The impact of silver nanoparticles on the co-composting of sewage sludge and agricultural waste: Evolutions of organic matter and nitrogen

Alternating electric field as an effective inhibitor of bioavailability and phytotoxicity of heavy metals during electric field-assisted aerobic composting

Changing the form of the electric field in the electric field-assisted aerobic composting (EAC) system from direct current to alternating current is confirmed as a potential strategy to enhance compost humification to the level of hyperthermophilic composting. This study pioneered the comparative evaluation of the effects of different electric field forms on the immobilization and phytotoxicity of heavy metals during composting. The results demonstrated that the humic acid content and humification index of alternating electric field-assisted aerobic composting (AEFAC) were approximately 22.0 % and 33.7 % higher than that of EAC, respectively. Morphometric analysis of various HMs (Cu, Zn, Cr, Cd, and Pb) revealed that the amounts in the exchangeable and reducible fractions were obviously lower in AEFAC than in EAC. AEFAC reduced the bioavailability of multiple HMs to about 15.11-40.21 %, indicating the higher passivation efficiency of several HMs than EAC. PLS-PM analysis indicated that AEFAC inhibited HMs bioavailability mainly through physicochemical properties, humification parameters, and microbial communities. Phytotoxicity experiments confirmed that AEFAC improves the growth indicators of cultivated crops, resulting in a 26.2 % increase in plant height and a 36.2 % increase in root length compared to EAC. Moreover, compared with EAC, AEFAC reduces the accumulation of Cu, Zn, Cr, Cd, and Pb in cultivated plants by approximately 27.0 %, 30.9 %, 32.2 %, 8.6 %, and 10.9 %, respectively. This study provides the first proof of principle that AEFAC effectively promotes the passivation of HMs, providing a practical strategy for efficient and environmentally friendly compost disposal.

Impact of Silver and Copper Oxide Nanoparticles on Anaerobic Digestion of Sludge and Bacterial Community Structure

The effect of metal nanoparticles on the anaerobic digestion of sludge and the sludge bacterial community are still not well-understood, and both improvements and inhibitions have been reported. This study investigated the impact of 2, 10, and 30 mg/g TS silver and copper oxide nanoparticles (AgNPs and CuONPs) on the mesophilic anaerobic digestion of sludge and the bacterial community structure. The reactors were monitored for changes in tCOD, sCOD, TS, VS, biogas generation, and cell viability. Also, the relative abundance and taxonomic distribution of the bacterial communities were analyzed at the phylum and genus levels, including the genera involved in anaerobic digestion. Both AgNPs and CuONPs exhibited some inhibition on anaerobic digestion of sludge and biogas generation, and the inhibition was more evident at higher concentrations. CuONPs had a stronger inhibitory effect compared to AgNPs. After the introduction of AgNPs and CuONPs, cell viability initially decreased over the first two weeks but recovered after that. At high concentrations, AgNPs and CuONPs decreased the overall bacterial diversity, and inhibited the dominant bacterial species, allowing those in less abundance to flourish. The relative abundance of the bacteria responsible for hydrolysis and acidogenesis increased and the relative abundance of acetogenic bacteria decreased with higher AgNP and CuONP concentrations. The majority of the parameters measured for monitoring the anaerobic digestion performance and bacterial community were not statistically significant at 2 mg/g TS of AgNPs and CuONPs, which represents naturally present concentrations in wastewater sludge that are below the USEPA ceiling concentration limits.

Enhanced effect of ferrous sulfate on nitrogen retention and PBAT degradation during co-composting by combing with biochar-loaded FN1 bacterial composites

The treatment of biodegradable plastics through composting has garnered increasing attention. This study aimed to investigate the effects of Biochar FN1 bacteria and ferrous sulfate on nitrogen retention, greenhouse gas emissions, and degradable plastics during composting and to elucidate their synergistic mechanisms on microbial communities. Compared with the control, applying biochar-loaded FN1 bacteria composites combined with Ferrous sulfate (SGC) markedly accelerated organic matter degradation and reduced cumulative CO2 and NH3 emissions. The synergistic interaction between the composites and Ferrous sulfate significantly enhanced NH4+-N levels in the thermophilic phase and NO3--N levels in the cooling phase, ultimately decreasing nitrogen loss by 14.9% (P < 0.05) and increasing the seed germination index (GI) by 22.5% (P < 0.05). Additionally, PBAT plastic degradation was improved by 31.6% (P < 0.05). The SGC treatment also altered the richness and diversity of the bacterial community in both the compost and the PBAT plastic sphere, particularly affecting Sphingobacterium, Pseudomonas, and Flavobacterium at the genus level. Symbiotic network analysis and Redundancy Analysis revealed that these functional degradation bacteria were significantly positively correlated with NO3--N levels and PBAT degradation. Furthermore, structural equation modelling indicated a positive relationship between PBAT degradation rate and composting temperature (r = 0.69, p < 0.05). The findings suggested that Fe2+ not only enhanced the FN1 activity but also promoted PBAT degradation by increasing ·OH content on the PBAT plastic sphere. Overall, the combined use of biochar-loaded FN1 bacteria and Ferrous sulfate effectively supports nitrogen retention and plastic degradation during composting.

Highly efficient degradation of tetracycline in groundwater by nanoscale zero-valent iron-copper bimetallic biochar: active [H] attack and direct electron transfer mechanism

Development of carbon materials with high activity was important for rapid degradation of emerging pollutants. In this paper, a novel nanoscale zero-valent iron-copper bimetallic biochar (nZVIC-BC) was synthesized by carbothermal reduction of waste pine wood and copper-iron layered double hydroxides (LDHs). Characterization and analysis of its structural, elemental, crystalline, and compositional aspects using XRD, FT-IR, SEM, and TEM confirmed the successful preparation of nZVIC-BC and the high dispersion of Fe-Cu nanoparticles in an ordered carbon matrix. The experimental results showed that the catalytic activity of nZVIC-BC (Kobs of 0.0219 min-1) in the degradation of tetracycline (TC) in anoxic water environment was much higher than that of Fe-BC and Cu-BC; the effective degradation rate reached 85%. It was worth noting that the negative effects of Ca2+, Mg2+, and H2PO4- on TC degradation at ionic strengths greater than 15 mg/L were due to competition for active sites. Good stability and reusability were demonstrated in five consecutive cycle tests for low leaching of iron and copper. Combined with free radical quenching experiments and XPS analyses, the degradation of TC under air conditions was only 62%, with hydroxyl radicals (·OH) playing a dominant role. The synergistic interaction between Fe2+/Fe3+ and Cu0/Cu+/Cu2+ under nitrogen atmosphere enhances the redox cycling process; π-π adsorption, electron transfer processes, and active [H] were crucial for the degradation of TC; and possible degradation pathways of TC were deduced by LC-MS, which identified seven major aromatic degradation by-products. This study will provide new ideas and materials for the treatment of TC.

SERS analysis, DFT, and solution effects regarding the structural and optical characteristics of folic acid biomolecule adsorbed on a Cu3 metal cluster

The optical characteristics of folic acid (ABP) and metal clusters of copper (Cu3) at various locations were investigated by means of density functional theory (DFT) computations. Mulliken charge analysis and molecular electrostatic potential (MEP) surface show how charge moves from Cu3 to ABP through the various groups. The peak in the UV-Vis spectra of ABP-Cu3 is caused by bonding and anti-bonding orbitals. In both vacuum and aqueous conditions, the polarizability values of ABP-Cu3 cluster are significantly higher than those of pure ABP, indicating a possible enhancement of the nonlinear optical (NLO) effect. Our research investigates the possibility of using ABP adsorbed metal clusters for NLO materials. Surface enhanced Raman scattering (SERS) in the ABP adsorbed metal clusters enhances the vibrational modes of ABP. Adsorption energies are found to be in the range -17.08 to -58.52 kcal/mol in vacuum and -53.34 to -93.44 kcal/mol in aqueous medium for the different configurations for ABP-Cu3. It indicates that metal clusters adsorbed by ABP are stable in the aqueous media. Experimental IR and UV-Vis of ABP is in agreement with theoretically predicted ones.

