Private Wastewater Treatment Plants

IDAHO ADMINISTRATIVE CODE IDAPA 58.01.16 Department of Environmental Quality Wastewater Rules Section 455 Page 39 01. Scope. Section 455 includes requirements in addition to Section 450 requirements for approval of private wastewater treatment plants. Individual extended treatment package systems for on-site systems are regulated by IDAPA 58.01.03, “Individual/Subsurface Sewage Disposal Rules and Rules for Cleaning of Septic Tanks.” (7-1-26) a. If the Department determines that a proposed private wastewater treatment plant is reasonably accessible to a wastewater system, the use of the private wastewater treatment plant may be denied. (7-1-26) b. A compliance agreement schedule authorized by Section 39-116A, Idaho Code, is required for each private wastewater treatment plant approved unless specifically waived by the Department in writing. If a private wastewater treatment plant installation is only a temporary or interim measure in a long-term plan, a compliance agreement schedule will include a sunset clause with a date for the private wastewater treatment plant to cease operation and will require the plant owner to fund and construct the eventual hookup to the municipal wastewater collection system when the system becomes reasonably accessible. The compliance agreement schedule will address such things as operation and maintenance requirements and monitoring, reporting requirements, and other project- specific items as applicable. The owner is responsible for complying with the requirements of the compliance agreement schedule. The compliance agreement schedule will be renewed every five (5) years; when ownership of the treatment plant changes; or at the request of the owners or Department, so long as the system is in operation. (7-1-26) c. Private wastewater treatment plants must be designed to provide service within the contiguous area including all adjacent and connected parcels or subdivisions that are part of the same overall planned development footprint and provide service to future phases of the planned development. The design capacity must account for buildout conditions or provide for means to readily expand capacity to accommodate future growth. Anticipated phases of development and future growth must be accounted for within the facility plan and PER. (7-1-26) d. The minimum size of a private wastewater treatment plant allowed under these rules is twenty-five thousand (25,000) gallons per day design capacity based on average day flows. (7-1-26) i. The minimum size requirements do not apply to proposed systems with suitably configured passive wastewater treatment technologies including, but not limited to, facultative lagoons, free water surface wetlands, and vegetated submerged beds. (7-1-26) ii. The Department may approve private wastewater treatment plants smaller than twenty-five thousand (25,000) gallons per day design capacity, based on average day flows, provided the treatment plant will be maintained under original ownership. (7-1-26) e. Prior to transfer of ownership of a private wastewater treatment plant to another entity, the proposed new owner must submit adequate documentation demonstrating sufficient technical, financial, and managerial capacity, as described in Section 409. (7-1-26) 02. Facility Plan and PER. The facility plan and PER for private wastewater treatment plants must include project-specific estimated permit effluent limits and requirements based on discussion with the applicable permitting agency, the information listed in this subsection, and information specified in Sections 410 and 411. (7-1-26) a. The private wastewater treatment plant will have at least two (2) full years of operating data on five (5) separate installations in the United States. The data submittal will include the name, address, and telephone number for a regulatory agency contact person or an owner or operator familiar with the performance of each reported installation. (7-1-26) b. The private wastewater treatment plant will be a dual train type (or equivalent/greater) with redundant pumps and blowers from influent works to the disposal site and provide sufficient redundancy to continue processing incoming wastewater at peak flows while any one (1) component or process is out of service. Standby or emergency power will be provided to fully operate the wastewater treatment plant during a power outage unless the water system would also be out during a power outage. (7-1-26) IDAHO ADMINISTRATIVE CODE IDAPA 58.01.16 Department of Environmental Quality Wastewater Rules Section 460 Page 40 03. Plan and Specification Approval. (3-31-22) a. Plans and specifications for the private wastewater treatment plants will not be approved until the owner is in receipt of one of the following (whichever is applicable): (7-1-26) i. A draft discharge permit for proposed surface water discharges; (7-1-26) ii. A draft reuse permit from the Department in accordance with IDAPA 58.01.17, “Recycled Water Rules”; (7-1-26) iii. Water balance calculations showing a net water loss for total containment lagoons included in approved PER; or (7-1-26) iv. A subsurface installation permit application submitted to the local public health district and a completed site evaluation or nutrient pathogen evaluation in accordance with Section 260. (7-1-26) b. A signed contract or other documentation acceptable to the Department that provides for ultimate legal disposal or use of the sludge must be submitted to the Department prior to plan and specification approval. (7-1-26) 456. -- 459. (RESERVED) 460. FACILITY AND DESIGN STANDARDS FOR MUNICIPAL WASTEWATER SYSTEMS: SCREENING AND GRIT REMOVAL. 