Abstract
Growing access to tap water and consequent expansion of water distribution systems has created numerous challenges to maintaining water quality between the treatment node and final consumer. Despite all efforts to develop sustainable monitoring systems, there is still a lack of low cost, continuous and real time devices that demonstrate potential for large-scale implementation in wide water distribution networks. The following work presents a study of a low-cost, optofluidic sensor, based on Trypthopan Intrinsic Fluorescence. The fluorospectrometry analysis performed (before sensor development) supports the existence of a measurable fluorescence output signal originating from the tryptophan contained within pathogenic bacteria. The sensor was mounted using a rapid prototyping technique (3D printing), and the integrated optical system was achieved with low-cost optical components. The sensor performance was evaluated with spiked laboratory samples containing E. coli and Legionella, in both continuous and non-continuous flow situations. Results have shown a linear relationship between the signal measured and pathogen concentration, with limits of detection at 1.4 × 103 CFU/mL. The time delay between contamination and detection of the bacteria was practically null. Therefore, this study supports the potential application of tryptophan for monitoring drinking water against water pathogens.
Highlights
In 2015, 71% of world population has access to a safe drinking water source [1]; this was one of the most important public health improvements achieved globally
To verify the optimal Tryptophan Intrinsic Fluorescence wavelength in order to implement it in the sensor, multiple excitation wavelength ranging from 268 nm until 288 nm, with a 2 nm step, were tested
The solvent polarity can only cause a shift to lower wavelengths if the wavelengths if the solvent has an high hydrophobicity, which is not the case; this means that the only solvent has an high hydrophobicity, which is not the case; this means that the only possibility for possibility for the shift found on the on the E. coli spectroscopy can be explained by the tryptophan the shift found on the on the E. coli spectroscopy can be explained by the tryptophan integration integration in E. coli proteins [20]
Summary
In 2015, 71% of world population has access to a safe drinking water source [1]; this was one of the most important public health improvements achieved globally. There are still two billion people that use drinking water sources which are contaminated with feces [1]; this clearly demonstrates that, despite the advances, we are still far from achieving worldwide drinking water safety For this reason, in the same year, the European Commission stated: “There is a strong need for new water monitoring and control systems to reduce unnecessary water analyses and concentrate on the threats that really matter.” [2]. In the same year, the European Commission stated: “There is a strong need for new water monitoring and control systems to reduce unnecessary water analyses and concentrate on the threats that really matter.” [2] This statement clearly criticizes the current water safety strategy, where most of the efforts have been in the direction of improving the water treatment process, which is the primary means of securing water safety, but by itself does not ensure final consumer safety. Through DWDSs, a high number of contamination cases can occur, among which the most common are biofilm deposition [3], pressure losses [4,5], aging of DWDSs, and short periods of poor treatment and rain induced infiltrations
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