Effects of adding lignocellulose-degrading microbial agents and biochar on nitrogen metabolism and microbial community succession during pig manure composting

This study assessed the influence of the additions of lignocellulose-degrading microbial agents and biochar on nitrogen (N) metabolism and microbial community succession during pig manure composting. Four treatments were established: CK (without additives), M (lignocellulose-degrading microbial agents), BC (biochar), and MBC (lignocellulose-degrading microbial agents and biochar). The results revealed that all treatments with additives decreased N loss compared with CK. In particular, the concentrations of total N and NO3--N were the highest in M, which were 21.87% and 188.67% higher than CK, respectively. Meanwhile, the abundance of denitrifying bacteria Flavobacterium, Enterobacter, and Devosia reduced with additives. The roles of Anseongella (nitrifying bacterium) and Nitrosomonas (ammonia-oxidizing bacterium) in NO3--N transformation were enhanced in M and BC, respectively. N metabolism pathway prediction indicated that lignocellulose-degrading microbial agents addition could enhance N retention effectively mainly by inhibiting denitrification. The addition of biochar enhanced oxidation of NH4+-N to NO2--N and N fixation, as well as inhibited denitrification. These results revealed that the addition of lignocellulose-degrading microbial agents individually was more conducive to improve N retention in pig manure compost.

Microbial bioprocess performance in nanoparticle-mediated composting

Microbial composting is one of the most cost-effective techniques for degradation, remediation, nutrition, etc. Currently, there is faster growth and development in nanotechnology in different sectors. This development leads nanoparticles (NPs) to enter into the composts in different ways. First, unintentional entry of NPs into the composts via: waste discharge, buried solid waste, surface runoff, direct disposal into wastes (consumer goods, food, pharmaceuticals, and personal care products). Second, intentional mediation of the NPs in the composting process is a novel approach developed to enhance the degradation rate of wastes and as a nutrient for plants. The presence of NPs in the composts can cause nanotoxicity. Conversely, their presence might also be beneficial, such as soil reclamations, degradation, etc. Alternatively, metal NPs are also helpful for all living organisms, including microorganisms, in various biological processes, such as DNA replication, precursor biosynthesis, respiration, oxidative stress responses, and transcription. NPs show exemplary performance in multiple fields, whereas their role in composting process is worth studying. Consequently, this article aids the understanding of the role of NPs in the composting process and how far their presence can be beneficial. This article reviews the significance of NPs in: the composting process, microbial bioprocess performance during nano composting, basic life cycle assessment (LCA) of NP-mediated composting, and mode of action of the NPs in the soil matrix. This article also sheds insight on the notion of nanozymes and highlights their biocatalytic characterization, which will be helpful in future composting research.

Composted sewage sludge utilization in phytostabilization of heavy metals contaminated soils

In phytostabilization, heavy metal-tolerant plants (e.g.,grasses) can be used to reduce the mobility of heavy metals in soils. The most important step in phytostabilization is the selection of the suitable plant species, in which growth and development can be supported by soil amendments. Sewage sludge compost could be a suitable additive, which provides nutrients for the plant species used for phytostabilization and contributes to an alternative solution for sewage sludge utilization. The aim of the study was to examine the potential of sewage sludge compost in phytostabilization for heavy metal contaminated matrices: identify the optimal ratio of sewage sludge compost to decrease phytotoxicity of the matrices, and assessment of feasible plant species for phytostabilization based on its bioaccumulation properties. In this research, perennial ryegrass (Lolium perenne), broad-leaved sorrel sorrel (Rumex acetosa), lettuce (Lactuca sativa) and cabbage (Brassica oleracea var. capitata) were used for phytotoxicity experiments as well as for testing sewage sludge compost amended phytostabilization of polluted flotation sludge and mine tailings. Sewage sludge compost increased the pH and electric conductivity of the matrices. High salt content and low acidity, altogether with heavy metals caused harmful physiological effects on plant species grown without any compost addition. In the root development test, as in the germination test, the application of 5% sewage sludge compost proved to be optimal. The lower translocation factors of broad-leaved sorrel and perennial ryegrass showed a higher rate of heavy metal accumulation in the roots. Perennial ryegrass, cabbage, and lettuce plant species reached their maximum biomass by adding 5% of sewage sludge compost. Based on the bioaccumulation, translocation and biomass properties, application of perennial ryegrass is recommended for phytostabilization of heavy metal contaminated sites. Furthermore, composted sewage sludge also had a significant effect on the reduction of heavy metal uptake by cabbage and lettuce, which highlights their role as indicator plants in ecotoxicological measurements.

Combined addition of biochar, lactic acid, and pond sediment improves green waste composting

Composting, as an eco-friendly method to recycle green waste (GW), converts the GW into humus-like compounds. However, conventional GW composting is inefficient and generates poor-quality compost. The objective of this research was to investigate the effects of the combined additions of biochar (BC; 0, 5, and 10 %), lactic acid (LA; 0, 0.5, and 1.0 %), and pond sediment (PS; 0, 20, and 30 %) on GW composting. A treatment without additives served as the control (treatment T1). The results showed that treatment R1 (with 5 % BC, 0.5 % LA, and 20 % PS) was better than the treatments with two additives or no additive and required only 32 days to generate a stable and mature product. Compared with T1, R1 improved water-holding capacity, electrical conductivity, available phosphorus, available potassium, nitrate nitrogen, OM decomposition, and germination index by 51 %, 48 %, 170 %, 93 %, 119 %, 157 %, and 119 %, respectively. R1 also increased the activities of cellulase, lignin peroxidase, and laccase. The results showed that the combined addition of BC, LA, and PS increased the gas exchange, water retention, and the microbial secretion of enzymes, thus accelerating the decomposition of GW. This study demonstrated the effects of BC, LA, and PS addition on GW composting and final compost properties, and analyzed the reasons of the effects. The study therefore increases the understanding of the sustainable disposal of an important solid waste.

Simultaneous reductions in antibiotic, antibiotic resistance genes and nitrogen loss during bioaugmentation tylosin fermentation dregs co-composting

Considering the main problems presented in the typical solid wastes antibiotic fermentation dregs (AFDs) composting that the residual antibiotics could result in the propagation of antibiotic resistance genes (ARGs), and the reduced value of agronomic production caused by the ammonia gas (NH₃) emissions. This study established a bio-augmented tylosin fermentation dregs (TFDs) aerobic co-composting system to investigate the effects of a novel isolated high-efficiency strain Klebsiella sp. TN-1 inoculation on tylosin degradation, reduction in ammonia emissions, and ARG abundances during this process. Results showed that the application of strain Klebsiella sp. TN-1 extended the thermophilic stage and promoted compost maturity. Moreover, bio-enhanced co-composting with strain Klebsiella sp. TN-1 led to a totally degradation of tylosin, and removed most of ARGs, metal resistance genes (MRGs) and mobile genetic elements (MGEs), and also effectively reduce ammonia emission by 49.76 %.via increasing ammoxidation rates. Principal co-ordinates analysis further suggested that the strain Klebsiella sp. TN-1 had little influence on the bacterial community composition, while the changes of other physical and chemical properties during this process were the main reasons for the evolution of bacterial community and propagation of ARGs in the TFDs co-composting. This study suggests the potential of the bio-enhanced strain Klebsiella sp. TN-1 for antibiotic biodegradation and its application for nitrogen conservation in the AFDs co-composting process, which could decrease the risk of ARGs spreading and make compost products more secure.

