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INACTIVATION OF MS2 VIRUS IN DRINKING WATER: TROJAN TECHNOLOGIES, INC., UVSWIFT ULTRAVIOLET SYSTEM MODEL 4L12, AT CHULA VISTA, CALIFORNIA.
Citation:
NSF International, Harza, AND San Diego. INACTIVATION OF MS2 VIRUS IN DRINKING WATER: TROJAN TECHNOLOGIES, INC., UVSWIFT ULTRAVIOLET SYSTEM MODEL 4L12, AT CHULA VISTA, CALIFORNIA. NSF 02/03/EPADWCTR, 2002.
Impact/Purpose:
to publish information
Description:
Verification testing of the Trojan Technologies UVSwift 4L12 system was conducted over a 45 day period from 9/1/01 to 10/15/01. The feedwater to the ultraviolet (UV) unit during the testing was the effluent from the Otay Water Treatment Plant (OWTP), a conventional plant with flocculation, sedimentation, and dual-media filtration of Otay lake water. In the first part of the testing, a virus seeding experiment was conducted at a flow rate of 695 gpm, UV transmittance of 84%, and at 81% lamp power setting. During this experiment the log inactivation of virus ranged from 2.1 logs to 3.0 logs. UV estimated effective dose using MS2 virus is used as an indicator to obtain the inactivation of other microorganisms such as Cryptosporidium and Giardia. A collimated beam test was performed using feed water collected during the seeding experiment and a dose-response curve generated to determine the UV sensitivity of the MS2 virus used as the seed stock during the flow-through reactor challenge study. The dose response curve determined that an effective dose of 42.8 mJ/cm2 was necessary to achieve 2-log inactivation of MS2. The log inactivation achieved during the virus seeding experiment was between 2.1 and 3.0 logs corresponding to an equivalent dose between 40.3 and 67.6 mJ/cm 2 obtained from the collimated beam dose response curve. The reactor was operarted for a period of more than 27 days at a flow rate of 400 gpm and 81% lamp power setting with daily cleaning. During the first 320 hours the following operting parameters were monitored regularly: flow rate, total flow, UV sensor readings, lamp cleaning frequency, lamp hours, lamp shut-down periods, lamp electric power consumption, operating pressure and headloss through the UV unit. Data indicate that the system can operate reliably under these testing conditions. Water quality data collected from both the UV feedwater and UV effluent included: temperture, pH, total alkalinity, hardness, total organic carbon (TOC), UV-254 absorbance,turbidity, true color, nitrate, iron, free chlorine, and total chlorine. No significant change in these water quality parameters was seen from the feed water to the effluent water. Heterotrophic Plate Count (HPC) and total coliforms were both below the detection limit in both the feed and effluent water. Continuous monitoring of the UV irradiance did not indicate a clear fouling trend during the testing period since the UV irradiance measured is a strong function of the UV transmittance of the water, which varied between 81% and 90% (field measurements). However, at the end of the testing period visual inspection of the lamp and sensor sleeves indicated that while the lamp sleeves were relatively clean, the sensor sleeve had fouled. 7% increase in the UV irradiance was observed when the fouled sensor sleeve was replaced by a new sensor sleeve. Replacing the lamp sleeve caused no further improvement. The sensor was found to drift from 1.8% to 11% of the reference sensor reading during the testing period but handling of the sensor window was found to contribute to approximately half of the sensor drift.