Idaho Administrative Code
Title IDAPA 58 - Environmental Quality, Department of
Rule 58.01.08 - IDAHO RULES FOR PUBLIC DRINKING WATER SYSTEMS
Section 58.01.08.532 - FACILITY AND DESIGN STANDARDS: DESIGN STANDARDS FOR SOFTENING

a. When split treatment is used, an accurate means of measuring and splitting the flow must be provided. (3-24-22)

b. Rapid mix basins must provide not more than thirty (30) seconds detention time with adequate velocity gradients to keep the lime particles dispersed. (3-24-22)

c. Equipment for stabilization of water softened by the lime or lime-soda process is required, see Section 537. (3-24-22)

d. Mechanical sludge removal equipment shall be provided in the sedimentation basin. (3-24-22)

e. Provisions must be included for proper disposal of softening sludges; see Section 540. (3-24-22)

f. The plant processes must be manually started following shut-down. (3-24-22)

a. Pre-treatment is required when the content of iron, manganese, or a combination of the two, is one milligram per liter (1 mg/l) or more. (3-24-22)

b. 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 Department. A manual override shall be provided on all automatic controls. (3-24-22)

c. Rate-of-flow controllers or the equivalent shall be used to control the hydraulic loading of cation exchange units. (3-24-22)

d. The bottoms, strainer systems and support for the exchange resin shall conform to the criteria provided for rapid rate gravity filters in Section 521. (3-24-22)

e. 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. (3-24-22)

f. A bypass must be provided around softening units to produce a blended water of desirable hardness. Totalizing meters must be installed on the bypass line and on each softener unit. The bypass line must have a shutoff valve. (3-24-22)

g. When the applied water contains a chlorine residual, the cation exchange resin shall be a type that is not damaged by residual chlorine. (3-24-22)

h. Smooth-nose sampling taps must be provided for the collection of representative samples. The taps shall be located to provide for sampling of the softener influent, effluent, blended water, and on the brine tank discharge piping. The sampling taps for the blended water shall be at least twenty (20) feet downstream from the point of blending. Petcocks are not acceptable as sampling taps. (3-24-22)

i. Brine and salt storage tanks shall meet the following requirements: (3-24-22)

j. Suitable disposal must be provided for brine waste; see Section 540. Where the volume of spent brine must be reduced, consideration may be given to using a part of the spent liquid concentrate for a subsequent regeneration. (3-24-22)

k. Pipes and contact materials must be resistant to the aggressiveness of salt. Plastic and red brass are acceptable piping materials. Steel and concrete must be coated with a non-leaching protective coating which is compatible with salt and brine. (3-24-22)

l. Bagged salt and dry bulk salt storage shall be enclosed and separated from other operating areas in order to prevent damage to equipment. (3-24-22)