Ultraviolet (UV) light for treating microbial contamination

What

Shining UV light through water can be used as a method to disinfect it by killing the microbes that contaminate the water. The UV light affects the strands of DNA in the virus or bacteria and makes it unable to reproduce and therefore unable to form infectious colonies.

Example of a UV light water treatment system used in a horticultural system.
Image source: ULTRAQUA.

Why

Disinfecting water with UV light on your farm could be beneficial for reducing microbial contaminants in wastewater applied to land and other discharges, ultimately reducing the microbial contaminants that get delivered to nearby waterways. UV light is only able to remove microorganisms and does not remove any other contaminants, such as heavy metals or nutrients.

Effectiveness

Several factors influence how effective UV disinfection is:

  • Intensity and wavelength(s) of the UV delivered; bacteria are killed fastest by intense light in a particular wavelength range. Therefore, the UV treatment unit should be installed as close to the point of use as possible.

  • Exposure period: the longer bacteria are exposed to UV light, the higher the percentage that are killed.

  • Design of the contact chamber where the water is irradiated; bacteria can escape full exposure to the light if design is poor.

  • Water quality (turbidity, colour, iron, manganese, hardness). These constituents of water absorb light or form deposits on lamp surfaces and reduce the effectiveness of the light.

Things to consider

  • Equipment design

  • Cost of establishment, power supply and maintenance

  • Placement of equipment to ensure maximum effectivity

References

Nelson, K. Y., McMartin, D. W., Yost, C. K., Runtz, K. J., & Ono, T. (2013). Point-of-use water disinfection using UV light-emitting diodes to reduce bacterial contamination. *Environmental Science and Pollution Research*, *20*(8), 5441-5448.

Li, X., Cai, M., Wang, L., Niu, F., Yang, D., & Zhang, G. (2019). Evaluation survey of microbial disinfection methods in UV-LED water treatment systems. Science of the Total Environment, 659, 1415-1427.

Wang, T., MacGregor, S. J., Anderson, J. G., & Woolsey, G. A. (2005). Pulsed ultra-violet inactivation spectrum of Escherichia coli. Water research, 39(13), 2921-2925.