020-12 Wyo. Code R. § 12-10

Current through April 27, 2019

Section 12-10 - Treatment

(a) Design capacity. The capacity of the water treatment or water production system shall be designed for the maximum daily demand at the design year.

(b) Presedimentation. Raw waters which have episodes of turbidity in excess of 1,000 TU for a period of one week or longer shall be presettled.

• (i) Detention time. Basins without mechanical sludge collection equipment shall have a minimum detention time of three days. Basins with mechanical sludge collection equipment shall have a minimum detention time of three hours.

• (ii) Inlet. Inlet flow shall be evenly dispersed along the inlet of the basin.

• (iii) Drains. Basins shall have a minimum of one 8-inch (20 cm) drain line to completely dewater the facility.

• (iv) Bottom slope. Basins shall have a bottom slope to drain of 1/4 inch per foot (20 mm/m) without mechanical sludge collection equipment and 2 inches per foot (16 cm/m) with mechanical sludge collection equipment.

• (v) Bypass. Basin bypass provisions shall be included in the process piping.

(c) Rapid mix. Rapid dispersal of chemicals throughout the water shall be accomplished by mechanical mixers, jet mixers, static mixers, or hydraulic jump.

• (i) Mixing intensity. For mechanical mixers, the minimum Gt (velocity gradient (sec-1) x t (sec)) provided at maximum daily flow shall be 27,000.

• (ii) Mixing time. The detention time in a flash mixing chamber shall not exceed 30 seconds at maximum daily flow conditions.

• (iii) Drain. The basin shall have a drain.

(d) Flocculation. The low velocity agitation of chemically treated water shall be accomplished by mechanical flocculators.

• (i) Detention time. A minimum of 10 minutes detention time shall be provided.

• (ii) Mixing intensity. The velocity gradient (G value) imposed shall be adjustable by providing variable speed drives or shall be designed to be 30 sec-1 if a single basin is provided, 20 sec-1 in the final basin of a two stage system, and 10 sec-1 in the final basin of a three stage system. For a single speed drive system, the tip speed of the mixer shall not exceed 3 feet per second (0.91 m/sec). Variable speed drives shall provide tip speeds of 0.5 to 3.0 feet per second (0.15-0.91 m/sec).

• (iii) Drains. Flocculation basins shall have a minimum of one drain line to dewater the facility.

• (iv) Piping. The velocity of flocculated water through pipes or conduits to settling basins shall not be less than 0.5 or greater than 1.5 feet per second (0.15-0.46 m/sec).

(e) Sedimentation basins.

• (i) Diameter. The maximum diameter in circular basins shall be 80 feet.

• (ii) Overflow rate. The basin overflow rate shall not exceed 1,000 gpd/ft² (41 m³/m^2·d) at design conditions.

• (iii) Weir loading rate. Weir loading rates shall not exceed 20,000 gpd/ft (2480 m³m·d) of length. The weir length shall be computed as the length of the centerline of the launder. Where the weir is located at 3/4 the radius, the weir may be loaded at 36,000 gpd/ft (4464 m³/m·d).

• (iv) Side water depth. The minimum basin side water depth shall be 8 feet (2.43 m) if mechanical sludge collection equipment is provided or basins or basin sludge hopper segments are less than 100 square feet (9.3 m) in surface area and 15 feet (4.6 m) if basins are manually cleaned. Mechanical sludge collection equipment includes mechanically driven drives that use scrapers or differential water level to collect the sludge.

• (v) Freeboard. The outer walls of settling basins shall extend at least 12 inches (30.5 cm) above the surrounding ground and provide at least 12 inches (30.5 cm) of freeboard to the water surface. Where basin walls are less than 4 feet (1.22 m) above the surrounding ground, a fence or other debris barrier shall be provided on the wall.

• (vi) Inlet devices. Inlets shall be designed to distribute the water equally and at uniform velocities. Open ports, submerged ports, and similar entrance arrangements are required. A baffle should be constructed across the basin close to the inlet end and should project several feet below the water surface to dissipate inlet velocities and provide uniform flows across the basin.

• (vii) Velocity. The velocity through settling basins shall not exceed 0.5 feet per minute (0.15 m/min). The basins must be designed to minimize short-circuiting.

• (viii) Sludge collection. If settleable organics are present in the water or if there is a history of organically related taste and odor problems, mechanical sludge collection shall be provided.

• (ix) Sludge removal. Sludge removal design shall provide that sludge pipes shall be not less than 6 inches (15.2 cm) in diameter and arranged to facilitate cleaning. Valves on the sludge line shall be located outside the tank.

• (x) Flushing lines. Flushing lines or hydrants shall be provided near the basins.

• (xi) Drainage. Basin bottoms shall slope toward the drain at not less than 1 inch per foot (8 cm/m) where mechanical sludge collection equipment is provided and 1/4 inch per foot (2 cm/m) where no mechanical sludge collection equipment is provided.

(f) Softening sedimentation - clarification. Conventional sedimentation -clarification as described above shall be provided in softening operations, except for softening a groundwater supply of constant quality. Where a groundwater supply is softened, the requirements may be modified as follows:

• (i) Overflow rate. The basin overflow rate at the design flow shall not exceed 2,100 gpd/ft² (86 m³/m^2·d).

• (ii) Sludge. Mechanical sludge removal shall be provided and shall be designed to handle a load of 40 lbs/foot (60 kg/m) of collector scraper arm length.

• (iii) Other design considerations shall be the same as conventional sedimentation - clarification.

(g) Solids contact units. These treatment units are acceptable for combined softening and clarification of well water where water quality characteristics are not variable and flow rates are uniform. The units shall be designed to meet the criteria detailed previously.

• (i) Such units may be considered for use as clarifiers without softening when they are designed to meet the criteria detailed in the conventional sedimentation - clarification.

• (ii) These units may also be used for other treatment purposes, such as rapid mixing, flocculation, etc., when the individual components of the solids contact units are designed in accordance with the design criteria for that individual treatment process as described above.

