Transparent exopolymer particles (TEPs)-associated protobiofilm: A neglected contributor to biofouling during membrane filtration

• Bacteria could easily and quickly attached onto TEP to form protobiofilms. • TEP-protobiofilm facilitate the transport of bacteria to membrane surface. • More significant flux decline was observed in the presence of TEP-protobiofilms. • Membrane fouling shows higher sensitivity to protobiofilm not to bacteria level. Transparent exopolymer particles (TEPs) are a class of transparent gel-like polysaccharides, which have been widely detected in almost every kind of feed water to membrane systems, including freshwater, seawater and wastewater. Although TEP have been thought to be related to the membrane fouling, little information is currently available for their influential mechanisms and the pertinence to biofouling development. The present study, thus, aims to explore the impact of TEPs on biofouling development during ultrafiltration. TEP samples were inoculated with bacteria for several hours before filtration and the formation of “protobiofilm” (pre-colonized TEP by bacteria) was examined and its influence on biofouling was determined. It was observed that the bacteria can easily and quickly attach onto TEPs and form protobiofilms. Ultrafiltration experiments further revealed that TEP-protobiofilms served as carriers which facilitated and accelerated transport of bacteria to membrane surface, leading to rapid development of biofouling on the ultrafiltration membrane surfaces. Moreover, compared to the feed water containing independent bacteria and TEPs, more flux decline was observed with TEP-protobiofilms. Consequently, it appeared from this study that TEP-protobiofilms play a vital role in the development of membrane biofouling, but unfortunately, this phenomenon has been often overlooked in the literature. Obviously, these findings in turn may also challenge the current understanding of organic fouling and biofouling as membrane fouling caused by TEP-protobiofilm is a combination of both. It is expected that this study might promote further research in general membrane fouling mechanisms and the development of an effective mitigation strategy.     

The impact trilemma of energy prices,taxation, and population on industrial and residential greenhouse gas emissions in Europe

Environmental Science and Pollution Research - As a major source of pollution and the cause of climate change, greenhouse gas emissions are attracting the attention of scholars, policymakers, and...     

TiO2@palygorskite composite for the efficient remediation of oil spills via a dispersion-photodegradation synergy

• A novel and multi-functional clay-based oil spill remediation system was constructed. • TiO₂@PAL functions as a particulate dispersant to break oil slick into tiny droplets. • Effective dispersion leads to the direct contact of TiO₂ with oil pollutes directly. • TiO₂ loaded on PAL exhibits efficient photodegradation for oil pollutants. • TiO₂@PAL shows a typical dispersion-photocatalysis synergistic remediation. Removing spilled oil from the water surface is critically important given that oil spill accidents are a common occurrence. In this study, TiO₂@Palygorskite composite prepared by a simple coprecipitation method was used for oil spill remediation via a dispersion-photodegradation synergy. Diesel could be efficiently dispersed into small oil droplets by TiO₂@Palygorskite. These dispersed droplets had an average diameter of 20–30 mm and exhibited good time stability. The tight adsorption of TiO₂@Palygorskite on the surface of the droplets was observed in fluorescence and SEM images. As a particulate dispersant, the direct contact of TiO₂@Palygorskite with oil pollutants effectively enhanced the photodegradation efficiency of TiO₂ for oil. During the photodegradation process, •O₂⁻and •OH were detected by ESR and radical trapping experiments. The photodegradation efficiency of diesel by TiO₂@Palygorskite was enhanced by about 5 times compared with pure TiO₂ under simulated sunlight irradiation. The establishment of this new dispersion-photodegradation synergistic remediation system provides a new direction for the development of marine oil spill remediation.     

Less attention paid to waterborne SARS-CoV-2 spreading in Beijing urban communities

• A survey on individual’s perception of SARS-CoV-2 transmission was conducted. • Waterborne transmission risks are far less perceived by individuals. • Precautions of preventing wastewater mediated transmission are implemented. • The precautions for wastewater transmission are less favored by the public. • Education level differs the most regarding to waterborne transmission perception. SARS-CoV-2 has been detected in various environmental media. Community and individual-engaged precautions are recommended to stop or slow environmentally-mediated transmission. To better understand the individual’s awareness of and precaution to environmental dissemination of SARS-CoV-2, an online survey was conducted in Beijing during March 14–25, 2020. It is found that the waterborne (especially wastewater mediated) spreading routes are far less perceived by urban communities. The precautions for wastewater transmission are less favored by the public than airborne and solid waste mediated spreading routes. Such risk communication asymmetry in waterborne transmission will be further enlarged in places with fragile water system. Furthermore, education level is the most significant attribution (Sig.<0.05) that causes the difference of awareness and precautions of the waterborne transmission among the respondents, according to the variance analysis results. Our survey results emphasize the urgent need for evidence-based, multifactorial precautions for current and future outbreaks of COVID-19.     

Magnetic graphene-based nanocomposites as highly efficient absorbents for Cr(VI) removal from wastewater

Environmental Science and Pollution Research - Due to the merits of their high adsorption and convenient separation, magnetic graphene-based composites have become a promising adsorbent in terms of...     