Effect of attapulgite on heavy metals passivation and microbial community during co-composting of river sediment with agricultural wastes

This paper investigated the effects of attapulgite addition on the physicochemical processes, heavy metal transformation, and microbial community during the composting of agricultural wastes and sediment. In addition, the correlation between environmental factors, heavy metals (HMs), and microbial community was also assessed by redundancy analysis (RDA). The results showed that pile B with attapulgite addition entered the thermophilic phase earlier and lasted longer than pile A as the control group. The reduction in the bioavailability of HMs (Cr, Cd, and Zn) was also greater in pile B, and the passivation of HMs was ranked as Cd > Zn > Cr. The relative abundance of phylum Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria was the highest throughout the composting process. Furthermore, the RDA showed that the bacterial community composition was significantly correlated with temperature and C/N ratio in pile A, while significantly correlated with organic matter and pH in pile B. And the addition of attapulgite facilitated the conversion of HMs into more stable fractions by Pseudomonas. The study would provide a reference for the application of attapulgite to remediate the river sediment polluted by HMs.

Effects of radiation with diverse spectral wavelengths on photodegradation during green waste composting

Composting is currently the best way to dispose of green waste (GW), which contains lignocellulose and other refractory substances that can prolong composting time. Although the natural degradation of litter involves photodegradation, few studies have considered the effects of photodegradation on GW composting. The current research investigated the influence of radiation with different spectral wavelengths (light-transmitting films were used to filter sunlight) on composting efficiency. Among six treatments that differed in the spectral wavelength of radiation, a no-UV-A treatment (the radiation between 320 nm and 380 nm was blocked by light-transmitting film) produced the best-quality compost product in only 34 days. Compared to the control (the full spectrum of light), the no-UV-A treatment increased total porosity, humus coefficient, optimal particle-size, and germination index by 10%, 2%, 3%, and 9%, respectively; increased available phosphorus, available potassium, and nitrate nitrogen by 21%, 17%, and 21%, respectively; decreased electrical conductivity, residual organic matter, and ammonium nitrogen by 9%, 13%, and 14%, respectively; and increased dehydrogenase, cellulase, and laccase activity by 76%, 66%, and 23%, respectively. These results indicated that the no-UV-A treatment resulted in the most complete degradation of lignocelluloses, the best nutrient properties, and the highest level of microbial activity in the GW compost. In addition, the bulk density, water-holding capacity, total porosity, void ratio, particle-size distribution, and coarseness index of the compost product were the closest to ideal ranges with the no-UV-A treatment and indicated that the no-UV-A compost product had the best granular structure in support of aeration, water drainage, and water retention. In a phytotoxicity assay, the compost produced by the no-UV-A treatment had the highest root length, seed germination rate, and germination index, indicating that the compost product was non-phytotoxic, mature, and suitable for use in agriculture and forestry.

Responses of bacterial communities and antibiotic resistance genes to nano-cellulose addition during pig manure composting

Treatment with exogenous additives during composting can help to alleviate the accumulation of antibiotic resistance genes (ARGs) caused by the direct application of pig manure to farmland. In addition, nano-cellulose has an excellent capacity for adsorbing pollutants. Thus, the effects of adding 300, 600, and 900 mg/kg nano-cellulose to compost on the bacterial communities, mobile genetic elements (MGEs), and ARGs were determined in this study. After composting, treatment with nano-cellulose significantly reduced the relative abundance of ARGs, which was lowest in the compost product with 600 mg/kg added nano-cellulose. Nano-cellulose inhibited the rebound in ARGs from the cooling period to the maturity period, and weakened the selective pressure of heavy metals on microorganisms by passivating bio-Cu. The results also showed that MGEs explained most of the changes in the abundances of ARGs, and MGEs had direct effects on ARGs. The addition of 600 mg/kg nano-cellulose reduced the abundances of bacterial genera associated with ermQ, tetG, and other genes, and the number of links (16) between ARGs and MGEs was lowest in the treatment with 600 mg/kg added nano-cellulose. Therefore, adding 600 mg/kg nano-cellulose reduced the abundances of ARGs by affecting host bacteria and MGEs. The results obtained in this study demonstrate the positive effect of nano-cellulose on ARG pollution in poultry manure, where adding 600 mg/kg nano-cellulose was most effective at reducing the abundances of ARGs.

The fate of antibiotic resistance genes and their influential factors during excess sludge composting in a full-scale plant

The alteration of antibiotic resistance genes (ARGs) during sludge composting has been less studied in a full-scale plant, causing the miss of practical implications for understanding/managing ARGs. Therefore, this study tracked the changes of ARGs and microbial communities in a full-scale plant engaged in excess sludge composting and then explored the key factors regulating ARGs through a series of analyses. After composting, the absolute and relative abundance of ARGs decreased by 91.90% and 66.57%, respectively. Additionally, pathway analysis showed that MGEs, composting physicochemical properties were the most vital factors directly influencing ARGs. Finally, network analysis indicated that Proteobacteria, Bacteroidetes, Firmicutes, and Actinobacteria were the main hosts of ARGs. Based on these findings, it can be known that full-scale composting could reduce ARGs risk to an extent.

Effects of additives on physical, chemical, and microbiological properties during green waste composting

Composting is an environmentally friendly and sustainable way to transform Green waste (GW) into a useful product. GW, however, contains substantial quantities of lignocelluloses that extend the composting period unless substances that accelerate composting are added. The objective of this research was to assess the influence of the following additives on GW composting (w/w dry matter contents of the additives were indicated): sugarcane bagasse at 15%; bean dregs at 35%; silage at 45%; flue gas desulfurization gypsum at 5%; maifanite at 4%; and furfural residue at 20%. Based on the composting temperature, compost density, porosity, particle-size distribution, water retention, pH, cation exchange capacity, available nutrient contents, humification coefficient, organic matter loss, microbial populations, and phytotoxicity, the best additives were 45% silage and 5% flue gas desulfurization gypsum. The latter two additives produced a high-quality product in only 35 and 37 days, respectively.

The antimicrobial effect of 400 nm femtosecond laser and silver nanoparticles on gram-positive and gram-negative bacteria

Silver nanoparticles are well-known for their antimicrobial effect. However, they are potentially toxic in high doses. We explored the possibility of enhancing the bactericidal effect of low concentrations of silver nanoparticles with blue light femtosecond laser irradiation, since such concentrations are less toxic. The growth dynamics of Pseudomonas aeruginosa, Listeria monocytogenes and methicillin-resistant Staphylococcus aureus grown in pre-synthesized silver nanoparticles were measured with or without pre-irradiation with 50 mW and 400 nm femtosecond laser irradiation. With each bacterium, combined treatment with laser and silver nanoparticles significantly reduced bacterial growth, indicating that this form of treatment could be beneficial in the ongoing efforts to reduce the deleterious effects of antibiotic resistant Gram-positive and Gram-negative bacteria. The combined treatment was more antimicrobial than treatment with silver nanoparticles alone or photo-irradiation alone. P. aeruginosa and L. monocytogenes were more susceptible to the bactericidal effects of silver nanoparticles, and the combination of laser treatment and silver nanoparticles than MRSA.

