A Novel System for Water Disinfection with UV Radiation

Bassam Younis,Nicholas Palomo,Laura Mahoney

doi:10.3390/w10091275

Abstract

We present a novel system for water disinfection with ultra-violet (UV) radiation. In this system, the UV lamps do not come into contact with the water and hence remain free of fouling. The system incorporates a diffusor and a nozzle, with stationary guide vanes built into each. Their combined purpose is to reduce the hydraulic losses while imparting a strong swirl component to the flow. The swirl significantly enhances turbulent mixing processes and provides a self-cleansing mechanism that renders the system tolerant to high levels of turbidity and scaling. The hydrodynamic performance of the system was optimized using Computational Fluid Dynamics, while the manufacture of its key components was accomplished using advanced mechanical design software and three-dimensional (3D) printing. Biodosimetry testing with the bacteriophage MS2 indicated the delivery of a UV dose of 215.6 mJ/cm2. This produced a 6.9 log10 reduction of E. coli and 7.12 log10 reduction of MS2. Assessment of the system with hard water containing high Ca, Mg, and Fe concentrations, and with water with turbidity of 18 NTU indicated that the log10 removal of E. coli remained above 5.

Highlights

Most commercial systems for water disinfection using UV radiation in use derive their basic structure from a patent dating back to 1934 [1]
A hydraulic tracer test was conducted to estimate the residence time in the system. Knowledge of this parameter yields a reasonable estimation of the overall hydraulic efficiency: too short a time would imply that an insufficient UV dose is being delivered, while too long a value would imply an oversized volume, or a low flow rate
The proposed design achieves these aims by locating the UV tubes outside the water-conveying quartz tube, and by imparting a strong swirling motion to the inlet flow that ensures uniform exposure to UV radiation and provides a self-cleansing mechanism that prevents the accumulation of bio-film and residues on the inside of the quartz

Summary

Introduction

Most commercial systems for water disinfection using UV radiation in use derive their basic structure from a patent dating back to 1934 [1]. In applications where the water flow is pressurized, such as in a drinking-water supply and distribution network, the water flows in the gap between the quartz cylinders and an outer casing that serves to maintain the interior pressure at above atmospheric, and to prevent damage to the users This method of irradiating water with UV radiation suffers from a number of drawbacks, of which three are relevant here. The second drawback of the conventional designs stems from the fact that obstructions placed in the path of a moving fluid lead to losses of kinetic energy [7,8,9] These losses lead to higher operating costs due to the increase in the power required to deliver water at a given flow rate. The third drawback stems from the difficulty of achieving thorough mixing of the water being

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