01. Screening Devices and Comminutors. (3-31-22) a. Screening, coarse or fine, or comminutors are required for all mechanical plants and will be addressed for other types of plants. These facilities must be designed for peak hourly flow. Multiple channels must be provided and equipped with the necessary gates to isolate flow from any screening unit. Provisions must also be made to facilitate dewatering each unit. The channel preceding and following the screen must be shaped to minimize settling of solids. (7-1-26) b. For mechanical plants with design flow less than one million gallons per day (1 mgd), and where a single mechanically cleaned screen is used, an auxiliary manually cleaned screen must be provided. Where two (2) or more mechanically cleaned screens are used, the design must provide for taking any unit out of service without sacrificing the capability to screen the design peak instantaneous flows. (7-1-26) 02. Grit Removal Facilities. Grit removal and handling facilities must be provided for all mechanical wastewater treatment plants. Consideration must be given to possible damaging effects on pumps, comminutors, and other preceding equipment, and the need for additional storage capacity in treatment units where grit is likely to accumulate. (7-1-26) 461. -- 469. (RESERVED) 470. FACILITY AND DESIGN STANDARDS FOR MUNICIPAL WASTEWATER SYSTEMS: SETTLING. 01. Settling Units. A minimum of two (2) settling units capable of independent operation must be provided in all plants where design flow exceeds one hundred thousand (100,000) gallons/day. Plants not having multiple units must include other provisions to assure continuity of treatment. (7-1-26) 02. Sizing. Sizing must be calculated for both average day flow and peak hour flow conditions, and the larger surface area determined must be used. (7-1-26) 03. Isolation. The plant design must allow for isolation of each unit and allow for sludge and scum removal. (7-1-26) IDAHO ADMINISTRATIVE CODE IDAPA 58.01.16 Department of Environmental Quality Wastewater Rules Section 480 Page 41 04. Baffling. Baffling must be designed to control solids carry-over. (7-1-26) 05. Minimum Side Depth. The minimum side depth for primary settling facilities must be ten (10) feet. The minimum side depth for secondary settling facilities must be twelve (12) feet. (7-1-26) 471. -- 479. (RESERVED) 480. FACILITY AND DESIGN STANDARDS FOR MUNICIPAL WASTEWATER SYSTEMS: SLUDGE PROCESSING, STORAGE, AND DISPOSAL. 01. Facilities. Facilities for processing sludge must be provided for all mechanical wastewater treatment plants. Facilities must be capable of processing sludge to a form suitable for ultimate disposal. Final disposal or utilization must be in accordance with applicable federal and state regulations. (7-1-26) 02. Design. Sludge processing, storage and disposal facility design must comply with the PER. (7-1-26) 03. Multiple Units. Multiple units capable of independent operation must be provided in plants where design average flows exceed one hundred thousand (100,000) gallons/day. Plants not having multiple units must include other provisions to assure continuity of treatment. The plant design must allow for isolation of each unit. (7-1-26) 481. -- 489. (RESERVED) 490. FACILITY AND DESIGN STANDARDS FOR MUNICIPAL WASTEWATER SYSTEMS: BIOLOGICAL TREATMENT. If biological treatment is used, the process must be determined in the PER. The choice must be based on influent characteristics and effluent requirements. (7-1-26) 01. Trickling Filters. (3-31-22) a. Trickling filters must be preceded by effective settling tanks equipped with scum and grease collecting devices or other suitable pretreatment facilities. (7-1-26) b. The flow must be uniformly distributed across the surface of the media. The piping system, including dosing equipment and distributor, must be designed to provide capacity for the design peak hour flow, including recirculation. (7-1-26) c. Media. (3-31-22) i. Trickling filter media must be appropriate for the wastewater and of sufficient strength to support itself under design loading and build up of biomass. (7-1-26) ii. The media must have a minimum depth of six (6) feet above the underdrains. (7-1-26) d. Underdrainage System. (3-31-22) i. Underdrains must be provided and the underdrainage system must cover the entire floor of the filter. Inlet openings into the underdrains must have an unsubmerged gross combined area equal to at least fifteen (15) percent of the surface area of the filter. (7-1-26) ii. The underdrainage system, effluent channels, and effluent pipe must be designed to permit free passage of air. (7-1-26) e. Special Features. (3-31-22) IDAHO ADMINISTRATIVE CODE IDAPA 58.01.16 Department of Environmental Quality Wastewater Rules Section 490 Page 42 i. All distribution devices, underdrains, channels, and pipes must be installed so that they may be properly maintained, flushed or drained. (7-1-26) ii. Covers must be provided to maintain operation and treatment efficiencies when climatic conditions are expected to result in problems due to cold temperatures. (7-1-26) iii. The piping system must be designed for recirculation as needed to achieve the design efficiency. The recirculation rate must be variable and subject to plant operator control at the range of 0.5:1 up to 4:1 (ratio of recirculation rate versus design flow). A minimum of two (2) recirculation pumps must be provided. (7-1-26) f. Mercury rotary distributor seals are not permitted. (7-1-26) g. Volumes of filter media must be based upon pilot testing with the particular wastewater or any of the various empirical design equations that have been verified through actual full scale experience. Such calculations must be submitted to the Department if pilot testing is not utilized. Trickling filter sizing design must consider peak organic load conditions including the oxygen demands due to solids and process recycle flows. (7-1-26) 02. Activated Sludge. (3-31-22) a. Aeration. (3-31-22) i. The size of the aeration tank for any particular adaptation of the process must be determined by full scale experience, pilot plant studies, or standard calculations based on solids retention time, food to microorganism ratio, and mixed liquor suspended solids levels. Other factors, such as size of treatment plant, diurnal load variations, and degree of treatment required, must also be considered. In addition, temperature, alkalinity, pH, and reactor dissolved oxygen must be considered when designing for nitrification. Calculations must be submitted to the Department in the PER to justify the basis for design of aeration tank capacity. (7-1-26) ii. Arrangement of Aeration Tanks. (3-31-22) (1) The dimensions of each aeration tank or return sludge reaeration tank must be able to maintain effective mixing and utilization of air. Horizontally mixed aeration