| |
|
 |
|
 |
|
|
|
|
Decorative water
fountains have become quite a common feature in many of the more elaborate and
high profile commercial properties, restaurants, casinos, and shopping malls.
However, for the engineering departments overseeing such equipment, decorative
fountains also create unique maintenance and liability problems.
Since they essentially operate in the
same manner and on the same principles of a typical cooling tower, decorative
fountains also share the associated maintenance problems of dirt, scaling, and
microbiological growth. All airborne dirt and organisms making contact with the
water become captured into the recirculating system, yet may not always show as
dirty water or discolored surface fixtures.
While the
filtration of particulates is standard practice, and can be easily achieved
using standard sand filtration, the remedies for microbiological problems are
often limited due to the generally confined indoor operating environment, and
the obvious concerns for human
health.
Clearly, any biological
contamination emanating from decorative fountains is of far greater concern to
building inhabitants than either dirt or scale - Legionnaires Disease being one
of the more serious and high profile threats. Yet, the same concern for human
health and possible adverse physical reactions often prohibits the use of those
biocides proven as most effective at treating the problem. Applying shock doses
of chlorine, bromine or various available non-oxidizing agents during off
operating hours, while somewhat effective, fail to provide the continuous level
of protection sought by most building operators.
Ultraviolet (UV)
light purification is one of the simplest and most effective methods of
destroying pathogenic (disease causing) microorganisms in water. Complete
sterilization of the water stream is accomplished without the use of heat,
chemicals or gases, and leaves no residual odor, taste, or corrosive or
irritating properties with the treated water. There is no deterioration or
oxidation of pool or fountain surfaces as exists when using high doses of
chlorine, ozone, or bromine.
Having proven
their effectiveness in countless commercial, industrial, and domestic
applications around the world for the past 50 years, simple and cost effective
prepackaged UV sterilization units offer a worthwhile add-on to any decorative
recirculating system.
Technically,
ultraviolet light is invisible radiation within the specific wavelength range
of 200 nm to 280 nm - nm meaning "nanometers" or millionths of a
millimeter. Given sufficient dosage, contact time, and absorption of UV energy
at the specific wavelength of 254 nm, UV will provide 100% disinfection of any
liquid medium that travels through
it.
This is accomplished at a UV dosage
rate of approximately 30,000 mw sec./cm2 -
causing deactivation of the cell DNA through the absorption of the UV radiation
energy into the microorganism cell structure. UV is effective against bacteria,
algae, protozoa, viruses, yeasts, and mold spores.
Various factors
influence the efficiency of UV disinfection including the flow rate of the
fluid, depth of the liquid across the UV source, absorption coefficient of the
liquid, dissolved or suspended particulate matter, water clarity, dissolved
iron, etc. Such factors must be carefully calculated into any UV recommendation
to ensure full sterilization. Given the proper size selection for the
application, installation can generally be handled in-house using PVC piping.
Since most decorative recirculating
fountains are low pressure, installation is simply a matter of piping the UV
sterilizer in line after the sand filter or particulate strainer. Sand
filtration is an absolute prerequisite. Electrical service is also required.
Maintenance is minimal, and generally requires periodic cleaning of the quartz
UV lamp. In the more advanced units, this lens cleaning procedure is
automated.
While the
addition of a UV sterilizer will dramatically reduce the organic load for any
open recirculating system, periodic sterilization and maintenance using
conventional chemical agents is still required in order to control surface
growths, as well as all growths at or above the water line.
A basic flow schematic of a typical UV
installation is shown below.
The installation
of a UV sterilizing unit offers significant protection against disease
originating from a decorative fountain. However, it remains as only part of a
total maintenance program that should be strictly followed.
©
Copyright
|
|
|
|
|
|
|
|
|
|
 |
|
|
