Oklahoma Administrative Code › Title 252 - Department of Environmental Quality › Chapter 626 - Public Water Supply Construction Standards › Subchapter 9 - Treatment › Section 252:626-9-4 - Ozonation

Current through Vol. 41, No. 20, July 1, 2024
Ozonation systems may be used in potable water systems for
				  disinfection, oxidation, and microflocculation. Although the installation may
				  be for a specific purpose, such as disinfection, the overall plant design must
				  have the capability to handle ozone by-products created by oxidation and
				  microflocculation. Positive or negative type ozonation systems are allowed. If
				  ozonation is used, it must meet the following:
(1)
Capacity.
The production
				rating of the ozone generators shall be stated in pounds per day and kW-hr per
				pound at a maximum cooling water temperature and maximum ozone concentration.
				The design shall ensure that the minimum concentration of ozone in the exit gas
				shall not be less than one percent (1%) by weight. Ozonation systems shall be
				sized to have sufficient reserve capacity so that the system does not operate
				at peak capacity for extended periods of time. The ozone production rate
				decreases as the temperature of the coolant increases. The design shall ensure
				that ozone can be produced at the maximum coolant temperature. Backup ozone
				generating equipment shall be provided.
(2)
Cooling.
Adequate cooling
				shall be provided. The cooling water must be properly treated to minimize
				corrosion, scaling and microbiological fouling of the water side of the tubes.
				Where cooling water is treated, cross connection control shall be provided to
				prevent contamination of the potable water supply.
(3)
Materials.
To prevent
				corrosion, ozone shell and tubes shall be constructed of Type 316L stainless
				steel.
(4)
Diffusers.
A minimum of two contact chambers each equipped with baffles to prevent short
				circuiting and induce countercurrent flow shall be provided. The diffusion
				system shall operate so that the ozone is fed at the bottom of the vessel and
				water is fed at the top of the vessel. Ozone shall be applied using porous-tube
				or dome diffusers. The minimum contact time shall be ten (10) minutes. A
				shorter time may occur, only with the approval of the DEQ, if justified by
				appropriate design and CT Value considerations. Porous diffusers shall not be
				used when precipitates are formed during ozone applications. The diffuser shall
				be fully serviceable by either cleaning or replacement.
(5)
Contactors.
Contactors shall
				be separate closed vessels that have no common walls with adjacent rooms. The
				contactor shall be kept under negative pressure and with sufficient monitors to
				protect worker safety. The contactor shall be placed where the entire roof is
				exposed to the open atmosphere. All openings into the contactor for pipe
				connections, hatchways and/or other openings shall be properly sealed using
				welds or ozone resistant gaskets. Multiple sampling ports shall be provided to
				enable sampling of each compartment's effluent water and to confirm CT Value
				calculations. A pressure or vacuum relief valve shall be provided in the
				contactor and piped to a location where there will be no damage to the unit.
				The depth of water in the contactor shall be a minimum of eighteen feet (18')
				and have a minimum of three feet (3') of freeboard. All contactors shall be
				equipped so that the contactor can be cleaned, maintained and drained. Each
				contactor compartment shall be equipped with an access hatchway.
(6)
Ozone destruction unit.
A
				system for treating the final gas-off from each unit shall be provided by
				either thermal destruction or thermal/catalytic destruction. The maximum ozone
				concentration in the release is 0.1 ppm by volume. At least two units shall be
				provided which are each capable of handling the entire gas flow. Exhaust
				blowers shall be provided in order to draw off-gas to the destruction unit.
				Catalysts shall be protected from froth, moisture and other impurities. The
				catalyst and heating elements shall be located to allow for
				maintenance.
(7)
Piping
				materials.
Only low carbon 304L and 316L stainless steel shall be used
				for ozone service.
(8)
Joints
				and connections.
Connections on piping used for ozone service shall be
				welded. Connections with meters, valves or other equipment shall be made with
				flanged joints with ozone resistant gaskets. A positive closing plug or
				butterfly valve plus a leak-proof check valve shall be provided in the piping
				between the generator and the contactor to prevent moisture reaching the
				generator.
(9)
Instrumentation.
Pressure gauges shall be provided at the
				discharge from the air compressor, at the inlet to the refrigeration dryers, at
				the inlet and outlet of the desiccant dryers, at the inlet to the ozone
				generators and contactors and at the inlet to the ozone destruction unit.
				Electrical power meters shall be provided for measuring electrical power
				supplied to the ozone generators. Each generator shall have a automatic shut
				down when wattage exceeds a preset level. Dew point monitors shall be provided
				for measuring the moisture of the feed gas from the desiccant dryers. Where
				there is a potential for moisture to enter the ozone generator from downstream
				from the unit or where moisture accumulation can occur in the generator during
				shutdown, post-generator dew point monitors shall be used. Air flow meters
				shall be provided for measuring air flow from the desiccant dryers to each of
				the ozone generator and air flow to each contactor, and purge air flow to the
				desiccant dryers. Temperature gauges shall be provided for the inlet and outlet
				of the ozone cooling water and the inlet and outlet of the ozone generators
				feed gas, and when necessary for the inlet and outlet of the ozone power supply
				cooling water. Water flow meters shall be installed to monitor the flow of
				cooling water to the ozone generators and when necessary to the ozone power
				supply. Ozone monitors shall be installed to measure ozone concentration in
				both feed-gas and off-gas from the contactor and in the off gas from the
				destruction unit. For disinfection systems, monitors shall also be provided for
				monitoring ozone residuals in the water. A minimum of one ambient ozone monitor
				shall be installed in the vicinity of the contactor and a minimum of one shall
				be installed in the vicinity of the generator. Ozone monitors shall be
				installed in any area where ozone gas may accumulate.
(10)
Alarms and shut-down
				systems.
Installation of alarms and /or shut-down systems are required.
				The following alarms and/or shutdown systems shall be installed:
(A) A dew-point shut-down alarm system, when
				the generator exceeds 60 degrees Celsius,
(B) Ozone generator cooling water flow
				shut-down alarm system for the generator to prevent potential harm,
(C) Ozone power supply cooling water flow
				shut-down alarm system, to prevent potential harm to the power supply in the
				event that cooling water flow decreases to the point that damage to the power
				supply could occur,
(D) Ozone
				generator cooling water temperature shut-down alarm system for the generator
				when either the inlet or outlet cooling water exceeds a preset
				temperature,
(E) Ozone power supply
				cooling water temperature shut-down alarm system to shut down the power supply
				if the inlet or outlet cooling water exceeds a certain preset
				temperature,
(F) Ozone generator
				inlet feed-gas temperature shut-down alarm system to the generator if the feed
				gas temperature is above a preset value,
(G) Ambient ozone concentration shut-down
				alarm system shall sound an alarm when the ozone levels in the ambient air
				exceed 0.1 ppm of ozone and shut down the system when the levels exceed 0.3 ppm
				of ozone, and
(H) Ozone destruction
				temperature alarm system sounding an alarm when the temperature exceeds a
				preset value.