Biorefinery of waste activated sludge: Nutrient recovery and microbial lipid production by Yarrowia lipolytica.

The rising generation of waste activated sludge (WAS) demands a fundamental shift towards resource reuse and recovery. The conventional methodologies used to manage this by-product derived from wastewater treatment plants are increasingly constrained due to stringent regulatory measures aimed at mitigating its adverse impacts on the environment and public health. Therefore, this work evaluated a promising strategy for the efficient management of WAS, transforming it into a valuable renewable source to produce high-value-added compounds, such as lipids and a slow-release fertilizer (struvite). Wet oxidation (WO) was identified as a suitable technique for solubilising WAS while generating short-chain fatty acids (primarily acetic acid). It was found that conducting WO at 200 °C for 120 min resulted in a 65% reduction of the total suspended solids (TSS) content and 87% of the volatile suspended solids (VSS) content. Additionally, under these conditions, 4440 ± 105 mg/L and 593 ± 21 mg/L of acetic and propionic acid were obtained, respectively, which were assimilated by Yarrowia lipolytica to produce biolipids. Furthermore, the rupture of WAS flocs also led to the solubilisation of 980 ± 8 mg/L of ammonium. During the struvite precipitation stage, a NH4:PO4:Mg ratio of 1:1.5:1.5 was found to be the most effective for removing soluble ammonium (97.4 ± 0.8%), resulting in a high-purity struvite formation, and enhancing the carbon/nitrogen (C/N) ratio of the oxidised WAS from 3 to 105. This improvement in the C/N ratio raised the lipid content from 36 ± 1% to 49 ± 1% during the cultivation of Y. lipolytica. The application of the sequencing batch culture strategy further increased lipid content to 59 ± 1%, with 6.0 ± 0.3 g/L as the final concentration after the fifth cycle. The lipids produced, mainly monounsaturated fatty acids with 40% of oleic acid, offer potential as biodiesel feedstock. This lipid composition led to biodiesel properties, including cetane number, iodine value, kinematic viscosity and density that met international standards. Therefore, this research presents a promising alternative not only for WAS management but also for harnessing valuable resources, thereby establishing a basis for large-scale studies.

Advanced thermal hydrolysis for biopolymer production from waste activated sludge: Kinetics and fingerprints.

Waste activated sludge (WAS) is the main residue of wastewater treatment plants, which can be considered an environmental problem of prime concern due to its increasing generation. In this study, a non-energetic approach was evaluated in order to use WAS as a renewable resource of high value-added products. For this reason, WAS was treated by thermal hydrolysis, H2O2 oxidation and advanced thermal hydrolysis (ATH) promoted by H2O2. The influence of temperature, H2O2 concentration and dosing strategy on biomolecule production (proteins and carbohydrates), size distribution (fingerprints) and various physico-chemical parameters (VSS, total and soluble COD, soluble TOC, pH and colour) was studied. The results revealed a synergistic effect between TH and H2O2 oxidation, which led to a significant increase in the production of both proteins and carbohydrates. In this sense, the concentration of proteins and carbohydrates obtained during TH at 85 °C for120 min was found to be 1376 ± 9 mg/L (121 mg/gVSSo) and 208 ± 4 mg/L (18 mg/gVSSo), respectively. However, in the presence of 4.5 mM H2O2/gVSSo under the same process conditions, the concentrations of proteins and carbohydrates exhibited a significant increase of 1.9-fold and 3.1-fold, respectively. Besides, the addition of H2O2 promoted the transformation of hydrophobic compounds, such as proteins and or lipids, into hydrophilic compounds, which presented low and medium sizes. An increase in temperature improved the solubilization rate and the yield of biomolecules significantly. Besides, the analysis of the kinetics related to the dosing strategy of H2O2 suggested the existence of two fractions during WAS solubilization, one of them being easily oxidizable, whereas the other one was more refractory to oxidation. Thus, the value of kH2O2 for the first addition of 1 mM H2O2/g VSSo was 0.020 L0.4 mgH2O2-0.4 min-1, while it was 4.3 and 8 times lower for the second and third additions, respectively.

