Idaho Administrative Code
Title IDAPA 58 - Environmental Quality, Department of
Rule 58.01.08 - IDAHO RULES FOR PUBLIC DRINKING WATER SYSTEMS
Section 58.01.08.522 - FACILITY AND DESIGN STANDARDS: SURFACE WATER TREATMENT: FILTRATION USING DIATOMACEOUS EARTH

Universal Citation: ID Admin Code 58.01.08.522

Current through August 31, 2023

The use of these filters may be considered for application to surface waters with low turbidity and low bacterial contamination, and may be used for iron removal for ground waters providing the removal is effective and the water is of satisfactory sanitary quality before treatment. (3-24-22)

01. Conditions of Use. Diatomaceous earth filters are expressly excluded from consideration for the following conditions: (3-24-22)

a. Bacteria removal; (3-24-22)

b. Color removal; (3-24-22)

c. Turbidity removal where either the gross quantity of turbidity is high or the turbidity exhibits poor filterability characteristics; or (3-24-22)

d. Filtration of waters with high algae counts. (3-24-22)

02. Treated Water Storage. Treated water storage capacity in excess of normal requirements shall be provided to allow operation of the filters at a uniform rate during all conditions of system demand at or below the approved filtration rate, and guarantee continuity of service during adverse raw water conditions without by-passing the system. (3-24-22)

03. Number of Units. A minimum of two (2) units for redundancy shall be provided for filtration such that plant design capacity can be maintained with any component out of service for maintenance or repairs. (3-24-22)

04. Precoat. A uniform precoat shall be applied hydraulically to each septum by introducing a slurry to the tank influent line and employing a filter-to-waste recirculation system. (3-24-22)

05. Body Feed. A body feed system to apply additional amounts of diatomaceous earth slurry during the filter run is required to avoid short filter runs or excessive head losses. (3-24-22)

a. The rate of body feed is dependent on raw water quality and characteristics and must be determined in the pilot plant study. See Subsection 501.19 for general information on conducting pilot studies. (3-24-22)

b. Continuous mixing of the body feed slurry is required. (3-24-22)

06. Filtration Requirements. (3-24-22)

a. Rate of filtration shall be controlled by a positive means. (3-24-22)

b. Head loss shall not exceed thirty (30) psi for pressure diatomaceous earth filters, or a vacuum of fifteen (15) inches of mercury for a vacuum system. (3-24-22)

c. A recirculation or holding pump shall be employed to maintain differential pressure across the filter when the unit is not in operation in order to prevent the filter cake from dropping off the filter elements. A minimum recirculation rate of one-tenth (0.1) gallon per minute per square foot of filter area shall be provided. (3-24-22)

d. The septum or filter elements shall be structurally capable of withstanding maximum pressure and velocity variations during filtration and backwash cycles, and shall be spaced such that no less than one (1) inch is provided between elements or between any element and a wall. (3-24-22)

e. The filter influent shall be designed to prevent scour of the diatomaceous earth from the filter element. (3-24-22)

07. Backwash. A satisfactory method to thoroughly remove and dispose of spent filter cake shall be provided. (3-24-22)

08. Appurtenances. The following shall be provided for every filter: (3-24-22)

a. Sampling taps for raw and filtered water. (3-24-22)

b. Loss of head or differential pressure gauge. (3-24-22)

c. Rate-of-flow indicator. (3-24-22)

d. A throttling valve used to reduce rates below normal during adverse raw water conditions. (3-24-22)

e. Evaluation of the need for body feed, recirculation, and any other pumps. (3-24-22)

f. Provisions for filtering to waste with appropriate measures for backflow prevention. (3-24-22)

09. Monitoring. A continuous monitoring turbidimeter with recorder is required on each filter effluent for plants treating surface water. (3-24-22)

Disclaimer: These regulations may not be the most recent version. Idaho may have more current or accurate information. We make no warranties or guarantees about the accuracy, completeness, or adequacy of the information contained on this site or the information linked to on the state site. Please check official sources.
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