tanks must have a depth of greater than five point five (5.5) feet. (7-1-26) (2) Total aeration tank volume plus redundancy requirements must be divided among two (2) or more equal units, capable of independent operation. (7-1-26) (3) Inlets and Outlets. (3-31-22) (a) Inlets and outlets for each aeration tank unit must be designed to control flow to any unit with reasonable accuracy and to maintain reasonably constant liquid level. The properties of the system must permit the design peak day flow to be treated with any single aeration tank unit out of service. The properties of the system must permit the design peak hour hydraulic flow to be carried with any single aeration tank unit out of service. (7-1-26) (b) Channels and pipes carrying liquids with solids in suspension must be designed to be self- cleansing. (7-1-26) (c) Aeration tanks must be designed to include adequate control or removal of scum and foam. (7-1-26) (4) All aeration tanks must have a freeboard of not less than eighteen (18) inches unless otherwise approved by the Department. (7-1-26) iii. Aeration Equipment. (3-31-22) (1) Oxygen requirements are based on maximum diurnal organic loading, degree of treatment, and level of suspended solids concentration to be maintained in the aeration tank mixed liquor. Aeration equipment must IDAHO ADMINISTRATIVE CODE IDAPA 58.01.16 Department of Environmental Quality Wastewater Rules Section 490 Page 43 be capable of maintaining a minimum of two point zero (2.0) mg/L of dissolved oxygen in the mixed liquor at all times and provide thorough mixing of the mixed liquor. For a horizontally mixed aeration tank system, an average velocity of one (1) foot per second must be maintained. In the absence of experimentally determined values, the design oxygen requirements for all activated sludge processes must be 1.1 lb 02 per lb of design peak hour BOD5 applied to the aeration tanks, except the extended aeration process, for which the value must be one point five (1.5) to include endogenous respiration requirements. (7-1-26) (a) Where nitrification is required or will occur, the oxygen requirement for oxidizing ammonia must be added to the above requirement for carbonaceous BOD5 removal and endogenous respiration requirements. The nitrogenous oxygen demand (NOD) must be four point six (4.6) times the diurnal peak hour total Kjeldahl nitrogen content of the aeration tank influent. In addition, the oxygen demands due to recycle flows must be considered due to the high concentrations of BOD5 and total Kjeldahl nitrogen associated with such flows. (7-1-26) (b) Aeration equipment design must meet maximum oxygen demand, maintain process performance with the largest unit out of service, and provide for varying the amount of oxygen transferred in proportion to the load demand on the plant. (7-1-26) (2) Air requirements including, but not limited to, process air, channel aeration, aerobic digestion, and miscellaneous plant air must be submitted to the Department in the PER. Blowers must be provided in multiple units, so arranged and in such capacities as to meet the maximum air demand with the single largest unit out of service. The design must also provide for varying the volume of air delivered in proportion to the load demand of the plant. Aeration equipment must be easily adjustable in increments and maintain solids suspension within these limits. (7-1-26) (3) Mechanical Aeration Systems. (3-31-22) (a) The mechanism and drive unit must be designed for the expected conditions in the aeration tank in terms of the power performance. Certified testing must be provided to verify mechanical aerator performance. Refer to applicable provisions of Subsection 490.02. In the absence of specific design information, the oxygen requirements must be calculated for mechanical aeration systems using a transfer rate not to exceed two (2) pounds of oxygen per horsepower per hour in clean water under standard test conditions. Design transfer efficiencies must be included in the specifications. (7-1-26) (b) Motors, gear housing, bearings, grease fittings, and other mechanical units, must be easily accessible and protected from inundation and spray as necessary for proper functioning of the unit. (7-1-26) (c) Where extended cold weather conditions occur, the aerator mechanism and associated structure must be protected from freezing due to splashing. Due to high heat loss, subsequent treatment units must be protected from freezing. (7-1-26) b. Non-aerated tanks or zones within aeration tanks must have mixing equipment adequate to fully mix the contents. Calculations must be provided in the PER for sizing this equipment. (7-1-26) c. Return Sludge Equipment. (3-31-22) i. The rate of sludge return must be varied by adjustable weirs or variable speed pumps to pump sludge. For very small wastewater systems, timers may be used for sludge return. The return sludge rate of withdrawal from the final settling tank is a function of the concentration of suspended solids in the mixed liquor entering it, the sludge volume index of these solids, and the length of time these solids are retained in the settling tank. (7-1-26) ii. If a consolidated return sludge pump facility is used, the maximum return sludge capacity must be obtained with the largest pump out of service. If individual sludge pumps are used at each settling basin, the pumps must be designed to facilitate their rapid removal and replacement with a standby unit stored at the treatment plant site. If air lifts are used for returning sludge from each settling tank hopper, no standby unit is required provided the design of the air lifts facilitate their rapid and easy cleaning and provided other suitable standby measures are made available. Air lifts must be at least three (3) inches in diameter unless otherwise approved by the Department. IDAHO ADMINISTRATIVE CODE IDAPA 58.01.16 Department of Environmental Quality Wastewater Rules Section 490 Page 44 (7-1-26) iii. Discharge piping must be at least four (4) inches in diameter and must be designed to maintain a velocity of not less than two (2) feet per second when return sludge facilities are operating at normal return sludge rates. Suitable devices for observing, sampling, and controlling return activated