Heavy metal solubilisation during the hydrothermal treatment of sludge.

The present study analyses the combined effects of temperature (from 160 to 200 °C), and, for the first time ever, type of atmosphere (oxidising or inert) and pressure (from 60 to 100 bar) on the solubilisation of heavy metals during the hydrothermal treatment of wet no-diluted sewage sludge. Results revealed that Cd, Pb, Al and Fe were hardly affected by neither the atmosphere nor temperature, remained almost completely in the solid phase during all the hydrothermal treatments tested; while Cr, Ni, Cu and Zn were partially solubilised, being this solubilisation favoured by the presence of an oxidising atmosphere. In contrast, initial dissolved Hg was partially precipitated under both types of atmosphere, although it was re-dissolved after 30 min under an inert atmosphere. Regarding the working conditions, the highest temperature (200 °C) caused the greatest metal immobilisation, whereas the range of pressures tested barely had any effect on it. Concerning the reaction time, the lowest concentration of metals in the liquid fraction of the hydrolysed sludge was obtained during the initial 30 min of treatment.

Inhaled Methoxyflurane Provides Greater Analgesia and Faster Onset of Action Versus Standard Analgesia in Patients With Trauma Pain: InMEDIATE: A Randomized Controlled Trial in Emergency Departments.

STUDY OBJECTIVE: The objective of the InMEDIATE study was to evaluate the change in intensity of traumatic pain over the first 20 min in adult patients treated with methoxyflurane versus standard analgesic treatment in Spain. This the first randomized, active-controlled, multicenter trial of methoxyflurane in the emergency setting in Europe. METHODS: This was a randomized, controlled study that enrolled adult patients with acute moderate to severe (score ≥4 on the 11-point Numeric Rating Scale) trauma-associated pain in 14 Spanish emergency departments. Patients were randomized 1:1 to methoxyflurane (up to 2×3 mL) or standard analgesic treatment. Coprimary endpoints were the change from baseline in Numeric Rating Scale pain intensity score during the first 20 minutes of treatment and time to first pain relief. RESULTS: Three hundred five patients were randomized (methoxyflurane 156; standard analgesic treatment 149). Most patients in the standard analgesic treatment group (70%) received intravenous first-step analgesics and 9.4% of patients were treated with opioids. Mean decrease from baseline in Numeric Rating Scale pain intensity score was greater for methoxyflurane than standard analgesic treatment at all points, with a significant treatment difference overall up to 20 minutes (repeated-measures model 2.47 versus 1.39; treatment difference 1.00; 95% confidence interval 0.84 to 1.32). Median time to first pain relief was significantly shorter for methoxyflurane than standard analgesic treatment (3 versus 10 minutes). Methoxyflurane achieved better patient and clinician ratings for pain control and comfort of treatment than standard analgesic treatment and exceeded patient and clinician expectations of treatment in, respectively, 77% and 72% of cases compared with 38% and 19% for standard analgesic treatment. CONCLUSION: These results support consideration of methoxyflurane as a nonnarcotic, easy-to-administer, rapid-acting, first-line alternative to currently available analgesic treatments for trauma pain.

Persulfate activation by modified red mud for the oxidation of antibiotic sulfamethoxazole in water.

Different pre-conditioning treatments were evaluated in order to stabilize red mud, a waste product from bauxite processing, for obtaining heterogeneous catalysts (named as B1-B3) that can be employed as suitable activators of sodium persulfate (SPS) for the degradation of sulfamethoxazole (SMX), a model antibiotic, in water. The presence of Fe3O4 in the composition of the catalysts was found to be a key factor for a suitable activation of SPS, according to the XPS measurements. The oxidation of SMX was successfully fitted to a pseudo-first-order kinetic model (r2 > 0.96), obtaining a 68% removal after 180 min when 0.8 mg/L of SMX was oxidized with 2 g/L of SPS and 2 g/L of catalyst B3. The presence of organic and/or inorganic constituents in the water matrix significantly hindered the degradation rate of SMX, the apparent kinetic constants being from 2 to 3 times lower than that determined in ultrapure water test. The use of ultrasound irradiation coupled to the addition of B3 catalyst improved importantly the SMX oxidation in real aqueous matrices, thus attaining values of removal which almost triplicated the ones obtained in absence of ultrasounds.

