Insight into the comparison of thermally and Fe(II) activated persulfate on sludge dewaterability and disintegration

The effects of thermally and Fe(II) activated potassium persulfate (PPS) on sludge dewatering performance were compared systematacially. Sludge dewaterability was monitored by measuring capillary suction time (CST) and sludge specific resistance to filtration (SRF), and the degradation effect was characterized by Chemical oxygen demand (COD), total organic carbon (TOC), ammonia nitrogen (NH4+-N) and extracellular polymeric substances (EPS). The Change of extracellular polymer substance (EPS) including soluble, loosely bound and tightly bound EPS (S-EPS, LB-EPS and TB-EPS) with time and PPS dosage was monitored to discuss the oxidation efficiency of thermally and Fe(II) activated PPS. Sludge supernate were analyzed by three dimensional fluorescence excitation-emission spectrum (3D-EEM) to confirm the proteins transformation. The result showed that sludge dewaterability in terms of CST and SRF were enhanced with increasing PPS dosage and condition time of both two activated methods. While Fe(II) activated PPS could reduce sludge CST and SRF to preferred values at low PPS dosage and short condition time. Maenwhile, sludge degradation effect was also more obvious. Mechanically, sludge TB-EPS in proteins and polysaccharides converted to SB-EPS was more quickly with Fe(II) activated PPS. Besides, thermally activated PPS tended to oxidize the protein in the supernatant first.

Nanomaterials for Treating Bacterial Biofilms on Implantable Medical Devices

Bacterial biofilms are involved in most device-associated infections and remain a challenge for modern medicine. One major approach to addressing this problem is to prevent the formation of biofilms using novel antimicrobial materials, device surface modification or local drug delivery; however, successful preventive measures are still extremely limited. The other approach is concerned with treating biofilms that have already formed on the devices; this approach is the focus of our manuscript. Treating biofilms associated with medical devices has unique challenges due to the biofilm’s extracellular polymer substance (EPS) and the biofilm bacteria’s resistance to most conventional antimicrobial agents. The treatment is further complicated by the fact that the treatment must be suitable for applying on devices surrounded by host tissue in many cases. Nanomaterials have been extensively investigated for preventing biofilm formation on medical devices, yet their applications in treating bacterial biofilm remains to be further investigated due to the fact that treating the biofilm bacteria and destroying the EPS are much more challenging than preventing adhesion of planktonic bacteria or inhibiting their surface colonization. In this highly focused review, we examined only studies that demonstrated successful EPS destruction and biofilm bacteria killing and provided in-depth description of the nanomaterials and the biofilm eradication efficacy, followed by discussion of key issues in this topic and suggestion for future development.

High-Loaded Bioflocculation Membrane Reactor of Novel Structure for Organic Matter Recovery from Sewage: Effect of Dissolved Oxygen on Bioflocculation and Membrane Fouling

In this study, a new structure of high-load membrane bioreactor (HLB-MR) was used to treat urban sewage, and the effects of dissolved oxygen (DO) on biological flocculation and membrane pollution were researched. Parallel comparative experiments were used to investigate the concentration and recovery efficiency of organic matter, the bioflocculation effect, the content of extracellular polymer substance (EPS), the concentration of metal cations, membrane fouling status and microbial community structure in the reactors under the conditions of 1–2 and 6–8 mg/L. The flocculation efficiency of HLB-MR was 83% and 89% when DO was 1–2 and 6–8 mg/L, respectively. Under DO of 6–8 mg/L, the contents of bound and free EPS in the HLB-MR were 15.64 mg/gVSS and 8.71 mg/L, respectively. These values were significantly higher than those obtained when DO was 1–2 mg/L (11.83 mg/gVSS and 6.56 mg/L, respectively). Moreover, the concentrations of magnesium and aluminum in the concentrate of the HLB-MR were significantly higher when DO was 6–8 mg/L. Under higher DO concentration, there would be more EPS combined with metal cations, and thus fixed in the sludge substrate, the process of which promoted the bioflocculation. Changes in the transmembrane pressure (TMP) showed that the HLB-MR at a higher DO concentration suffered more serious membrane fouling. The species difference between the supernatant and precipitate was more significant under a higher DO concentration. The plankton species in the supernatant, e.g., norank_p__Saccharibacteria, norank_f__Neisseriaceae, and 12up, were likely to exacerbate membrane fouling. However, the species in the precipitate like Trichococcus, Ornithinibacter, and norank_f__Saprospiraceae may have a positive effect on bioflocculation.

