Assessment of toxicity and antimicrobial performance of polymeric inorganic coagulant and evaluation for eutrophication reduction.

In this study, the efficacy of the promising iron-based polymeric inorganic coagulant (POFC) was assessed for the reduction of eutrophication effect (freshwater toxicity) and the microbial loads from wastewater. Toxicity assessment for POFC was conducted on mice and skin cell lines. The results confirm the lower toxicity level of POFC. The POFC showed excellent antibacterial efficacy against Gram-positive and Gram-negative bacteria. Moreover, it demonstrated a remarkable effectiveness against black fungus such as Aspergillus niger and Rhizopus oryzae. Additionally, POFC showed antiviral effectiveness against the highly pathogenic H5N1 influenza virus as well as Middle East respiratory syndrome coronavirus (MERS-CoV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). POFC-based treatment gives excellent removal percentages for phosphate, and phosphorus at doses below 60 ppm with a low produced sludge volume that leads to 84% decrease in the rate of eutrophication and freshwater toxicity. At a POFC concentration of 60 ppm, remarkable reduction rates for total coliforms, fecal coliforms, and E. coli were achieved. After POFC-based coagulation, the produced sludge retains a lower bacterial density due to the antibacterial activity of POFC. Furthermore, it revealed that the observed removal efficiencies for fungi and yeasts in the produced sludge reached 85% at a POFC dose of 60 ppm. Overall, our research indicates that POFC has potential for application in pre-treatment of wastewater and serves as an antimicrobial agent.

Bioactive Azadirachta indica and Melia azedarach leaves extracts with anti-SARS-CoV-2 and antibacterial activities.

The leaves of Azadirachta indica L. and Melia azedarach L., belonging to Meliaceae family, have been shown to have medicinal benefits and are extensively employed in traditional folk medicine. Herein, HPLC analysis of the ethyl acetate fraction of the total methanolic extract emphasized the enrichment of both A. indica L., and M. azedarach L. leaves extracts with phenolic and flavonoids composites, respectively. Besides, 4 limonoids and 2 flavonoids were isolated using column chromatography. By assessing the in vitro antiviral activities of both total leaves extracts against Severe Acute Respiratory Syndrome Corona virus 2 (SARS-CoV-2), it was found that A. indica L. and M. azedarach L. have robust anti-SARS-CoV-2 activities at low half-maximal inhibitory concentrations (IC50) of 8.451 and 6.922 µg/mL, respectively. Due to the high safety of A. indica L. and M. azedarach L. extracts with half-maximal cytotoxic concentrations (CC50) of 446.2 and 351.4 µg/ml, respectively, both displayed extraordinary selectivity indices (SI>50). A. indica L. and M. azedarach L. leaves extracts could induce antibacterial activities against both Gram-negative and positive bacterial strains. The minimal inhibitory concentrations of A. indica L. and M. azedarach L. leaves extracts varied from 25 to 100 mg/mL within 30 min contact time towards the tested bacteria. Our findings confirm the broad-spectrum medicinal value of A. indica L. and M. azedarach L. leaves extracts. Finally, additional in vivo investigations are highly recommended to confirm the anti-COVID-19 and antimicrobial activities of both plant extracts.

Bacterial community structure of electrogenic biofilm developed on modified graphite anode in microbial fuel cell.

Formation of electrogenic microbial biofilm on the electrode is critical for harvesting electrical power from wastewater in microbial biofuel cells (MFCs). Although the knowledge of bacterial community structures in the biofilm is vital for the rational design of MFC electrodes, an in-depth study on the subject is still awaiting. Herein, we attempt to address this issue by creating electrogenic biofilm on modified graphite anodes assembled in an air-cathode MFC. The modification was performed with reduced graphene oxide (rGO), polyaniline (PANI), and carbon nanotube (CNTs) separately. To accelerate the growth of the biofilm, soybean-potato composite (plant) powder was blended with these conductive materials during the fabrication of the anodes. The MFC fabricated with PANI-based anode delivered the current density of 324.2 mA cm-2, followed by CNTs (248.75 mA cm-2), rGO (193 mA cm-2), and blank (without coating) (151 mA cm-2) graphite electrodes. Likewise, the PANI-based anode supported a robust biofilm growth containing maximum bacterial cell densities with diverse shapes and sizes of the cells and broad metabolic functionality. The alpha diversity of the biofilm developed over the anode coated with PANI was the loftiest operational taxonomic unit (2058 OUT) and Shannon index (7.56), as disclosed from the high-throughput 16S rRNA sequence analysis. Further, within these taxonomic units, exoelectrogenic phyla comprising Proteobacteria, Firmicutes, and Bacteroidetes were maximum with their corresponding level (%) 45.5, 36.2, and 9.8. The relative abundance of Gammaproteobacteria, Clostridia, and Bacilli at the class level, while Pseudomonas, Clostridium, Enterococcus, and Bifidobacterium at the genus level were comparatively higher in the PANI-based anode.

