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The primary objective of the present study is to enhance the denitrification process in constructed wetlands (CWs), employed as an ecological and natural technology for wastewater treatment. Eco-friendly approaches have been tested to improve the nitrate removal efficiency in pilot-scale subsurface flow CWs. Initially, the system's performance was enhanced by using a natural substrate, namely cork, as a filter medium. Another approach is bio-inoculation into the rhizosphere of a bacterial strain with the potential capacity for nitrate removal, thereby reinforcing the synergy between the plant and microorganisms. Finally, the approaches were combined, and nitrate removal was assessed. The main results showed that the most effective nitrate removal from wastewater was achieved with cork (80%) compared to gravel (60%). Bio-inoculation into the rhizosphere of denitrifying bacteria significantly improved nitrate removal. Indeed, the nitrate removal rate by the inoculated CW filled with gravel, was higher than the non-inoculated system, with rates of 78% and 60%, respectively. Moreover, the highest removal rate of 99.77% was obtained with the inoculated system filled with cork. [ABSTRACT FROM AUTHOR]

The aim of this study was to enhance the rhizobacterium potential in horizontal subsurface flow constructed wetland (CW) system planted by Phragmites australis using specific and lytic phages. The bioinoculation of specific bacteriophage for target bacteria; Salmonella typhi, and the monitoring of bacterial inactivation under different conditions showed the effectiveness of this methodology to enhance bacteria reduction and consequentially ameliorate purification performance of this studied biological treatment system. The injection of the phage at a concentration equal to 103 UFP/mL within the rhizosphere of the inoculated filter (F) was allowed 1 U-Log10 of improvement of bacterial inactivation compared to the control filter (T) nearly 1 logarithmic unit thus, a 90% improvement of bacteria reduction. When we increased the phage titer (105 UFP/mL), the bacterial reduction equal to 2.75 U-Log10 (N/N0) was registered that corresponds to a decrease of nearly 99.9%. According to the first-order model, the inactivation coefficient is equal to 2.29 min−1 (0.88 min−1 for the first experiment) and the bacterial reduction rate is 5 times higher than that determined for the control filter. This results show the positive impact of the phage in the bacterial inactivation and the improvement of water treatment of the biofilter C. [ABSTRACT FROM AUTHOR]

We purpose in this study to develop a reliable and low-cost method for the detection of Viable but nonculturable (VBNC) bacteria. Indeed, after water disinfection, injured-VBNC bacteria can be underestimated using conventional assessment methods, causing false-negative results and, posing a significant and potential health risk. The VBNC bacterial survival strategy can hide the real microbial quality of treated water. To overcome this bacterial assessment limitation, we were used a specific and lytic phage to monitor the presence of active bacteria; Pseudomonas aeruginosa after photocatalytic treatment. Within 2 h of phage-target bacteria contact, the reduction of phage amplification rate (At) can reveal the ability of specific-lytic phage to recognize and to attach to their host cells with a probability of new infectious phages release despite their lose of cultivability in the usual media. The determination of phage reactivation coefficient (Rt) after 2 and 8 h of phage-target cell contact time reveals the ability of phages to reactive their infectivity and their amplification in positive correlation with their host cells viability and activity. The increase in phage reactivation coefficient (Rt) after an extension of the latent period was directly related to the positive interaction between infectious phages and potential active bacteria. The use of this method can improve the water disinfection process and avoid public health-hazardous especially related to the resuscitation of active-nonculturable bacteria mainly for pathogenic bacteria. [ABSTRACT FROM AUTHOR]

In this study, we propose the development of a rapid and reliable method to control and to monitor microbial water quality. The methylene blue (MB) decolorization assay was based on the analysis of spectral profiles of dye in interaction with a different bacterial concentration. The determination of dye decolorization rate (DDR) shows a correlation between the MB reduction rate and the bacterial density. Moreover, the kinetic of the monomer and dimer equilibrium of MB in water mainly, the monitoring of bounded MB species in relationship with a knowed concentration of target bacteria, was allowed to establish a relationship between MB decolorization rate and bacterial density. Furthermore, this method was applied to evaluate the water quality after photocatalysis. Based on this method, the photocatalytic effects on bacterial density was highlighted by the decrease in DDR after photocatalytic treatment with fractioned times (0 to 5 h); this increase was followed by a decrease of bounded MB species and, an increase in free MB forms miming the reduction of bacterial density due to the biocide effects of photocatalysis process. However, the analysis of spectra profiles shows a weak but a continuous decrease in bounded MB dimer and monomer forms in the treated water samples exempt of culturable bacteria. Moreover, the MB spectra profiles were tended toward a negative control spectrum without superposition. Thus, the possibility of the presence of viable but non-culturable bacteria was expected; therefore, to optimize this tertiary water treatment process, an extending on proceeding time was recommended to avoid the bacterial resuscitation after photocatalysis. [ABSTRACT FROM AUTHOR]