Biodegradation of dissolved humic substances by fungi.

Humic and fulvic acids constitute humic substances, a complex mixture of many different acids containing carboxyl and phenolate groups, which are not only the principal soil fertility factors but also the main pollutants present in landfill leachates or natural organic matter in water. Due to their low bacterial biodegradability, fungal biodegradation processes are key for their removal. The present study compiles and comments all the available literature on decomposition of aqueous humic substances by fungi or by their extracellular enzymes alone, focusing on the influence of the reaction conditions. The biodegradation extent mainly depends on the characteristics and concentration of the humic compounds, the type of microorganisms selected, the inoculation mode, the C and N sources, the presence of certain chemicals in the medium, the availability of oxygen, the temperature, and the pH.

Sludge hydrothermal treatments. Oxidising atmosphere effects on biopolymers and physical properties.

In this work, the role of an oxidising atmosphere during the hydrothermal treatment of an activated sludge at 160 °C and 40 bar, was determined. The composition and molecular weight sizes of the soluble biopolymers generated during the sludge treatment in presence (wet oxidation "WO") or absence (thermal hydrolysis "TH") of oxygen were compared. Likewise, the characteristics of organic material, settleability, colour and pH of the treated sludge during both treatments were analysed. The thermal treatment in presence of oxygen provided better results in terms of solubilisation, settleability and mineralisation. WO initially favoured a more intense cellular lysis, causing a higher degree of solubilisation than that achieved by TH. Either in presence or absence of oxygen, thermal treatments caused a marked worsening of the settleability of the sludge. However, the degradation of biopolymers during WO led subsequently to an improvement of the settleability properties for longer reaction times. Both treatments caused a fast solubilisation of biopolymers at the beginning by effect of the release of extracellular and intracellular material from sludge. Subsequently, the presence of oxygen produced a significant decrease in the concentration of those biopolymers. In contrast, the proteins were the only one biopolymer that was degraded during TH.

Life cycle assessment of introducing an anaerobic digester in a municipal wastewater treatment plant in Spain.

Anaerobic digestion (AD) is being established as a standard technology to recover some of the energy contained in the sludge in wastewater treatment plants (WWTPs) as biogas, allowing an economy in electricity and heating and a decrease in climate gas emission. The purpose of this study was to quantify the contributions to the total environmental impact of the plant using life cycle assessment methodology. In this work, data from real operation during 2012 of a municipal WWTP were utilized as the basis to determine the impact of including AD in the process. The climate change human health was the most important impact category when AD was included in the treatment (Scenario 1), especially due to fossil carbon dioxide emissions. Without AD (Scenario 2), increased emissions of greenhouse gases, mostly derived from the use of electricity, provoked a rise in the climate change categories. Biogas utilization was able to provide 47% of the energy required in the WWTP in Scenario 1. Results obtained make Scenario 1 the better environmental choice by far, mainly due to the use of the digested sludge as fertilizer.

Wet oxidation of activated sludge: transformations and mechanisms.

Wet oxidation (WO) is an interesting alternative for the solubilization and mineralization of activated sludge. The effects of different temperatures (160-200 °C) and pressures (4-8 MPa), on the evolution of chemical composition and rheological characteristics of a thickened activated sludge during WO are analyzed in this work. Soluble COD increases initially to a maximum and then diminishes, while the apparent viscosity of the mixture falls continuously throughout the experiment. Based on the experimental evolution of the compositions and rheological characteristics of the sludge, a mechanism consisting of two stages in series is proposed. Initially, the solid organic compounds are solubilized following a pseudo-second order kinetic model with respect to solid COD. After that, the solubilized COD was oxidized, showing a pseudofirst kinetic order, by two parallel pathways: the complete mineralization of the organic matter and the formation of highly refractory COD. Kinetic parameters of the model, including the activation energies are mentioned, with good global fitting to the experiments described.