New insights for tracking bacterial community structures in industrial wastewater from textile factories to surface water using phenotypic, 16S rRNA isolates identifications and high-throughput sequencing.

Industrial wastewater can possibly change the microbial ecological environment. There are few studies that focus on the bacterial variety in textile wastewater effluents and after combination with domestic wastewater. Thus, this study aimed to determine dye degrading bacteria from textile wastewater and environmental water samples using cultural method followed by phenotypic using BIOLOG and genotypic identification (16S rRNA) for dye degrading isolates identifications. Moreover, the bacterial communities in three textile and four environmental samples using Illumina MiSeq high-throughput sequencing were investigated. The findings revealed that in textile water samples, the ratio of dye-degrading bacteria (DDB) to total bacterial counts (TBC) was 27%. The identified DDB genera by 16S rRNA based on the cultural approach were Citrobacter spp., Klebsiella spp., Enterobacter spp., Pseudomonas spp., and Aeromonas spp. Regarding to the metagenomics analyses, the environmental samples had 5,598 Operational Toxanomic Units (OTUs) more than textile wastewater samples (1,463 OTUs). Additionally, the most abundant phyla in the textile wastewater were Proteobacteria (24.45-94.83%), Bacteriodetes (0.5-44.84%) and Firmicutes (3.72-67.40%), while, Proteobacteria (30.8-76.3%), bacteroidetes (8.5-50%) and Acentobacteria (0.5-23.12%) were the most abundant phyla in the environmental samples. The maximum abundant bacteria at species level in environmental samples were Aquabacterium parvum (36.71%), Delftia tsuruhatensis (17.61%), Parabacteriodes chartae (15.39%) and Methylorubrum populi (7.51%) in El-Rahawy Drain water (RDW), River Nile water (RNW), wastewater (RWW) from WWTP in Zennin and El-Rahawy Drain sediment (RDS), respectively, whereas the maximum abundant bacteria at species level in textile wastewater were Alkalibacterium pelagium (34.11%), Enterobacter kobei (26.09%) and Chryseobacterium montanum (16.93%) in factory 1 (HBT) sample, SHB sample (before mixing with domestic wastewater) and SHB sample (after mixing with domestic wastewater), respectively. In conclusion, the microbial communities in textile wastewaters are similar to those in environmental samples at the phylum level but distinct at the genus and species levels because they are exposed to a wider range of environmental circumstances.

Novel electro-oxidation unit for electro-disinfection of E. coli and some waterborne pathogens during wastewater treatment: batch and continuous experiments.

The prime objective of the current investigation is to evaluate a promising alternative method for disinfection wastewater using a novel electro-oxidation unit. The study focused on determining the best-operating conditions from a techno-economic point of view to be applied to continuous flow simulating actual disinfection modules. The treatment unit consisted of a Plexiglas container with a 3 L volume containing nine cylindrical shape electrodes (6 graphite as anode and 3 stainless steel as a cathode) connected to a variable DC power supply. Determination of the best operating parameters was investigated in batch mode on synthetic wastewater by studying the effect of contact time, current density (CD), total dissolved solids concentration (TDS), and bacterial density. Moreover, the continuous mode experiment was considered on real wastewater from an agricultural drain and the secondary wastewater treatment plant effluent before chlorination. The batch mode results revealed that the best applicable operational conditions that achieved the complete removal of E. coli were at a contact time of less than 5 min, TDS of 2000 mg/L, and CD of 4 mA/cm2. Application of these conditions on the continuous mode experiment indicated the complete removal of all bacterial indicators after 5 min in the drainage wastewater and after 3 min in the secondary treated wastewater. Physico-chemical characterization also suggested that no chlorine by-products displaying the hydroxide ion formed due to water electrolysis is the main reason for prohibiting the growth of pathogenic microbes. The electrical consumption was calculated in the continuous mode and found to be 0.5 kWh/m3 with an operational cost of about 0.06 $/m3, including the cost of adding chemicals to increase the TDS. The results proved that this novel electro-oxidation unit is a robust and affordable disinfection method for complete bacterial removal from wastewater and is more environmentally benign than other conventional disinfection methods.

