Tannic acid (TA), a phenolic compound, may be considered as a sludge conditioning agent on account of its ability to precipitate protein. In this study, the effectiveness of TA conditioning on ...enhancing waste activated sludge (WAS) dewatering was investigated at various pH values. The results indicated that with the conditioning of 0.15 mmol TA per gram of total solid (TS), the WAS dewaterability was affected distinctly by the pH regulation. The reductions of 86.8% capillary suction time (CST), 96.3% specific resistance of filtration (SRF), and 23.6% water content (Wc) of dewatered sludge cake were achieved at an optimal pH value of 4.0. Meanwhile, obvious alterations were observed in some aspects like supernatant viscosity, zeta potential, particle size and extracellular polymeric substances (EPS) polymers. Correlation analysis indicated that the proteins in slime EPS and loosely bound EPS dominantly governed sludge dewaterability. Fluorescence quenching analysis indicated that in the range of acidity, the increase of pH value afforded more binding sites of sludge EPS for TA. However, the removal of EPS protein depended on the combined effect of TA conditioning and pH regulation. The findings provided a novel approach and explanation of WAS dewaterability enhancement using organic additive conditioning and pH regulation.
Display omitted
•Tannic acid conditioning altered sludge properties obviously.•High correlation between extracellular protein and sludge dewaterability.•The pH value affected binding sites of sludge EPS available for tannic acid.•Combined effect of tannic acid and pH conditioning contributed to protein removal.
Microbial extracellular polymeric substances (EPS) widely exist in natural environments and affect the migration and transformation of pollutants in aquatic environments. Previous works report that ...EPS have some reducing functional groups and can reduce heavy metals. However, because of the weak reducing capability of EPS, the reduction of heavy metals by EPS without cells is extremely slow, and its effect on heavy metals species is insignificant. In this work, the accelerated reduction of silver ions (Ag+) by EPS from Shewanella oneidensis MR-1 under illumination was investigated. UV–visible spectroscopy, transmission electron microscopy (TEM) coupled with an energy dispersive spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS) were used to confirm the formation of silver nanoparticles (AgNPs) via the reduction of Ag+ by EPS under light illumination. The Ag+ reduction by EPS follows pseudo-first-order kinetics under both visible and UV light, and the light irradiation can significantly accelerate AgNPs formation. On the one hand, visible light can excite AgNPs for their surface plasma resonance (SPR) and accelerate the electrons from the EPS to adjacent Ag+. On the other hand, EPS molecules may be excited by UV light to produce strong reducing species, which enhance Ag+ reduction. Moreover, pH, dissolved oxygen were found to affect the formation of AgNPs by EPS. This work proves the reducing capability of EPS on the reduction of Ag+, and this process can be accelerated under light illumination, which may affect the speciation and transformation of heavy metals in natural waters.
Display omitted
•AgNPs formation via reduction of Ag+ by EPS under illumination was confirmed.•Light illumination can significantly enhance the reduction of Ag+ by EPS.•The Ag+ reduction by EPS follows pseudo-first-order kinetics.•The mechanism of effect of light on the reduction of Ag+ by EPS was proposed.•pH and dissolved oxygen will influence the reduction of Ag+ by EPS.
Display omitted
•The Na+ + Lysozyme pretreatment increased the yield of SCFAs in WAS by 7.6 times.•A synergistic effect was occurred between Na+ and lysozyme in promoting cell lysis.•Na+ + Lysozyme ...pretreatment significantly shortened the hydrolysis and acidification reaction times.•87% of the carbon source recovery in the liquid phase can be achieved after PAC conditioning.
Augmentation of the anaerobic treatment efficiency of waste activated sludge (WAS) to achieve better resource utilization is an effective approach for reducing carbon emissions and minimizing solid waste generation. However, resource recovery from WAS is often limited by the insufficient release and hydrolysis of organic matters within microbial cells. To overcome these issues, a novel Na+ and lysozyme co-pretreatment method has been used in this study to accelerate the production of short-chain fatty acids (SCFAs) by promoting cell lysis. Experimental results have revealed that the maximal SCFAs production of 302.8 ± 47.8 mg COD/g VSS is achieved with 10 % w/w lysozyme and 0.34 mol/L Na+ co-pretreatment on day 2, which is 7.6-fold higher than that of the control. Mechanism exploration has also exposed that Na+ and lysozyme exhibit a pronounced synergistic effect in cell lysis, where 1 + 1 > 2. The maximum sludge disintegration degree (DDM) and SCFAs conversion efficiency have been achieved by combined pretreatment, reaching 68.5 % and 74 %, respectively. The structure of extracellular polymeric substance (EPS) including protein content and looseness are also modified by Na+ or Na+ + Lysozyme pretreatment, which further confirm the impact of Na+ on the permeability of EPS. The carbon sources generated through Na+ and lysozyme pretreated WAS can be efficiently recovered through PAC conditioning, with a high recovery rate of 87 %. The Na+ and lysozyme reagents implemented in the present study are all non-toxic and cost-effective, thereby promising a green and efficient solution for the carbon recovery and separation from the WAS.