Could biochar amendment be a tool to improve soil availability and plant uptake of phosphorus? A meta-analysis of published experiments

Environmental Science and Pollution Research - As one of the most important nutrients for plant growth, phosphorus was often poorly available in soil. While biochar addition induced improvement of...     

Novel perspective for urban water resource management: 5R generation

• 5R (Recover, Reduce, Recycle, Resource and Reuse) approaches to manage urban water. • 5R harvests storm water, gray water and black water in several forms. • 5R offers promise for moving solutions for urban water scarcity in practice. Demand for water is expanding with increases in population, particularly in urban areas in developing countries. Additionally, urban water system needs a novel perspective for upgradation with urbanization. This perspective presents a novel 5R approach for managing urban water resources: Recover (storm water), Reduce (toilet flushing water), Recycle (gray water), Resource (black water), and Reuse (advanced-treated wastewater). The 5R generation incorporates the latest ideas for harvesting storm water, gray water, and black water in its several forms. This paper has briefly demonstrated each R of 5R generation for water treatment and reuse. China has the chance to upgrade its urban water systems according to 5R principles. Already, a demonstration project of 5R generation has been installed in Qingdao International Horticultural Exposition, and Dalian International Convention Center (China) has applied 5R, achieving over 70% water saving. The 5R offers promise for moving solutions for urban water scarcity from “hoped for in the future” to “realistic today”.     

Lithium extraction from salt lake brines with high magnesium/lithium ratio: a review

Environmental Chemistry Letters - The demand for lithium is growing rapidly with the increase in electric vehicles, batteries and electronic equipments. Lithium can be extracted from brines, yet...     

Influence of pore structure on biologically activated carbon performance and biofilm microbial characteristics

• Pore structure affects biologically activated carbon performance. • Pore structure determines organic matter (OM) removal mechanism. • Microbial community structure is related to pore structure and OM removal. Optimizing the characteristics of granular activated carbon (GAC) can improve the performance of biologically activated carbon (BAC) filters, and iodine value has always been the principal index for GAC selection. However, in this study, among three types of GAC treating the same humic acid-contaminated water, one had an iodine value 35% lower than the other two, but the dissolved organic carbon removal efficiency of its BAC was less than 5% away from the others. Iodine value was found to influence the removal of different organic fractions instead of the total removal efficiency. Based on the removal and biological characteristics, two possible mechanisms of organic matter removal during steady-state were suggested. For GAC with poor micropore volume and iodine value, high molecular weight substances (3500–9000 Da) were removed mainly through degradation by microorganisms, and the biodegraded organics (soluble microbial by-products,<3500 Da) were released because of the low adsorption capacity of activated carbon. For GAC with higher micropore volume and iodine value, organics with low molecular weight (<3500 Da) were more easily removed, first being adsorbed by micropores and then biodegraded by the biofilm. The biomass was determined by the pore volume with pore diameters greater than 100 μm, but did not correspond to the removal efficiency. Nevertheless, the microbial community structure was coordinate with both the pore structure and the organic removal characteristics. The findings provide a theoretical basis for selecting GAC for the BAC process based on its pore structure.     

Catalytic fast pyrolysis of walnut shell for alkylphenols production with nitrogen-doped activated carbon catalyst

• N-doped activated carbon was prepared for catalytic pyrolysis of walnut shell. • Alkylphenols were selectively produced from catalytic pyrolysis process. • The alkylphenols yield increased by 8.5 times under the optimal conditions. • Formation mechanism of alkylphenols was proposed. Alkylphenols are a group of valuable phenolic compounds that can be derived from lignocellulosic biomass. In this study, three activated carbons (ACs) were prepared for catalytic fast pyrolysis (CFP) of walnut shell to produce alkylphenols, including nitrogen-doped walnut shell-derived activated carbon (N/WSAC), nitrogen-doped rice husk-derived activated carbon (N/RHAC) and walnut shell-derived activated carbon (WSAC). Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) experiments were carried out to reveal the influences of AC type, pyrolytic temperature, and AC-to-walnut shell (AC-to-WS) ratio on the product distributions. Results showed that with nitrogen doping, the N/WSAC possessed stronger capability than WSAC toward the alkylphenols production, and moreover, the N/WSAC also exhibited better effects than N/RHAC to prepare alkylphenols. Under the catalysis of N/WSAC, yields of alkylphenols were significantly increased, especially phenol, cresol and 4-ethylphenol. As the increase of pyrolytic temperature, the alkylphenols yield first increased and then decreased, while high selectivity could be obtained at low pyrolytic temperatures. Such a trend was also observed as the AC-to-WS ratio continuously increased. The alkylphenols production achieved a maximal yield of 44.19 mg/g with the corresponding selectivity of 34.7% at the pyrolytic temperature of 400°C and AC-to-WS ratio of 3, compared with those of only 4.67 mg/g and 6.1% without catalyst. In addition, the possible formation mechanism of alkylphenols was also proposed with the catalysis of N/WSAC.