Mitigation of biofouling in agricultural water distribution systems with nanobubbles

Effect of nanobubble concentrations on fouling control capacity in biogas slurry wastewater distribution systems

Nanobubble (NB) represents a promising practice for mitigating fouling in biogas slurry distribution systems. However, its anti-fouling effectiveness and optimal use dosage are unknown. This study investigated the NB anti-fouling capacity at six concentrations (0 %-100 %, denoting the ratio of maximum NB-infused water; particle concentrations in 0 % and 100 % ratios were 1.08 × 107 and 1.19 × 109 particles mL-1, respectively). Results showed that NB effectively mitigated multiple fouling at 50 %-100 % ratios, whereas low NB concentration exacerbated fouling. NB functioned both as an activator and a bactericide for microorganisms, significantly promoting biofouling at 5 %-25 %, and inhibiting biofouling at 50 %-100 %. Owing to an enhanced biofilm biomineralization ability, low NB concentration aggravated precipitate fouling, whereas high NB doses effectively mitigated precipitates. Additionally, higher NB concentrations demonstrated superior control efficiency against particulate fouling. This study contributes insights into NB effectiveness in controlling various fouling types within wastewater distribution systems.

Combination of magnetic field and ultraviolet for fouling control in saline wastewater distribution systems

Fouling is a significant challenge for recycling and reusing saline wastewaters for industrial, agricultural or municipal applications. In this study, we propose a novel approach of magnetic field (MaF) and ultraviolet (UV) combined application for fouling mitigation. Results showed, combination of MaF and UV (MaF-UV) significantly decreased the content of biofouling and reduced the complexity of microbial networks, compared to UV and MaF alone treatments. This was due to MaF as pretreatment effectively reduced the water turbidity, improve the influent water quality of UV disinfection and increases UV transmittance, eliminating the adverse impacts of UV scattering and shielding, hence increased the inactivation effectiveness of UV disinfection process. MaF assisted UV also reduced the abundance of UV-resistant bacteria and inhibited the risk of bacterial photoreactivation and dark repair. Meanwhile, MaF-UV drastically reduced the contents of precipitates and particulate fouling by accelerating the transformation rate of CaCO3 crystal from compact calcite to loosen hydrated amorphous CaCO3, and enhancing the flocculation process. These findings demonstrated that MaF-UV is an effective anti-fouling strategy, and provide insights for sustainable application of saline wastewaters.

Targeted Anti-Biofilm Therapy: Dissecting Targets in the Biofilm Life Cycle

Biofilm is a crucial virulence factor for microorganisms that causes chronic infection. After biofilm formation, the bacteria present improve drug tolerance and multifactorial defense mechanisms, which impose significant challenges for the use of antimicrobials. This indicates the urgent need for new targeted technologies and emerging therapeutic strategies. In this review, we focus on the current biofilm-targeting strategies and those under development, including targeting persistent cells, quorum quenching, and phage therapy. We emphasize biofilm-targeting technologies that are supported by blocking the biofilm life cycle, providing a theoretical basis for design of targeting technology that disrupts the biofilm and promotes practical application of antibacterial materials.

Effect of air nanobubbles on oxygen transfer, oxygen uptake, and diversity of aerobic microbial consortium in activated sludge reactors

Nanobubbles have the potential to curtail the loss of oxygen during activated sludge aeration due to their extensive surface areas and lack of buoyance in solution. In this study, nanobubble aeration was explored as a novel approach to enhance aerobic activated sludge treatment and benchmarked against coarse bubble aeration at the lab scale. Nanobubble aerated activated sludge reactors achieved greater dissolved oxygen levels at faster rates. Higher soluble chemical oxygen demand removal by 10% was observed when compared to coarse bubble aeration with the same amount of air. The activated sludge produced compact sludge yielding easier waste sludge for subsequent sludge handling. The samples showed fewer filamentous bacteria with a lower relative abundance of floc forming Corynebacterium, Pseudomonas, and Zoogloea in the sludge. The microbiome of the nanobubble-treated activated sludge showed significant shifts in the abundance of community members at the genus level and significantly lower alpha and beta diversities.