Effects of TiO2 and ZnO nanoparticles on vermicomposting of dewatered sludge: studies based on the humification and microbial profiles of vermicompost

Nanoparticles (NPs) are prevalent in dewatered sludge, and their presence increases the environmental risks associated with the subsequent sludge treatment process. However, until now, their potential effects on sludge vermicomposting have not been clarified. This study investigated the effects of NPs on sludge humification and microbial profiles during vermicomposting by comparing fresh dewatered sludge substrates with substrates mixed with 0 mg/kg NPs (control), 100 mg/kg TiO₂, 500 mg/kg TiO₂, 100 mg/kg ZnO, and 500 mg/kg ZnO. The results showed that addition of TiO₂ and ZnO NPs to sludge did not significantly affect the growth rate of earthworms and the superoxide dismutase activity in their guts during vermicomposting. Moreover, higher concentrations of the selected NPs promoted the humification index of sludge by 20.7-49.6%, through the formation of polysaccharides, aromatic substances, and organic acids in final vermicomposts. Compared with the control without NP addition, bacterial community diversity was enhanced in treatments with TiO₂ and ZnO NPs, and dominant genera differed according to the type and concentration of NPs. This study suggests that the presence of TiO₂ and ZnO NP residuals modify the microbial community of sludge, thus promoting sludge humification during vermicomposting.

Evolution of humic substances and the forms of heavy metals during co-composting of rice straw and sediment with the aid of Fenton-like process

The Fenton-like process was established by Fe₃O₄ nanomaterials (NMs) and Phanerochaete chrysosporium or oxalate, and applied to the co-composting of rice straw and sediment to study its effect on the formation of humic substance and the bioavailability of Cd, Cu, and Pb. Results shown that the application of Fenton-like process significantly promoted the passivation of Cd and Cu, while not shown obvious enhancement for Pb. The decrease of exchangeable fraction Cd (EXC-Cd) and the humic acid (HA) content in pile B with Fe₃O₄ NMs and oxalate were highest, which were 22.35% and 20.3 g/kg, respectively. Redundancy analyses (RDA) manifested that the Fenton-like process enhanced the influence of humus substance on the bioavailability of Cd, Cu, and Pb. Excitation-emission matrix (EEM) fluorescence spectra analysis suggested that Fenton-like process could obviously enhance the generation of humic substance. This research provides a new perspective and way for composting to remediate heavy metals pollution.

In-situ remediation of nitrogen and phosphorus of beverage industry by potential strains Bacillus sp. (BK1) and Aspergillus sp. (BK2)

The bioremediation of beverage (treated and untreated) effluent was investigated in the current study by using the potential strains of Bacillus sp. (BK1) and Aspergillus sp. (BK2). Effluent was collected from the beverage industry (initial concentration of nitrogen were 3200 ± 0.5 mg/L and 4400 ± 0.6 mg/L whereas phosphorus were 4400 ± 2 mg/L and 2600 ± 1 mg/L in treated and untreated effluent correspondingly). Further, the BK1 and BK2 exhibited high removal competence after 1 week of incubation; BK1 removed phosphorus 99.95 ± 0.7% and BK2 95.69 ± 1% in treated effluent while nitrogen removed about 99.90 ± 0.4% by BK1 and 81.25 ± 0.8% by BK2 (initial concentration of phosphorus 4400 ± 2 mg/L and nitrogen 3200 ± 0.5 mg/L). Next, in the untreated effluent BK1 removed 99.81 ± 1% and BK2 99.85 ± 0.8% of phosphorus while removed nitrogen 99.93 ± 0.5% by BK1 and 99.95 ± 1.2% by BK2 correspondingly, (initial concentration of phosphorus 2600 ± 1 mg/L and nitrogen 4400 ± 0.6 mg/L). The physiochemical composition of sample such as pH, total carbohydrates, total proteins, total solids of treated and untreated effluent were also analysed before and after treatment of both the samples. BK1 and BK2 increased the pH by 8.94 ± 0.3 and 9.5 ± 0.4 correspondingly in treated effluent whereas 6.34 ± 0.5 and 7.5 ± 0.2 correspondingly in untreated effluent (initial pH of treated and untreated effluent 7.07 ± 0.8 and 4.85 ± 0.3 correspondingly). Total Carbohydrates removed about 17,440 ± 4.6 mg/L and 10,680 ± 3.2 mg/L by BK1 and BK2 correspondingly in treated effluent whereas 18,050 ± 3.5 mg/L and 18,340 ± 2.3 mg/L correspondingly in untreated effluent (initial concentration of treated and untreated effluent 25,780 ± 1.6 mg/L and 35,000 ± 1.5 mg/L correspondingly) while BK1 and BK2 removed total proteins by 30.336 ± 4.6 mg/L and 40.417 ± 2.3 mg/L correspondingly in treated effluent whereas 18.929 ± 1.2 mg/L and 17.526 ± 0.8 mg/L correspondingly in untreated effluent (initial concentration of treated and untreated effluent 49.225 ± 1.5 mg/L and 20.565 ± 1 mg/L correspondingly). Next, total solids removed by BK1 and BK2 2.5 ± 0.3 mg/L and 1.6 ± 0.6 mg/L correspondingly in treated effluent whereas 5.5 ± 0.8 mg/L and 4.6 ± 0.6 mg/L in untreated effluent (initial concentration of treated and untreated effluent 5.6 ± 1.5 mg/L and 9.48 ± 1.2 mg/L correspondingly). Both the strains BK1 and BK2 are highly efficient in the nitrogen and phosphorus removal therefore this strain may be applied for the potential remediation.

Alternating magnetic field mitigates N2O emission during the aerobic composting of chicken manure

Nitrous oxide (N₂O) emission is an environmental problem related to composting. Recently, the electric field-assisted aerobic composting process has been found to be effective for enhancing compost maturity and mitigating N₂O emission. However, the insertion of electrodes into the compost pile causes electrode erosion and inconvenience in practical operation. In this study, a novel alternating magnetic field-assisted aerobic composting (AMFAC) process was tested by applying an alternating magnetic field (AMF) to a conventional aerobic composting (CAC) process. The total N₂O emission of the AMFAC process was reduced by 39.8% as compared with that of the CAC process. Furthermore, the results demonstrate that the AMF weakened the expressions of the amoA, narG, and nirS functional genes (the maximum reductions were 96%, 83.7%, and 95.5%, respectively), whereas it enhanced the expression of the nosZ functional gene by a maximum factor of 36.5 as compared with that in CAC. A correlation analysis revealed that the nitrification and denitrification processes for N₂O emission were suppressed in AMFAC, the main source of N₂O emission of which was denitrification. The findings imply that AMFAC is an effective strategy for the reduction of N₂O emission during aerobic composting.

Porous Hybrids Structure between Silver Nanoparticle and Layered Double Hydroxide for Surface-Enhanced Raman Spectroscopy

Silver nanoparticle (AgNP), in terms of antibacterial, catalytic, electronic, and optical applications, is an attractive material. Especially, when prepared to furnish sharp edge and systematic particle orientation on the substrate, AgNPs can take advantage of surface-enhanced Raman spectroscopy (SERS). In this research, we suggested a synthetic method to immobilize the AgNP on metal oxide by utilizing Ag-thiolate and layered double hydroxide (LDH) as precursor and template, respectively. The layer-by-layer structure of LDH and Ag-thiolate transformed through reductive calcination to metal oxide and AgNP array. Physicochemical characterization, including powder X-ray diffraction, N₂ adsorption–desorption, microscopies, and X-ray photoelectron spectroscopy, revealed that the AgNP with sufficient crystallinity and particle gap was obtained at relatively high calcination temperature, ~600 °C. UV-vis diffusion reflectance spectroscopy showed that the calcination temperature affected particle size and electronic structure of AgNP. The prepared materials were subjected to SERS tests toward 4-nitrothiophenol (4-NTP). The sample obtained at 600 °C exhibited 50 times higher substrate enhancement factor (SEF) than the one obtained at 400 °C, suggesting that the calcination temperature was a determining parameter to enhance SERS activity in current synthetic condition.

