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.

Design of a bioaugmented multistage biofilter for accelerated municipal wastewater treatment and deactivation of pathogenic microorganisms.

Biological treatment of municipal wastewater for reuse in irrigation is highly required, especially with the current global financial and water shortage crises. Bioaugmentation is a simple and cost-effective technology which could be a useful tool in alleviating this challenge. Thus, this study aimed to enhance the biological treatment of municipal wastewater using a bioaugmented substance supplemented in a three-stages bio-filter consisting of a sedimentation step followed by gravel biofiltration and then sand biofiltration at a laboratory scale. Also, a toxicity assay, the antimicrobial effect of the bioaugmented substance against pathogenic microorganisms, and identification of the synergistic effect of the bacterial consortium involved in the bioaugmented substance were studied. The bioaugmented substance was nontoxic and had an antimicrobial effect against the tested potentially pathogenic microorganisms (Escherichia coli, Pseudomonas aeruginosa, Listeria monocytogenes, Staphylococcus aureus, and Candida albicans). The minimum effective concentration of the bioaugmented substance for organic, inorganic and microbial pollutants removal from high strength wastewater was 2.5 ppm with a contact time of 6-8 h. The removal efficiencies of H2S, COD, BOD5, total solids (TS), total dissolved solids, total suspended solids, ammonia, nitrate, phosphorus, and oil and grease reached 85, 93.4, 83.5, 37, 49.2, 93.4, 100, 55.7, 76.6 and 76.6%, respectively in the treated effluent after sand biofiltration. The physicochemical parameters of the treated wastewater effluent were below the Egyptian recommended limits (Law 84/1984) for use in irrigation. However, COD and BOD values were 90.33 and 38.46 mgO2/L, respectively, and were still above the regulations (COD ≤60 and BOD ≤20). The high fecal coliforms count in the wastewater influent (8.4 × 108 MPN-index/100 mL) were 95.1% removed after the sedimentation stage, and 99.99% removal was achieved after gravel and sand biofiltration. Thus, this study successfully designed a bioaugmented multistage biofiltration system for the effective removal of pollutants from wastewater, especially in resource-limited areas.