12 Va. Admin. Code § 5-590-1004 - Ozonation

A. Ozone may be considered as a pre-oxidant to control tastes and odors, reduce color, oxidize iron and manganese, reduce DBPPs, and used for primary disinfection. Where ozone is used, consideration shall be given to the level of bromide and formation of brominated byproducts.

B. Ozone systems are typically comprised of four basic subsystems: ozone generation, feed gas preparation, ozone contactors, and off-gas disposal.

C. The PER shall evaluate water and gas flow rates, oxygen source, generator selection and sizing, contactor design, treatment process location, exhaust gas collection and destruction, and operator requirements.

D. Treatability studies using bench-scale or pilot-scale tests may be required as part of the PER to address the following:

1. Alternate points of ozone application;

2. Ozone demand tests, applied dose, transferred dose, and decay rates; and

3. Ozone byproducts, including bromide and bromate analyses.

E. Ozone systems shall be granted disinfection credit for Giardia lamblia, Cryptosporidium, and viruses, in accordance with 12VAC5-590-401 E 7 and 12VAC5-590-500, provided that they meet the requirements of this section.

1. Ozone residual levels shall be monitored continuously and recorded. For waterworks that claim inactivation credit for ozone, a minimum of two dedicated, online monitors per ozone contactor shall be provided. The location of the monitors shall be acceptable to the department. A portable ozone monitor shall be provided as a backup.

2. Ozone systems using multiple, consecutive contact chambers with gaseous ozone injected in the initial chambers, shall be designed to measure the ozone residual and compute log inactivation of Giardia and virus using the C_effluentT₁₀ Method or the Log Integration CT₁₀ Method, as described in the "Long Term 2 Enhanced Surface Water Treatment Rule Toolbox Guidance Manual," EPA Office of Water (4606), EPA 815-R-09-016, April 2010.

3. Sampling lines shall be designed to minimize the reaction time (typically less than 10 seconds conveyance time).

F. Alarms shall be provided for ozone process control safety. Automatic shutdown features shall be considered.

Notes

12 Va. Admin. Code § 5-590-1004

Derived from Virginia Register Volume 37, Issue 20, eff. 6/23/2021.

Statutory Authority: §§ 32.1-12 and 32.1-170 of the Code of Virginia.