La. Admin. Code tit. 51 § XII-181

Current through Register Vol. 50, No. 11, November 20, 2024

Section XII-181 - Softening

A. Lime or Lime-Soda Process. Design standards for rapid mix, flocculation and sedimentation are in §175 of this Part. Additional consideration must be given to the following process elements.

1. Hydraulics. When split treatment is used, the bypass line should be sized to carry total plant flow, and an accurate means of measuring and splitting the flow shall be provided.

2. Rapid Mix. Rapid mix detention times should be instantaneous, but not longer than 30 seconds with adequate velocity gradients to keep the lime particles dispersed.

3. Stabilization. Equipment for stabilization of water softened by the lime or lime-soda process is required. (see §189 of this Part).

4. Sludge Collection. A means for sludge removal shall be provided in the sedimentation basin.

5. Sludge Disposal. Provisions shall be included for proper disposal of softening sludges. (see Subchapter F. §257-275 of this Part).

B. Cation Exchange Process. Design criteria for cation exchange process shall be as follows.

1. Pre-treatment requirements. Iron, manganese, or a combination of the two, should not exceed 0.3 mg/L in the water as applied to the ion exchange resin. Pre-treatment is required when the content of iron, manganese, or a combination of the two, is one milligram per liter or more (see §187 of this Part). Waters having 5 units or more turbidity should not be applied directly to the cation exchange softener.

2. Design. The units may be of pressure or gravity type, of either an upflow or downflow design. Automatic regeneration based on volume of water softened shall be used unless manual regeneration is justified and is approved by the state health officer. A manual override shall be provided on all automatic controls.

3. Exchange Capacity. The design capacity shall be in accordance with the manufacturers specifications for hardness removal.

4. Depth of Resin. The depth of the exchange resin shall not be less than three feet.

5. Flow Rates. The rate of softening shall not exceed seven gallons per minute per square foot of bed area and the backwash rate shall be between six and eight gallons per minute per square foot of bed area. Rate-of-flow controllers or the equivalent shall be installed for the above purposes.

6. Freeboard. The freeboard will depend upon the size and specific gravity of the resin and the direction of water flow. Adequate freeboard shall be provided to prevent loss of media during backwashing.

7. Underdrains and Supporting Gravel. The bottoms, strainer systems and support for the exchange resin shall conform to criteria provided for rapid rate gravity filters (see §177. A.6 and §177. A.7 of this Part).

8. Brine Distribution. Facilities should be included for even distribution of the brine over the entire surface of both upflow and downflow units.

9. Cross-Connection Control. Backwash, rinse and air relief discharge pipes shall be installed in such a manner as to prevent any possibility of back-siphonage.

10. Bypass Piping and Equipment. Bypass shall be provided around softening units to produce a blended water of desirable hardness. Totalizing meters shall be installed on the bypass line and on each softener unit. The bypass line shall have a shutoff valve and should have an automatic proportioning or regulating device.

11. Additional Limitations. When the applied water contains a chlorine residual, the cation exchange resin shall be a type that is not damaged by residual chlorine.

12. Sampling Taps. A means of collecting samples shall be provided for the collection of representative samples. If sample taps are provided, they shall be Smooth-nose type. The taps sampling locations shall be located to provide for sampling of the softener influent, effluent and blended water. The sampling locations for the blended water shall be at least 20 feet downstream from the point of blending.

13. Brine and Salt Storage Tanks. Design criteria for brine and salt storage tanks shall be as follows.

a. Salt dissolving or brine tanks and wet salt storage tanks shall be covered and must be corrosion-resistant.

b. The make-up water inlet shall be protected from back-siphonage.

c. Wet salt storage basins shall be equipped with manholes or hatchways for access and for direct dumping of salt from truck or railcar. Openings shall be provided with raised curbs and watertight covers having overlapping edges. Each cover shall be hinged on one side, and shall have locking device.

d. Overflows, where provided, shall be protected with corrosion resistant screens and must terminate with either a turned downed bend having a proper free fall discharge or a self-closing flap valve.

e. The salt shall be supported on graduated layers of gravel placed over a brine collection system.

14. Stabilization. Refer to §189 of this Part.

15. Waste Disposal. Suitable disposal shall be provided for brine waste (see Subchapter F. §257-275 of this Part).

16. Construction Materials. Pipes and contact materials shall be resistant to the aggressiveness of salt. Steel and concrete must be coated with a non-leaching protective coating which is compatible with salt and brine.

17. Housing. Bagged salt and dry bulk salt storage shall be enclosed and separated from other operating areas in order to prevent damage to equipment.

La. Admin. Code tit. 51, § XII-181

Promulgated by the Department of Health, Office of Public Health, LR 44322 (2/1/2018), effective 8/1/2018.

AUTHORITY NOTE: Promulgated in accordance with the provisions of R.S. 40:4.A.(8), 40:4.13.D.(1)(2) and 40:5.A.(2)(3)(5)(6)(7)(17).