(h) Settling tube clarifiers. Shallow depth sedimentation devices or tube clarifier systems of the essentially horizontal or steeply inclined types may be used when designed as follows:

• (i) Sludge removal. Sludge shall be removed using 45 or steeper hoppered bottoms, or mechanical devices that move the sludge to hoppers, or devices that remove settled sludge from the basin floor using differential hydraulic level.

• (ii) Tube cleaning. A method of tube cleaning shall be provided. This may include a provision for obtaining a rapid reduction in clarifier water surface elevation, a water jet spray system, or an air scour system. Where cleaning is automatic, controls shall be provided to cease clarifier operation during tube cleaning and a 20 minute rest period.

• (iii) Tube placement. Tops of tubes shall be more than 12 inches (0.3 m) from the underside of the launder and more than 18 inches (0.46 m) from the water surface.

• (iv) Loading rates. The maximum overflow rate shall be less than 2.0 gpm/sq ft (62.7 m³/m²·d) based on the surface area of the basin covered by the tubes.

• (v) Effluent launderers. The spacing between effluent launderers shall not exceed three times the distance from the water surface to the top of the tube modules.

(i) Filtration.

• (i) Pressure granular media filters. Vertical or horizontal pressure filters shall not be used for filtration of surface waters. Pressure filters may be used for groundwater filtration, including iron and manganese removal.