Wet oxidation of real coke wastewater containing high thiocyanate concentration.

Coke wastewaters, in particular those with high thiocyanate concentrations, represent an important environmental problem because of their very low biodegradability. In this work, the treatment by wet oxidation of real coke wastewaters containing concentrations of thiocyanate above 17 mM has been studied in a 1-L semi-batch reactor at temperatures between 453 and 493 K, with total oxygen pressures in the range of 2.0-8.0 MPa. A positive effect of the matrix of real coke wastewater was observed, resulting in faster thiocyanate degradation than was obtained with synthetic wastewaters. Besides, the effect of oxygen concentration and temperature on thiocyanate wet oxidation was more noticeable in real effluents than in synthetic wastewaters containing only thiocyanate. It was also observed that the degree of mineralization of the matrix organic compounds was higher when the initial thiocyanate concentration increased. Taking into account the experimental data, kinetic models were obtained, and a mechanism implying free radicals was proposed for thiocyanate oxidation in the matrix considered. In all cases, sulphate, carbonates and ammonium were identified as the main reaction products of thiocyanate wet oxidation.

Hydrolyzed sewage sludge as raw bio-based material for hermetic bag production.

This study aimed to assess the potential of sewage sludge, a significant residue of wastewater treatment plants (WWTPs), as a sustainable resource for producing a bio-based material for hermetic bags (BMHB), in order to reduce the dependency on petroleum-derived plastics. The approach involved the application of thermal hydrolysis to solubilize sewage sludge, and it systematically examined critical process parameters, including temperature (120-150 °C), residence time (1-4 h), and medium pH (6.6-10). Results revealed that alkaline thermal hydrolysis significantly enhanced biomolecule solubilization, particularly proteins (289 ± 1 mg/gVSSo), followed by humic-like substances (144 ± 6 mg/gVSSo) and carbohydrates (49 ± 2 mg/gVSSo). This condition also increased the presence of large-and medium-sized compounds, thereby enhancing BMHB mechanical resistance, with puncture resistance values reaching 63.7 ± 0.2 N/mm. Effective retention of UV light within the 280-400 nm range was also observed. All BMHB samples exhibited similar properties, including water vapor permeability (WVP) (∼3.9 g * mm/m2 * h * kPa), hydrophilicity (contact angles varied from 35.4° ± 0.3 to 64° ± 5), solubility (∼95%), and thermal stability (∼74% degradation at 700 °C). Notably, BMHB proved to be an eco-friendly packaging for acetamiprid, an agricultural pesticide, preventing direct human exposure to harmful substances. Testing indicated rapid pesticide release within 5 min of BMHB immersion in water, with only 5% of BMHB residues remaining after 20 min. Additionally, the application of this material in soil was considered safe, as it met regulatory limits for heavy metal content and exhibited an absence of microorganisms.

Valorisation of the residual aqueous phase from hydrothermally liquefied black liquor by persulphate-based advanced oxidation.

Hydrothermal liquefaction of Kraft black liquor is a promising method for the production of valuable organic chemicals. However, the separation of the biochar and biocrude leaves a residual aqueous phase in large volumes, which needs to be properly managed to make the process profitable. In this work, the persulphate-based advanced oxidation was assessed, for the first time ever, as a pretreatment of this aqueous phase to reduce its content of phenolic compounds and alcohols, which hinder further valorisation strategies. Results revealed that the phenolic compounds and the alcohols were oxidised in presence of low persulphate anion concentrations (<50 mM), mainly to quinone-like compounds and organic acids. At higher oxidant concentrations, these intermediates were subsequently oxidised to valuable acetic acid. When Fe (II) was added as the catalyst, low concentrations (<9 mM) enhanced the degradation of both phenolic compounds and alcohols due to the increase of the sulphate radicals, consequently reducing persulphate requirements for their removal. Nevertheless, higher Fe (II) doses produced the sequestration of sulphate radicals, thus decreasing the oxidation performance and generating undesired parallel reactions.