In this study, we have monitored the potential activity of a foodborne and waterborne pathogenic bacterium, Salmonella typhi, under starvation conditions. The interaction between lytic phage and starved-VBNC pathogenic bacteria was studied to establish reliable methods for the detection of active cells before resuscitation. The analysis of phage kinetic parameters has demonstrated the flexibility of lytic with the quantity and mainly the quality of host cells. After 2 h of phage-starved-VBNC bacteria interaction, the reduction of phage amplification rate can reveal the ability of specific-lytic phage to recognize and to attach to their host cells with a probability of burst and release of infectious phages by active bacteria. After an extension of the latent period, the boost of the phage amplification rate was directly related to the positive interaction between potential intracellular 'engaged' phages and potential active bacteria. Furthermore, the modeling of the Salmonella-specific phage growth cycle in relationship with starved host cells can highlight the impact of the viability and the activity state of the host cells on the phage's growth cycle. [ABSTRACT FROM AUTHOR]

The main goal of the present study was to enhance the rhizobacterium potential in horizontal subsurface flow constructed wetland system planted byPhragmites australisusing biotechnology. The bioinoculation of denitrifier promoting rhizobacteria fluorescentPseudomonasspp. has been used to confer higher rhizosphere competence by environmentally friendly biological approaches. In order to study the behaviour or the denitrifying potential of the inoculated bacteriaex situandin situ, the models of Chick–Watson and Series-Event were used with modifications. The comparison of kinetic parameters: (k): the denitrifying coefficient (h−1) and the denitrifying rate at the first contact with a determined concentration of nitrate (A) for different bioassays has shown that the application of the bioinoculation increases remarkably the efficiency of the water treatment system for the reduction of nitrates even by an individual bioinoculated bacterium. [ABSTRACT FROM PUBLISHER]

To improve the ultraviolet (UV) water disinfection process and to better understand the impact of the harmful effects of germicidal radiation on the DNA molecule, we have developed a reliable biological monitoring system based on PCR 16S ribosomal DNA (rDNA) and terminal restriction fragment length polymorphism analysis. The PCR analysis was performed using the bacteria-specific 27F and 905R primers to replicate a fragment of the rDNA gene. This new and versatile method can be used to evaluate the effects of direct UV radiation on DNA (UV dose/response) and to estimate the potential of bacteria to mitigate UV lethal effects via photoreactivation and dark repair. [ABSTRACT FROM AUTHOR]

The infectivity rates of Salmonella typhi's phage was used as a bio-indicator to detect the presence of viable but non cultivable bacteria after irradiation by an increasing number of pulsed UV light. Indeed, the combination of a conventional method used to measure colony-forming ability of UV-irradiated bacteria, and the study of relationship between host bacteria and a suitable phage can reveal the existence of active bacteria which lose the cultivability in usual culture media, but keep viability and phage susceptibility. [ABSTRACT FROM AUTHOR]

ZnO nanorods (NRs) with an average length and diameter of 186 and 20 nm, respectively, were prepared through a mild solvothermal route and used as photocatalysts either as dispersed powder or immobilized on glass slides. The ZnO NRs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). Dispersed ZnO NRs and, to a lesser extent, immobilized ZnO NRs were demonstrated to exhibit high photocatalytic activity under simulated sunlight of low intensity (5.5 mW/cm2) both for the degradation of the Orange II dye and for Escherichia coli bacterial decontamination (2.5-fold survival decrease after 180 min irradiation for immobilized NRs). SEM, atomic force microscopy (AFM), fluorescence spectroscopy, and epifluorescence microscopy demonstrate that cell surface damages are responsible of bacterial inactivation. The immobilized ZnO NRs could be reused up to five times for bacterial decontamination at comparable efficiency and therefore have great potential for real environmental applications. [ABSTRACT FROM AUTHOR]