• (ii) Gravity filters.
  • (A) Slow rate sand filters. These types of filters may be used when maximum raw water turbidity is less than 50 TUs and the turbidity present is not attributable to colloidal clay. Maximum color shall not exceed 30 units.
    • (I) Loading rates. The allowable loading rates at maximum daily demands shall not exceed 0.1 gpm/ft² (5.9 m³/m^{2 ·}d) unless satisfactory pilot testing is completed prior to design which shows a higher rate is appropriate.
    • (II) Number of filters. At least two units shall be provided. Where only two units are provided, each shall be capable of meeting the plant design capacity at the maximum filtration rate. Where more than two filter units are provided, the filters shall be capable of meeting the plant design at the maximum filtration rate with one filter removed from service.
    • (III) Underdrains. Each filter unit shall be equipped with a main drain and an adequate number of lateral underdrains to collect the filtered water. The underdrains shall be so spaced that the maximum velocity of the water flow in the lateral underdrain will not exceed 0.75 feet per second (0.22 m/sec). The maximum spacing of the laterals shall not exceed 12 feet (3.7 m).
    • (IV) Filter material. Filter sand shall be placed on graded gravel layers for a minimum sand depth of 30 inches (0.76 m). The effective size shall be between 0.15 mm and 0.35 mm. The uniformity coefficient shall not exceed 2.0. The sand shall be clean and free from foreign matter. The supporting gravel shall conform to the size and depth distribution provided for rapid rate gravity filters.
    • (V) Depth of water on filter beds. Design shall provide a depth of at least 3 feet (0.91 m) of water over the sand. Influent water shall enter the water surface at a velocity of less than 2 feet per second (0.61 m/sec). An overflow shall be provided at the maximum water surface elevation.
    • (VI) Appurtenances. Each filter shall be equipped with loss of head gauge; an orifice, Venturi meter, or other suitable metering device installed on each filter to control the rate of filtration; and an effluent pipe designed to maintain the water level above the top of the filter sand.
    • (VII) Covers. When covers are provided for temperature or sunlight control, they shall be designed to allow adequate headroom above the top of the sand and adequate access ports or manholes.
  • (B) Rapid rate filters.
    • (I) Loading rates. The maximum allowable loading rates at maximum daily demands shall not exceed 3 gpm/ft² (177 m³/m²·d) for single media filters or 5 gpm/ft² (295 m³/m²·d) for dual or mixed media filters. Each filter shall have a rate limiting device to prevent the filter from exceeding the maximum rate.
    • (II) Filter compartment design. The filter media compartment shall be constructed of durable material not subject to corrosion or decay and structurally capable of supporting the loads to which it will be subjected.
      • (1.) There shall be an atmospheric break between filtered and non-filtered water, accomplished by double wall construction.
      • (2.) The compartment walls shall be vertical and shall not protrude into the filter media.
      • (3.) There shall be a minimum of 2½ feet (0.76 m) of headroom above the top of the filter compartment walls.
      • (4.) Neither floor nor roof drainage shall enter the filter. If the top of the filter compartment is at floor level, a minimum 4 inch curb shall be constructed around the box.
      • (5.) Walkways or observation platforms shall be provided for each filter compartment. Walk-ways around the filter shall be a minimum of 24 inches wide.
      • (6.) Effluent line shall be trapped or submerged below the low water level in the clearwell to prevent air from entering the filter bottom. The velocity in the filter influent line shall not exceed 4 feet per second (1.2 m/sec). An overflow from the influent of the filter compartment shall be provided.
      • (7.) The distance between the operating water level in the filter and the high water level in the clearwell or effluent trap shall be 10 feet (3.05 m) minimum. The minimum operating water level over the media shall be 3 feet (0.91 m), and the minimum depth of the filter box shall be 8-1/2 feet (2.6 m).
    • (III) Washwater troughs. Washwater troughs shall be constructed to provide for not more than 6 feet (1.8 m) clear distance between troughs. The troughs shall not cover more than 25 percent of filter area.
      • (1.) Minimum clearance between the bottom of trough and top of unexpanded media shall be 12 inches (30.5 cm).
      • (2.) Minimum distance between the weir of the trough and the unexpanded media shall be 30 inches (0.76 m).
      • (3.) The trough and washwater waste line shall be sized to carry a filter backwash rate of 20 gpm/ft² (1181 m³/m²·d) plus a surface wash rate of 2.0 gpm/ft² (118 m³/m²·d).
    • (IV) Backwash system.
      • (1.) The backwash system shall be sized to provide a minimum backwash flow rate of 20 gpm/ft² (1181 m³/m²·d). Washwater storage shall be designed to provide two 20 minute washes in rapid succession. Where multiple units are not required and only one filter compartment is present, backwash storage capabilities may be reduced to provide one 20 minute backwash. Where pumps are used to provide backwash to the filter or to supply water to a washwater tank, the washwater pumps shall be in duplicate.
      • (2.) The backwash and surface wash washwater supply shall be filtered and disinfected.
      • (3.) Washwater rate shall be controlled by a separate valve, manual or automatic, on the main washwater line. Washwater flow rates shall be metered and indicated.
      • (4.) Air-assisted backwash systems may be used when the design precludes disturbing the gravel support.
      • (5.) A surface wash system shall be provided. The system shall be capable of supplying 0.5 gpm/ft² (29.5 m³/m²·d) for system with rotating arms and 2.0 gpm/ft² (118 m³/m²·d) with fixed nozzles, at a minimum pressure of 50 psi (344 kPa). The surface wash shall use filtered and disinfected water or air and filtered disinfected water. The supply system shall be provided with adequate backflow prevention.
    • (V) Filter materials. For rapid rate filters, coarse-to-fine beds of mixed or dual media or fine-to-coarse single media beds may be used.
      • (1.) Types of filter media: ·
        • a. Anthracite. Clean crushed anthracite, or a combination of anthracite and other media shall have an effective size of 0.45 mm - 0.55 mm with uniformity coefficient not greater than 1.65 when used alone, or an effective size of 0.8 mm - 1.2 mm with a uniformity coefficient not greater than 1.65 when used as a cap. The anthracite shall meet the requirements of AWWA B100.
        • b. Sand. Sand shall have an effective size of 0.45 mm to 0.55 mm, a uniformity coefficient of not greater than 1.65, and shall meet the requirements of AWWA B100.
        • c. Granular activated carbon (GAC). Granular activated carbon media may be used in place of anthracite. There must be means for periodic treatment of granular activated carbon filter material for control of bacterial and other growths. Provisions must be made for replacement or regeneration if GAC is used for filtration.
        • d. Torpedo sand or garnet. A layer of torpedo sand or garnet shall be used as a supporting media for filter sand.
      • (2.) Sand for single media beds. The media shall be clean silica sand having a depth of not less than 24 inches (0.61 m), an effective size of from 0.45 mm to 0.55 mm, and a uniformity coefficient not greater than 1.65. A 3 inch (7.6 cm) layer of torpedo sand or other high density material shall be used as a supporting media for the filter sand. The material shall have an effective size of 0.8 mm to 2.0 mm, and a uniformity coefficient not greater than 1.7.
      • (3.) Anthracite for single media beds. Clean crushed anthracite or a combination of sand and anthracite may be used. Such media shall have an effective size from 0.45 mm to 0.55 mm, and a uniformity coefficient not greater than 1.65.
      • (4.) Gravel. When used as a supporting media, gravel shall consist of coarse aggregate in which a high proportion of the particles are rounded and tend toward a generally spherical or equidimensional shape. It shall possess sufficient strength and hardness to resist degradation during handling and use, be substantially free of harmful materials, and exceed the minimum density requirement. The gravel shall meet the requirements of AWWA B100.
      • (5.) Multi-media. Filter beds of this type shall contain a depth of fine media made up of anthracite coal, specific gravity 1.5; silica sand, specific gravity 2.6; and garnet sand or ilemite, specific gravity 4.2 - 4.5.
        • a. Bed depths and distribution of the media shall be determined by the water quality, but shall not be less than 10 inches (0.25 m) of fine sand and 24 inches (0.61 m) of coal. The relative size of the particles shall be such that hydraulic grading of the material during backwash will result in a filter bed with pore space graded progressively from coarse to fine in the direction of filtration (down).
        • b. The multi-media shall be supported on two layers of special high density gravel placed above the conventional silica gravel supporting bed. The special gravel shall have a specific gravity not less than 4.2. The bottom layer shall consist of particles passing No. 5 and retained on No. 12 U.S. mesh sieves and shall be 1-1/2 inches (3.8 cm) thick. The top layer shall consist of particles passing No. 12 and retained on No. 20 U.S. mesh sieves, and shall be 1-1/2 inches (3.8 cm) thick.
      • (6.) Dual media. Coal sand filters shall consist of a coarse coal layer above a layer of fine sand. The media shall consist of not less than 8 inches (20 cm) of sand and 15 inches (0.38 m) of coal on a torpedo sand or garnet layer support of not less than 3 inches (7.8 cm) on the gravel support.
    • (VI) Filter bottoms. Acceptable filter bottoms and strainer systems shall be limited to pipe, perforated pipe laterals, tile block and perforated tile block. Perforated plate bottoms or plastic nozzles shall not be used.
    • (VII) Appurtenances. Every filter shall have influent and effluent sampling taps; indicating loss of head gauge; indicating effluent turbidimeter; a waste drain for draining the filter compartment to waste; and a filter rate flow meter. Every filter shall provide polymer feed facilities including polymer mixing and storage tank and at least one feed pump for each filter compartment. On plants having a capacity in excess of 0.5 MGD, recorders shall be provided on the turbidimeters.
    • (VIII) Filter rate control. Filter rate control shall be such that the filter is not surged. Filter rate of flow shall not change at a rate greater than 0.3 gpm/ft² (17.7 m³/m²·d) per minute. Filters that stop and restart during a cycle shall have a filter to waste system installed. Declining flow rate filters shall not be used unless the flow rate for each filter is controlled to rates less than allowed in 10 (i)(ii)(B) and there are four or more individual filters.
    • (IX) A filter to waste cycle shall be provided after the filter backwash operation. The filter to waste cycle shall be at least 10 minutes.

(j) Diatomaceous earth filtration. These types of filters may be used as the filtration process to remove turbidity from surface waters where turbidities entering the filters do not exceed 25 TU and where total raw water coliforms do not exceed 100 organisms/100 ml. These filters may be used where the raw water quality exceeds the above limits when flocculation and sedimentation are used preceding the filters. Diatomaceous earth filters may also be used for removal of iron from groundwaters.

• (i) Types of filters. Pressure or vacuum diatomaceous earth filtration units will be considered for approval.

