximate and Ultimate Analysis: A Novel Approach

Biomass is the organic matter formed by photosynthesis that occurs on the earth’s surface. They contain all forms of waste compost, including urban solid waste, municipal bio solids, animal wastes, forestry and agricultural wastes, and some industrial wastes. Efficient use of biomass oil would aid in the resolution of issues caused by fossil fuels. However, the biggest issue about using this energy is due to the gas composition of biomass material. As a result, properties of biomass are the critical parameter for assessing the fuel content of a special biomass substance in energetic applications. Gasification is the most mature thermo-chemical conversion technique available among the various methods of transforming biomass materials to bio resources. In this context, proximate and ultimate analysis has been used to classify two groups of biomass material that carry out in this experiment. The proximate analysis results have been obtained by the TGA technique while the ultimate analysis results will obtain by the GC mechanism. Then, based on the proximate analysis data various empirical equations containing linear and nonlinear terms were evaluated in order to predict the higher heating values (HHV) of the entire sample range. Since, the biomasses used in this analysis have different properties and fuel characteristics, the estimated HHV for the wood pellet sample are between 15.33 and 19.71 MJ/kg, while the rubber seed sample is between 15.18 and 18.64 MJ/kg. According to the experimental findings, the HHV of wood pellet is at around 2.95 MJ/Nm3 while the HHV of rubber seed of about 4.99MJ/Nm3. The comparison on the theoretical analysis have been show 0.19% compared to the results on wood pellet while the rubber seed have at around 2.07% difference compare each other. The experimental results on wood pellets, the findings reveal a 15.35% difference, while rubber seed indicates a 13.81% difference. Nonetheless, the finding and analysis on the properties, the results can be considered within reasonable limits.

Crescimento inicial de mudas de zínia em substrato com diferentes proporções de biossólido

Abstract Zinnia (Zinnia elegans Jacq.) is a widely cultivated species and used as an ornamental plant in the world flower market. Although it has great potential for phytoremediation and compounds with anti-infective and antioxidant activities there are few studies that address the process of production of its seedlings especially using substrates from organic waste. This study aimed to evaluate the potential of biosolid as a substrate component in the initial growth of Zinnia elegans seedlings. The seedlings were produced in nursery conditions with 50% light control. The experimental design was entirely randomized. There were six treatments, four repetitions and five plants per plot. The treatments consisted of substrates resulting from the mixture of subsoil (SS) and biosolid (BIO) in different proportions: 100% SS (control); 80% SS + 20% BIO; 60% SS + 40% BIO; 40% SS + 60% BIO; 20% SS + 80% BIO; T6 100% BIO. The morphological and quality characteristics of the seedlings were evaluated. Polynomial regression analysis and Pearson correlation coefficient were performed. Quadratic regression fitting was observed for plant height, stem diameter, leaf area, total chlorophyll, and shoot and root dry mass, as well as total dry mass. The shoot height/stem diameter ratio was the characteristic that correlated least with the others, being observed a positive correlation only with plant height. The use of biosolid in the proportion of 60% in the substrate composition proved to be efficient for the initial growth of seedlings as it showed the best responses for most morphological and quality characteristics of the seedlings.

Liming and co‐application of water treatment residuals with biosolids for conditioning sandy soils

AbstractApplication of water treatment residuals (WTR) and biosolids (BS) might ameliorate fragile soils. However, studies integrating impacts of waste preparation methods such as liming and grinding associated with co‐application approaches for soil conditioning are lacking. The present study aimed to evaluate the feasibility of agricultural use of WTR as well as their co‐application with BS to ameliorate a sandy soil through assessing impacts on selected soil quality indicators and on nutrient and potentially toxic element concentration in plant tissue in addition to the biomass yield of annual crops. The following treatments were evaluated: non‐amended soil (control); drying plus grinding and liming WTR; WTR co‐application with BS at 3:1 ratio; and a soil amendment commercially available in Brazil. All treatments were soil incorporated in the 0.0–0.2 m layer at 30 Mg ha−1 dose (dry mass). Selected soil physical, hydraulic, and chemical parameters were determined. Furthermore, nutrients and potentially toxic elements concentration in plant tissue as well as the agronomic performance of maize and ryegrass were measured. The co‐application of WTR and BS increased the soil content of P, Zn, and Cu in the 0.0–0.1 m layer. The concentration of these nutrients also was greater in ryegrass tissue and promoted the biomass yield in 51%. WTR did not increase contaminants and did not decrease the P content in soil and in plant tissue, independently of drying plus grinding and liming. Considering the conditions investigated in our study, WTR/BS co‐application was environmentally safe and effective in ameliorating soil quality.

Laccase-Driven Transformation of High Priority Pesticides Without Redox Mediators: Towards Bioremediation of Contaminated Wastewaters.

