Slurry Treatment Research Articles

Ecological circular agriculture: A case study evaluating biogas slurry applied to rice in two soils

In the context of carbon peak, neutrality, and circular agricultural economy, the use of renewable resources from agricultural processing for plant cultivation still needs to be explored to clarify material flow and its ecological effects. Paddy-upland rotation is an effective agricultural strategy to improve soil quality. This study evaluated the effects of biogas slurry application against those of chemical fertilisers in these two typical Chinese cropping soils. The application of biogas slurry increased total carbon content in paddy soil by 73.4%, and that in upland soil by 65.8%. Conversely, application of chemical fertiliser reduced total carbon in both soil types. There were significant positive correlations between total carbon and Zn, Cu, and Pb in rice husks grown in paddy soil (R2 = 0.95, 0.996, 0.95; p < 0.05). The content of amylose in biogas slurry treatment of paddy soil increased by 35.9%, while that in upland soil decreased by 19.2%. After biogas slurry was applied, the contents of fulvic acid- and humic acid-like substances in paddy soil average increased by 40.9% and 45.6%, while the contents of protein-like components were enhanced by 46.8% in upland soil. This result was consistent with predictions of microbial community function. Microorganisms in paddy soil generally preferred carbon fixation, while those in upland soil preferred hydrocarbon degradation and chemoheterotrophy. Understanding the changes in soil carbon stock and microbial function after biogas slurry application will contribute to sustainable agricultural development and food security.

Development of microalgae-bacteria symbiosis system for enhanced treatment of biogas slurry

In this study, microalgae-bacteria consortia were developed using bacteria and microalgae isolated from biogas slurry for enhanced nutrients recovery and promoted microalgae growth in wastewater. The enhancement rate was introduced to quantify the interaction between bacteria and microalgae. Co-culture of the indigenous microalgae and bacteria could significantly improve the tolerance of microorganisms to pollutants, increase value-added products’ production, promote nutrients removal, and reduce carbon emissions compared to mono-culture. The co-culture of Chlorella sp. GZQ001 and Lysinibacillus sp. SJX05 performed best, with its biomass, lipid, protein and fatty acid methyl ester productivities achieved 113.3, 19.2, 40.9 and 3.7 mg·L−1·d−1, respectively. The corresponding nutrients removal efficiencies for ammonia nitrogen, total nitrogen, total organic carbon, and total phosphorus were 83.2%, 82.1%, 34.0% and 76.6%, respectively. These results indicated that co-culture of certain indigenous bacteria and microalgae is beneficial to biogas slurry treatment and microalgae growth.

Metagenomic and HT-qPCR analysis reveal the microbiome and resistome in pig slurry under storage, composting, and anaerobic digestion

Direct application of pig slurry to agricultural land, as a means of nutrient recycling, introduces pathogens, antibiotic resistant bacteria, or genes, to the environment. With global environmental sustainability policies mandating a reduction in synthetic fertilisation and a commitment to a circular economy it is imperative to find effective on-farm treatments of slurry that maximises its fertilisation value and minimises risk to health and the environment. We assessed and compared the effect of storage, composting, and anaerobic digestion (AD) on pig slurry microbiome, resistome and nutrient content. Shotgun metagenomic sequencing and HT-qPCR arrays were implemented to understand the dynamics across the treatments. Our results identified that each treatment methods have advantages and disadvantages in removal pollutants or increasing nutrients. The data suggests that storage and composting are optimal for the removal of human pathogens and anaerobic digestion for the reduction in antibiotic resistance (AMR) genes and mobile genetic elements. The nitrogen content is increased in storage and AD, while reduced in composting. Thus, depending on the requirement for increased or reduced nitrogen the optimum treatment varies. Combining the results indicates that composting provides the greatest gain by reducing risk to human health and the environment. Network analysis revealed reducing Proteobacteria and Bacteroidetes while increasing Firmicutes will reduce the AMR content. KEGG analysis identified no significant change in the pathways across all treatments. This novel study provides a data driven decision tree to determine the optimal treatment for best practice to minimise pathogen, AMR and excess or increasing nutrient transfer from slurry to environment.

