Section 58.01.08.525 - LOW PRESSURE MEMBRANE FILTRATIONLow pressure filtration, as used herein, refers to microfiltration or ultrafiltration processes. Low pressure membrane systems can provide greater than 3-log removal of Giardia lamblia and Cryptosporidium, and ultrafiltration systems can also provide up to 2-log virus removal. The Department will determine maximum available removal credits for the specific membrane under consideration. The actual log removal credit that a low pressure membrane filtration system will receive is the lower of the values determined by the following: the removal efficiency demonstrated during challenge testing, or the maximum log removal that can be verified by direct integrity testing required during the course of normal operation. Membrane systems must contain sufficient design to allow for offline direct integrity testing of all units or modules at the required interval while retaining the capability to supply maximum day demand to the PWS. Membrane systems must have at least two (2) units unless it can be demonstrated to the satisfaction of the Department that a secondary source or treatment component can supply the required minimum plant design capacity.
01.Membrane Selection and Design Considerations.a. Challenge testing involves seeding feed water with an organism or particulate and measuring the log reduction of the organism or particulate between the feed and filtrate. It is a one-time product-specific test event performed by an approved third party designed to demonstrate the removal ability of the membrane. Challenge testing must be conducted by the third party entity in general conformance with the USEPA Membrane Filtration Guidance Manual referenced in Subsection 002.02 (Membrane Filtration Guidance Manual). The challenge test report is to be submitted to the Department along with the PER for the project. The Department may accept another state's challenge test report approval.b. A review of historical source water data must be conducted to determine the degree of pretreatment needed if any, the feasibility of membrane filtration, and an estimated cost of the system. At a minimum, the following parameters are to be investigated: Seasonal temperature and turbidity profiles, total organic loading, occurrence of algae, microbial activity, iron, manganese, and hardness levels, and any other inorganic or physical parameters determined to be necessary by the Department. The data will be used to determine anticipated fouling and scaling, backwash and cleaning cycles and regimens, acceptable trans-membrane pressure differentials, and design flux, especially during lowest anticipated water temperature.c. A pilot study must be conducted for a period that is determined by the design engineer and approved by the Department. The duration will include the season of lowest water temperatures and the season including the highest anticipated turbidity, algal bloom, TOC, and iron/manganese event or otherwise cover four seasons of source water quality conditions. The Department may approve a shorter duration proof pilot to verify design criteria that affect the reliable production capacity of the membrane system. The Department may approve the use of a full scale pilot study where the full scale facility will act as the pilot study. The Department may also waive the pilot study requirement. Proof pilot studies, full scale pilot studies, and the waiving of the pilot study requirement will only be approved in circumstances where source water conditions and fouling characteristics are already well understood. Such source waters include but are not limited to groundwater under the influence of surface water, waters with existing membrane plants, waters where sufficient pilot test data has already been generated, and extensively used or tested membrane products where production or test data on similar waters is available (i.e., same lake, reservoir, or same reach for stream sources). In addition to the requirements in Subsection 501.19, the pilot study must include:i. A means to identify the best membrane to use for the anticipated water quality;ii. Analysis of any need for pretreatment;iii. Range of anticipated flux rates;iv. Operating and transmembrane pressure;v. Fouling and scaling potential;vi. Backwash and recovery cleaning, cleaning processes, and intervals;vii. Efficiency and process mass balance;viii. Waste stream volume, characterization, and disposal method;x. Integrity testing results and procedures.02.Monitoring and Compliance Requirements for Membranes. PWSs that use low pressure membrane filtration must comply with the following requirements. a. Initial Start-Up. i. Notify the Department at least one (1) week in advance of the planned start-up date.ii. The design engineer will oversee start-up procedures.iii. All monitoring equipment will be calibrated prior to start-up.iv. The system must pass direct integrity testing prior to going on-line and producing water for distribution.v. A method for the disposal of start-up water needs to be approved by the Department prior to start-up.b. Direct Integrity Testing. i. Testing must be conducted on each membrane skid in service at least daily for the first year of operation.ii. The test method used must have a resolution of three (3) pm or less for Cryptosporidium and Giardia lamblia removal credit.iii. The test method used must have sensitivity sufficient to verify the ability of the membrane filtration system to remove the constituent at a level commensurate with the credit awarded by the Department.(1) Formulae for sensitivity calculation for pressure-based tests are available in the Membrane Filtration Guidance Manual referenced in Subsection 002.02. The volumetric concentration factor used in the calculation may be either calculated or determined experimentally.