Explore the vast range of titles available.

Fate of biofilm sloughing was assessed in a laboratory-scale (LS) integrated fixed-film sequencing batch reactor (IF-SBR) treating synthetic wastewater and in a full-scale (FS) integrated fixed-film activated sludge (IFAS) system treating municipal wastewater. It was observed that the properties of biofilms and flocs, including sludge volume index (SVI), mixed liquor suspended solids (MLSS), effluent suspended solids (ESS), relative hydrophobicity, and composition of extracellular polymeric substance (EPS) were associated with biofilm sloughing and formation of large granular flocs in the LS IF–SBR. In the FS IFAS system, the changes were studied at the molecular level. For example, the extracted EPS content results (the protein to polysaccharide ratio decreased in the flocs and increased in the biofilms, with biofilm sloughing) were complemented with the confocal laser scanning microscopy (CLSM) coupled with molecular specific staining. CLSM analyses revealed that micro-colonies rich in polysaccharides readily sloughed from the carriers. Live-dead staining revealed areas of the biofilm where the viability of biomass was a contributing factor associated with areas of the biofilm susceptible to sloughing. 16S rRNA gene sequencing (Illumina) of FS IFAS samples revealed greater diversity (α-diversity) in biofilms compared to flocs. Biofilm sloughing resulted in a decrease in diversity in biofilms and a corresponding increase in the flocs during sloughing. Microbial population dynamics revealed that bacteria known for denitrification (for example, Comamonadaceae ) detached from the biofilms during sloughing, readily associated with the suspended biomass, and were retained in the bioreactors.

Anaerobic digestion and fermentation processes in wastewater sludge treatment are limited by several factors, including the slow breakdown of complex organic matter and solubilization of solids. In this study, thermochemical pretreatment of thickened waste activated sludge using high temperature (>170 °C) was investigated to understand the impact of the pretreatment on the volatile fatty acids (VFA) production and its fractions during the fermentation process. Furthermore, the influence the thermochemical pretreatment on sludge disintegration and methane recovery was investigated. A range of acidic and alkaline conditions over the pH range of 4.5–10 was examined. Sludge (pH adjusted) was exposed to hydrothermal pretreatment (HTP) at a temperature of 170 °C for 30 min. Pretreated samples were then subjected to batch fermentation and methane potential tests which revealed that acidic and alkaline conditions resulted in increased sludge solubilization during HTP. Acidic conditions were associated with a higher VFA production yield of up to 185 mg chemical oxygen demand/g total chemical oxygen demand. Alkaline conditions led to a higher methane production yield where the maximum yield (276 mL CH4/g total chemical oxygen demandadded) was found to occur at pH 10. Therefore, alkaline sludge used for fermentation has shown technical and economic feasibility for sludge carbon recovery.

Emerging contaminants, including pharmaceutical and personal care products, are receiving considerable attention owing to their potential to negatively impact the environment and to pose risks to human health. The widespread use of antibiotics and their fate and transport in the environment pose further risks with respect to public health and the development of antibiotic resistant organisms (AROs). While the occurrence of AROs is important, there is increasing interest in antibiotic resistance genes (ARGs). An urgent need exists to improve our understanding of the mechanisms associated with the spread and development of ARGs in both clinical and veterinary settings, the human body (gastrointestinal tract and microbiome) as well as in engineered (wastewater treatment plants) and natural (soil, sediments and water) environments. This review focuses on ARGs as an emerging environmental contaminant. The factors and mechanisms involved in ARG dissemination in a variety of environments are explored in detail. The unique challenges of ARGs with respect to policy-making and environmental monitoring are identified, and recommendations regarding how these challenges might be addressed are provided.

As the effects of climate change become increasingly evident, the need for effective CO 2 management is clear. Microalgae are well-suited for CO 2 sequestration, given their ability to rapidly uptake and fix CO 2 . They also readily assimilate inorganic nutrients and produce a biomass with inherent commercial value, leading to a paradigm in which CO 2 -sequestration, enhanced wastewater treatment, and biomass generation could be effectively combined. Natural non-axenic phototrophic cultures comprising both autotrophic and heterotrophic fractions are particularly attractive in this endeavour, given their increased robustness and innate O 2 -CO 2 exchange. In this study, the interplay between CO 2 -consuming autotrophy and CO 2 -producing heterotrophy in a non-axenic phototrophic biofilm was examined. When the biofilm was cultivated under autotrophic conditions (i.e. no organic carbon), it grew autotrophically and exhibited CO 2 uptake. After amending its growth medium with organic carbon (0.25 g/L glucose and 0.28 g/L sodium acetate), the biofilm rapidly toggled from net-autotrophic to net-heterotrophic growth, reaching a CO 2 production rate of 60 μmol/h after 31 hours. When the organic carbon sources were provided at a lower concentration (0.125 g/L glucose and 0.14 g/L sodium acetate), the biofilm exhibited distinct, longitudinally discrete regions of heterotrophic and autotrophic metabolism in the proximal and distal halves of the biofilm respectively, within 4 hours of carbon amendment. Interestingly, this upstream and downstream partitioning of heterotrophic and autotrophic metabolism appeared to be reversible, as the position of these regions began to flip once the direction of medium flow (and hence nutrient availability) was reversed. The insight generated here can inform new and important research questions and contribute to efforts aimed at scaling and industrializing algal growth systems, where the ability to understand, predict, and optimize biofilm growth and activity is critical.