• (ii) Precoat. A precoating system shall be provided.
  • (A) Application. A uniform precoat shall be applied hydraulically to each septum by introducing a precoat slurry to the filter influent line and employing a filter to waste or recirculation system.
  • (B) Feed capabilities. Diatomaceous earth in the amount of 0.20 lb/ft² (1 Kg/m²) minimum of filter area shall be used with recirculation. When precoating is accomplished with a filter to waste system, 0.3 lbs/ft² (1.5 Kg/m²) minimum shall be provided.

• (iii) Body feed. A body feed system to apply diatomaceous earth slurry continuously during the filter run shall be provided. Continuous mixing of the body feed slurry tank during the filter cycle shall be provided.

• (iv) Filtration.
  • (A) Rate of filtration. The maximum rate of filtration shall not exceed 1.5 gpm/ft² (88.6 m³/m²·d) of septum area. The filtration rate shall be controlled by a positive means.
  • (B) Head loss. The head loss shall not exceed 30 psi (206 kPa) for pressure diatomaceous earth filters, or a vacuum of 15 inches of mercury (50.8 kPa) for vacuum system.
  • (C) Recirculation. A recirculation or holding pump shall be provided 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 0.1 gallons per minute per square foot (5.9 m³/m²·d) of filter area shall be provided. The filter control system shall prevent automatic restart after power failure.
  • (D) Septum or filter element. The filter elements shall be structurally capable of withstanding maximum pressure and velocity variations during filtration and cleaning cycles, and shall be spaced so that not less than 2 inches (5.1 cm) are provided between elements or between any element and a wall.
  • (E) Inlet design. The filter influent shall be designed to prevent scour of the diatomaceous earth from the filter element.

• (v) Appurtenances. Every filter shall provide sampling taps for raw and filtered water; loss of head or differential pressure gauge; rate of flow indicator, with totalizer; and a throttling valve used to reduce rates during adverse raw water conditions.

• (vi) Monitoring. A continuous monitoring turbidimeter is required on the filter effluent from each filter unit for plants treating surface water.

(k) Disinfection. Chlorine, chlorine dioxide, ozone or other disinfectant as approved by the administrator may be used for disinfection. Where the primary disinfectant is ozone, chlorination equipment shall be provided to enable maintaining a residual disinfectant throughout the distribution system. Automatic proportioning of disinfectant feed to flow rate is required where the plant flow control is automatic.

• (i) Chlorination equipment.
  • (A) Type. Solution feed gas chlorinators or hypochlorite feeders of the positive displacement type shall be provided.
  • (B) Capacity. The chlorinator capacity shall be such that a minimum 5 mg/L disinfection dose can be added on the maximum day. The equipment shall be of such design that it will operate accurately over the desired feeding range.
  • (C) Standby equipment. Standby equipment of sufficient capacity shall be available to replace the largest chlorinator unit, except for a well water system providing no treatment other than disinfection.
  • (D) Automatic switchover. Automatic switch-over of chlorine cylinders shall be provided.
  • (E) Diffuser. The chlorine solution injection/diffuser shall provide a rapid and thorough mix with all the water being treated. If the application point is to a pipeline discharging to a clearwell, the chlorine shall be added to the center of the pipe at least 10 pipe diameters upstream of the discharge into the clearwell.
  • (F) Injector/Eductor. For gas feed chlorinators, the injector/eductor shall be selected based on solution water pressure, injector waterflow rate, feed point backpressure, and chlorine solution line length and size. The maximum feed point backpressure shall not exceed 110 psi (759 kPa). Where backpressure exceeds 110 psi (750 kPa), a chlorine solution pump shall be used. Gauges shall be provided for chlorine solution pressure, feed water pressure and chlorine gas pressure, or vacuum.

• (ii) Points of application and contact time.
  • (A) At plants treating surface water, provisions shall be made for applying disinfectant to the raw water, filter influent, and filtered water.
  • (B) For plants treating groundwater, provisions shall be made for applying disinfectant to a point in the finished water supply line prior to any commercial, industrial, or municipal user. Agricultural users may remove water from the supply line prior to disinfectant application point.
  • (C) Where free chlorine residual is provided, 1/2 hour contact time shall be provided for groundwaters and 2 hours for surface waters. Where combined residual chlorination is provided, 2 hours contact time for groundwater and 3 hours contact for surface water shall be provided.
  • (D) When chlorine is applied to a groundwater source for the purpose of maintaining a residual, no contact time is required.

• (iii) Testing equipment. Chlorine residual test equipment recognized in the 15th Edition of Standard Methods for the Examination of Water and Wastewater shall be provided and shall be capable of measuring residuals to the nearest 0.1 mg/L in the range below 0.5 mg/L, to the nearest 0.3 mg/L between 0.5 mg/L and 1.0 mg/L and to the nearest 0.5 mg/L between 1.0 mg/L and 2.0 mg/L.

• (iv) Chlorinator piping.
  • (A) Cross-connection protection. The chlorinator water supply piping shall be designed to prevent contamination of the treated water supply. At all facilities treating surface water, pre- and post- chlorination systems shall be independent to prevent possible siphoning of partially treated water into the clearwell. The water supply to each eductor shall have a separate shutoff valve. No master shutoff will be allowed. Chlorine solution feed water shall be finished water.
  • (B) Pipe material. The pipes carrying liquid or gaseous chlorine shall be Schedule 80 black steel pipe with forged steel fittings. Bushings shall not be used. Vacuum piping for gaseous chlorine may be polyethylene tubing. Gas piping between the chlorine pressure reducing valve of the chlorinator and the ejector shall be PVC or polyethylene. Piping for aqueous solutions of chlorine beyond the ejector shall be PVC, fiberglass or steel pipe lined with PVC or saran.

• (v) Maximum withdrawal. The maximum withdrawal rate of gaseous chlorine shall be limited to 40 lbs/day (18.1 kg/day) for 100 or 150 lb (45.4 or 68.0 kg) cylinders and 400 lbs/day (181 kg/day) for 2,000 lb (907 kg) cylinders, unless chlorine evaporators are employed.

