Section 811.39. Feed equipment.

 

(1)   Number of feeders. If chemical feed, such as chlorination, coagulation or other essential processes, is necessary to produce a water quality meeting the primary maximum contaminant levels, a minimum of 2 feeders shall be provided so that a standby unit or combination of units will be available to replace the largest unit during shut-downs. Spare parts shall be available for all feeders to replace parts which are subject to wear and damage.

(2)   Design and capacity. The design and capacity of chemical feed equipment shall meet all of the following requirements:

(a) Separate chemical feed systems. Separate chemical feed systems shall be provided in accordance with the following requirements:

1. A separate feed system shall be provided for each chemical.

2. Separate disinfection chemical feed systems shall be provided if pre- and post- water treatment disinfection application points are installed.

3. Each chemical feed pump or gas feeder shall take suction from its own dedicated chemical solution tank or gas cylinders. The department may approve multiple chemical feed pumps or gas feeders for the same process application point taking suction from the same chemical solution tank or gas cylinders in the following situations:

a. Where multiple water sources are discharging to the same location. In this case, a means shall be provided for determining the flow from each individual water source.

b. Where multiple pumps are pumping from the same water source and discharging to the same location through a combined header pipe. In this case, a means shall be provided for measuring total flow.

c. For the situations in subd. 3. a. and b. , a single chemical feeder with a single feed point or multiple chemical feeders with multiple feed points may be used, provided the installation meets the other requirements of this subchapter.

(b) Acceptable chemical feed pumps. Positive displacement diaphragm metering pumps, peristaltic chemical feed pumps or other pumps, as approved by the department, shall be used to feed liquid chemicals. Pumps shall be sized to match or exceed maximum head conditions found at the point of injection.

(c) Chemical feeder settings. Feeders shall be able to supply, at all times, the necessary amounts of chemical at an accurate rate, throughout the range of feed. All positive displacement diaphragm metering pumps shall be operated at a minimum speed setting of 12 strokes per minute. For positive displacement diaphragm metering pumps with an adjustable stroke length the pumps shall be operated at a minimum of 20 percent of the maximum stroke length. Peristaltic chemical feed pumps shall be operated at a minimum of 10 percent of the maximum feeder output for the given interior diameter of the feed tube installed. If these operating requirements cannot be met using stock chemical solution, dilution of the chemical shall be required.

(d) Flow paced chemical feed. Automatic proportioning of chemical feed to rate of water flow shall be provided when water flow rates will vary. Chemical feed pumps shall be proportionally flow paced by a signal from a water meter when discharge rates from a well or service pump will be variable over the pump cycle. When applicable, this includes variable output control devices as required by s. NR 811.34 (5) .

(e) Anti-siphon devices. Chemical feed pumps shall be provided with anti-siphon devices meeting the following requirements:

1. All electronic positive displacement diaphragm metering pumps shall be provided with a spring-opposed diaphragm type anti-siphon device or a spring opposed diaphragm type anti-siphon and back pressure valve device installed in the discharge piping of the chemical feed pump. The anti-siphon and back pressure functions may be part of a common device or separate devices. Any back pressure valve shall be set to open at a pressure greater than the maximum pressure in the piping or facilities into which the chemical feed pump will discharge. When a back pressure valve is installed on the discharge piping of a chemical feed pump, it shall be preceded by a pressure relief valve and a pressure gauge or other department approved means to verify that the back pressure valve is operating satisfactory.

2. Digitally controlled diaphragm metering pumps shall be provided with a spring opposed diaphragm type anti-siphon and back pressure valve device installed in the discharge piping of the chemical feed pump in accordance with the requirements of subd. 1.

3. Peristaltic chemical feed pumps shall be provided with a back pressure valve device installed in the discharge piping of the chemical feed pump in accordance with the requirements of subd. 1.

4. The department may be contacted to request approval of an equivalent anti-siphon device or equivalent means of providing anti-siphon protection if the installation of the anti-siphon devices as required in subds. 1. to 3. is not practical given the properties of the chemical to be fed. Adequate justification shall be provided to the department for the request.

(f) Location of chemical injection.

1. Chemical solutions shall be prevented from being siphoned into the water supply. Anti siphon protection shall be provided by discharging chemicals at points of positive pressure and by providing anti-siphon devices in accordance with par. (e) , or through a suitable air gap or other effective means approved by the department. A point of continuous positive pressure shall be assured on the system side of the last shut-off valve. If a second shut-off valve is provided downstream of the primary shut-off valve, the point of injection may be between the 2 shut-off valves.

2. All chemicals shall be fed downstream of the check valve. Strong acids and bases such as fluorosilicic acid and sodium hydroxide shall be fed downstream of both the check valve and the shut-off valve.

3. If chemical feeding is at a location without continuous positive pressure, one of the following installation requirements shall be met to prevent siphoning of chemical solutions:

a. A suitable air gap shall be provided which is at a higher elevation than the chemical solution tank.

b. A dual head feeder with a small break tank located higher than the chemical solution tank shall be provided.

c. A chemical feed pump discharging without any air gap or break box may be approved by the department on a case-by-case basis if the installation is provided with a spring opposed diaphragm type anti-siphon and back pressure valve device. The back pressure valve shall be installed as close as possible to the point of chemical addition. The spring opposed diaphragm type anti-siphon and back pressure valve device shall be installed in accordance with the requirements of par. (e) 1.