Summary
Members of the Arabidopsis thaliana TCP transcription factor (TF) family affect plant growth and development. We systematically quantified the effect of mutagenizing single or multiple TCP ...TFs and how altered vegetative growth or branching influences final seed yield. We monitored rosette growth over time and branching patterns and seed yield characteristics at the end of the lifecycle. Subsequently, an approach was developed to disentangle vegetative growth and to determine possible effects on seed yield. Analysis of growth parameters showed all investigated tcp mutants to be affected in certain growth aspects compared with wild‐type plants, highlighting the importance of TCP TFs in plant development. Furthermore, we found evidence that all class II TCPs are involved in axillary branch outgrowth, either as inhibitors (BRANCHED‐like genes) or enhancers (JAW‐ and TCP5‐like genes). Comprehensive phenotyping of plants mutant for single or multiple TCP TFs reveals that the proposed opposite functions of class I and class II TCPs in plant growth needs revision and shows complex interactions between closely related TCP genes instead of full genetic redundancy. In various instances, the alterations in vegetative growth or in branching patterns result into negative trade‐off effects on seed yield that were missed in previous studies, showing the importance of comprehensive and quantitative phenotyping.
Significance Statement
This study shows the importance of the TCP transcription factor family during Arabidopsis growth and development, coupled to yield and plant architecture. It was found that all class II TCPs are involved in axillary bud outgrowth and that the proposed opposite functioning of class I and class II TCPs requires revision.
•Sludge enhanced dewatering technologies are comprehensively reviewed.•Mechanisms of different sludge enhanced dewatering technologies are discussed.•Process adaptability of different sludge ...conditioning methods are analysed.•Sludge electro-dewatering and its coupled processes are discussed.•Sludge enhanced dewatering technology and its coupled processes are prospected.
Sludge is an inevitable by product of sewage treatment, and it includes pathogens, heavy metals, organic pollutants and other toxic substances. The components of sludge are complex and variable with extracellular polymeric substances (EPS) being one. EPS are highly hydrophilic and compressible, and make sludge dewatering difficult. Therefore, the development of efficient sludge-dewatering technology is an important means of mitigating rapid sludge growth. At present, the main methods used for sludge deep-dewatering technology are chemical preconditioning with high-pressure filtration and electrical mechanical dewatering. The selection of chemical preconditioning directly determines the final efficiency of the sludge-dewatering process. In this paper, we conduct a comprehensive review of the problems related to sludge dewatering and systematically summarise the impact of different chemical conditioning technologies on the efficiency of sludge dewatering. Furthermore, the characteristics of different enhanced dewatering technologies are evaluated and analysed for their adaptability and final disposal methods. We believe that this review can clarify the chemical conditioner mechanism to improve sludge dewatering, provide reference debugging information for the sludge-dewatering process and promote the development of efficient and environmentally friendly sludge-dewatering technology.
•Exergy analysis of diesel engine fuelled with various SBE biodiesel–diesel blends containing EPS.•Profound effect of engine speed and load on exergetic performance parameters of diesel ...engine.•Selection of B5 containing 50g EPS/L biodiesel as the best mixture.•Potential application of the applied framework for optimizing sustainability index of IC engines.
Exergy analysis of a DI diesel engine running on several biodiesel/diesel blends (B5) containing various quantities of expanded polystyrene (EPS) was carried out. Neat diesel and B5 were also investigated during the engine tests. The biodiesel used was produced using waste oil extracted from spend bleaching earth (SBE). The experiments were conducted to assess the effects of fuel type, engine speed, and load on thermal efficiency, exergetic parameters, and sustainability index of the diesel engine. The obtained results revealed that the exergetic parameters strongly depended on the engine speed and load. Generally, increasing engine speed remarkably decreased the exergy efficiency and sustainability index of the diesel engine. However, increasing engine load initially enhanced the exergy efficiency and sustainability index, while its further augmentation did not profoundly affect these parameters. The maximum exergy efficiency and sustainability index of the diesel engine (i.e. 40.21% and 1.67, respectively) were achieved using B5 containing 50g EPS/L biodiesel. Generally, the approach presented herein could be a promising strategy for energy recovery from polymer waste, emissions reduction, and performance improvement. The findings of the present study also confirmed that exergy analysis could be employed to minimize the irreversibility and losses occurring in modern engines and to enhance the sustainability index of combustion processes.