To evaluate the dimensional accuracy and hardness of gypsum cast on repeated immersion in sodium hypochlorite and peroxygenic acid: An in-vitro study

Microbes, fungi, and viruses present in the dental atmosphere have been linked to debilitating and life threatening diseases. Transmission of infected materials from the clinic to the dental laboratory results in a high level of cross contamination. The objective of the study was to evaluate the dimensional accuracy and hardness of gypsum cast on repeated immersion in 0.525 percent Sodium hypochlorite and 1percent Peroxygenic acid. 72 specimens of type 3 dental stone were created. 24 specimens were immersed in slurry, 0.525 percent Sodium hypochlorite, and 1 percent Peroxygenic acid solutions for 30 minutes, then air dried for 24 hours. For testing purposes, this process was repeated seven times. The hardness of stone cylindrical specimens was evaluated using a Rockwell hardness testing equipment. The values obtained by Kruskal-Wallis and Mann-Whitney tests, which were employed for statistical analysis at α=0.05, were used to evaluate dimensional accuracy and hardness. When compared to the 0.525 percent Sodium hypochlorite and slurry treatments, the specimens treated with 1 percent peroxygenic acid showed more dimensional change. Maximum hardness was achieved with 1 percent peroxygenic acid. Slurry & 0.525 percent sodium hypochlorite is dimensionally stable than 1 percent Peroxygenic acid. Hardness of type III dental stone samples disinfected by 1 percent Peroxygenic acid was the highest. Given the other benefits of virkon as a disinfectant agent, as well as the lowest reduction in gypsum mechanical strength, it can be recommended for the disinfection of stone casts in the clinic and laboratory.

Component analysis and risk assessment of biogas slurry from biogas plants

Massive amounts of biogas slurry are produced due to the development of biogas plants. The pollution features and the risk of biogas slurry were fully evaluated in this work. Thirty-one biogas slurry samples were collected from sixteen different cities and five different raw materials biogas plants ( e . g . cattle manure, swine manure, straw-manure mixture, kitchen waste and chicken manure). The chemical oxygen demand (COD), ammonia nitrogen ( NH 4 + ‐ N ), anions ( e . g . Cl − , SO 4 2 ‐ , NO 3 ‐ and PO 4 3 ‐ ), antibiotics ( e . g . sulphonamides, quinolones, β 2 -receptor agonists, macrolides, tetracyclines and crystal violet) and heavy metals ( e . g . Cu, Cd, As, Cr, Hg, Zn and Pb) contents from these biogas slurry samples were systematically investigated. On this basis, risk assessment of biogas slurry was also performed. The concentrations of COD, NH 4 + ‐ N and PO 4 3 ‐ in biogas slurry samples with chicken manure as raw material were significantly higher than those of other raw materials. Therefore, the biogas slurry from chicken manure raw material demonstrated the most serious eutrophication threat. The antibiotic contents in biogas slurry samples from swine manure were the highest among five raw materials, mostly sulphonamides, quinolones and tetracyclines. Biogas slurry revealed particularly serious arsenic contamination and moderate potential ecological risk. The quadratic polynomial stepwise regression model can quantitatively describe the correlation among NH 4 + ‐ N , PO 4 3 ‐ and heavy metals concentration of biogas slurry. This work demonstrated a universal potential threat from biogas slurry that can provide supporting data and theoretical basis for harmless treatment and reuse of biogas slurry.

