The effectiveness of ultraviolet (UV) light irradiation for inactivation of nitrifying
bacteria is demonstrated in this study. The destruction of total chlorine and formation of nitrite
were evaluated. Bench scale experiments were conducted, in which water with the
nitrifying bacteria was passed through a low-pressure UV-lamp. UV-dose was varied by
passing water at different flow rates and by covering the portion of the lamp quartz sleeve
with the aluminum foil. The approximate UV-dose range was estimated based on lamp
specifications, water flow rate, and lamp coverage. UV-irradiated water was ammoniated
and stored in the dark bottles in the incubator at 15 and 25ºC for up to three weeks to
determine the effective dose and nitrifying bacteria regrowth. A UV dose estimated to be
on the order of magnitude of 20 mJ/cm<sup>2</sup> was optimal to inactivate nitrifying bacteria,
minimize total chlorine destruction and nitrite formation. UV light doses reported here
should be used only in relative terms; no attempt was made to measure the exact dose.
Pilot scale experiments evaluated the feasibility of the UV light for the control of an ongoing
nitrification episode in a flow-through pilot water storage tank supplied with
chloraminated water. Two application concepts were tested: UV-irradiation of the
bulk water; and, UV-irradiation of the water collected at the tank walls with an
aquarium squeegee. The water in both cases was recirculated into the nitrifying storage
tank. An approximate UV-dose, turnover of UV-irradiated water recirculated through the
water storage tank (typically 7 days), and tap water turnover rate through the pilot tank
were varied. A limited number of pilot UV experiments conducted were not successful
in controlling an on-going nitrification episode. However, pilot tests demonstrated that
the UV irradiation of the bulk water slowed down the uptake of ammonia. Several
concepts were discussed, which could be tested to evaluate full-scale process feasibility. Includes 5 references, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 460 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 16 |
| Published : | 06/01/2006 |