• (vi) Ozonation equipment.
  • (A) Capacity. The ozonator capacity shall be such that an applied dose of at least 10 mg/L can be attained at the maximum daily flows. The equipment shall be of such design that it will operate 5 percent over the desired feeding range.
  • (B) Piping. Injection equipment and piping in contact with ozonated air and air water emulsions shall be of stainless steel, teflon or other material resistant to ozone. Valves carrying ozonized air shall be made of metal coated with ozone resistant materials.
  • (C) Application. Ozone may be applied to the water directly as a gas or by an injector system similar to a chlorine injector system. In gas applications, depth of submergence of the diffusers shall be a minimum of 10 feet (3.05 m). Diffusion shall be fine bubble or mixed.
  • (D) Contact time and point of application. Ozone shall be applied at a point which will provide contact time not less than 30 minutes. At plants treating surface water, provisions should be made for applying a disinfectant to the raw water, filter influent, filtered water and final contact basin. At plants treating groundwater, provisions should be made for applying ozone to the clear-well inlet.
  • (E) Testing equipment. Testing equipment shall enable measurement of residuals to the nearest 0.1 mg/L in the range below 0.5 mg/L and to the nearest 0.2 mg/L above 0.5 mg/L.
  • (F) Ozone destruct. An ozone destruct device shall be provided to destruct all ozone contractor off gases.
  • (G) The use of ozone for disinfection will be allowed only if a chlorine or combined chlorine residual is provided in the distribution system.

(l) Softening.

• (i) Lime or lime soda process. Design standards for rapid mix, flocculation and sedimentation are the same as for conventional treatment previously outlined. Lime or lime soda softened effluent shall be filtered.
  • (A) Hydraulics. When split treatment is used, the bypass line shall be sized to carry total plant flow, and a means of measuring and splitting the flow shall be provided.
  • (B) Chemical feed point. Lime and recycled sludge shall be fed directly into the rapid mix basin.
  • (C) Stabilization. Provisions shall be made to chemically stabilize waters softened by the lime or lime soda process.
  • (D) Sludge collection. Mechanical sludge removal equipment shall be provided in the sedimentation basin. Sludge recycling to the rapid mix shall be provided.
  • (E) Disinfection. The use of excess lime shall not be considered a substitute for disinfection. Disinfection, as previously outlined, shall be provided.

• (ii) Cation exchange process.
  • (A) Pretreatment requirements. Pretreatment is required when the content of iron, manganese, or a combination of the two, is 1 mg/L or more. Water with 5 units or more turbidity shall not be applied directly to the cation exchange softener.
  • (B) 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. A manual override shall be provided on all automatic controls.
  • (C) Exchange capacity. The design capacity for hardness removal shall not exceed 20,000 grains per cubic foot (45,880 g/L) when resin is regenerated with 0.3 pounds (.14 kg) of salt per kilograin (2.29 g/L) of hardness removed.
  • (D) Depth of resin. The depth of the exchange resin shall not be less than 2 feet (0.6 m).
  • (E) Flow rates. The flow applied to the softening unit shall not exceed 7 gpm/ft² (413 m³/m²·d) of bed area. The minimum backwash rate shall be 6 gpm/ft² (354 m³/m²·d) of bed area or shall provide a minimum of 150 percent bed expansion at winter water temperatures. A positive means of controlling flow must be present.
  • (F) Underdrains and supporting gravel. The bottoms, strainer systems and support for the exchange resin shall conform to criteria provided for rapid rate gravity filters.
  • (G) Brine distribution. Facilities shall be included for even distribution of the brine over the entire surface of both upflow and downflow units.
  • (H) 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.
  • (I) Bypass piping and equipment. A by-pass shall 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. An automatic proportioning or regulating device and shutoff valve shall be provided on the bypass line.
  • (J) Additional limitations.
    • (I) Silica gel resins shall not be used for waters having a pH above 8.4 or containing less than 6 mg/L silica and shall not be used when iron is present.
    • (II) When the applied water contains a chlorine residual, the cation exchange resin shall be a type that is not damaged by residual chlorine.
    • (III) Phenolic resin shall not be used.
  • (K) Brine and salt storage tanks.
    • (I) Salt dissolving or brine tanks and wet salt storage tanks shall be covered and constructed of corrosion-resistant materials.
    • (II) The makeup water inlet shall be protected from back siphonage. Water for filling the tank shall be distributed over the entire surface by pipes above the maximum brine level in the tank. The tanks shall be provided with an automatic declining level control system on the makeup water line.
    • (III) 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 similar to those required for finished water reservoirs.
    • (IV) Overflows, if provided, must be turned down, have a proper free fall discharge and be protected with corrosion-resistant screens or self-closing flap valves.
    • (V) Two wet salt storage tanks or compartments designed to operate independently shall be provided.
    • (VI) The salt shall be supported on graduated layers of gravel under which is a suitable means of collecting the brine.
  • (L) Salt and brine storage capacity. Total salt storage capacity shall provide for at least 30 days of operation.
  • (M) Brine pump or eductor. An eductor may be used to transfer brine from the brine tank to the softeners. If a pump is used, a brine measuring tank or means of metering shall be provided to obtain proper dilution.
  • (N) Stabilization. Facilities for stabilizing corrosion control shall be provided.
  • (O) Construction materials. Pipes and contact materials shall be resistant to the aggressiveness of salt. Plastic and red brass are acceptable piping materials. Steel and concrete shall be coated with a non-leaching protective coating which is compatible with salt and brine.
  • (P) Housing. Bagged salt and dry bulk salt storage shall be enclosed and separated from other operating areas in order to prevent damage to equipment.

(m) Aeration. Aeration may be used to help remove tastes and odors due to dissolved gases from decomposing organic matter; to reduce or remove objectionable amounts of carbon dioxide, hydrogen sulfide, etc.; to introduce oxygen to assist in iron and/or manganese removal; and to strip volatile organic compounds for controlling the formation of trihalomethanes by removing the trihalomethane precursors.

• (i) Natural draft aeration - tray type. The design shall provide perforations in the distribution pan to provide uniform distribution of water over the top tray. The discharge shall be through a series of three or more trays. Tray material shall be resistant to aggressiveness of the water and dissolved gases. The loading rate shall not exceed five gpm/ft² (203 L/m²) of total tray area.

