Comparison of exogenous degrader-enhanced bioremediation with low-dose persulfate oxidation for polycyclic aromatic hydrocarbon removal in alkaline soil:efficiency and influence on ecological health

Polycyclic aromatic hydrocarbon(PAH)-contaminated soils are usually complex and characterized by a lack of nutrition and soil salinization,resulting in difficulties in soil remediation.In this study,bioaugmentation with a PAH-degrading Bacillus PheN7(BA)and low-dose persulfate oxidation(PS),along with natural biodegradation,were utilized to remediate alkaline PAH-contaminated soil.The soil used in the study had a pH of 9.35,and the total PAH content was 568.8±31.0 mg/kg dry soil.After 42 d of remediation,the degradation efficiency of PAHs was 96.72%and 93.88%using persulfate oxidation and bioaugmentation,respectively,whereas 38.66%of PAHs were degraded in natural attenuation(NA).Bacillus was the dominant genera throughout the process of bioremediation with the relative abundance of 79.3%on day 42 in the BA system,whereas,Alcanivorax was enriched and became the dominant genera in PS systems.In the meantime,PAH degradation genes were detected with remarkably higher level in the BA system than in PS system during the remediation.In addition to the degradation of contaminants,persulfate oxidation promotes microbial bioremediation efficiency mainly by lowering the pH to neutral and increasing the active phosphorus content in the soil.Microbial species and ecological niches were less reduced in the PS system than in the BA system.Collectively,persulfate oxidation had a better impact on the soil microbiome and is more suitable for long-term soil health than bioaugmentation through PheN7 addition.

Overview of key operation factors and strategies for improving fermentative volatile fatty acid production and product regulation from sewage sludge

In recent years,volatile fatty acid(VFA)production through anaerobic fermentation of sewage sludge,instead of methane production,has been regarded as a high-value and promising roadmap for sludge stabilization and resource recovery.This review first presents the effects of some essential factors that influence VFA production and composition.In the second part,we present an extensive analysis of conventional pretreatment and co-fermentation strategies ultimately addressed to improving VFA production and composition.Also,the effectiveness of these approaches is summarized in terms of sludge degradation,hydrolysis rate,and VFA production and composition.According to published studies,it is concluded that some pretreatments such as alkaline and thermal pretreatment are the most effective ways to enhance VFA production from sewage sludge.The possible reasons for the improvement of VFA production by different methods are also discussed.Finally,this review also highlights several current technical challenges and opportunities in VFA production with spectrum control,and further related research is proposed.

Feasibility of bioleaching combined with Fenton oxidation to improve sewage sludge dewaterability

A novel joint method of bioleaching with Fenton oxidation was applied to condition sewage sludge. The specific resistance to filtration（SRF） and moisture of sludge cake（MSC） were adopted to evaluate the improvement of sludge dewaterability. After 2-day bioleaching, the sludge p H dropped to about 2.5 which satisfied the acidic condition for Fenton oxidation.Meanwhile, the SRF declined from 6.45 × 1010 to 2.07 × 1010s2/g, and MSC decreased from91.42% to 87.66%. The bioleached sludge was further conditioned with Fenton oxidation. From an economical point of view, the optimal dosages of H2O2 and Fe2＋were 0.12 and 0.036 mol/L,respectively, and the optimal reaction time was 60 min. Under optimal conditions, SRF,volatile solids reduction, and MSC were 3.43 × 108s2/g, 36.93%, and 79.58%, respectively. The stability and settleability of sewage sludge were both improved significantly. Besides,the results indicated that bioleaching-Fenton oxidation was more efficient in dewatering the sewage sludge than traditional Fenton oxidation. The sludge conditioning mechanisms by bioleaching-Fenton oxidation might mainly include the flocculation effects and the releases of extracellular polymeric substances–bound water and intercellular water.

Enhancement of ultrasonic disintegration of sewage sludge by aeration

Sonication is an effective way for sludge disintegration,which can significantly improve the efficiency of anaerobic digestion to reduce and recycle use of sludge.But high energy consumption limits the wide application of sonication.In order to improve ultrasonic sludge disintegration efficiency and reduce energy consumption,aeration was introduced.Results showed that sludge disintegration efficiency was improved significantly by combining aeration with ultrasound.The aeration flow rate,gas bubble size,ultrasonic density and aeration timing had impacts on sludge disintegration efficiency.Aeration that used in later stage of ultrasonic irradiation with low aeration flow rate,small gas bubbles significantly improved ultrasonic disintegration sludge efficiency.At the optimal conditions of 0.4 W/m L ultrasonic irradiation density,30 m L/min of aeration flow rate,5 min of aeration in later stage and small gas bubbles,ultrasonic sludge disintegration efficiency was increased by 45% and one third of ultrasonic energy was saved.This approach will greatly benefit the application of ultrasonic sludge disintegration and strongly promote the treatment and recycle of wastewater sludge.

Electrochemical dual-oxidation strategy enables access toα-chlorosulfoxides from sulfides

Electrochemistry contributes a strong tool for the manufacture of molecules,addressing intractable challenges in synthetic chemistry by enabling innovative reaction pathways.Herein,a bifunctional reagent,aqueous hydrochloric acid,is used to establish an electrochemical selective dual-oxidation approach that gives access toα-chlorosulfoxides from sulfides.This strategy presents broad substrate scope,high diastereoselectivity,and regioselectivity.The late-stage modification of amino acids and pharmaceutical derivatives further highlights the utility.Furthermore,detailed mechanistic studies reveal that the key success for this selective chemical transformation is the dual-oxidation process at the anode.This electrochemical dual-oxidation strategy may have wide universality;we anticipate diverse applications of this protocol across the many fields of chemistry.

Enhancement of sludge gravitational thickening with weak ultrasound

Gravitational thickening is the prevailing method to reduce sludge volume but the process is slow and usually requires addition of polyelectrolyte（s）. This paper investigated the potential benefits of sonication on enhancing the sludge gravitational thickening with very low energy dose, so called ＂weak ultrasound＂. Results showed that weak sonication significantly changed the sludge settlability and the main mechanism was release of the loosely bounded extracellular polymeric substances. The changes in sludge behaviors by sonication were strongly influenced by power density and sonication duration. Lower sound frequency was slightly better than higher frequency. Weak sonication （ 〈 680 kJ.kg1 DS） improved the sludge gravitational thickening while high ultrasonic energy deteriorated the process. Considering both the sludge thickening efficiency and energy con- sumption the optimum conditions were 0.15 W. mL-l, 7 s, and 25 kHz. Under such conditions, the energy dose was only 155 kJ.kg-1 DS, much lower than literature reports, and the sludge settling time was shortened from 24 h to 12 h. Weak sonication could substitute expensive poly- electrolyte coagulant for sludge thickening. Combination of weak sonication and polyelectrolyte could further reduce the settling time to 6 h. The final water content of the thickened sludge was not changed after sonication or polyelectrolyte addition.