(2) Formulae for sensitivity calculation for marker-based tests are available in the Membrane Filtration Guidance Manual referenced in Subsection 002.02.iv. A control limit must be established within the sensitivity limits of the direct integrity test that is indicative of an integral membrane unit capable of achieving the log removal credit awarded by the Department.(1) If the direct integrity test results exceed the control limit for any membrane unit, that unit must be removed from service.(2) Any unit taken out of service for exceeding a direct integrity test control limit cannot be returned to service until repairs are confirmed by subsequent direct integrity test results that are within the control limit.v. Direct integrity testing must be conducted on each membrane unit at a frequency of at least once per day that the unit is in operation. The Department may extend testing frequency up to a duration of once per week after one (1) year of daily testing showing a less than five percent (5%) testing failure rate for the previous year. During weekly testing, if at any time the system fails more than two (2) direct integrity tests within a three (3) month period, the system must return to daily testing.c. Indirect Integrity Monitoring. i. Testing must be conducted on each membrane unit in service.ii. Continuous indirect integrity monitoring must be conducted using turbidity monitoring unless the Department approves an alternative method.iii. Continuous indirect integrity monitoring must be conducted at a frequency of at least one (1) reading every fifteen (15) minutes. The Department may allow a time delay in reporting compliance turbidity measurements if it can be demonstrated that elevated turbidity readings above fifteen hundredths (0.15) NTU immediately following direct integrity testing or maintenance are the result of factors related to entrained air or membrane wettability and are not related to membrane integrity.iv. If the continuous indirect integrity monitoring results exceed the specified control limit for any membrane unit for a period greater than fifteen (15) minutes (i.e., two (2) consecutive readings at fifteen (15) minute intervals), direct integrity testing must be immediately conducted on that unit. (1) The control limit for turbidity monitoring is fifteen hundredths (0.15) NTU.(2) Control limits for Department approved alternative methods will be established by the Department.d. A project specific operation and maintenance manual must be provided as required in Subsection 501.12. See definition of Operation and Maintenance Manual in Section 003 for the typical contents of an operation and maintenance manual and the included operations plan. The operations plan in the operation and maintenance manual for membrane systems must include, but is not limited to the following information: i. Filtration: (1) Control of feed flow to the membrane system;(2) Measurement of inlet/outlet pressures and filtrate flows;(3) Measurement of transmembrane pressure changes during filter run; and(4) Feed flow control in response to temperature changes.ii. Membrane backwashing: (1) Programming automated frequency;(2) Proper backwash venting and disposal; see Section 540; (3) Appropriate backwash rate; and(4) Monitoring during return of filter to service.iii. Chemical cleaning:(1) Selection of proper chemical washing sequence;(2) Proper procedures for dilution of chemicals;(3) Monitoring of pH through chemical cleaning cycle;(4) Rinsing of membrane system following chemical clean; and(5) Return of filter to service.iv. Chemical feeders (in the case that chemical pretreatment is applied):(2) Settings and adjustments (how they are made); and(3) Dilution of chemicals and polymers (proper procedures).v. Monitoring and observing operation:(1) Observation of feed water or pretreated water turbidity;(2) Observation of trans-membrane pressure increase between backwashes;(3) Filtered water turbidity;(4) Procedures to follow if turbidity breakthrough occurs.vi. Troubleshooting: (1) No raw water (feed water) flow to plant;(2) Can't control rate of flow of water through equipment;(3) Valving configuration for direct flow and cross-flow operation modes;(4) Poor raw water quality (raw water quality falls outside the performance range of the equipment);(5) Poor filtrate quality;(6) Failed membrane integrity test;(7) Low pump feed pressure;(8) Automatic operation (if provided) not functioning;(9) Filtered water turbidity too high;(10) Head loss builds up excessively rapidly;(12) Machine will not start and "Power On" indicator off;(13) Machine will not start and "Power On" indicator on;(15) Valve stuck or won't operate; ande. The sensitivity, resolution, and frequency of the direct integrity test proposed for use with the full-scale facility must be reported to the Department prior to initial operation. The following must be reported to the Department on a monthly basis:i. Any direct integrity test results exceeding the control limit, as well as the corrective action taken in response, must be reported to the Department within ten (10) days of the end of the monthly monitoring cycle on a Department reporting form. The form is available at www.deq.idaho.gov;ii. Any continuous indirect integrity monitoring results triggering direct integrity testing, as well as any corrective action taken in response, must be reported to the Department within ten (10) days of the end of the monthly monitoring cycle on a Department reporting form. The form is available at www.deq.idaho.gov;iii. Any additional information considered necessary by the Department on a case-specific basis to verify proper operation and maintenance of the membrane filtration process; andiv. All direct integrity test results and continuous indirect integrity monitoring results must be retained for a minimum of three (3) years.Idaho Admin. Code r. 58.01.08.525