Characterization and reuse of waste from the magnesium nitrate fertilizer industry.

Currently, liquid fertilizers are considered strategic products in the sector, particularly those with nitrogen and magnesium in their composition. During their synthesis, the generated muddy and sticky residue is usually managed as a toxic waste because its properties and feasible valorization methods have not yet been studied. For the first time, this residue has been thoroughly characterized, and, on the results obtained, its possible reuse options have been discussed. This material, with 47 % moisture content, a neutral pH, and a specific density of 0.85, still contains 35 % dry weight of nitromagnesite. These findings, together with a high cation exchange capacity and the presence of iron, aluminium, calcium and silicon as minority components, make its reintroduction into the manufacturing process of fertilizers the most viable option for its valorization, having two alternatives for this purpose. The first is to use it as a feedstock for the production of solid fertilizers by adding 30 % quicklime to the residue to improve its mechanical properties, thus obtaining a fertilizer with 5.7 %, 5.0 % and 24.3 % (dry weight) of magnesium, nitrogen and calcium, respectively. The second option, which focused on obtaining a liquid fertilizer, allowed the recovery of approximately 86 % of the remaining nitromagnesite in the residue by washing it with nitric acid, reducing its initial dry mass by 77 %. Then, the resultant liquid phase, with 16 % magnesium nitrate, could be enriched to the 35 % concentration demanded by liquid fertilizer consumers by a subsequent acid attack of the raw rock.

Structure of the humic acid-like compounds of raw and hydrothermally treated sewage sludge.

Humic acids are of great interest in many fields; however, they are inhibitors of fermentative processes applied to hydrothermally treated sewage sludge. Hence, the structure and composition of soluble and bound humic acid-like fractions from raw and hydrothermally treated sewage sludge were studied. Lipid, polysaccharide, protein and aromatic fractions were identified, as well as a high nitrogen content (7-10 %) and low solubility in alkaline media. Thus, they do not strictly meet the chemical definition of 'humic acids'. The soluble humic acid-like compounds had more aromatic and less protein content. Thermal hydrolysis of sewage sludge increased their aromaticity to the detriment of protein and polysaccharide fractions, while wet oxidation caused an increase in all structural fractions. Regarding the bound compounds, lipid, polysaccharide and aromatic fractions increased markedly during both treatments, although oxygen produced higher degradation of the protein fraction and, from 1 h, the partial degradation of aromatic compounds and an increase in the C/N atomic ratio (from 5.0 to 18.7 after 2 h). Therefore, hydrothermal treatments have a positive impact on the hydrolysate biodegradability due to the organic matter solubilisation, but also a negative impact linked to the higher solubilisation of the humic acid-like compounds and their structural changes.

Decision criteria for the selection of wet oxidation and conventional biological treatment.

The suitability of wet oxidation or biological treatments for the degradation of industrial wastewaters is here discussed. Advantages of these operations, either singly or in combination, are discussed on the basis of previous experimental results from laboratory and industry. Decision diagrams for the selection of conventional biological treatment, wet oxidation or a combination of both techniques are suggested according to the type of pollutant, its concentration and the wastewater flow rate.

BOF slag as a new alkalizing agent for the stabilization of sewage sludge.

This study assessed, for the first time ever, the use of basic oxygen furnace (BOF) slag as alkalinizing material during the sludge conditioning, as an environmentally-friendly alternative to CaO and other conventional alkalis. Its effects on the dewatering, solubilisation and stabilization of sewage sludge were studied, testing increasing dosages of BOF from 0 to 6 gBOF/gTSS0 at room temperature and under constant mechanical agitation was evaluated. Results revealed that the addition of BOF slag to sewage sludge produced similar degrees of solubilisation to those obtained using lime, reaching a maximum of 34% of total COD for 3.00 gBOF/gTSS0. The use of BOF slag also involved a low solubilisation of either nitrogen, carbon or phosphorous, a negligible mobilization of heavy metals and a positive effect on its biological hygienisation. A Class A biosolid for doses of 4.50gBOF/gTSS0 or higher was achieved, which can be applied directly to the soil for agricultural purposes in accordance with current legislation.