A Machine Learning Based Intelligent Decision Support System for Flotation Dynamics in Simulation of Clay Minerals

In coal mines, process management is related with planning and flow of coal minerals from their mining points to journey’s end. The process is dependent on the operational decisions, which should be completed during coal production. In these systems, simulation modelling is assumed a powerful tool for decision making. The simulation modelling can further be enhanced through applying artificial intelligence (AI) and machine learning (ML) methods. The communication of water with clay minerals upholds the water adsorption on the clay surface, which makes them complex systems. Therefore, evading the water absorption from the clay turns out to be a hard job. The computational trainings of clay minerals are needed to comprehend the dynamics of water distribution. Tradition of coal slurry treatment is completed by adding medicament of its mineral flocculation sedimentation. As a result of coal, slime water contains a lot of clay minerals that are rich in kaolinite versatility and it is difficult to settle. The flotation will be one of the kaolinite recycling. In this paper, clay minerals containing a variety of minerals were taken as samples, and sodium dodecyl sulfate and sodium oleate were used as collectors to explore the flotation effect through test and molecular dynamics simulation. A machine learning based intelligent decision support system is designed to improve the outputs of the simulation model. The results show that when the pH value is 8 and the amount of collector and sec-octanol are 150 g/t and 250 g/t, respectively, the flotation rate of fine mineral can reach 63.25%. According to the molecular dynamics simulation results, the addition of the collector can reduce the hydrophilicity of the kaolinite surface, and the physical adsorption of SDS only occurs on the (001) surface.

Simultaneous biogas upgrading and biogas slurry treatment by different microalgae-based technologies under various strigolactone analog (GR24) concentrations

In this research, the effects of exogenous strigolactone analog (GR24) on the growth rate, daily productivity and photosynthesis of symbiotes of Chlorella vulgaris (C. vulgaris)–Ganoderma lucidum (G. lucidum)–endophytic bacteria, C. vulgaris–G. lucidum–activated sludge and C. vulgaris–G. lucidum–multi-walled carbon nanotube, and the simultaneous treatment of biogas slurry and biogas were examined. The C. vulgaris–G. lucidum–endophytic bacteria symbiote achieved the best treatment effectiveness for biogas slurry and biogas, with removal efficiencies of chemical oxygen demand, total nitrogen, total phosphorus and CO2 of 81.4 ± 7.6%, 79.6 ± 7.6%, 82.5 ± 8.2%, and 67.3 ± 6.3% under the optimal GR24 concentration of 10-9 M. Moreover, the treatment effects were positively correlated with growth performance and photosynthesis efficiency of the symbiote. These findings advance the development and application of symbiotic systems in the field of wastewater treatment and biogas upgrading.

Contrasting responses of fungal and bacterial communities to biogas slurry addition in rhizospheric soil of poplar plantations

Rhizosphere microorganisms can affect the nutrient uptake of plant roots, and therefore contribute significantly to plant growth and nutrient cycling in forest ecosystems. Our previous studies revealed that the application of biogas slurry, an available organic fertilizer, increased the signal intensity and diversity of functional microbial genes in bulk soil. Further study of the response of rhizosphere soil microbial community structure to biogas slurry fertilization is of great significance for elucidating the mechanisms of nutrient cycling in forest ecosystems. In this study, our aim was to investigate the effects of biogas slurry application at different concentrations (Control, no treatment; Low, 250 m3 ha−1 yr−1; High, 375 m3 ha−1 yr−1) on the microbial community structures in the rhizospheric soil of poplar plantations. We found that the treatments with the highest biogas slurry concentration had the greatest fungal community Shannon diversity and richness. Among these, the Shannon diversity of rhizospheric soil fungal communities increased significantly with the high-concentration biogas slurry treatment compared with the control. However, the Shannon index of bacterial communities in rhizospheric soil exhibited negligible changes with the addition of biogas slurry. Further analyses revealed that the relative abundance of the fungal community in rhizospheric soil significantly changed in response to the quantity of biogas slurry. In particular, the abundance of several functional fungi, that play important roles in plant growth, significantly altered with the application of biogas slurry. These may be due to the changes of rhizosphere soil physicochemical properties, such as C/N ratio and available P, caused by biogas slurry application. Our results suggest that fertilization with biogas slurry can elevate fungal community diversity, but not bacterial diversity, in rhizospheric soil.

