|  | Public Health Safety | Public Health

The Negative Impacts of UV Disinfection of Water

Radiation produced by special UV lamps render harmful viruses, bacteria and parasites inactive. The UV light literally penetrates the cell walls of microorganisms and kills or inactivates them. However, water's chemical and microbial characteristics contribute to the disadvantages and limitations of UV water disinfection. For example, suspended solids and soluble materials reduce UV radiation's performance.

  1. Low Dose Risk

    • UV systems are only effective when doses of energy destroy viruses and bacteria. Calcium has a tremendously negative impact on UV absorbency. If the organism does not fully absorb the radiation, damaging its genetic material alone will not disrupt its activity. The microorganism's type and distance from the light source are also variables that call for continuous disinfection. Therefore, the use of two UV units better protects this method's reliability during occasions when system service is necessary.

    Solids Shielding

    • Agriculture and Agri-Food Canada reports the importance of suspended solids remaining below 10 mg per liter. If the count is higher, the excessive amounts of solids can shield microbes from the damaging impact of UV radiation exposure. The disease-causing microorganisms will be free to pass through the system active and harmful. The inorganic matter and foulants that create dissolved solids can produce a similar shielding effect by preventing the penetration of UV light. Consequently, Agriculture and Agri-Food Canada recommends that total dissolved solids remain less than 800 to 1000 mg per liter.

    No Disinfection Residual

    • Disinfection residual prevents contamination when the water is in storage. Residual disinfectant is also necessary for reducing the risk of recontamination during pipe distribution. The process of UV disinfection does not produce disinfection residual.

    Lack of Standardization

    • The National Drinking Water Clearinghouse calls attention to the lack of a standard means to certify the effectiveness of equipment before or after installation. They also find there are no standardized mechanisms to measure calibration.

    High Cost

    • The lack of disinfection residual in UV disinfection of water requires the purchasing of secondary disinfectants. Replacement of UV lamps on an annual basis, or when their light decreases to 70 percent efficiency, is an additional expense. UV disinfection demands large amounts of electrical energy, thus increasing costs as well.

    Vulnerable Gravity Flow Systems

    • The UV disinfection process is dependent on electrical energy. In the event of a power outage, UV disinfection systems must stop the flow of water or employ an alternate disinfection method. Gravity flow systems are particularly vulnerable. Systems dependent on electrically powered pumps are less vulnerable because they will shut off when the power goes out.

Public Health - Related Articles