sludge flow from each settling tank hopper must be provided. (7-1-26) iv. Means for observing, measuring, sampling, and controlling waste activated sludge flow must be provided. (7-1-26) d. Sequencing Batch Reactors. (7-1-26) i. The fill and draw mode of the activated sludge process commonly termed the Sequencing Batch Reactor may be used in Idaho. The design must be based on experience at other facilities and meet the applicable provisions under Sections 450, 470 and 490, except as modified in Subsections 490.02.d.ii. through 490.02.d.xii. Continuity and reliability of treatment equal to that of the continuous flow through modes of the activated sludge process must be provided. (7-1-26) ii. At least two (2) tanks must be provided. (7-1-26) iii. The decantable volume and capacity of the sequencing batch reactor system with the largest basin out of service must be sized to pass at least seventy-five (75) percent of the design maximum day flow without changing cycle times. A decantable volume of at least four (4) hours with the largest basin out of service based on one hundred (100) percent of the design maximum day flow is permissible. (7-1-26) iv. System reliability with any single tank unit out of service and the instantaneous delivery of flow must be evaluated in the design of decanter weirs and approach velocities. (7-1-26) v. Reactor design must provide for scum removal and prevent overflow of settled solids. (7-1-26) vi. An adequate zone of separation between the sludge blanket and the decanters must be maintained throughout the decant phase. Decanters which draw the treated effluent from near the water surface throughout the decant phase are recommended. (7-1-26) vii. Solids management to accommodate basin dewatering must be considered. (7-1-26) viii. The blowers must be provided in multiple units, so arranged and in such capacities as to meet the maximum air demand in the oxic portions of the fill/react and react phases of the cycle with the single largest unit out of service. (7-1-26) ix. Mechanical mixing independent of aeration must be provided for all systems where biological phosphorus removal or denitrification is required. (7-1-26) x. All twenty-four (24) hour effluent quality composite samples for compliance reporting or monitoring plant operations must be flow-paced and include samples collected at the beginning and end of each decant phase. (7-1-26) xi. A programmable logic controller (PLC) must be provided. Multiple PLCs must be provided as necessary to assure rapid process recovery or minimize the deterioration of effluent quality from the failure of a single controller. An uninterruptible power supply with electrical surge protection must be provided for each PLC to retain program memory (i.e., process control program, last-known set points and measured process/equipment status, etc.) through a power loss. A hard-wired backup for manual override must be provided in addition to automatic process control. Both automatic and manual controls must allow independent operation of each tank. In addition, a fail-safe control allowing at least twenty (20) minutes of settling between the react and decant phases must be provided. The fail-safe control must not be adjusted by the operator. (7-1-26) xii. A sufficient quantity of spare parts must be on hand and consideration given to parts with a low IDAHO ADMINISTRATIVE CODE IDAPA 58.01.16 Department of Environmental Quality Wastewater Rules Section 493 Page 45 mean time between failure such as electrical relays and solid state electronics. (7-1-26) 03. Other Biological Systems. (3-31-22) a. Biological treatment processes not included in these rules must be in accordance with Subsection 450.03. (7-1-26) b. Details for Membrane Bioreactor (MBR) plants must be submitted and approved in the PER. In addition to the provisions of Section 411, details must include plant layout, calculations for hydraulic capacity and air required, membrane technology considered and membrane type and model selected, results from similar type MBR plants already in operation, and anticipated sludge production. (7-1-26) 491. -- 492. (RESERVED) 493. FACILITY AND DESIGN STANDARDS FOR MUNICIPAL WASTEWATER SYSTEMS: WASTEWATER LAGOONS. 01. General. (3-31-22) a. These rules pertain to all new, and existing material modified, municipal wastewater lagoons, including discharging or total containment lagoons, municipal wastewater treatment lagoons, municipal wastewater or recycled water storage lagoons, and any other municipal wastewater lagoons not regulated under IDAPA 58.01.03, “Individual/Subsurface Sewage Disposal Rules and Rules for Cleaning of Septic Tanks,” that have the potential to degrade waters. Lagoons are also sometimes referred to as ponds. Section 493 does not apply to industrial lagoons or mining tailings ponds, single-family dwellings utilizing a single lagoon, two (2) cell infiltrative system, those animal waste lagoons excluded from review under Section 39-118, Idaho Code, or storm water ponds. (7-1-26) b. Lagoons utilized for equalization and sludge storage do not have to meet the requirements of Subsections 493.06 through 493.08, but must comply with all other applicable subsections. (7-1-26) 02. Seepage Testing. (7-1-26) a. All lagoons covered under this section must be seepage tested at an interval of at least every ten (10) years by or under the supervision of an Idaho licensed professional engineer or an Idaho licensed professional geologist. (7-1-26) b. As part of the construction process, all new lagoons must be seepage tested by or under the supervision of an Idaho licensed professional engineer or an Idaho licensed professional geologist. (7-1-26) c. Lagoons must be seepage tested if a change of condition to the liner occurs that may affect its permeability, including but not limited to liner repair below the high water line, liner replacement, lagoon dewatering of soil-lined lagoons which results in desiccation of the soil liner, seal installation, or earthwork affecting liner integrity. Prior to performing activities that may affect liner permeability, such as solids removal, the system owner must contact the Department in writing to determine if a seepage test will be required prior to returning the lagoon to service. (7-1-26) d. The