In this study, Pleurotus dryinus was grown on municipal biosolids (BS) as the substrate to produce laccase for the removal of pesticides (fungicides, herbicides, and insecticides) from wastewater. Among the various types of BS tested, sterilized biosolids were the most promising substrate for laccase production by P. dryinus with a maximal laccase activity (162.1 ± 21.1 U/g dry substrate), followed by hygenized biosolids (96.7 ± 17.6 U/g dry substrate), unsterilized biosolids (UBS) (31.9 ± 1.2 U/g dry substrate), and alkali-treated biosolids (8.2 ± 0.4 U/g dry substrate). The ultrasound-assisted extraction of this enzyme from fermented UBS was carried out with 0.1 M phosphate buffer at pH 7.0, which increased the enzyme activity of the crude extract by 30%. To test the catalytic potential of the biocatalyst in real matrices, 1 U/ml of recovered crude laccase extract was applied for 24 h for the removal of 29 pesticides (nine fungicides, 10 herbicides, and 10 insecticides) either separately or as a mixture from spiked biologically treated wastewater effluent. When treated with crude enzyme extract, high-priority herbicides metolachlor and atrazine were completely removed, while 93%–97% of the insecticides aldicarb, spinosad, and azinphos-methyl and up to 91% of kresoxim-methyl were removed. Promising results were obtained with BS-derived crude enzyme extract exhibiting improved pesticides removal, which may be due to the mediator effect resulting from the catalytic transformation of other molecules in the cocktail. The results demonstrated a promising integrated bioprocess for the removal of pesticides in wastewater using crude laccase obtained from BS.

Crescimento inicial de mudas de Syagrus romanzoffiana em substrato à base de biossólido

ABSTRACT Substrate composition is a major factor influencing seedling quality. This study aimed to evaluate the potential of biosolid as a substrate component in the initial growth of Syagrus romanzoffiana (Cham.) Glassman seedlings. The experimental design was completely randomized, with six treatments, five replicates and seven plants per plot. The treatments consisted of substrates resulting from the mixture of subsoil (SS) and biosolid (BIO) at different proportions: 100 % SS; 20 % BIO + 80 % SS; 40 % BIO + 60 % SS; 60 % BIO + 40 % SS; 80 % BIO + 20 % SS; 100 % BIO. The seedling quality and morphological characteristics were evaluated. There was an increase up to the proportion of 60 % of biosolid for shoot height, stem diameter, number of leaves, leaf area, total chlorophyll content, root length, shoot dry matter and Dickson’s quality index. For the root and total dry matter, increases occurred up to the proportion of 40 % of biosolid. Therefore, the use of biosolid in the proportions of 40 and 60 % in the substrate composition proved to be efficient, as they promoted a satisfactory initial growth (all seedlings presented shoot height between 30 and 40 cm and stem diameter of 5 mm) and quality of the evaluated seedlings.

Integrated Biotechnology Management of Biosolids: Sustainable Ways to Produce Value—Added Products

Biosolids (BS) are organic dry matter produced from wastewater treatment plants (WWTPs). The current yearly worldwide production of BS is estimated to be around 100–125 million tons and is expected to continuously increase to around 150–200 million tons by 2025. Wastewater treatment industries across the globe strive to achieve a green and sustainable manufacturing base for the management of enormous amounts of municipal BS, which are rich in nutrients and organic dry matter along with contaminants. The management of these organic-rich wastes through environmentally friendly recovery technologies is a major challenge. The need to improve waste biomass disposal by biological development and develop more economically viable processes has led to a focus on the transformation of waste resources into value-added products (VAP). This paper assesses the leading disposal methods (based on volume and contaminant reduction) and reviews the state of biotechnological processes for VAP recovery from municipal wastewater sludge (untreated solid waste residual) and BS (stabilized solid waste which meets criteria for its use in land). A review of the anaerobic and aerobic digestion processes is presented to provide a holistic overview of this growing research field. Furthermore, the paper also sheds light on the pollutant reduction and resource recovery approaches for enzymes, bioflocculants, bioplastics, biopesticides, and biogas as a mean to represent BS as a potential opportunity for WWTPs. However, only a few technologies have been implemented for VAP resource recovery and a shift from WWTPs to waste resource recovery facilities is still far from being achieved.

Industrial Symbiosis through the Use of Biosolids as Fertilizer in Romanian Agriculture

Biosolids’ use in agriculture is an example of industrial symbiosis. The application of biosolids (BS) in agriculture is considered one of the most sustainable sewage sludge (SS) management options, but the quality of biosolids has to meet certain requirements regarding the characteristics of the sludge, those of the land and of the type of crop. Web of Science database has been used to search for the relevant literature. The review of studies undertaken in order to determine the economic effects of the use of biosolids in agriculture shows, in the majority, an increase in crop yield and the reduction in costs, due to the reduction in the requirements for the application of chemical or synthetic fertilizers. If the entire sewage sludge production in Romania for 2019 had been used as fertilizer, the estimated cost reduction for farmers would have been almost 3 million Euros—considering the 230.59 thousand tons of dry matter produced in 2019. The estimated savings for 2019 of the sewage and water utilities, if the sewage sludge had been used in agriculture instead of depositing it at the landfill, would have been about 3.9 million Euros. However, the limits of the symbiosis are due to the size of the farms, the type of plants cultivated, pH, slope inclination, heavy metal content and social acceptance. It is impossible to use all the sewage sludge in agriculture, but these figures are a good estimation of the economic effects.