Wet oxidation of salicylic acid solutions.

Salicylic acid is a frequent pollutant in several industrial wastewaters. Uncatalyzed wet air oxidation, which is a promising technique for the treatment of phenolic effluents, has not been analyzed yet for the removal of salicylic acid. The effect of different conditions of pH (1.3-12.3), pressure (1.0-4.1 MPa), temperature (413-443 K), and initial concentrations (1.45-14.50 mM) on the wet oxidation of salicylate/salicylic acid solutions have here been investigated. The pH value of the reaction media was found to be a key parameter for the rate of the oxidation process with an optimum at pH 3.1, when the concentrations of salicylic acid and salicylate were similar. The oxidation reaction followed pseudofirst-order kinetics with respect to salicylic acid and 0.82 order with respect to dissolved oxygen. Additionally, the evolution of the color during the wet oxidation was analyzed and discussed in relation with the formation of intermediate compounds. Then, a reaction pathway for the noncatalytic wet oxidation of the salicylic acid was proposed.

The wet oxidation of aqueous humic acids.

Humic acids are highly distributed in aqueous environments. This article examines in depth the advanced oxidation of humic acid aqueous solutions, in order to understand more complex oxidation processes such as those of the sewage sludge or landfill leachate, or the matrix effects triggered by the humic acids of natural organic matter (NOM) in the oxidation of other aqueous compounds as herbicides. Humic acids were efficiently oxidized; higher temperatures (180-220 °C) involved higher mineralization, the formation of intermediates with lower colour and also led to a higher concentration of organic acids at the end of the treatment, particularly acetic and oxalic ones. Nevertheless, humic acid wet oxidation was not sensitive to changes in the pressure, at least in the range tested (65-95 bar), but the initial pH (4-13) was found to be a key factor. Thus, alkaline media accelerated the humic acid removal, but more refractory intermediates were generated, and the organic acids, excepting malic acid, were more stable than in neutral or acidic media. Eventually, a lumped kinetic model was proposed and successfully fitted to the experimental data, including the effect of all the operating variables studied.

Role of Inhaled Methoxyflurane in the Management of Acute Trauma Pain.

Adequate treatment of trauma pain is an integral part of the management of trauma patients, not just for ethical reasons but also because undertreated pain can lead to increased morbidities and worse long-term outcomes. Trauma pain management presents challenges in the pre-hospital setting, particularly in adverse or hostile environments as well as in busy emergency departments (EDs). Inhaled methoxyflurane, administered at analgesic doses via a disposable inhaler, has recently become available in Europe for the emergency treatment of moderate to severe pain in conscious adult trauma patients. A growing body of evidence demonstrates that inhaled methoxyflurane is well tolerated and effective in providing a rapid onset of analgesia. In this paper, we discuss the rationale for methoxyflurane use in trauma pain management, data from clinical trials recently conducted in Europe, its efficacy and safety profile compared to current standard treatments, its place in therapy and organizational impact. We conclude that inhaled methoxyflurane represents an effective treatment option in the different settings where trauma patients require rapid and flexible pain resolution, with potential organizational advantages.

Production of carboxylic acids from the non-lignin residue of black liquor by hydrothermal treatments.

The present study assesses, for the first time, the use of the non-lignin residue from Kraft black liquor as a renewable source of carboxylic acids. For this purpose, the liquid fraction obtained after separating the lignin from the black liquor by acid precipitation was subjected to different hydrothermal treatments. It was found that the formation of carboxylic acids can be maximized at 190 °C, 70 bar and under an inert atmosphere, with concentrations after 2 h of 29.0 g/l of oxalic acid, 1.8 g/L of malic acid, 10.0 g/L of lactic acid, 4.1 g/L of formic acid, 11.8 g/L of acetic acid and 3.4 g/L of propionic acid. The presence of an oxidizing atmosphere generated a less concentrated, but more purified, stream of acids than that obtained by thermal hydrolysis, simplifying the subsequent downstream processing.