procedure for performing a seepage test or alternative analysis must be approved by the Department prior to conducting the test, and the test results must be submitted to the Department for review. (7-1-26) 03. Allowable Seepage Rates. (3-31-22) a. Lagoons must be designed and sealed such that seepage loss through the seal is as low as possible. Seals consisting of soils, bentonite, or synthetic liners may be considered, provided the permeability, durability, and integrity of the proposed material can be satisfactorily demonstrated for anticipated conditions. (7-1-26) b. The seepage rate for lagoons constructed after April 15, 2007, must be no more than zero point one hundred twenty-five (0.125) inches (1/8 inch) per day. The leakage rate for existing lagoons constructed prior to April IDAHO ADMINISTRATIVE CODE IDAPA 58.01.16 Department of Environmental Quality Wastewater Rules Section 493 Page 46 15, 2007, must be no more than zero point twenty-five (0.25) inches (1/4 inch) per day. (7-1-26) c. For lagoons located over sensitive aquifers or with a documented direct hydraulic connection to a 303d listed stream segment, the seepage rate may be no more than zero point one hundred twenty-five (0.125) inches (one-eighth (1/8) inch) per day. (7-1-26) 04. Lagoons Leaking Above the Allowable Amount. If a lagoon is found to be leaking at a rate higher than allowed, the owner of the lagoon, in accordance with a schedule negotiated with and approved by the Director, is required to: (7-1-26) a. Repair the leak and retest for compliance; (3-31-22) b. Re-line the lagoon and retest for compliance with a leakage rate of no more than zero point one hundred twenty-five (0.125) inches (1/8 inch) per day regardless of the original lagoon construction date; (7-1-26) c. Drain the lagoon in an approved manner and stop using the lagoon; or (3-31-22) d. Determine the impact of the leaking lagoon on the environment based on groundwater sampling and modeling. The procedure for performing groundwater sampling and monitoring must be approved by the Department. Any impact must comply with IDAPA 58.01.11, “Groundwater Quality Rule,” and IDAPA 58.01.02, “Water Quality Standards.” If the impact does not comply with IDAPA 58.01.11, and IDAPA 58.01.02, the owner of the lagoon must follow one (1) of the steps set out in Subsections 493.04.a. through 493.04.c. (7-1-26) 05. Location. (3-31-22) a. Wastewater lagoons must be placed in accordance with the provisions in Subsection 450.01.c. In all cases, the design location must consider odors, nuisances, etc. This distance is to the toe of the exterior slope of the dike or to the top of the cut for a lagoon placed into a hillside. More restrictive planning and zoning or other local requirements may apply. (7-1-26) b. A minimum separation of two (2) feet between the bottom of the lagoon and the maximum groundwater elevation must be provided in the design. (7-1-26) c. A minimum separation of two (2) feet between the lagoon bottom and any bedrock formation must be provided in the design. (7-1-26) 06. Basis of Design. (3-31-22) a. Design variables such as climatic conditions, odor, lagoon depth, multiple units, detention time, and additional treatment units must be considered with respect to applicable standards for BOD5, total suspended solids (TSS), fecal coliform, dissolved oxygen (DO), pH, and other effluent requirements and limits. (7-1-26) b. The PER must include all design criteria for the development of the lagoon design. (7-1-26) c. The reaction rate coefficient for domestic wastewater which includes some industrial wastes, other wastes, and partially treated wastewater must be determined experimentally for various conditions which might be encountered in the lagoons or actual data from lagoons in similar climates. Conversion of the reaction rate coefficient at other temperatures must be made based on experimental data. (7-1-26) d. Oxygen requirements are based on the design average BOD5 loading, the degree of treatment, and the concentration of suspended solids to be maintained. If needed for treatment objectives, aeration equipment must be designed to maintain a minimum dissolved oxygen level of two (2) mg/L in the lagoons at all times. Suitable protection from weather must be provided for electrical controls. Aerated cells must be followed by a polishing cell with a detention time of a minimum of twenty-four (24) hours. (7-1-26) 07. Industrial Wastes as a Part of the Municipal Wastewater. (3-31-22) IDAHO ADMINISTRATIVE CODE IDAPA 58.01.16 Department of Environmental Quality Wastewater Rules Section 493 Page 47 a. Design must account for the type and effects of industrial wastes on the treatment process. (7-1-26) b. Industrial wastes must not be discharged to lagoons without assessment of the effects such substances may have upon the treatment process or disposal requirements in accordance with state and federal laws. (7-1-26) 08. Number of Cells. (7-1-26) a. A wastewater treatment lagoon system must consist of a minimum of three (3) cells designed to facilitate both series and parallel operations. Two (2) cell systems may be utilized in very small installations of less than fifty thousand (50,000) gallons per day average day flow. (7-1-26) b. All systems must be designed with piping flexibility to permit isolation of any cell without affecting the transfer and disposal capabilities of the total system. (7-1-26) 09. Lagoon Construction Details. (7-1-26) a. Embankments and Dikes. (3-31-22) i. Dikes must be constructed of relatively impervious soil and compacted to at least ninety-five (95) percent Standard Proctor Density to form a stable structure. Vegetation and other unsuitable materials must be removed from the area where the embankment is to be placed. (7-1-26) ii. The minimum dike top width must be ten (10) feet to permit access for maintenance vehicles. (7-1-26) iii. Inner and outer dike slopes must not be steeper than one (1) vertical to three (3) horizontal (1:3). (7-1-26) iv. Inner slopes must not be flatter than one (1) vertical to four (4) horizontal (1:4). Flatter slopes can be specified for larger installations because of wave action but have the disadvantage of added shallow areas being conducive to emergent vegetation. Outer slopes