A novel bioflocculant for chromium (Ⅵ) and arsenic (Ⅲ) removal: Extracellular polymeric substance (EPS) of Pseudomonas fluorescens

<p>Bioflocculants produced by microorganisms have advantages in removing heavy metals because of their environmental friendliness and biodegradability. In this study, the bioflocculant from a soil bacteria was investigated for its application in chromium (Ⅵ) and arsenic (Ⅲ) removal. The bioflocculant-producing strain was indentified as Pseudomonas fluorescens. It showed maximum flocculating activity of 2579.94 U/mL and yield of 4.84 g/L under optimal condition. With a fed‑batch fermentation strategy, bioflocculant production was further enhanced by 32.6%. The bioflocculant was as extracellular polymer substance composed of 76.67% polysaccharides and 15.8% protein with a molecular weight of 117 kDa. It showed excellent capacities in heavy metal removal, 80.13 and 45.93 mg/g for chromium(Ⅵ) and arsenic (Ⅲ), respectively. The bioflocculant outperformed conventional adsorption materials and could represent a promising biotechnology for the remediation of environmental problems.</p>

Role of Biofilms in Microbiologically Influenced Corrosion of Metals

Data obtained in the recent years on the effect of bio-films in the development of metal microbiologically influenced corrosion (MIC) are summarized. The main way of sessile cells adaptation and survival on metal surfaces lies in formation of biofilms consisting of living cells surrounded by a multicomponent extracellular polymer substance (EPS). Biosystem created possesses new properties that are different from the properties of individual components. Biofilm ways of formation, growth and survival, functions of the extracellular matrix in regard to the microbial consortium and to the metal surface are presented. Mechanisms of biocorrosion involving the electron transmembrane transition from a metal to the living cell cytoplasm, as well as the extracellular pathways of metal oxidation under aerobic and anaerobic conditions, are considered.

Influence of microbial adherence on corrosion of UNS 1008 carbon steel and hybrid nano-structured coatings

Purpose Microbes that are able to grow on different surfaces can cause the deterioration of the underlying layers because of their metabolic activity. The purpose of this study is report the ability of fungi-bacteria consortium (FBC) in anaerobic media, and marine strain bacteria, to attach onto UNS 1008 carbon steel and zinc epoxy coats. Design/methodology/approach Impedance analysis, scanning electronic microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were used to evaluate the adherence, biofilm formation and corrosion effect of FBC and marine bacteria onto UNS1008 carbon steel in anaerobic and aired conditions, respectively. In a similar way, the anticorrosive performance of hybrid coats on UNS 1008 carbon steel against marine bacteria. Findings In aerobic conditions, the outer layer shows a micro-crack appearance and several semi-sphere products that could be because of spore formation. In anaerobic conditions, evidence of iron sulfide surrounded by a mixture of sulfur-containing extracellular polymer substance was observed by SEM images and EDS analysis. The presence of hybrid coats (zinc epoxy with carbon nanotubes CNT content) affected the level of microbial adherence and the concentration of corrosion products (Fe2O3, Fe(OH)2 and FeS); the cell attachment was lower when the steel surface was coated with Zn/CNTs. Originality/value This study opens a window for further evaluations of CNTs associated with metals as active materials to assess the corrosion on extreme corrosive environments, like in oil and gas industries the microorganisms play an important role either to increase or reduce the corrosion processes.

Mechanism and kinetics of biofilm growth process influenced by shear stress in sewers

Sewer biofilms play an important role in the biotransformation of substances for methane and sulfide emission in sewer networks. The dynamic flows and the particular shear stress in sewers are the key factors determining the growth of the sewer biofilm. In this work, the development of sewer biofilm with varying shear stress is specifically investigated to gain a comprehensive understanding of the sewer biofilm dynamics. Sewer biofilms were cultivated in laboratory-scale gravity sewers under different hydraulic conditions with the corresponding shell stresses are 1.12 Pa, 1.29 Pa and 1.45 Pa, respectively. The evolution of the biofilm thickness were monitored using microelectrodes, and the variation in total solids (TS) and extracellular polymer substance (EPS) levels in the biofilm were also measured. The results showed that the steady-state biofilm thickness were highly related to the corresponding shear stresses with the biofilm thickness of 2.4 ± 0.1 mm, 2.7 ± 0.1 mm and 2.2 ± 0.1 mm at shear stresses of 1.12 Pa, 1.29 Pa and 1.45 Pa, respectively, which the chemical oxygen demand concentration is 400 mg/L approximately. Based on these observations, a kinetic model for describing the development of sewer biofilms was developed and demonstrated to be capable of reproducing all the experimental data.