Production of volatile fatty acids and H2 for different ratio of inoculum to kitchen waste

The aim of this study was to evaluate the effect of different inoculum ratio on the dark fermentation of kitchen waste in terms of volatile fatty acids (VFAs) and H₂ production. The experiments were performed in batch bioreactors of effective volume 1 L without pH regulation. The ratio between the DS and KW was being increased from 0.11 to 0.51 on a volatile solids (VS) basis, while the initial content of KW was equal to 34.1 g VS/L. Increase of the DS/KW ratio from 0.11 to 0.28 resulted in the rise of VFAs and H₂ production. Further increase in the amount of added DS did not cause a significant change in the production of VFAs and H₂. In the bioreactor with the DS/KW ratio of 0.28, the production of VFAs and H₂ was equal to 16.0 g/L and 68.1 mL/g VS, respectively. Acetic and butyric acids were produced in the largest amount and their content, for DS/KW ratio of 0.28, were equal 37% and 43%, respectively. At the ratio of DS/KW above 0.4, the caproic acid content attained the level of 25%. Based on the DS and KW microbiological analysis, it was observed that dominant bacteria were Bacteroidetes, Firmicutes, Proteobacteria, Spirochaetes and WWE1 at the phylum level.

Insights into factors driving the transmission of antibiotic resistance from sludge compost-amended soil to vegetables under cadmium stress

Sludge compost is often used as a fertilizer for crops, although it might be enriched with antibiotic resistance genes (ARGs) and heavy metals that cannot be removed through composting. A robust understanding of the factors affecting the transmission of ARGs to vegetables grown in soils treated with sludge products is lacking. In this study, target ARGs in the bulk and rhizosphere soils and endophytes of shallots under heavy metal stress (i.e., Cd) were assessed, and the factors driving the transmission of ARGs were identified. Cd stress resulted in an increase in the relative abundances of target ARGs in the bulk and rhizosphere soils and endophytes. The driving factors were different in soils and plants under different degrees of Cd stress. The fungal community composition was the main driving factor of ARG variation in both bulk and rhizosphere soils. Moreover, endophytic bacteria played a crucial role in transferring ARGs to plants. Higher Cd stress promoted the transfer of most target ARGs from the below-ground plant parts to the above-ground parts. These findings indicate that application of sludge contaminated with heavy metals, such as Cd, can facilitate the dissemination of ARGs into vegetables, which must be considered while assessing the risks to public health.

Stimulating methane production from microalgae by alkaline pretreatment and co-digestion with sludge

Methane production through anaerobic digestion (AD) is a solution of energy recovery from microalgae, but some features of microalgae limit the efficiency of AD. In this study, alkaline pretreatment and co-digestion with sludge were both applied to enhance the methane production from microalgae in batch experiments. The results showed that alkaline pretreatment increased the disintegration degree of microalgae from 20% to 34% at maximum after 12-h treatment, but the specific methane production (SMP) only increased from 279 to 298 ml/g volatile solids (VS). Co-digestion with sludge stimulated methane production, and the best synergy with an SMP of 343 ml/g VS occurred when the ratio of microalgae to sludge reached 2:1 based on their VS. The yield was 12.4% and 20.0% higher than those from mono digestion of microalgae and sludge, respectively, and the synergy was evaluated at 14.8%. Therefore, co-digestion is a better choice for improving methane production from microalgae.

Enzymatic activities triggered by the succession of microbiota steered fiber degradation and humification during co-composting of chicken manure and rice husk

The carbon to nitrogen ratio (C/N) is well known for its importance in the composting process, however the fiber degradation and humification associated with enzymatic activity and microbial variation derived from different C/N ratios are poorly studied. Here, we designed two treatments of chicken manure with 15% (initial C/N ratio 9.61) and 50% (initial C/N ratio 17.3) rice husk to adjust the moisture of mixtures for turning feasibly by towable fertilizer turner in industrial level. Compared to the C/N ratio 9.61, the suitable C/N ratio of 17.3 significantly enhanced the composting efficiency and the final germination index (23.7%). Moreover, the suitable C/N ratio increased the relative abundance of Bacilli, which played an important role during the mesophilic and thermophilic phases. Bacilli abundance was related to cellulose and β-glycosidase activities, thus improved fiber degradation and humification. This study not only seeks a swift method in industrial level to process chicken manure but also provides insight into the enzymatic activity of microbial community related to high-efficient composting.

Effect of nutritional energy regulation on the fate of antibiotic resistance genes during composting of sewage sludge

Sludge composting is increasingly adopted due to its end product for application as a soil nourishment amendment. Although the ratio of C/N is significant in the quality and process of composting, little information has been obtained from the effects of nutritional energy (carbon and nitrogen) on the fate of antibiotic resistance genes (ARGs) during sludge composting. Dynamic variations of ARGs, microbial community as well as functional characteristics during composting of sludge were investigated in this study. Three levels of carbon to nitrogen (20:1, 25:1 and 30:1) were developed for the composting of sludge with fermented straw plus a control which was just sewage sludge (C/N = 9.5:1). A novel finding of this work is that the highest initial C/N ratio (30:1) could prolong the thermophilic period, which was helpful to reduce some target ARGs. Some ARGs (sul1, sul2, and aadA1) had negative correlation with multiple metabolic pathways, which were difficult to remove.

Evidence for positive response of soil bacterial community structure and functions to biosynthesized silver nanoparticles: An approach to conquer nanotoxicity?

The environmental impacts of biosynthesized nanoparticles on the soil bacterial community assemblage and functions are not sufficiently understood. Given the broad application of silver nanoparticles (AgNPs), the present study aims to reveal the effects of biosynthesized AgNPs (~12 nm) on the soil bacterial community structure and functions. Specifically, we used a quantitative real-time PCR (qPCR) approach to quantify the relative abundance of bacterial taxon/group and representative functional genes (AOA, AOB, NirK, NirS, NosZ, and PhoD). Results showed high relative abundance of Actinobacteria (1.53 × 10⁷, p = 0.000) followed by Alphaproteobacteria (1.18 × 10⁶, p = 0.000) and Betaproteobacteria (2.01 × 10⁶, p = 0.000) in the soil exposed to biosynthesized AgNPs (100 mg/kg soil) after 30 days of treatment. Bacteroidetes group was observed to be negatively affected by AgNPs treatment. In the case of functional genes abundance, more pronounced impact was observed after 30 days of application. The biosynthesized AgNPs treatment accounted for significant increase in the relative abundance of all targeted functional genes except NirS. We conclude that the biosynthesized AgNPs did not cause toxic effects on nitrifiers, denitrifiers and organic phosphorus metabolizing bacterial community. While AgNO₃ caused higher toxicity in the soil bacterial community structure and function. Based on our findings, we propose two key research questions for further studies; (i) is there any adaptation strategy or silver resistance embraced by the soil microbial community? and (ii) are biosynthesized nanoparticles environmentally safe and do not pose any risk to the soil microbial community? There is a necessity to address these questions to predict the environmental safety of biosynthesized AgNPs and to apply appropriate soil management policies to avoid nanotoxicity. Since this study provides preliminary evidence for the positive response of the soil bacterial community structure and functions to biosynthesized AgNPs, additional investigations under different soil conditions with varying soil physico-chemical properties are required to authenticate their environmental impact.