must be sufficient to prevent surface runoff from entering the lagoons. (7-1-26) v. Minimum freeboard must be three (3) feet, except for small systems of less than fifty thousand (50,000) gallons per day average day flow, two (2) feet is acceptable. (7-1-26) vi. The minimum operating depth must be designed to prevent growth of aquatic plants and damage to the dikes, bottom, control structures, aeration equipment, and other appurtenances. Operating depth must not be less than two (2) feet. (7-1-26) b. Lagoon Bottom. (7-1-26) i. Soil used in constructing the lagoon bottom (not including the seal) and dike cores must be relatively incompressible and tight and compacted to at least ninety-five (95) percent Standard Proctor Density. (7-1-26) ii. Lagoons must be sealed such that seepage loss through the seal complies with Subsection 493.03. Results of a testing program which substantiates the adequacy of the proposed seal must be incorporated into or accompany the PER. (7-1-26) c. Miscellaneous. (3-31-22) i. The lagoon area must be enclosed with an adequate fence to prevent livestock entering and discourage trespassing. This requirement does not apply to lagoon areas which store or impound Class A recycled water. (7-1-26) IDAHO ADMINISTRATIVE CODE IDAPA 58.01.16 Department of Environmental Quality Wastewater Rules Section 500 Page 48 ii. An all-weather access road must be provided to the lagoon site to allow year-round maintenance of the facility. (7-1-26) iii. Appropriate permanent signs must be provided along the fence around the lagoon to designate the nature of the facility and advise against trespassing. At least one (1) sign must be provided on each side of the site and one (1) for every five hundred (500) feet of its perimeter. (7-1-26) iv. Flow measurement requirements are provided in Subsection 450.06.c. Effective weather protection must be provided for the recording equipment. (7-1-26) v. A groundwater monitoring plan must be submitted to the Department for review and approval as a part of the PER. Unless otherwise approved by the Department, a system of wells or lysimeters is required around the perimeter of the lagoon site to facilitate groundwater monitoring. (7-1-26) 10. Closure. The owner must notify the Department at least six (6) months prior to permanently removing any wastewater lagoon facility from service, including any treatment or storage lagoon. Prior to commencing closure activities, the owner must: (7-1-26) a. Participate in a pre-closure on-site meeting with the Department; (3-31-22) b. Develop a site closure plan that identifies specific closure, site characterization, or cleanup tasks with scheduled task completion dates in accordance with agreements made at the pre-closure on-site meeting; and (7-1-26) c. Submit the completed site closure plan to the Department for review and approval within forty-five (45) days of the pre-closure on-site meeting. The facility must complete the Department approved site closure plan. (7-1-26) 494. -- 499. (RESERVED) 500. FACILITY AND DESIGN STANDARDS FOR MUNICIPAL WASTEWATER SYSTEMS: DISINFECTION. 01. General. Disinfection of treated wastewater must be provided as necessary to meet applicable standards. The design of new municipal wastewater treatment facilities, or municipal wastewater treatment facilities undergoing material modifications, must meet the bacterial standards and the disinfectant residual limit for the effluent. The disinfection process must be selected after due consideration of waste characteristics, type of treatment process provided prior to disinfection, waste flow rates, pH of waste, disinfectant demand rates, current technology application, cost of equipment and chemicals, power cost, and maintenance requirements as determined in the PER. Where a disinfection process other than chlorination, ultraviolet disinfection, or ozone is proposed, supporting data from pilot plant installations or similar full scale installations are required as a basis for the design of the system. (7-1-26) 02. Determining the Necessity for Disinfection. Disinfection at a municipal wastewater treatment facility is required when: (7-1-26) a. Required by a surface water discharge permit; or (7-1-26) b. The effluent is disposed to a facility required to meet the disinfection requirements in IDAPA 58.01.17, “Recycled Water Rules.” (7-1-26) c. The effluent is disposed to a facility, where groundwater contamination has exceeded the bacterial limit in IDAPA 58.01.11, “Groundwater Quality Rule,” and it has been determined by the Department that disinfection is required. (7-1-26) 03. Chlorine Disinfection. (3-31-22) IDAHO ADMINISTRATIVE CODE IDAPA 58.01.16 Department of Environmental Quality Wastewater Rules Section 500 Page 49 a. Chlorine is available for disinfection in gas, liquid (hypochlorite solution), and pellet (hypochlorite tablet) form. The type of chlorine must be evaluated in the facility plan or PER. (7-1-26) b. For disinfection, the capacity must be adequate to produce an effluent that will meet the applicable bacterial limits specified by the regulatory agency for that installation. Required disinfection capacity will vary, depending on the uses and points of application of the disinfection chemical. The chlorination system must be designed on a rational basis and calculations justifying the equipment sizing and number of units and submitted for the whole operating range of flow rates for the type of control to be used. System design considerations must include the controlling wastewater flow meter (sensitivity and location), telemetering equipment, and chlorination controls. (7-1-26) c. Piping systems must be as simple as practicable, specifically selected and manufactured to be suitable for chlorine service, with consideration for minimizing number of joints. Piping must be well supported and protected against temperature extremes. Venting of excess gas must be provided. Special considerations must be given to piping and fixture selection for hypochlorite and chlorine use. (7-1-26) d. Standby equipment of sufficient capacity must be available to replace the largest unit during shutdowns. Spare parts must be available for all disinfection equipment to replace parts which are subject to wear and