(g) Makeup water lines. The makeup water supply lines to chemical feed tanks shall be protected from contamination by chemical solutions either by equipping the supply line with backflow or backsiphonage prevention devices, or by providing an air gap between the supply line and the top of the solution tank.

(h) Chemical resistance. Materials and surfaces coming in contact with chemicals shall be resistant to the aggressiveness of the chemical solution.

(i) Dry chemical feeders. Dry chemical feeders shall meet the following requirements:

1. Measure chemicals volumetrically or gravimetrically.

2. Provide effective dissolving and mixing of the chemical in the solution pot and provide gravity feed from solution pots, if possible.

3. Completely enclose chemicals to prevent emission of dust to the operating room.

(j) Direct sewer connections prohibited. No direct connection shall be made between any sanitary or storm sewer and a drain or overflow from any feeder or solution chamber or tank.

(3)   Location. Chemical feed equipment shall meet the following requirements:

(a) Be located near points of application to minimize length of feed lines.

(b) Be readily accessible for servicing or repair and observation of operation.

(c) Be located and have protective containment curbs so that chemicals from equipment failure, spillage, or accidental drainage may not enter the water in conduits, treatment, or storage basins.

(d) Be located within a containment basin capable of receiving accidental spills, drainage, or overflows without an uncontrolled discharge outside of the containment basin. A common containment basin may be provided for each group of compatible chemicals. At minimum, the containment basin shall be sized to contain the volume of the largest tank that could fail. Chemical containment basins shall not be provided with floor drains. Trapped and vented floor drains discharging to sanitary sewers, holding tanks or the ground surface in accordance with s. NR 811.25 (1) (h) may be installed for chemical rooms outside of containment basins. Chemical feed pumps shall be located within the containment basin. Piping shall be designed to minimize or contain chemical spills in the event of pipe ruptures.

(e) Be located above grade, except if this requirement is waived by the department.

(f) Be located in accordance with s. NR 811.48 (5) if gas chlorine feeders are used.

(g) Be located in accordance with s. NR 811.51 (2) if fluorosilicic acid is used.

(4)   Control. Chemical feeders shall be controlled in accordance with the following requirements:

(a) Feeders may be manually or automatically controlled if the water supply pumps are manually controlled. Where pumps are automatically controlled, the feeders shall be automatically controlled. In all cases, automatic control shall be capable of reverting to manual control when necessary.

(b) The operation of the chemical feed pumps shall be interlocked with the operation of the appropriate well or service pump. Any controlled electrical outlet used for any chemical feed pump shall be clearly marked.

(c) Secondary control of chemical feed equipment shall be provided for fluoride chemical feed equipment in accordance with s. NR 811.51 (4) or when required by the department.

(d) Feeders shall be designed and controlled to provide chemical feed rates proportional to flow and for variable flow rates shall be paced by a water meter.

(e) Automatic chemical feed rate control in combination with residual analyzers which have alarms for critical values and SCADA system reporting or recording charts may be used.

(5)   Solution tanks. The requirements for solution tanks, in s. NR 811.40 on storage and handling apply.

(6)   Weighing scales. Weighing scales shall meet the following requirements:

(a) Be provided for weighing cylinders at all plants utilizing chlorine gas.

(b) Be required for other solution feed unless comparable means for determining usage is approved by the department.

(c) Be required for volumetric dry chemical feeders.

(d) Be accurate enough to measure increments of 0.5% of load.

(7)   Feed lines. Feed lines shall meet the following requirements:

(a) Be as short as possible in length of run, of durable, corrosion resistant material, easily accessible throughout the entire length, protected against freezing, and readily cleanable.

(b) Slope upward from chemical source to feeder when conveying gases.

(c) Introduce corrosive chemicals in a manner to minimize potential for corrosion.

(d) Be designed consistent with scale-forming or solids-depositing properties of the water, chemical, solution, or mixture conveyed.

(e) Not carry chlorine gas under pressure beyond the chlorine feeder room.

(f) Include corporation stops and removable injection nozzles when application is into a pipe line of adequate diameter. Injection nozzles installed in a horizontal section of pipe shall be installed up into the bottom half of the pipe.

(g) Be color coded in accordance with s. NR 811.28 (6) .

(8)   Service and carrier water supply. Water used for dissolving dry chemicals, diluting liquid chemicals, operating chemical feeders or as carrier water to deliver chemicals to injection locations shall be from a safe, approved source with appropriate backflow prevention provided. The department may grant an exception in cases where the finished water quality will not be affected by addition of the chemical mixed with untreated water.

History: CR 09-073 : cr. Register November 2010 No. 659 , eff. 12-1-10.

Note

An example of subd. 3. a. would be multiple wells discharging to a single reservoir or water treatment plant. An example of subd. 3. b. would be multiple high-lift pumps taking suction from a single reservoir and discharging to a combined pump discharge pipe. Microsoft Windows NT 6.1.7601 Service Pack 1 It is recommended that all chemicals be fed downstream of both the check valve and the shutoff valve. Microsoft Windows NT 6.1.7601 Service Pack 1 It is recommended that indicating and recording type scales be used. Microsoft Windows NT 6.1.7601 Service Pack 1