An Experimental Study on the Treatment of Engineering Waste Slurry by Using Agent Conditioning-Combined Pressure Filtration

Taking the waste high-moisture slurry produced at a construction site in Shanghai as the research object, the pressure filtration effect of the slurry under the condition of agent conditioning was studied. First of all, the geotechnical characteristics of the waste slurry under agent conditioning were studied through laboratory experiments, and the selection and addition amount of the agent were preliminarily determined. Then, the influence of agent addition, stirring time, and pressure filtration time on the pressure filtration efficiency was studied through field experiments. Finally, a method to guide the field filtration time by the indoor model test was put forward.

Sulfur fertilization strategy affects grass yield, nitrogen uptake, and nitrate leaching: A field lysimeter study#

AbstractBackgroundGlobally and at the European Union level there are mounting concerns regarding nitrogen (N) losses from agricultural systems and pressure to reduce N losses to water and air. Suboptimal plant sulfur (S) availability can reduce plant N efficiency and thereby increase N loss potential. Climate change action demands lower sulfur dioxide emissions thus S deposition levels are at an all‐time low.AimsThe objectives of the current study were to (1) determine the potential for adequate S nutrition to increase grassland yield and N efficiency, (2) determine if alleviating S deficiency reduces nitrate leaching, and (3) evaluate a number of strategies for applying S including the use of cattle slurry.MethodsThis work was completed using a free‐draining sandy loam grassland lysimeter facility. There were six treatments using calcium ammonium nitrate (CAN), CAN + calcium sulfate (CAN+S), ammonium sulfate + CAN (AS+CAN), and slurry (Slurry+CAN and Slurry+CAN+S, respectively) to deliver S strategies. The yield, plant N and S uptake, and nitrate and sulfate leachate were measured to compare treatments.ResultsApplication of mineral S fertilizer increased yields significantly (up to 2,907 kg ha–1) and increased apparent fertilizer nitrogen recovery from 39% to 47–49%. Alleviating S deficiency also significantly decreased nitrate leaching to levels not differing significantly from the control. There was a reduction of 46% in nitrate leaching with the addition of mineral S (CAN+S and AS+CAN) compared to N only. The nitrate concentration standard for drinking water was not breached for treatments that included S (6.6–11 mg NO3–‐N L–1), whereas it was breached for those without S (23–40 mg NO3–‐N L–1). The S applied in the slurry treatment was not adequate (9 kg S ha–1) to meet plant requirements.ConclusionThis study provides evidence that optimization of S nutrition has the potential to deliver large agronomic and environmental benefits along with potential as a nitrate leaching migration strategy on S‐deficient soils.

A step towards the production of manure-based fertilizers: Disclosing the effects of animal species and slurry treatment on their nutrients content and availability

In a context of climate change and circular economy, it is fundamental to produce animal manure-based fertilizers attractive to farmers who are reluctant to use heterogeneous materials, poorly characterized and with unbalanced nutrient contents, namely N:P ratios different from plant requirements. Hence, the aim of the present study was to assess the potential of different treated and non-treated animal manures to produce tailor-made manure-based fertilizers with known N:P ratios. Seven manures were considered: cattle, caprine and poultry solid manures, two contrasting cattle slurries and two contrasting swine slurries. Slurries were further treated by solid-liquid separation, acidification, and acidification followed by solid-liquid separation. Raw and treated manures were fully characterized to assess the effect of manure type and treatment on their nutrient contents and N:P ratios, to incorporate them in manure-based fertilizers with selected N:P ratio. The present results were essential to support the manure-based fertilizer production and identify which materials could be considered: it appears clearly that the pig slurry with all stages of production and the correspondent liquid fraction cannot be used due to their low nutrients content. It was shown that the solid fractions rich in P and with a NT:N–NH4+ ratio close to 1 are an excellent material to prepare manure-based fertilizers. Acidification, combined with solid-liquid separation, produced a liquid fraction rich in both N and P and with a NT:PT ratio close to 1, with the additional benefit of a slow N-release material. Some of the manures or sub-products obtained after treatment provided the usual N:P ratio required by farmers and could be used directly as substitutes of mineral fertilizers. Nevertheless, the blending of some of these materials has a stronger potential to the production of specific manure-based fertilizer.