Heat Energy and Gas Emissions during Composting of Sewage Sludge

The composting of sewage sludge and maize straw mixtures was investigated in this study. The aim was to analyze the influence of different proportions of sewage sludge and maize straw in the mixtures on composting process dynamics (expressed by heat production) and gas emissions. The results showed that all examined mixtures reached a strong thermophilic phase of composting; however, the lowest dynamic of temperature growth was observed in the case of the biggest sewage sludge content (60% of sewage sludge in the composting mixture). The ammonia concentration inside bioreactor chambers was directly related to the content of sewage sludge in the composted mixture. Excessive contents of sewage sludge had a considerable effect on very low C/N ratios and high losses through ammonia emissions. Tests were carried out in reactors with a capacity of 160 dm3 under controlled conditions. All mixtures were aerated by the average air-flow of about 2.5 dm3∙min−1, i.e., the minimum air-flow that allows a temperature of about 70 °C to be reached and a sufficiently long thermophilic phase, which ensures proper composting.

Changes in structure and function of bacterial and fungal communities in open composting of Chinese herb residues

In this study, dynamic changes in bacterial and fungal communities, metabolic characteristics, and trophic modes in Chinese herb residues open composting for 30 days were analyzed by using high-throughput sequencing, PICRUSt, and FUNGuild, respectively. Bacillaceae and Basidiomycota predominated at the early composting stage, while Proteobacteria and Ascomycota became the dominant phyla during the active phase. Aerobic composting had a significant effect on bacterial metabolic characteristics and fungal trophic modes over the composting time. The function of the bacterial communities changed from environmental information processing to metabolism. Fungal communities changed as well, with the pathogenic fungi decreasing and wood saprotrophs increasing. These results indicated that open composting of Chinese herb residues not only influenced microbial community structure but also changed metabolic characteristics and trophic modes, which became the internal dynamics of composting.

Genetic associations as indices for assessing nitrogen transformation processes in co-composting of cattle manure and rice straw

In this study, mechanism of nitrogen transformation was investigated in terms of genetic associations (nitrogen-related gene groups) in co-composting of cattle manure and rice straw. Mutual validation among KEGG, Pearson correlation, stepwise regression, and Path analyses indicated that the functional genes synergistically affected on nitrogen transformation in composting process. NxrA/qnorB (0.9419 ± 0.0334) and (amoA + anammox)/Bacteria (0.7187 ± 0.0334) were the key functional gene groups mediating NH₄⁺-N transformation. AmoA/(narG + napA) (-0.8400 ± 0.0129), amoA/bacteria (0.8692 ± 0.0273), and (nirK + nirS)/nosZ (1.1652 ± 0.0089) determined NO₃^--N, NO₂^--N and N₂O transformation, respectively. AmoA/(napA + narG) mediated both NO₃^--N and NO₂^--N transformation. AmoA/anammox (-0.7172 ± 0.0591) and (nirK + nirS)/nosZ (-0.6626 ± 0.0825) served as predominant factors for total nitrogen removal. These results provided a molecular-level insight that nitrification, anaerobic ammonia oxidation and denitrification (SNAD) might simultaneously contribute to nitrogen transformation during composting, rather than sequentially.

Impact of adding metal nanoparticles on anaerobic digestion performance - A review

Anaerobic digestion is the most widely adopted biological waste treatment processes with renewable energy production. The effects of adding metal nanoparticles (NPs) on improving digestion performance are well noted. This paper reviewed the traditional view on the cytotoxicity of NPs to living organisms and the contemporary view of mechanisms for enhancement in anaerobic digestion performance in the presence of metal NPs. The complicated interactions acquire further studies for comprehending the physical and chemical interactions of metal NPs to the constituent compounds and to the living cells, and the involvement of mechanisms such as direct interspecies electron transfer for better design and control of the "NP strategy" for anaerobic digestion performance enhancement.

A fast and easy method for predicting agricultural waste compost maturity by image-based deep learning

Large amounts of agricultural wastes are generated in agricultural production, and composting this waste is one of the best ways to recycle resources. Compost maturity is an important criterion for measuring the quality of compost-products. Biochemical tests are conventional methods to evaluate compost maturity, but they are time consuming and difficult to perform. Therefore, convolutional neural networks (CNNs) were introduced to realize fast evaluation of compost maturity by analyzing images of different composting stages. Images of 3 different composting materials were collected to build 4 data sets, which included nearly 30,000 images, and a series of experiments were performed on them. The accuracy of proposed method was 99.7%, 99.4%, 99.7% and 99.5% on the 4 test sets, respectively. Experimental results demonstrate that the proposed CNN-based prediction model produces state of the art results and can be used to predict compost maturity during the composting process.

Evolutions of different microbial populations and the relationships with matrix properties during agricultural waste composting with amendment of iron (hydr)oxide nanoparticles

This study investigated the evolutions of different microbial populations and multivariate relationships between their abundances and environmental variables during composting with amendment of Fe (hydr)oxide nanoparticles. Piles treated with nanohematite and nanomagnetite were denoted as T-nanohematite and T-nanomagnetite, and another one was T-control. It was found that nanohematite more effectively increased bacteria and fungi abundances with 1.24∼1.58 times average value of T-control, while nanomagnetite was more useful to actinomycetes. As the most significant variable, the total effect of temperature in T-control and T-nanomagnetite was increased to 0.87 and 0.92, respectively, because both the direct and indirect effects were positive, while it in T-nanohematite was reduced to 0.18 by the negative indirect effect. Partial redundancy analysis suggested that each microbial abundance shared different relationships with composting parameters. Overall, actinomycetes was more sensitive to changes of composting parameters than bacteria and fungi.

Influence of FeONPs amendment on nitrogen conservation and microbial community succession during composting of agricultural waste: Relative contributions of ammonia-oxidizing bacteria and archaea to nitrogen conservation

Composting amended with iron oxide nanoparticles (FeONPs, α-Fe₂O₃ and Fe₃O₄ NPs) were conducted to study the impacts of FeONPs on nitrogen conservation and microbial community. It was found that amendment of FeONPs, especially α-Fe₂O₃ NPs, reduced total nitrogen (TN) loss, and reserved more NH₄⁺-N and mineral N. Pearson correlation analysis revealed that decrease of ammonia-oxidizing bacteria (AOB) in FeONPs treatments played more important role than ammonia-oxidizing archaea (AOA) in reserving more NH₄⁺-N and mineral N, and reducing TN loss. Bacterial community composition at phylum level did not shift with addition of FeONPs. Firmicutes, Actinobacteria, and Proteobacteria were the three most dominant phyla in all treatments. Overall, this study provides a method to reduce TN loss and improve mineral N reservation during composting, and gives a deep insight into the role of AOB and AOA in nitrogen transformation.

Adding Phosphate Fertilizer and Apple Waste to Pig Manure during Composting Mitigates Nitrogen Gas Emissions and Improves Compost Quality

Calcium superphosphate and apple ( Mill.) waste can be used for controlling N loss and improving compost quality during composting, whereas integrated addition of the two additives on composting process remains unexplored. Therefore, this study was conducted to investigate the effects of combined use of calcium superphosphate and apple waste on NH and NO emissions and compost quality during pig manure and wheat ( L.) straw composting. Mixtures of pig manure and wheat straw were combined with 6% phosphate fertilizer (PF), 15% apple waste (AW), 3% phosphate fertilizer + 7.5% apple waste (PA1), or 1.8% phosphate fertilizer + 10.5% apple waste (PA2) based on dry weight of the initial mixtures; a treatment with no additives served as a control (CK). The PF treatment took 3 d longer to reach thermophilic phase than the CK, PA1, and PA2 treatments. The treatments of PF and PA1 reduced NH and NO emissions by 67 and 45%, respectively. Moreover, N loss in PF and PA1 treatments (31.8 and 30.1%, respectively) was significantly less than in the CK. A pot experiment showed that application of the compost with PA1 treatment could increase plant height and dried biomass of Chinese pakchoi ( L. ssp.). We recommend adding 3% phosphate fertilizer and 7.5% apple waste to pig manure during composting.