• (ii) Forced or induced draft aeration. Devices shall:
  • (A) Be constructed and located so that air introduced into the column shall be free from obnoxious fumes, dust, and dirt. All sections of the aerator shall be easily reached or removed for maintenance.
  • (B) Provide distribution of water uniformly over the top tray and discharge through a series of five or more trays.
  • (C) Be constructed so that the water outlet is adequately sealed to prevent unwarranted loss of air. Material shall be resistant to the aggressiveness of the water and dissolved gases. Loading shall be provided at a rate not to exceed five gpm/ft² (203 L/m²) of total tray area.

• (iii) Pressure aeration. Pressure aeration may be used for oxidation purposes only; it is not acceptable for removing dissolved gases.

• (iv) Protection of aerators. All aerators except those discharging to lime softening or clarification plants shall be protected from contamination by birds and insects by using louvers and 24 mesh screen.

• (v) Disinfection. Disinfection must be provided as a final treatment to all waters receiving aeration treatment.

• (vi) Bypass. A bypass shall be provided around all aeration units.

• (vii) Volatile organics removal. Volatile organic compounds may be stripped by packed tower or diffused aeration methods.

(n) Iron and manganese control. Iron and manganese control, as used here, refers solely to treatment processes designed specifically for this purpose.

• (i) Removal by oxidation, detention, and filtration.
  • (A) Oxidation. Oxidation may be accomplished by aeration or by chemical oxidation using chlorine, potassium permanganate, ozone, hydrogen peroxide, or chlorine dioxide.
  • (B) Detention following aeration. A minimum detention time of 20 minutes shall be provided following aeration. The detention basin shall be designed as a holding tank with sufficient baffling to prevent short-circuiting. Sedimentation basins shall be provided when treating water with iron and/or manganese above 2 mg/L, or where chemical coagulation is used to reduce the load on the filters. Provisions for sludge removal shall be made.
  • (C) Filtration. Gravity or pressure filters shall be provided. Where pressure filters are used, the following criteria supplements that found in Section 10(i).
    • (I) Rate of filtration. The rate shall not exceed 3 gpm/ft² (176 m³/m²·d) of filter area.
    • (II) Design criteria. The filters shall have a minimum side wall shell height of 5 feet, and an air release valve on the highest point of each filter. Each filter shall have a means to observe the wastewater during backwashing and also a manhole to facilitate inspection and repairs.

• (ii) Removal by the lime soda softening process. These processes shall conform to the lime soda process in Section 10(i).

• (iii) Removal by manganese greensand filtration. Provide feed capability of potassium permanganate to the influent of a manganese greensand filter.
  • (A) An anthracite media cap of at least 6 inches (0.15 m) shall be provided over manganese green-sand.
  • (B) The filtration rate shall not exceed 4 gpm/ft² (236 m³/m²·d).
  • (C) Provide a minimum backwash capability of 12 gpm/ft² (708 m³/m²·d), with a rate control device.
  • (D) Air washing or surface washing is required.

• (iv) Removal by ion exchange. This process of iron and manganese removal shall not be used for water containing more than 0.3 mg/L of iron, manganese or combination of the two. This process is not acceptable where either the raw water or washwater contains dissolved oxygen.

• (v) Sequestration by polyphosphates. This process shall not be used when iron, manganese or a combination of the two as exceeds 1.0 mg/L. The total phosphate applied shall not exceed 10 mg/L as PO₄. Where phosphate treatment is used, facilities shall be provided for maintaining a 0.5 mg/L free or combined chlorine residual at remote points in the distribution system.
  • (A) The stock phosphate solution tank shall be covered. Facilities shall be provided for disinfecting the solution tank. The facilities shall be capable of providing a minimum of 10 mg/L free chlorine residual.
  • (B) Polyphosphates shall not be applied ahead of iron and manganese removal treatment. The point of application shall be prior to any aeration, oxidation or disinfection if no iron or manganese removal treatment is provided.

• (vi) Sequestration by sodium silicates. Sodium silicate sequestration of iron and manganese shall be used for groundwater supplies prior to air contact. Rapid oxidation of the metal ions by chlorine, chlorine dioxide, ozone, hydrogen peroxide, or other strong oxidant must accompany or closely precede the sodium silicate addition. Injection of sodium silicate shall not occur at a point more than 15 seconds after oxidation feed point. Feed and dilution equipment shall be sized on the basis of feed solutions stronger than 5 percent silica as Si0₂. Sodium silicate addition may be used only on water containing up to 2 mg/L of iron, manganese or a combination of the two. Sodium silicate addition shall not be used on waters where 20 mg/L or more Si0₂ is required or where the amount of added and naturally occurring silicate will exceed 60 mg/L as Si0₂.
  • (A) Facilities shall be provided for maintaining a chlorine residual of 0.5 mg/L throughout the distribution system.
  • (B) Sodium silicate shall not be applied ahead of iron or manganese removal treatment.

• (vii) Testing equipment. Testing equipment shall be provided for all iron and manganese control plants.
  • (A) The equipment should have the capacity to measure the iron content to a minimum of 0.1 mg/L and the manganese content to a minimum of 0.05 mg/L.
  • (B) Where polyphoshate sequestration is practiced, phosphate testing equipment shall be provided.

(o) Fluoridation and defluoridation.

• (i) Fluoride compound storage. Storage tanks shall be covered; all storage shall be inside a building. Storage tanks for hydrofluosilic acid shall be vented to the atmosphere at a point outside the building.

• (ii) Chemical feed equipment. Fluoride feed equipment shall meet the following requirements.
  • (A) Scales or loss of weight recorders shall be provided for dry chemical feeds. Feeders shall be accurate to within five percent of any desired feed rate.
  • (B) The point of application of hydrofluosilic acid, if into a horizontal pipe, shall be in the lower half of the pipe. Fluoride compound shall not be added before lime soda softening or ion exchange softening.
  • (C) A fluoride solution shall be applied by a positive displacement pump having a stroke rate not less than 20 nor more than 95 strokes per minute. Fluoride solutions shall not be injected to a point of negative pressure.
  • (D) All fluoride feed lines and dilution water lines shall be isolated from potable water supplies by either an air gap above the solution tank or a reduced pressure principal backflow preventor.
  • (E) Water used for sodium flouride dissolution shall have a hardness not exceeding 50 mg/L. Softening shall be provided for the solution water where hardness exceeds 45 mg/L.
  • (F) Flow meters for treated flow rate and fluoride solution water shall be provided.