Electrochemical treatment of landfill leachate using different electrodes

This article has as its objective a comparative study of the electrochemical treatment of slurry generated in landfills carried out with Dimensionally Stable Anodes (DSA) (Ti/Ru0.3Ti0.7O2) and Boron Doped Diamond (BDD). From the capacity planning and control (PCC), the central composite rotated design (DCCR) was obtained, whose independent variables in the electrolysis process were current density, time and electrolyte concentration. The removal of Total Organic Carbon (dependent variable) was 15.40% with current density 158 mA cm-², electrolysis time 15 minutes and 0.2 mol L-1 of the NaCl electrolyte using DSA. With the BDD, at the optimum point at 82 mA cm-², 18.5 minutes and 0.19 mol L-1, 77% removal of the organic load and discoloration of approximately 40% Ultraviolet-Visible.

Properties and mechanisms of brick-concrete recycled aggregate strengthened by compound modification treatment

This study aims to enhance the physical and mechanical properties of brick-concrete recycled aggregate (BCRA) using pozzolan slurry combined with sodium silicate and silicon-based additives. To investigate the modification mechanism, the particle shape characteristics, pore structure, and microstructure of BCRA were studied before and after the compound modification treatment. The research results showed that the apparent density of BCRA after compound modification treatment can be increased by 2.6%, and the water absorption and crushing index can be reduced by 42.4% and 28.5%, respectively. Specifically, the modification treatment of pozzolan slurry combined with sodium silicate has advantages in improving the apparent density and mechanical strength of BCRA, while the modification treatment of pozzolan slurry combined with silicon-based additives is more effective in reducing the water absorption of BCRA. Macro, meso, and microstructure changes were observed in the treated BCRA, where surface homogeneity, low porosity, and increased compactability were observed. The dynamic water absorption characteristics were also tested to evaluate the hydrophilic and hydrophobic behaviors of the untreated and treated BCRAs. Finally, a compound modification mechanism model for the BCRA was established.

Contribution of vitamin B12 to biogas upgrading and nutrient removal by different microalgae-based technology.

The algae-based technology has a positive effect on the treatment of biogas slurry and the purification of biogas, while vitamin B12 (VB12) is one of the important regulatory substances in the algae-based cultivation system. In this study, different concentrations of VB12 were used in three microalgal treatment technologies to assess their effect on simultaneous removal of nutrients from biogas slurry and removal of CO2 from raw biogas. Results showed that Chlorella vulgaris exhibited higher growth rate, mean daily productivity, chlorophyll a content, carbonic anhydrase activity and better photosynthetic properties when co-cultivated with Ganoderma lucidum, rather than when co-cultivated with activated sludge or under mono-cultivation. Maximum mean chemical oxygen demand, total nitrogen, total phosphorus and CO2 removal efficiencies were found to be 84.29 ± 8.28%, 83.27 ± 8.14%, 85.27 ± 8.46% and 65.71 ± 6.35%, respectively when microalgae were co-cultivated with Ganoderma lucidum under 100ngL-1 of VB12. This study shows the potential of microalgae and fungi co-cultivation supplemented with VB12 for the simultaneous upgradation of biogas production as well as for the purification of biogas slurry.

Combined Treatments of Underground Coal Slurry: Laboratory Testing and Field Application