Species distribution models (SDMs) are widely used to predict the occurrence of species. Because SDMs generally use presence-only data, validation of the predicted distribution and assessing model ...accuracy is challenging. Model performance depends on both sample size and species' prevalence, being the fraction of the study area occupied by the species. Here, we present a novel method using simulated species to identify the minimum number of records required to generate accurate SDMs for taxa of different pre-defined prevalence classes. We quantified model performance as a function of sample size and prevalence and found model performance to increase with increasing sample size under constant prevalence, and to decrease with increasing prevalence under constant sample size. The area under the curve (AUC) is commonly used as a measure of model performance. However, when applied to presence-only data it is prevalence-dependent and hence not an accurate performance index. Testing the AUC of an SDM for significant deviation from random performance provides a good alternative. We assessed the minimum number of records required to obtain good model performance for species of different prevalence classes in a virtual study area and in a real African study area. The lower limit depends on the species' prevalence with absolute minimum sample sizes as low as 3 for narrow-ranged and 13 for widespread species for our virtual study area which represents an ideal, balanced, orthogonal world. The lower limit of 3, however, is flawed by statistical artefacts related to modelling species with a prevalence below 0.1. In our African study area lower limits are higher, ranging from 14 for narrow-ranged to 25 for widespread species. We advocate identifying the minimum sample size for any species distribution modelling by applying the novel method presented here, which is applicable to any taxonomic clade or group, study area or climate scenario.
The occurrences, transformation of antibiotics in biological wastewater treatment plants have attracted increasing interests. However, roles of extracellular polymeric substances (EPS) of activated ...sludge on the fate of antibiotics are not clear. In this study, the roles of EPS in the migration and removal of one typical antibiotic, sulfamethazine (SMZ), in activated sludge process were investigated. The interaction between EPS and SMZ was explored through a combined use of fluorescence spectral analysis, laser light scattering and microcalorimetry techniques. Results show that SMZ interacted with the proteins in EPS mainly with a binding constant of 1.91 × 105 L/mol. The binding process proceeded spontaneously, and the driving force was mainly from the hydrophobic interaction. After binding, the structure of EPS was expanded and became loose, which favored the mass transfer and pollution capture. The removal of SMZ was influenced by interaction with EPS. SMZ could be effectively adsorbed on EPS, which accounted for up to 61.8% of total SMZ adsorbed by sludge at the initial adsorption stage and declined to around 35.3% at the subsequent biodegradation stage. The enrichment of SMZ by EPS was beneficial for SMZ removal and acquisition by microbes at the subsequent biodegradation stage.
Display omitted
•Interaction between EPS and SMZ plays an important role in SMZ removal.•A multi-technique approach is used to explore the mechanism of the interaction.•SMZ mainly interacts with the proteins in EPS by hydrophobic interaction.•Configuration changes of EPS might enhance the pollution capture efficiency.
Androdioecy is the rarest sexual system among plants. The majority of androdioecious species are herbaceous plants that have evolved from dioecious ancestors. Nevertheless, some woody and ...androdioecious plants have hermaphrodite ancestors, as in the Annonaceae, where androdioecious genera have arisen several times in different lineages. The majority of androdioecious species of Annonaceae belong to the Neotropical tribe Malmeeae. In addition to these species, Pseudoxandra spiritus-sancti was recently confirmed to be androdioecious. Here, we describe the morphology of male and bisexual flowers of Pseudoxandra spiritus-sancti, and investigate the evolution of androdioecy in Malmeeae. The phylogeny of tribe Malmeeae was reconstructed using Bayesian inference, maximum parsimony and maximum likelihood of 32 taxa, using DNA sequences of 66 molecular markers of the chloroplast genome, sequenced by next generation sequencing. The reconstruction of ancestral states was performed for characters associated with sexual systems and floral morphology. The phylogenetic analyses reconstructed three main groups in Malmeeae, (Malmea (Cremastosperma, Pseudoxandra)) sister to the rest of the tribe, and (Unonopsis (Bocageopsis, Onychopetalum)) sister to (Mosannona, Ephedranthus, Klarobelia, Oxandra, Pseudephedranthus fragrans, Pseudomalmea, Ruizodendron ovale). Hermaphroditism is plesiomorphic in the tribe, with four independent evolutions of androdieocy, which represents a synapomorphy of two groups, one that includes three genera and 14 species, the other with a single genus of seven species. Male flowers are unisexual from inception and bisexual flowers possess staminodes and functional stamens. Pseudoxandra spiritus-sancti is structurally androdioecious.
Adsorption is an effective and reliable method to recover phosphorus (P) from sewages. Extracellular polymeric substances (EPS) and agarose are common polysaccharides bioresources, and their ...carboxylic and phenolic hydroxyl groups can directly adsorb P via ion exchange and hydrogen bonding mechanisms. Here, we designed EPS-based and Fe-modified hydrogels (agarose (AG)- and agarose-humic (AH)- based hydrogels) for P recovery. The results showed that AG and AH hydrogels could adsorb 33.9 and 67.7 mg P g−1, respectively. Both as-developed hydrogels showed > 75% of the maximal adsorption capacity in the tested pH conditions (3−10). Coexisting anions (i.e., SO42-, NO3-, and CO32-) did not significantly affect the adsorption performance, except for CO32- which inhibited the process. Intraparticle diffusion controlled the adsorption process. After adsorption, large amounts of FePO4 and Fe2(HPO4)3 were generated in the hydrogels, confirming that ligand exchange was the major driving force.
Display omitted
•EPS-based hydrogels are made from agarose and humic acid.•EPS-based hydrogel appeared to have excellent phosphorus adsorption performance.•Ligand exchange is the major driving force for hydrogels to trap phosphate.
PDF