Huwa-San peroxide (hydrogen peroxide; HSP) is a NSF Standard 60 (maximum 8 mg/L(-1)) new generation peroxide stabilized with ionic silver suitable for continuous disinfection of potable water. Experiments were undertaken to examine the mechanism of HSP against planktonic and biofilm cultures of indicator bacterial strains. Contact/kill time (CT) relationships that achieve effective control were explored to determine the potential utility in primary disinfection. Inhibitory assays were conducted using both nutrient rich media and a medium based on synthetic wastewater. Assays were compared for exposures to three disinfectants (HSP, laboratory grade hydrogen peroxide (HP) and sodium hypochlorite) at concentrations of 20 ppm (therefore at 2.5 and 5 times the NSF limit for HP and sodium hypochlorite, respectively) and at pH 7.0 and 8.5 in dechlorinated tap water. HSP was found to be more or equally effective as hypochlorite or HP. Results from CT assays comparing HSP and HP at different bacterial concentrations with neutralization of residual peroxide with catalase suggested that at a high bacterial concentration HSP, but not HP, was protected from catalase degradation possibly through sequestration by bacterial cells. Consistent with this hypothesis, at a low bacterial cell density residual HSP was more effectively neutralized as less HSP was associated with bacteria and therefore accessible to catalase. Silver in HSP may facilitate this association through electrostatic interactions at the cell surface. This was supported by experiments where the addition of mono (K(+)) and divalent (Ca(+2)) cations (0.005-0.05M) reduced the killing efficacy of HSP but not HP. Experiments designed to distinguish any inhibitory effect of silver from that of peroxide in HSP were carried out by monitoring the metabolic activity of established P. aeruginosa PAO1 biofilms. Concentrations of 70-500 ppm HSP had a pronounced effect on metabolic activity while the equivalent concentrations of ionic silver (50- 375 ppb) had a negligible effect, demonstrating that the microbiocidal activity of HSP was due to peroxide rather than silver. Overall, it was found that the antimicrobial activity of HSP is enhanced over that of hydrogen peroxide; the presence of the ionic silver enhances interactions of HSP with the bacterial cell surface rather than acting directly as a biocide at the tested concentrations.

Background Wastewater treatment plants (WWTPs) are considered hotspots for the environmental dissemination of antimicrobial resistance (AMR) determinants. Vancomycin-Resistant Enterococcus (VRE) are candidates for gauging the degree of AMR bacteria in wastewater. Enterococcus faecalis and Enterococcus faecium are recognized indicators of fecal contamination in water. Comparative genomics of enterococci isolated from conventional activated sludge (CAS) and biological aerated filter (BAF) WWTPs was conducted. Results VRE isolates, including E. faecalis ( n  = 24), E. faecium ( n  = 11), E. casseliflavus (n = 2) and E. gallinarum (n = 2) were selected for sequencing based on WWTP source, species and AMR phenotype. The pangenomes of E. faecium and E. faecalis were both open. The genomic fraction related to the mobilome was positively correlated with genome size in E. faecium ( p  < 0.001) and E. faecalis ( p  < 0.001) and with the number of AMR genes in E. faecium ( p  = 0.005). Genes conferring vancomycin resistance, including van A and van M ( E. faecium ), van G ( E. faecalis ), and van C ( E. casseliflavus / E. gallinarum ), were detected in 20 genomes. The most prominent functional AMR genes were efflux pumps and transporters. A minimum of 16, 6, 5 and 3 virulence genes were detected in E. faecium , E. faecalis , E. casseliflavus and E. gallinarum, respectively. Virulence genes were more common in E. faecalis and E. faecium , than E. casseliflavus and E. gallinarum . A number of mobile genetic elements were shared among species. Functional CRISPR/Cas arrays were detected in 13 E. faecalis genomes, with all but one also containing a prophage. The lack of a functional CRISPR/Cas arrays was associated with multi-drug resistance in E. faecium . Phylogenetic analysis demonstrated differential clustering of isolates based on original source but not WWTP. Genes related to phage and CRISPR/Cas arrays could potentially serve as environmental biomarkers. Conclusions There was no discernible difference between enterococcal genomes from the CAS and BAF WWTPs. E. faecalis and E. faecium have smaller genomes and harbor more virulence, AMR, and mobile genetic elements than other Enterococcus spp .