breakage. (7-1-26) e. Housing. (3-31-22) i. Gas chlorination equipment and chlorine cylinders must be housed in a building. If this building is used for other purposes, a gas-tight room must separate this equipment from any other portion of the building. Floor drains from the chlorine room must not be connected to floor drains from other rooms. Doors to this room must open only to the outside of the building and be equipped with panic hardware. Rooms must permit easy access to all equipment. Local and state safety requirements must be satisfied. (7-1-26) ii. Electrical and ventilation equipment must comply with local and state codes. (7-1-26) iii. Respiratory air-pac protection equipment must be available where chlorine gas is handled, and be stored at a convenient location, but not inside any room where chlorine is used or stored. Instructions for using the equipment must be posted. (7-1-26) 04. Dechlorination. (3-31-22) a. Types. (3-31-22) i. Dechlorination of wastewater effluent must be provided when required to meet effluent limits to reduce the toxicity due to chlorine residuals. (7-1-26) ii. The type of dechlorination system must be selected considering the type of chemical storage required, amount of chemical needed, ease of operation, compatibility with existing equipment, and safety. (7-1-26) b. The dosage of dechlorination chemical must consider the residual chlorine in the effluent, the final residual chlorine limit, and the form of the dechlorinating chemical used. (7-1-26) c. The same requirements apply for standby equipment and spare parts as chlorination systems. See Subsection 500.03.d. (7-1-26) d. The requirements for housing sulfur dioxide gas equipment must follow the same guidelines as used for chlorine gas. Refer to Subsection 500.03.e. for specific details. When using solutions of the dechlorinating compounds, the solutions must be stored in a room that meets the safety and handling requirements set forth in Subsection 450.07. The mixing, storage, and solution delivery areas must be designed to contain or route solution spillage or leakage away from traffic areas to an appropriate containment unit. (7-1-26) e. The respiratory air-pac protection equipment is the same as for chlorine. See Subsection IDAHO ADMINISTRATIVE CODE IDAPA 58.01.16 Department of Environmental Quality Wastewater Rules Section 500 Page 50 500.03.e.iii. (7-1-26) 05. Ultraviolet (UV) Radiation. (3-31-22) a. The following documents or other references acceptable to the Department must be used for UV system sizing and facility design. (7-1-26) i. “Wastewater Engineering, Treatment and Reuse,” Metcalf and Eddy. (7-1-26) ii. For recycled water applications, “Ultraviolet Disinfection Guidelines for Drinking Water and Water Reuse,” National Water Research Institute/AWWA Research Foundation. (7-1-26) b. All UV disinfection must be designed based on expected ranges of UV transmittance (UVT). For facilities larger than five million gallons per day (5 mgd) (design peak hour flow), or facilities that have industries that vary flows throughout the year, collection of one (1) year’s worth of UVT data (four (4) times per day) prior to the PER is required unless otherwise approved by the Department. (7-1-26) c. All UV disinfection facilities must include the following: (7-1-26) i. A minimum of two (2) channels (or justification for using a smaller system); and (7-1-26) ii. A minimum of two (2) banks of UV lamps per channel (or justification for using a smaller system). (7-1-26) d. The PER for all UV disinfection facilities must include a description of the following: (7-1-26) i. The redundancy provided; (7-1-26) ii. The upstream flow splitting device (which splits flow to the two (2) or more UV channels); (7-1-26) iii. Water level control device; (7-1-26) iv. Method used to take a channel off-line for maintenance, and method to dewater a channel; (7-1-26) v. Type of UV system technology (low-pressure low-intensity, low-pressure high-intensity, medium pressure, etc.), with consideration given to power consumption; (7-1-26) vi. Summary of UVT data and collimated beam data; (7-1-26) vii. Climate controls system requirements to ensure adequate UV system performance during summer peak temperature period; (7-1-26) viii. Maintenance requirements including removal (cleaning) of biofilms from the channel walls upstream and downstream of the UV system; (7-1-26) ix. Alarming and controls; (7-1-26) x. Procedure used for UV system sizing; and (7-1-26) xi. Design criteria must include: (7-1-26) (1) Design UVT; (7-1-26) (2) TSS; (7-1-26) (3) Design water temperature range; (7-1-26) IDAHO ADMINISTRATIVE CODE IDAPA 58.01.16 Department of Environmental Quality Wastewater Rules Section 510 Page 51 (4) Dose; (7-1-26) (5) End of lamp life factor; (7-1-26) (6) Fouling factor; (7-1-26) (7) Quartz sleeve transmittance factor; (7-1-26) (8) Design peak hour flow; (7-1-26) (9) Existing minimum flow; (7-1-26) (10) Number of channels; (7-1-26) (11) Disinfection requirements (coliform concentration); and (7-1-26) (12) Maximum head-loss from upstream of the first bank to downstream of the last bank of lamps (lamp spacing divided by two (2)). (3-31-22) e. Use of bioassay method of UV system sizing is encouraged if all manufacturers under consideration have existing bioassays performed using identical protocol, and the bioassay was performed under conditions similar to the design application. Use of the bioassay method of UV system sizing is discouraged if these conditions cannot be met. (7-1-26) f. Closed chamber units will be reviewed on a case-by-case basis in accordance with Subsection 450.03.b. (7-1-26) 06. Ozone. Ozone systems for disinfection will be evaluated by the Department on a case-by-case basis. Design of these systems must be based upon experience at similar full-scale installations or thoroughly documented prototype testing of the wastewater. (7-1-26) 501. -- 509. (RESERVED) 510. FACILITY AND DESIGN STANDARDS FOR MUNICIPAL WASTEWATER SYSTEMS: SUPPLEMENTAL TREATMENT PROCESSES. 