Reducing the composting time of broiler agro-industrial wastes: The effect of process monitoring parameters and agronomic quality

The aim of this study was to evaluate the effect of considering different composting times on compost quality before the end of the bio-oxidative phase and after the maturation and storage phases. This study may provide useful information to optimize the composting process and increase the economic feasibility of the technology and its adoption without decreasing the quality of the end-product. In this study, three composts were prepared using chicken meat processing wastes mixed with urban tree trimmings, serving as a bulking agent, to evaluate the effect of reducing the durations of the bio-oxidative phase and the maturity stage on the different physico-chemical properties. Specifically, we evaluate water-soluble organic matter transformations by using excitation-emission matrix (EEM) fluorescence spectroscopy. The obtained results have shown that a composting time of 35 days combined with eight turnings was efficient for achieving the standard process control parameters for agro-industrial waste composting in the studied conditions and allowed for the production of stable and mature compost that is suitable for agricultural use.

Impacts of iron oxide nanoparticles on organic matter degradation and microbial enzyme activities during agricultural waste composting

The effects of iron oxide nanoparticles (IONPs, including Fe₂O₃ NPs and Fe₃O₄ NPs) on composting were investigated through evaluating their influences on organic matter (OM) degradation, dehydrogenase (DHA) and urease (UA) activities, and quality of the final compost product. Results showed that composting amended with Fe₂O₃ NPs was more effective to facilitate OM degradation. At the end of composting, the total OM loss in T-C, T-Fe₂O₃ NPs and T-Fe₃O₄ NPs was 66.19%, 75.53% and 61.31%, respectively. DHA and UA were also improved on the whole by the amendment of IONPs, especially Fe₂O₃ NPs. Although relationships between enzyme activities and environmental variables were changed by different treatments, temperature was the most influential to variations of both DHA and UA in all treatments, which independently explained 75.1%, 34.7% and 38.4% of variations in the two enzyme activities in T-C, T-Fe₂O₃ NPs and T-Fe₃O₄ NPs, respectively. Compared with DHA, UA was more closely related to the environmental parameters. The germination index in T-C, T-Fe₂O₃ NPs and T-Fe₃O₄ NPs was 134.49%, 153.64% and 146.76%, and the average shoot length was 3.16, 3.87 and 3.45 cm, respectively, indicating that amendment of IONPs, especially Fe₂O₃ NPs, could promote seed germination and seedling growth. Therefore, composting amended with IONPs was a feasible and promising method to improve composting performance, enzyme activities as well as quality of the final compost product.

Insights into functional microbial succession during nitrogen transformation in an ectopic fermentation system

The ectopic fermentation system (EFS) is an advanced technology for treating farm wastewater, and it reduces ammonia nitrogen emission and nitrogen loss of fermentation products. This study observed the functional bacteria succession related to nitrogen metabolism in EFS by high throughput sequencing, and evaluated their associations with environmental factors. Results revealed that with the changes of temperature, pH, moisture content, and nitrogen content during fermentation, the species richness and diversity of ammonia oxidizing bacteria (AOB) with amoA increased, but those of denitrifying bacteria carrying nirK and nosZ decreased. During the fermentation process, the dominant bacterial populations of AOB and denitrifying bacteria changed significantly, and different bacterial populations showed different positive/negative correlations with the environmental factors. This study revealed the role of functional bacteria in ammonia removal and nitrogen conservation of EFS, and provided a theoretical basis for the improvement of microbial agents and EFS application.

Study on transformation and degradation of bisphenol A by Trametes versicolor laccase and simulation of molecular docking

As a typical class of environmental endocrine disruptors, bisphenol A poses a potential threat to the sustainable survival and reproduction of living beings and human beings. In this study, the interaction between Trametes versicolor laccase and bisphenol A (BPA) was studied by molecular docking simulation, and the catalytic degradation of BPA was verified by experiments. The conditions for the laccase production of T. versicolor were optimized by orthogonal design, and the degradation of BPA was studied using its crude enzyme solution. The optimum degradation conditions were obtained by response surface methodology (RSM). Ultimately, the transformation products after 3 and 6 h of reaction were detected by gas chromatography-mass spectrometry. Docking results demonstrated that the reaction between laccase and BPA was spontaneous, and the degradation rate in 24 h reached 88.76%. RSM results showed that the highest BPA degradation rate of 97.68% was reached after 1 h reaction at 44.6 °C, 5 mg/L initial BPA concentration, and pH 5.20. The intermediate products of BPA catalyzed by laccase included ethylbenzene, p-xylene, and cyclohexanone 1-methyl-4-isopropenyl-2-cyclohexenol. This finding reveals that BPA degradation by the crude laccase from T. versicolor starts from the C atoms between two benzene rings that connect BPA. Compared with expensive pure enzyme, the crude laccase solution prepared by T. versicolor showed greater efficiency in BPA degradation. This work provides theoretical references and experimental methods for the biological processing of harmful pollutants.

Mature landfill leachate treatment using sonolytic-persulfate/hydrogen peroxide oxidation: Optimization of process parameters

The suitability of stand-alone ultrasound (US) system, coagulation pre-treatment followed by US, hydrogen peroxide added US system (US-H₂O₂) and persulfate added US system (US-PS) for the treatment of matured landfill leachate was investigated. With US system, around 67% COD removal and an increase in BOD/COD ratio were observed (from 0.033 to 0.142) after 15 min at 30% US amplitude. However, the energy input required for landfill leachate treatment in US system was found to be very high due to the presence of fixed solids. Coagulation pretreatment using alum was carried out to improve the overall COD removal and reduce the cost of treatment. As a result, the COD removal was increased to 78% (42% in pretreatment and 36% in US) in 15 min. On the other hand, US-H₂O₂ and US-PS hybrid systems have shown significant improvement in COD removals (93% and 86%, respectively) from raw leachate after 15 min. Subsequently, a three factor (i.e. PS dose (mg/L), H₂O₂ dose (mol/L), and US amplitude (%)) 5-level design of experiment was used to maximize the COD removal efficiency by response surface methodology (RSM). The RSM model generated a quadratic equation to accurately analyze the influence of input variables on COD removal efficiency (R² of 0.92). A maximum COD removal of 98.3% was predicted using the model and the corresponding optimal experimental condition were identified as follows: PS dose ∼4700 mg/L, H₂O₂ dose ∼0.7 mol/L and US amplitude ∼49%. The overall observations reveals that PS and H₂O₂ coupled with US system has a great prospective to treat mature landfill leachate.

