SECTION 252:626-9-14. Anion exchange

(a)   Pilot study. A pilot study protocol shall be approved prior to conducting the pilot study. A pilot study is required prior to submission of an engineering report and must be conducted for a minimum duration of time sufficient to process water through at least one full bed volume and resin regeneration cycle, or 3 days, whichever is longer. The results of the pilot study shall be included in the engineering report.

(b)   Pretreatment. Pretreatment shall be required if the total concentration of iron, manganese, and heavy metals exceeds 0.1 mg/L.

(c)   Process Design.

(1)   Redundancy. Redundancy of control components, including, but not limited to, valves, air supply and computers, shall be provided. Anion exchange units shall be provided that meet the design capacity at a level below the nitrate/nitrite MCL with the largest unit out of service.

(2)   Automatic controls. Automatic regeneration based on volume of water treated shall be provided unless manual regeneration can be justified and is approved by DEQ. A manual override shall be provided for all automatic controls.

(3)   Exchange capacity. The design capacity of the anion exchange system shall not exceed the manufacturer's recommended design capacity of the resin and regeneration.

(4)   Flow rates. The design shall not exceed 7 gallons/min/ft of bed area for the treatment flow rate. The backwash flow rate should be 2-3 gallons/min/ft of bed area with a fast rinse approximately equal to the service flow rate.

(5)   Flow meters. Flow meters shall be provided on the source water influent piping and the plant finished water piping.

(6)   Blending. If a portion of the water is bypassed around the treatment unit and blended with the treated water, the maximum blend ratio allowable must be determined based on the highest anticipated raw water nitrate level. If a bypass line is provided, a totalizing meter and a proportioning or regulating device or flow regulating valves must be provided on the bypass line.

(7)   Stabilization. Stabilization for corrosion control shall be provided.

(8)   Appurtenances. An adequate underdrain and supporting gravel system, brine distribution equipment, and cross connection control shall be provided.

(9)   Construction material. Pipes and contact materials must be resistant to the aggressiveness of salt.

(10)   Cross connections. Anion exchange system piping shall be designed to prevent any cross connection with any potable water supply, in accordance with OAC 252:626-5-15.

(d)   Sampling and monitoring.

(1)   Sampling taps. Smooth-nose sampling taps for the collection of representative samples shall be provided. The taps shall be located to provide sampling of the anion exchange unit influent, effluent, and blended water. Sampling taps for the blended water shall be located at least 20 feet downstream from the point of blending.

(2)   Water quality test equipment. Test equipment for pH, alkalinity, stability, total hardness, and nitrate shall be provided to determine treatment effectiveness.

(3)   Monitoring. The treated water nitrate/nitrite level shall be monitored using continuous monitoring and recording equipment with a high nitrate level alarm. In addition to continuous monitoring and recording equipment, the finished water nitrate/nitrite levels shall be determined (using a test kit) no less than once per day, preferably just prior to regeneration of the unit.

(e)   Brine System.

(1)   Brine and salt storage tanks. Cover brine measuring or salt dissolving tanks and wet salt storage facilities and construct them of corrosion-resistant material. The make-up water inlet shall have a free fall discharge of two pipe diameters above the maximum liquid level of the unit or obtain DEQ approval of other methods of protection from back-siphonage. Support the salt on graduated layers of gravel with a suitable means of collecting the brine. Equip wet salt storage basins with manhole or hatchway openings having raised curbs and watertight covers with overhanging edges similar to those required for finished water storage. Overflow, where provided, must have a free fall discharge and terminate at an approved brine waste disposal facility.

(2)   Salt storage capacity. Design salt storage large enough to accommodate a 30-day supply.

(3)   Housing. Enclose and separate salt storage from other operating areas.

(f)   Waste disposal. A DEQ approved disposal plan is required for brine waste. If brine waste is disposed of in a lagoon, then the lagoon must be permitted and constructed in accordance with OAC 252:656 and lined with a synthetic liner in accordance with the requirement contained in OAC:626-13-4.

[Source: Added at 29 Ok Reg 1035, eff 7-1-12; Amended at 33 Ok Reg 1472, eff 9-15-16]