Four parameters affecting hydrothermal pretreatment (HTP) of municipal sludge prior to anaerobic digestion and fermentation were investigated. Partial factorial design including several key HTP parameters at two distinct levels, including temperature (170 and 190 °C), retention time (RT) (10 and 30 min), pH (4 and 10), and solid content (SC) (4% and 16%), were studied. Further, the impact of HTP parameters on mesophilic and thermophilic fermentation was explored and compared. Results revealed a significant effect of all HTP parameters on COD solubilization, VFA, and methane yield. There were correlations between HTP parameters and process responses such as VFA yield and methane yield. HTP was found to increase COD solubilization and VFA production between 15 and 20% during thermophilic fermentation in relation to mesophilic treatment. All parameters, including SC, temperature, pH, and RT, were important contributing factors affecting methane production during anaerobic digestion. The highest methane production yield of 269 mL CH4/g TCOD added was observed at the highest SC (16%) and pH (10) and at the lower temperature (170 °C) and RT (10). HTP is expected to be combined with other intensification routes to treat waste with high solid contents improving the fermentation and anaerobic digestion processes.

The estimated global population growth of 81 million people per year, combined with increased rates of urbanization and associated industrial processes, result in volumes of high strength ammonia wastewater that cannot be treated in a cost-effective or sustainable manner using the floc-based conventional activated sludge approach of nitrification and denitrification. Biofilm and aerobic granular sludge technologies have shown promise to significantly improve the performance of biological nitrogen removal systems treating high strength wastewater. This is partly due to enhanced biomass retention and their ability to sustain diverse microbial populations with juxtaposing growth requirements. Recent research has also demonstrated the value of hybrid systems with heterogeneous bioaggregates to mitigate biofilm and granule instability during long-term operation. In the context of high strength ammonia wastewater treatment, conventional nitrification–denitrification is hampered by high energy costs and greenhouse gas emissions. Anammox-based processes such as partial nitritation–anammox and partial denitrification–anammox represent more cost-effective and sustainable methods of removing reactive nitrogen from wastewater. There is also growing interest in the use of photosynthetic bacteria for ammonia recovery from high strength waste streams, such that nitrogen can be captured and concentrated in its reactive form and recycled into high value products. The purpose of this review is to explore recent advancements and emerging approaches related to high strength ammonia wastewater treatment.

Climate change brought about by anthropogenic CO2 emissions has created a critical need for effective CO2 management solutions. Microalgae are well suited to contribute to efforts aimed at addressing this challenge, given their ability to rapidly sequester CO2 coupled with the commercial value of their biomass. Recently, microalgal biofilms have garnered significant attention over the more conventional suspended algal growth systems, since they allow for easier and cheaper biomass harvesting, among other key benefits. However, the path to cost-effectiveness and scaling up is hindered by a need for new tools and methodologies which can help evaluate, and in turn optimize, algal biofilm growth. Presented here is a novel system which facilitates the real-time in situ monitoring of algal biofilm CO2 sequestration. Utilizing a CO2-permeable membrane and a tube-within-a-tube design, the CO2 sequestration monitoring system (CSMS) was able to reliably detect slight changes in algal biofilm CO2 uptake brought about by light–dark cycling, light intensity shifts, and varying amounts of phototrophic biomass. This work presents an approach to advance our understanding of carbon flux in algal biofilms, and a base for potentially useful innovations to optimize, and eventually realize, algae biofilm-based CO2 sequestration.

As the effects of climate change become increasingly evident, the need for effective CO.sub.2 management is clear. Microalgae are well-suited for CO.sub.2 sequestration, given their ability to rapidly uptake and fix CO.sub.2 . They also readily assimilate inorganic nutrients and produce a biomass with inherent commercial value, leading to a paradigm in which CO.sub.2 -sequestration, enhanced wastewater treatment, and biomass generation could be effectively combined. Natural non-axenic phototrophic cultures comprising both autotrophic and heterotrophic fractions are particularly attractive in this endeavour, given their increased robustness and innate O.sub.2 -CO.sub.2 exchange. In this study, the interplay between CO.sub.2 -consuming autotrophy and CO.sub.2 -producing heterotrophy in a non-axenic phototrophic biofilm was examined. When the biofilm was cultivated under autotrophic conditions (i.e. no organic carbon), it grew autotrophically and exhibited CO.sub.2 uptake. After amending its growth medium with organic carbon (0.25 g/L glucose and 0.28 g/L sodium acetate), the biofilm rapidly toggled from net-autotrophic to net-heterotrophic growth, reaching a CO.sub.2 production rate of 60 [mu]mol/h after 31 hours. When the organic carbon sources were provided at a lower concentration (0.125 g/L glucose and 0.14 g/L sodium acetate), the biofilm exhibited distinct, longitudinally discrete regions of heterotrophic and autotrophic metabolism in the proximal and distal halves of the biofilm respectively, within 4 hours of carbon amendment. Interestingly, this upstream and downstream partitioning of heterotrophic and autotrophic metabolism appeared to be reversible, as the position of these regions began to flip once the direction of medium flow (and hence nutrient availability) was reversed. The insight generated here can inform new and important research questions and contribute to efforts aimed at scaling and industrializing algal growth systems, where the ability to understand, predict, and optimize biofilm growth and activity is critical.