01. Chemical Treatment. Chemical treatment in various forms can be used to aid in phosphorus and nitrogen removal, pH adjustment, enhanced clarification, and sludge conditioning. (7-1-26) a. Chemical treatment must be evaluated for each specific treatment process in the PER and must be compatible with other liquids, solids and air treatment processes. Laboratory tests such as jar tests or pilot-scale studies on actual process wastewater must be used to select appropriate chemicals and dosage ranges. (7-1-26) b. When settling aids are used during the primary clarification process to enhance solids removal in the primary treatment process, the additional solids volume must be accounted for in pumping, solids handling, stabilization, and disposal processes. The coagulant must be added and mixed before the sedimentation process. Flocculants, if used, must be added after the coagulant. The design must provide for chemical addition points at several locations to give process personnel the opportunity to adjust for optimum performance. (7-1-26) 02. Filtration for Tertiary Treatment. Details for treatment facilities with tertiary treatment utilizing membrane, media, cloth, or reverse osmosis must be submitted and approved in the PER. In addition to the provisions of Section 411, the PER must include plant layout, calculations for hydraulic capacity and air required, filtration technology considered and the type and model selected, results from similar type filtration systems already in operation, and anticipated sludge production. (7-1-26) 511. -- 518. (RESERVED) IDAHO ADMINISTRATIVE CODE IDAPA 58.01.16 Department of Environmental Quality Wastewater Rules Section 519 Page 52 519. FACILITY AND DESIGN STANDARDS FOR MUNICIPAL WASTEWATER SYSTEMS: SEPTAGE TRANSFER STATIONS. Prior to construction of a new septage transfer station or upon material modification of an approved existing station, the owner of the station must satisfy the following requirements. (7-1-26) 01. Design. Septage holding tanks, transfer/storage tanks, and transfer hoses for either type of tank will meet the applicable provisions of Subsections 519.01.a. through 519.01.c. (7-1-26) a. All tanks will be watertight, not open to the air, and provided with containment structures to prevent the discharge of septage spills to the surrounding environment. (7-1-26) b. All piping, transfer hoses, valves, and connections will be watertight, accessible, and capable of being cleaned, repaired, and replaced. (7-1-26) c. All inlet and outlet connections will be constructed and maintained such that septage will not leak, spill, or overflow the holding tank. (7-1-26) d. No septage holding or transfer/storage tank will be permitted within the one hundred (100) year flood plain as defined and delineated by the flood insurance rate maps published by the Federal Emergency Management Agency. (7-1-26) e. Odor controls will be provided to mitigate nuisance odor during transfer. Odor control may be attained by employing appropriate setback distances to neighboring facilities, using appropriate air scrubbing technologies in conjunction with an enclosed transfer station or other suitably engineered configuration that provides assurances of minimal odor nuisances. (7-1-26) f. The property is owned by the individuals operating the septage transfer station, or the property owner has granted permission to use the property. (7-1-26) g. Septage transfer stations will provide total containment for the entire volume of the holding tanks and transfer/storage tanks in the event of spilled septage. (7-1-26) h. Truck washing facilities will be constructed to retain all wash water on site. (7-1-26) 02. Plans and Specifications. In addition to the provisions of Section 400, plans and specifications for septage transfer stations will provide or identify: (7-1-26) a. A map which identifies the proposed septage holding or transfer/storage tank location; (7-1-26) b. The footprint of the proposed activity area; (7-1-26) c. All access roads and access control measures; (7-1-26) d. All roads, property boundary lines, and structures within two hundred (200) feet of the septage holding or transfer/storage tank location; any structures on the property; and any easements or rights-of-way which exist on the property; (7-1-26) e. Surrounding land use within two hundred (200) feet of the footprint of the proposed activity area on which the septage holding or transfer/storage tank is proposed to be located; and (7-1-26) f. A spill response plan, describing spill response equipment and disinfection and containment capability at the septage transfer station, must be submitted to and approved by the Department. (7-1-26) 03. Record Keeping. Every owner of a septage transfer station will maintain the following records for a minimum of five (5) years. (7-1-26) IDAHO ADMINISTRATIVE CODE IDAPA 58.01.16 Department of Environmental Quality Wastewater Rules Section 520 Page 53 a. For each load of septage received: (3-31-22) i. The date received or picked up; (3-31-22) ii. The name and address of the clients from whom the septage was received; and (7-1-26) iii. The volume of the septage received, in gallons; and (3-31-22) b. Records indicating the final disposal destinations for septage removed from the transfer/storage tank. (7-1-26) 520. FACILITY AND DESIGN STANDARDS FOR MUNICIPAL WASTEWATER SYSTEMS: HANDLING AND TREATMENT OF SEPTAGE AT A WASTEWATER TREATMENT FACILITY. 01. General. Septage disposal at a wastewater treatment plant is at the discretion of the owner of the wastewater treatment plant, unless other conditions apply. All treatment facilities require special design considerations prior to the acceptance of septage. Prior to acceptance of septage at a wastewater treatment facility, the plan for doing so must be addressed in the Facility Plan or PER. (7-1-26) 02. Characteristics. Prior to acceptance at a treatment facility, septage must be characterized. The U.S. EPA Handbook entitled “Septage Treatment and Disposal” 1984, EPA-625/6-84-009) may be used to estimate common parameters for septage and municipal wastewater. (7-1-26) 03. Considerations. An engineering evaluation of the existing treatment facility and the anticipated septage loading must be conducted prior to receiving septage at the treatment facility. For proposed treatment facility expansion and upgrading, the PER or facility plan must include anticipated septage loading in addressing treatment facility sizing and process selection. (7-1-26) 521. -- 599. (RESERVED)