The role of biofilm in the development and dissemination of ubiquitous pathogens in drinking water distribution systems: an overview of surveillance, outbreaks, and prevention.

A variety of pathogenic microorganisms can survive in the drinking water distribution systems (DWDS) by forming stable biofilms and, thus, continually disseminating their population through the system's dynamic water bodies. The ingestion of the pathogen-contaminated water could trigger a broad spectrum of illnesses and well-being-related obstacles. These waterborne diseases are a significant concern for babies, pregnant women, and significantly low-immune individuals. This review highlights the recent advances in understanding the microbiological aspects of drinking water quality, biofilm formation and its dynamics, health issues caused by the emerging microbes in biofilm, and approaches for biofilm investigation its prevention and suppression in DWDS.

The destruction of Escherichia coli adhered to pipe surfaces in a model drinking water distribution system via various antibiofilm agents.

The aim of the study is to estimate the effectiveness of three antibiofilm agents against Escherichia coli biofilm that formed in six different types of pipelines. A laboratory-scale water system was built for this work to allow for the creation of biofilm in the pipelines studied. The level of the growth rate of E. coli biofilm cells was monitored over 90 days on those tested pipe materials. The results of bacterial cell densities displayed that the highest biofilm growth was observed in the biofilm formed on the iron (Fe) pipe. In contrast, the biofilm formation rate was significantly lower on copper (Cu) pipe compared to other materials. Three antibiofilm agents, including chlorine, silver ions (Ag+ ), and silver nanoparticles (AgNPs), were employed to eradicate the biofilm cells. E. coli counts indicated that AgNPs are more efficient in destructing any formed biofilm cells on all tested materials. At the same time, the chlorine was only useful in the case of biofilm developed on plastic and Cu. However, the antibiofilm efficiency of Ag+ performs similarly to chlorine against E. coli biofilm cells. Ultimately, AgNPs are considred the most powerful antibiofilm agent among the other agents toward the biofilm cells in their maturation stage, which offers an encouraging way for the long-term functioning of water systems. PRACTITIONER POINTS: The growth rate of E. coli biofilm cells was investigated on different materials. The count of biofilm cells developed on iron pipes was higher than other materials. The E. coli biofilm on iron pipe could resist chlorine and AgNPs to a large extent. The developed biofilm on copper pipe was more sensitive to chlorine, Ag+ . and AgNPs. The biofilm cells could be easily eradicated from plastic-based materials with all tested disinfectants.

Metagenomics analysis of bacterial structure communities within natural biofilm.

The bacterial profiles of natural household biofilm have not been widely investigated. The majorities of these bacterial lineages are not cultivable. Thus, this study aims (i) to enumerate some potential bacterial lineages using culture based method within biofilm samples and confirmed using Biolog GEN III and polymerase chain reaction (PCR). (ii) To investigate the bacterial profiles of communities in two biofilm samples using next generation sequencing (NGS). Forty biofilm samples were cultured and colonies of each selected prevailing potential lineages (E. coli, Salmonella entrica, Pseudomonas aeruginosa, Staphylococcus aureus and Listeria monocytogenes) were selected for confirmation. From obtained results, the counts of the tested bacterial lineages in kitchen biofilm samples were greater than those in bathroom samples. Precision of PCR was higher than Biolog GEN III to confirm the bacterial isolates. Using NGS analysis, the results revealed that a total of 110,554 operational taxonomic units (OTUs) were obtained for two biofilm samples, representing kitchen and bathroom biofilm samples. The numbers of phyla in the kitchen biofilm sample (35 OTUs) was higher than that in bathroom sample (18 OTUs). A total of 435 genera were observed in the bathroom biofilm sample compared to only 256 in the kitchen sample. Evidences have shown that the empirical gadgets for biofilm investigation are becoming convenient and affordable. Many distinct bacterial lineages observed in biofilm are one of the most significant issues that threaten human health and lead to disease outbreaks.