• (iii) Protective equipment. Protective equipment, including air purifying respirators approved by the National Institute of Occupational Safety and Health and emergency showers, shall be provided for operators handling fluoride compounds.

• (iv) Dust control.
  • (A) Provisions shall be made to allow the transfer of dry fluoride compounds from shipping containers to storage bins or hoppers in such a way as to minimize the quantity of fluoride dust which may enter the room in which the equipment is installed. The enclosure shall be provided with an exhaust fan and dust filter which places the hopper under a negative pressure. Air exhausted from fluoride handling equipment shall discharge through a dust filter to the outside atmosphere of the building. The discharge shall not be located near a building fresh air intake.
  • (B) A floor drain shall be provided.

• (v) Testing equipment. Equipment shall be provided for measuring the quantity of fluoride in the water.

• (vi) Defluoridation. Where fluoride removal is required the following methods are acceptable:
  • (A) Activated alumina may be employed in open gravity filter tanks or pressure filter tanks. The minimum media depth shall be 5 feet. The units shall not be loaded at a rate exceeding 4 gallons per minute per square foot (236 m³/m²·d). The activated alumina media shall be in mesh sizes ranging from 28 to 48. Regeneration facilities shall be provided to regenerate the media. These shall include both weak caustic and weak acid systems.
  • (B) Bone char filtration or lime softening with magnesium addition.

(p) Stabilization. Stabilized water is a water that does not tend to corrode the pipe nor deposit large quantities of scale.

• (i) Carbon dioxide addition.
  • (A) Recarbonation basin design shall provide a minimum total detention time of 20 minutes. Two compartments consisting of a mixing compartment having a detention time of at least three minutes and a reaction compartment are required. Each compartment shall have a minimum depth of 8 feet (2.4 m).
  • (B) Plants generating carbon dioxide from combustion shall have top recarbonation tanks in order to dissipate carbon monoxide gas. Care shall be taken to prevent the basin off-gases from entering any treatment plant structure.
  • (C) The recarbonation basin shall be sloped to a drain.

• (ii) Acid addition. Facilities shall be provided for feeding both acid and alkalinity, such as sodium carbonate, lime or sodium bicarbonate.

• (iii) Polyphosphates. The feeding of polyphosphates is applicable for sequestering calcium in lime softened water, corrosion control, and in conjunction with alkali feed following ion exchange softening. Chlorination equipment and feed points shall be available to chlorinate the phosphate solution tank to maintain a 10 mg/L free chlorine residual and to maintain a 0.5 mg/L residual in the distribution system.

• (iv) Alkali feed. Unstable water created by ion exchange softening shall be stabilized by an alkali feed. An alkali feeder shall be provided for all ion exchange water softening plants.

• (v) Control. Laboratory equipment shall be provided for determining the effectiveness of stabilization treatment. This shall include testing equipment for hardness, calcium, alkalinity, pH and magnesium, as a minimum.

(q) Taste and odor control. Provision shall be made for the control of taste and odor at all surface water treatment plants.

• (i) Flexibility. Plants treating water that is known to have taste and odor problems shall be provided with equipment that makes at least two of the control processes available.

• (ii) Chlorination. When chlorination is used for the removal of some objectionable odors, two hours of contact time must be provided to complete the chemical reactions involved.

• (iii) Chlorine dioxide. Chlorine dioxide can be used in the treatment of any taste and odor that is treatable by an oxidizing compound. Provisions shall be made for proper storing and handling of the sodium chlorite to eliminate any danger of explosion.

• (iv) Powdered activated carbon. Provisions shall allow the addition of carbon to the presedimentation basin influent, rapid mix basin, and clarifier effluent. Carbon feed equipment shall be capable of feeding from 0 to 40 mg/L at plant design flows.

  A provision shall be made for adequate dust control. Powdered activated carbon shall be handled as a potentially combustible material. It shall be stored and used in a building or compartment as nearly fireproof as possible. Carbon feeder rooms shall be designed for hazardous locations, National Electric Code, Class 1, Groups C and D, Division 1.

• (v) Granular activated carbon adsorption units. Open or closed carbon contacting may be used for taste and odor control by adsorption of organics. The loading rate shall not exceed 10 gpm/ft² (236 m³/m²·d). The minimum empty bed contact time shall be 20 minutes. Provisions shall be made for moving carbon to and from the contactors.

• (vi) Potassium permanganate. The application point shall be in the raw water or ahead of the clarifier influent. Facilities shall be capable of feeding not less than 10 mg/L of permanganate.

• (vii) Ozone. Thirty minutes of contact time must be provided to complete the chemical reactions involved. The facilities shall be capable of an applied ozone feed rate of 15 mg/L minimum.

(r) Microscreening. A microscreen will be allowed as a mechanical supplement to treatment. The microscreening shall be capable of removing suspended matter from the water by straining. It may be used to reduce nuisance organisms and organic loadings. It shall not be used in place of filtration or coagulation.

• (i) Screens shall be of a corrosion-resistant material, plastic or stainless steel.

• (ii) Bypass piping shall be provided around the unit.

• (iii) Protection against back siphonage shall be provided when potable water is used for washing the screen.

• (iv) Washwaters shall be wasted and not recycled to the microscreen.

(s) Organics removal by granular carbon adsorption.

• (i) Adsorption of organics on granular activated carbon. Water to be treated may be contacted with granular activated carbon. The pH of the water shall be less than 9.0. The turbidity of the applied water shall be less than 2 TU when packed beds are used.

• (ii) Contact time. The carbon beds or columns shall provide a minimum of 20 minutes of empty bed contact time at design flow. Surface loading rates shall not exceed 10 gpm/ft² (590 m³/m²·d).