Global trends and characteristics of nano- and micro-bubbles research in environmental engineering over the past two decades: A scientometric analysis

The present study has two primary goals, the first goal is to investigate a bibliometric analysis and assess the trends to evaluate the global scientific production of microbubbles and nanobubbles from 2000 to 2020. The aim is to elucidate the cornucopia of benefits the two technologies (micro and nanobubbles) can offer in environmental sciences and environmental amelioration such as wastewater treatment, seed germination, separation processes, etc. The second goal is to explicate the reason behind every chart and trend through environmental engineering perspectives, which can confer value to each analysis. The data was acquired from the Web of Science and was delineated by VOS viewer software and GraphPad Prism. Considering 1034 publications in the area of micro-and nanobubbles, this study was conducted on four major aspects, including publication growth trend, countries contribution assessment, categories, journals and productivity, and keywords co-occurrence network analysis. This article revealed a notable growth in microbubbles and nanobubbles-related publications and a general growth trend in published articles in a 20-year period. China had the most significant collaboration with other countries, followed by the USA and Japan. The most dominant categories for microbubbles were environmental sciences and environmental engineering comprising 22.5% of the total publications, while multidisciplinary subjects such as nanotechnology and nanosciences (8%) were among the dominant categories for nanobubbles. Keyword's analysis results showed that microbubbles had reached the apex since their discovery. Consequently, they are being used mostly in water/wastewater treatment or environmental improvement. On the other hand, nanobubbles are still in their infancy, and their pervasive use is yet to be fully materialized. Most of the publications are still striving to understand the nature of nanobubbles and their stability; however, a critical analysis showed that during the past two years, the trend of using nanobubbles as a cost-effective and environmentally friendly approach has already begun.

Electrochemical biofilm control by reconstructing microbial community in agricultural water distribution systems

Biofilm causes considerable technical challenges in agricultural water distribution systems. Electrochemical treatment (ECT) is a potential technique for controlling biofilm in the systems. Given the limited information on how ECT performance changes of irrigation systems and microbial biofilm community shifts. In this study, the effect of anti-biofilm was assessed. Illumina Miseq high-throughput sequencing, combined with molecular ecological network analysis, were applied to detect the effects of ECT on attached biofilm microbial communities. We found that ECT effectively mitigated biofilm formation with the fixed-biofilm biomass reduced by 37.5 %-79.9 %. ECT significantly shifted the bacterial community structures in the biofilm, reduced the communities' diversity, and changed the dominant species. Molecular ecological network analysis showed that the complexity and size of bacterial networks were destabilized under ECT and decreased the interactions among bacterial species. The reconstruction in bacterial community and networks were responsible for the decline in extracellular polymer substances and biofilm biomass. However, chlorine-resistant bacteria were found increased after ECT, and higher relative abundance and low biofilm removal was identified in continuous ECT as compared with intermittent ECT. These results aimed to highlight the opportunity for biofouling mitigation by ECT for irrigation systems, and reveal the potential anti-biofilm microbial mechanisms of ECT.

Response of Plant Rhizosphere Microenvironment to Water Management in Soil- and Substrate-Based Controlled Environment Agriculture (CEA) Systems: A Review

As natural agroecology deteriorates, controlled environment agriculture (CEA) systems become the backup support for coping with future resource consumption and potential food crises. Compared with natural agroecology, most of the environmental parameters of the CEA system rely on manual management. Such a system is dependent and fragile and prone to degradation, which includes harmful bacteria proliferation and productivity decline. Proper water management is significant for constructing a stabilized rhizosphere microenvironment. It has been proved that water is an efficient tool for changing the availability of nutrients, plant physiological processes, and microbial communities within. However, for CEA issues, relevant research is lacking at present. The article reviews the interactive mechanism between water management and rhizosphere microenvironments from the perspectives of physicochemical properties, physiological processes, and microbiology in CEA systems. We presented a synthesis of relevant research on water-root-microbes interplay, which aimed to provide detailed references to the conceptualization, research, diagnosis, and troubleshooting for CEA systems, and attempted to give suggestions for the construction of a high-tech artificial agricultural ecology.