Carboxymethyl cellulose thiol-imprinted polymers: Synthesis, characterization and selective Hg(II) adsorption

Sulfur containing ion imprinted polymers (S-IIPs) were applied for the uptake of Hg(II) from aqueous solution. Cysteamine which was used as the ligand for Hg(II) complexation, was grafted along the epichlorohydrin crosslinked carboxylated carboxymethyl cellulose polymer chain through an amide reaction. The adsorption ability of S-IIPs towards Hg(II) was investigated by kinetic and isotherm models, which, corresponding, showed that the adsorption process followed a pseudo-second-order, fitted well with the Langmuir isotherm with a maximum adsorption capacity of 80 mg/g. Moreover, thermodynamic studies indicated an endothermic and spontaneous reaction with the tendency of an enhanced randomness at the surface of the S-IIPs with temperature increases. S-IIPs indicated a high degree of selectivity towards Hg(II) in the presence of Cu²⁺, Zn²⁺, Co²⁺, Pb²⁺ and Cd²⁺. Furthermore, the efficiency of S-IIPs was also evaluated against real samples showing 86.78%, 91.88%, and 99.10% recovery for Hg(II) wastewater, ground water and tap water, respectively. In this study, the adsorbent was successfully regenerated for five cycles, which allows for their reuse without significant loss of initial adsorption capability.

Effect of temperature on the fuel properties of food waste and coal blend treated under co-hydrothermal carbonization

A blended feedstock containing food waste and coal was used to perform co-hydrothermal carbonization (Co-HTC) at different temperatures to observe the effect of temperature on the solid fuel properties of different hydrochars. Moreover, these hydrochars were mixed with molasses which act as a binder to prepare high mechanical strength pellets. A range of techniques was used to characterise the hydrochars and pellets. Food waste and coal hydrochars produced at 300 °C exhibited high heating value (HHV) of 31.1 and 31.4 MJ/kg respectively, however, high heating value of the Co-HTC 300 °C hydrochar decreased to 28.6 MJ/kg. The ash content of hydrochar obtained via the Co-HTC at 300 °C, was 53% less than the ash content of raw coal. Combustion results showed that the Co-HTC of food waste and coal is thermally more suitable than HTC of food waste and coal. During pelletization molasses played an important role in making solid bridge between the hydrochars. The tensile strength of all the hydrochars ranged between 2 and 4.5 MPa. The blend treated at 300 °C showed the highest tensile strength of 4.5 MPa. The mass density of food waste and blend increased as the temperature was increased, however, the mass density of the coal sample showed a decreasing trend. The energy densities of all the hydrochars ranged between 22.2 and 39 GJ/m³ and the energy density of the blends were higher than the coal and food waste hydrochar.

The binding properties of copper and lead onto compost-derived DOM using Fourier-transform infrared, UV-vis and fluorescence spectra combined with two-dimensional correlation analysis

Three dissolved organic matter (DOM) samples were obtained from municipal solid wastes at the initial (C0), high-temperature (C7) and mature (C51) period during composting. Two-dimensional correlation spectroscopy (2D-COS) analysis on Fourier-transform infrared (FTIR), ultraviolet visible (UV-vis), and synchronous fluorescence spectra (SFS) were used to investigate the metal binding properties of compost-derived DOM. Synchronous and asynchronous maps of 2D-FTIR-COS of DOM-Cu(II) and DOM-Pb(II) were similar, however, the susceptibility and binding sequence of the corresponding spectral region was different. The N-H (amide I), phenolic OH, and C-O of alcohols, ethers, and esters were the most susceptive in the C0, C7, and C51 samples, respectively. 2D absorption COS indicated that the preferential binding with Cu(II) was shown to be at 305 nm for C0, at 236 nm for C7 and C51, and with Pb(II) at 247 nm for C0, at 233 nm for C7 and C51. 2D-SFS-COS indicated that protein-like matter showed a higher susceptibility and preferential binding with Cu(II) than humic-like substances. DOM showed a higher complexing affinity with Cu(II) than Pb(II) on the basis of the log K values. Spectral techniques combined with 2D-COS are useful to understand the binding heterogeneities of ligand sites within DOM-Cu(II) or Pb(II) during the composting.

Biological impact of octyl d-glucopyranoside based surfactants

Development of many branches of industry has stimulated the search for new, effective surfactants with interesting properties. Potential use of alkyl glucose derivatives on a large scale, raises questions about the possible risks associated with their entry into the natural environment. To be able to evaluate this risk, the aim of the study was to determine the physicochemical properties of octyl d-glucopyranoside and its three derivatives: N-(octyl d-glucopyranosiduronyl)aspartic acid, N-(octyl d-glucopyranosiduronyl)glicyne and octyl d-glucopyranosiduronic acid. Moreover, their biodegradability by pure bacterial strains and biocenosis present in river water was examined. While descriptions of sugar-based surfactants on microbial cells are limited, the essential element of the study was to determine the effect of surfactants on cell surface properties of microorganisms isolated from activated sludge and compare it to the effects of the petroleum based surfactants and the surfactants produced from renewable materials. The results obtained indicate that physicochemical properties of surface active agents differ depending on the presence of functional groups in the surfactants molecules. What is more, the presence of amino acid substituent in the derivatives of octyl d-glucopyranoside resulted in a slight decrease in the surfactants biodegradation efficiency, in comparison to the compounds that did not contain such a substituent, prolonging this process from 5 to 10 days. Interestingly, even relatively slightly different derivatives modified the cell surface properties in a different way. Importantly, the surfactants based on octyl d-glucopyranoside have less negative impact on environmental microorganism and better biodegradability than the surfactant synthesized from petroleum products.

Effects of long-term straw incorporation on lignin accumulation and its association with bacterial laccase-like genes in arable soils

In this study, we aimed to investigate lignin accumulation and its relationship with the composition of bacterial laccase-like genes in three arable lands (i.e., upland limestone soil (UL), upland red soil (UR), and upland-paddy rotation red soil (UPR)), which are subjected to long-term straw incorporation. After 9-13 years of straw incorporation, the lignin content significantly increased from 337.1, 414.5, and 201.6 mg/kg soil to 2096.5, 2092.4, and 1972.2 mg/kg soil in UL, UR, and UPR, respectively. The dominant lignin monomer changed from vanillyl (V)-type to cinnamyl (C)-type in UR. Both V- and C-types were the dominant monomers in UPR, and V-type monomer remained the dominant monomer in UL. Compared with the treatment without straw, straw incorporation significantly promoted the activity of laccase enzyme and the abundance of bacterial laccase-like genes in all soils. The redundancy analysis showed that the main influencing factors on lignin accumulation patterns with straw incorporation were the laccase enzyme activity, nitrogen availability, and some specific bacterial communities possessing the laccase-like genes (e.g., Thermotogae and Acidobacteria). The variation partitioning analysis confirmed that the strongest influencing factor on lignin accumulation was the composition of bacterial laccase-like genes (explained 31.4% of variance). The present study provides novel insights into the importance of bacterial laccase-like genes in shaping lignin monomer accumulation with straw incorporation in arable soils.

The correlation of methanogenic communities' dynamics and process performance of anaerobic digestion of thermal hydrolyzed sludge at short hydraulic retention times

Requirement of a long hydraulic retention time (HRT) for efficient degradation restrains the anaerobic digestion of hydrothermal pretreated sludge. Shortening the HRT can increase the treatment capacity of a plant but may also induce digester instability. This study investigated the impact of HRT on process performance and microbial community by consecutively operating a reactor for 145 days. The HRT was gradually decreased from 20 to 10, 5, and 3 days. The methane yield declined from 0.28 to 0.12 L/g-VS_in with this shortening, and acetate concentration increased from 38 to 376 mg/L. Methanoculleus (58%) dominated methanogens at a 20 days HRT. However, the methanogenic structure shifted toward an increased level of Methanospirillum, representing 95% of the total archaea at a 3 days HRT. Microorganisms were almost washed out at the end of experiment. Conclusively, shortening HRTs is a feasible strategy to increase treatment capacity and produce more biogas at existing plants.