During the coal mining process, underground water is generated from the longwall face. In the meantime, the coal cutting process would produce coal particles. Coal slurry is generated in the underground working site, especially for water abundant coal mines. The generated coal slurry is treated to prevent water pollution. Due to the extensively existing of the suspended solid, the traditional process method would often introduce new problems. In this study, laboratory testing was conducted to investigate the characteristics, including the particle size distribution of the coal sludge, coal slurry compositions, slurry viscosity and coal mine water quality. In order to improve the coal slurry treatment efficiency, based on the laboratory results, a novel combined treatment of underground coal slurry is proposed. First, the coarse grained coal slurry is process by a vibrating screening machine. Then, the coal slurry containing fine coal powders is processed through a settling pond. The sedimentation results of the coal solid materials are analyzed. The polymer flocculant is also added into the coal slurry to improve the sedimentation. These combined treats of the coal slurry significantly remove the suspended solid and improve the quality of the coal mine water. Based on the laboratory testing, the specific details of the field applications are designed. The key novelty of this paper is the underground background. All of these treatments are based on the underground environment and are capable of being applied in underground workings. From field applications and observations, these novel combined treatments of coal slurry in the underground site are effective. This study provides a novel method to treat the coal slurry, which has innovations from engineering aspect. These procedures are useful for the underground coal slurry treatment, especially for water-abundant coal mines. The normal coal production is guaranteed and less affected by the coal slurry discharge process. Meanwhile, the water pollution problem is much addressed and the damage of coal slurry to the environment is reduced.

Treatment of recycled concrete aggregate to enhance concrete performance

Recycled concrete aggregates (RCA) have received the attention of several researchers over the last few decades to overcome aggregate shortages and to push towards sustainable and environmental-friendly concrete. Nevertheless, utilizing recycled aggregates at a full replacement level may cause a reduction in its fresh, mechanical, and durability characteristics compared to concrete produced with normal coarse aggregates (NCA). This study aims at investigating the following influencing parameters: (a) four replacement levels of 0%, 33%, 67%, and 100% of recycled aggregate, (b) two maximum aggregate sizes of 10 and 20 mm, and (c) three treatment methods of (i) cement-silica fume slurry treatment (T1), (ii) sodium silicate solution treatment (T2), and (iii) Los Angeles (LA) abrasion treatment (T3). The test results revealed that the fresh properties of concrete were negatively impacted by the utilization of the untreated RCA, especially at higher replacement levels, irrespective of maximum aggregate sizes. The treated RCA with T1, T2, and T3 enhanced the concrete slump by 15%-35% compared to the untreated RCA. While the reduction in compressive strength for the untreated specimens was noticeable compared to the control specimens. The enhancement in the compressive strength for the treated RCA by T1, T2, and T3 was more pronounced regardless of the maximum aggregate size. The reduction in the water absorption for the treated RCA was clearly noticeable for the bigger aggregate size (20 mm) than that of 10 mm.

Effect of reduced exposed surface area and enhanced infiltration on ammonia emission from untreated and separated cattle slurry

Ammonia (NH 3 ) loss during field application of liquid manure (slurry) causes loss of nutrients for the crops and contributes to contamination of the environment. The emission can be mitigated by different low-emission application technologies and slurry treatment prior to application. It is assumed that a reduced area for air-slurry interaction will reduce the emission. The NH 3 emission mitigation potential of technologies intended to reduce manure-air contact by reducing the exposed surface area (ESA) of the slurry or enhancing slurry infiltration was investigated for cattle slurry applied on grassland. Treatments tested were: 1) removing solids by solid–liquid separation of the slurry, 2) reduced ESA by narrow band application, and 3) application with a sub-surface-deposition (SSD) slurry application (creating aeration slots). For untreated cattle slurry NH 3 emission was not reduced by reducing ESA, but application over aeration slots significantly decreased emission. However, reduced ESA by band application reduced emission from separated slurry compared to broadcast applied slurry, but no additional reduction was obtained by using the SSD technique. Lower emission was generally observed from separated slurry compared to untreated slurry for all application methods. This study shows that a reduction in NH 3 emission is not necessarily obtained solely by reducing the ESA. It is hypothesized that rapid surface drying or crust formation of the untreated slurry in the relatively warm sunny conditions of these trials mitigated NH 3 emission, thereby masking the effects of a reduced ESA. • Surface crust formation can counteract NH 3 emission increases at high temperatures. • Reduced mitigating effect of lowering ESA on NH 3 emission under warm conditions. • Enhanced infiltration by separation of cattle slurry reduced NH 3 emission.