• (iii) Carbon bed or column design.
  • (A) If an upflow countercurrent contactors is used, it may be either packed or expanded. A single unit is acceptable. If a downflow contactor is used, two or more beds in parallel are required.
  • (B) Contactors may be designed as open gravity units, or pressure beds. They may be constructed of concrete, steel, or fiberglass reinforced plastic. Steel vessels shall be protected against corrosion by coaltar epoxy coating, rubber or glass lining, or other means.
  • (C) All carbon beds or columns shall be equipped with provisions for flow reversal and bed expansion. Combination downflow filter contactors shall have backwashing facilities to provide up to 50 percent bed expansion and shall meet the same backwash criteria as rapid filters.
  • (D) Inlet and outlet screens shall be 304 or 316 stainless steel or other suitable materials.
  • (E) Carbon beds and columns shall have a means for removing spent carbon and introducing makeup or regenerated carbon.
  • (F) Pressure contactors shall be equipped with air-vacuum release valves fitted with a stainless steel screen, slot size 0.036 mm (0.14 inches), to prevent plugging with carbon.

(t) Radionuclides. Where radionuclide removal is practiced, the waste shall be evaluated for its classification as a hazardous or low level radioactive waste and disposed of as required by the Nuclear Regulatory Commission or other appropriate authority.

(u) Waste handling and disposal. Disposal of any waste sludge or liquid shall meet all the requirements of Chapter 11 of the Water Quality Rules and Regulations where applicable.

• (i) Sanitary and laboratory wastes. The sanitary and laboratory wastes from water treatment plants, pumping stations, etc., shall not be recycled to any part of the water plant. Waste from these facilities must be discharged directly to a sanitary sewer system when feasible, or to an on-site waste treatment facility permitted by the Wyoming Department of Environmental Quality.

• (ii) Brine waste. The waste from ion exchange plants, demineralization plants, etc., may not be recycled to the plant. Where discharging to a sanitary sewer, a holding tank shall be provided to prevent the overloading of the sewer and/or interference with the waste treatment processes. The effect of brine discharge to sewage lagoons may depend on the rate of evaporation from the lagoons. Where disposal to an off-site waste treatment system is proposed, it must be demonstrated that the sewer and the facility have the required capacity and dilution capability. The impact on any treatment system discharge shall be evaluated.

• (iii) Lime softening sludge. Acceptable methods of treatment and disposal are as follows:
  • (A) Sludge lagoons. Lagoons shall be designed on the basis of providing a surface area of 0.7 acres (.28 ha) per million gallons per day (3785 m³/day) (average day) per 100 mg/L of hardness removed, based on a usable lagoon depth of 5 feet (1.5 m). At least 2 lagoons shall be provided. An acceptable means of final sludge disposal must be provided. Provisions must be made for convenient cleaning of the lagoons.

    The design of lagoons shall provide for location above the 100-year flood or adequately protected from the 100-year flood. There shall be means of diverting surface water runoff so that it does not flow into the lagoons. Minimum free-board of 3 feet (0.66 m) shall be present. An adjustable decanting device for recycling the overflow shall be present. There shall be an accessible effluent sampling point.

  • (B) Land application of liquid lime sludge shall comply with Part E of Chapter 11 of the Water Quality Rules and Regulations.
  • (C) Disposal at a suitable landfill shall be authorized by the Solid Waste Management Program of the Department of Environmental Quality.
  • (D) Mechanical dewatering of sludge may be employed.
  • (E) Recalcination of sludge may be employed.
  • (F) Lime sludge drying beds shall not be used.

• (iv) Alum sludge.
  • (A) Lagooning may be used as a storage and interim disposal method for alum sludge. The volume of alum sludge storage lagoons shall be at least 100,000 gallons (378.5 m³) per 1,000,000 gpd (3,785 m³/d) of treatment plant capacity.
  • (B) Discharge of alum sludge to sanitary sewers may be used only when the sewage system has the capability to adequately handle the flow and sludge.
  • (C) Mechanical dewatering of sludge may be employed.
  • (D) Alum sludge drying beds may be used.
  • (E) Alum sludge may be acid treated and recovered.
  • (F) Disposal at a suitable landfill shall be authorized by the Solid Waste Management Program of the Department of Environmental Quality.

• (v) Iron and manganese waste. Waste filter washwater from iron and manganese removal plants may be disposed by filtration, by lagooning, or by discharge to the sewer system.
  • (A) Sand filters. Sand filters should have a total filter area of not less than 100 square feet (9.29 m²) in a minimum of 2 compartments. The filter shall have sufficient surface area and capacity to contain, in a volume of 2 feet (0.61 m) above the level of the sand, the entire volume of washwater produced by washing the production filters.
    • (I) The filter shall not be subject to flooding by surface runoff or flood waters. Finished grade elevation shall be such as to facilitate maintenance, cleaning and removal of surface sand as required.
    • (II) The filter media shall consist of a minimum of 12 inches (30.4 cm) of sand, 3 inches (7.6 cm) of supporting small gravel or torpedo sand, and 9 inches (0.22 m) of gravel in graded layers. All sand and gravel shall be washed to remove fines. Filter sand shall have an effective size of 0.3 to 0.5 mm and a uniformity coefficient not to exceed 3.5.
    • (III) The filter shall be provided with an underdrain collection system, and provision shall be made for an accessible sample point.
    • (IV) Overflow devices from these filters shall not be permitted.
    • (V) Where freezing may occur, provisions shall be made for covering the filters during the winter months.
    • (VI) Iron and manganese waste filters shall provide an atmosphere air break between adjacent compartments that contain finished water and unfiltered water.
  • (B) Washwater recovery lagoons. Filter backwash wastewater may be recovered by washwater recovery lagoons. Decanted filter backwash wastewater from the lagoons shall be recycled to the head of the plant. Lagoons shall provide 250,000 gallons of storage (946 m³) for each 1,000,000 gallons per day (3,785 m³/day) of treatment capacity. Lagoons shall have a minimum usable depth of 3 feet (0.91 m), a length 4 times the width, and a width of at least 3 times the water depth.

020-12 Wyo. Code R. § 12-10