Comparison between CaO- and MgO-activated ground granulated blast-furnace slag (GGBS) for stabilization/solidification of Zn-contaminated clay slurry

Stabilization/solidification (S/S) is a low-cost and effective remedial technique for dredged contaminated sediments. Quick lime (CaO)-activated and reactive magnesia (MgO)-activated ground granulated blast furnace slag (GGBS) are effective and low-carbon S/S binders. However, the existence of metals, especially Zn, in contaminated sediments, may hinder the hydration of GGBS. This study compared the performance and mechanisms of CaO-GGBS, MgO-GGBS and ordinary Portland cement (OPC) for the treatment of Zn-contaminated clay slurry using unconfined compressive strength (UCS) test, one-stage batch leaching test, and mineralogical and thermal analyses. The results showed that the application of the MgO-GGBS (GGBS dosage of 10 % and MgO of 0 %–3 % (of dry clay by mass)) had positive effects on the mechanical strength and Zn immobilization of the contaminated clay slurry while the CaO-GGBS affected negatively and the situation became even worse at a higher CaO dosage (0 %–1.5 % of dry clay by mass). In comparison with OPC, the application of MgO-GGBS produced higher mechanical strength and that for CaO-GGBS was the lowest. The Zn leaching difference depends on initial Zn concentrations. X-ray diffraction (XRD) and thermogravimetric analysis (TGA) results showed that a retarder, calcium zinc hydroxide, formed in the immobilization process when adding the CaO-GGBS binder, hindering the GGBS hydration and further leading to inferior strength and higher Zn leachability. The clay slurry treated by the MgO-GGBS binder was found to have a higher calcium silicate hydrate content which explained its high strength and low leachability.

Comparison of Efficiency and Cost of Methods for Conditioning of Slurries of Steam-Pretreated Softwood

Inhibitors formed during pretreatment impair lignocellulose bioconversion by making enzymatic saccharification and microbial fermentation less efficient, but conditioning of slurries and hydrolysates can improve fermentability and sometimes also enzymatic digestibility. Conditioning of pretreated softwood using four industrial reducing agents (sodium sulfite, sodium dithionite, sodium borohydride, and hydrogen) was compared with standard methods, such as overliming and treatment with activated charcoal. A dosage of approx. 1 mM sulfur oxyanion (sulfite or dithionite) per percent water-insoluble solids (WIS) in the slurry was found to result in good fermentability. Treatment of 10–20% WIS slurries with 15 mM sulfur oxyanion under mild reaction conditions (23°C, pH 5.5) resulted in sulfonation of the solid phase and saccharification improvements of 18–24% for dithionite and 13–16% for sulfite. Among the different conditioning methods studied, treatment of slurries with sodium sulfite was superior with respect to cost-efficient improvement of fermentability. Treatments of slurry or pretreatment liquid with 15 mM sulfite or dithionite resulted in 58–76% reduction of the content of formaldehyde. The comparison indicates that conditioning of pretreated biomass using sulfur oxyanions warrants further attention.

Copper atoms inlaid in titanium zirconium oxide spherical shell confine free radicals for the robust Fenton-like treatment of complex biogas slurry

A novel Fenton-like system based on single-atom catalysts was developed for the treatment of biogas slurry under 90 °C conditions. First, a binary composite was synthesized in which porous TiZrO4 hollow spheres provided sites for embedding Cu atoms and confining generated free radicals to promote the efficiency of oxidation reactions. The TiZrO4/Cu catalyst mediated the simultaneous oxidation of approximately 69 % of the chemical oxygen demand and at least 55 % of total nitrogen in biogas slurry within 1 h, and the residual organics, including simple acetic acid and propionic acid, possessed high biodegradability. Correspondingly, all of the fluorescent fulvic acids, proteins, polysaccharides, and humic acids disappeared. DFT calculations further confirmed that the electron-rich single Cu atoms generated hydroxyl radicals by capturing and reducing H2O2, thus improving the treatment efficiency. The special catalyst structure with dispersed Cu atoms maintained excellent catalytic activity and durability with negligible Cu leakage over multiple cycles.