5.0 CHEMICAL APPLICATION - RECOMMENDED STANDARDS FOR WATER WORKS 1997

CHEMICAL APPLICATION

5.0 GENERAL
5.1 FACILITY DESIGN
5.2 CHEMICALS
5.3 OPERATOR SAFETY
5.4 SPECIFIC CHEMICALS


5.0 GENERAL

No chemicals shall be applied to treat drinking waters unless specifically permitted by the reviewing authority.

5.0.1 Plans and specifications

Plans and specifications shall be submitted for review and approval, as provided for in Part 2, and shall include

a. descriptions of feed equipment, including maximum and minimum feed ranges,

b. location of feeders, piping layout and points of application,

c. storage and handling facilities,

d. specifications for chemicals to be used,

e. operating and control procedures including proposed application rates, and

f. descriptions of testing equipment and procedures.

5.0.2 Chemical application

Chemicals shall be applied to the water at such points and by such means as to

a. assure maximum efficiency of treatment,

b. assure maximum safety to consumer,

c. provide maximum safety to operators,

d. assure satisfactory mixing of the chemicals with the water,

e. provide maximum flexibility of operation through various points of application, when appropriate, and

f. prevent backflow or back-siphonage between multiple points of feed through common manifolds.

5.0.3 General equipment design

General equipment design shall be such that

a. feeders will be able to supply, at all times, the necessary amounts of chemicals at an accurate rate, throughout the range of feed,

b. chemical-contact materials and surfaces are resistant to the aggressiveness of the chemical solution,

c. corrosive chemicals are introduced in such a manner as to minimize potential for corrosion,

d. chemicals that are incompatible are not stored or handled together,

e. all chemicals are conducted from the feeder to the point of application in separate conduits,

f. chemical feeders are as near as practical to the feed point,

g. chemical feeders and pumps operate at no lower than 20 per cent of the feed range, and

h. chemicals are fed by gravity where practical.


5.1 FACILITY DESIGN


5.1.1 Number of feeders

a. Where chemical feed is necessary for the protection of the supply, such as chlorination, coagulation or other essential processes,

1. a minimum of two feeders shall be provided, and

2. the standby unit or a combination of units of sufficient capacity should be available to replace the largest unit during shut-downs;

3. where a booster pump is required, duplicate equipment should be provided and, when necessary, standby power.

b. A separate feeder shall be used for each chemical applied.

c. Spare parts shall be available for all feeders to replace parts which are subject to wear and damage.


5.1.2 Control

a. Feeders may be manually or automatically controlled, with automatic controls being designed so as to allow override by manual controls.

b. At automatically operated facilities, chemical feeders shall be electrically interconnected with the well or service pump and should be provided a nonstandard electrical receptacle.

c. Chemical feed rates shall be proportional to flow.

d. A means to measure water flow must be provided in order to determine chemical feed rates.

e. Provisions shall be made for measuring the quantities of chemicals used.

f. Weighing scales

1. shall be provided for weighing cylinders, at all plants utilizing chlorine gas,

2. may be required for fluoride solution feed,

3. should be provided for volumetric dry chemical feeders, and

4. shall be capable of providing reasonable precision in relation to average daily dose.

g. Where conditions warrant, for example with rapidly fluctuating intake turbidity, coagulant and coagulant aid addition may be made according to turbidity, streaming current or other sensed parameter.


5.1.3 Dry chemical feeders

Dry chemical feeders shall

a. measure chemicals volumetrically or gravimetrically,

b. provide adequate solution water and agitation of the chemical in the solution pot,

c. provide gravity feed from solution pots, and

d. completely enclose chemicals to prevent emission of dust to the operating room.


5.1.4 Positive displacement solution pumps

Positive displacement type solution feed pumps should be used to feed liquid chemicals, but shall not be used to feed chemical slurries. Pumps must be sized to match or exceed maximum head conditions found at the point of injection.


5.1.5 Liquid chemical feeders - Siphon control

Liquid chemical feeders shall be such that chemical solutions cannot be siphoned into the water supply, by

a. assuring discharge at a point of positive pressure, or

b. providing vacuum relief, or

c. providing a suitable air gap, or

d. other suitable means or combinations as necessary.


5.1.6 Cross-connection control

Cross-connection control must be provided to assure that

a. the service water lines discharging to solution tanks shall be properly protected from backflow as required by the reviewing authority,

b. liquid chemical solutions cannot be siphoned through solution feeders into the water supply as required in Section 5.1.5, and

c. no direct connection exists between any sewer and a drain or overflow from the feeder, solution chamber or tank by providing that all drains terminate at least six inches or two pipe diameters, whichever is greater, above the overflow rim of a receiving sump, conduit or waste receptacle.


5.1.7 Chemical feed equipment location

Chemical feed equipment

a. shall be readily accessible for servicing, repair, and observation of operation, and

b. should be located in a separate room to reduce hazards and dust problems, and

c. should be conveniently located near points of application to minimize length of feed lines, and

d. should be located such that the flow to the rapid mix is by gravity.


5.1.8 In-plant water supply

In-plant water supply shall be:

a. ample in quantity and adequate in pressure,

b. provided with means for measurement when preparing specific solution concentrations by dilution,

c. properly treated for hardness, when necessary,

d. properly protected against backflow, and

e. obtained from a location sufficiently downstream of any chemical feed point to assure adequate mixing.


5.1.9 Storage of chemicals

a. Space should be provided for

1. at least 30 days of chemical supply,

2. convenient and efficient handling of chemicals,

3. dry storage conditions, and

4. a minimum storage volume of 1 ½ truck loads where purchase is by truck load lots.

b. Storage tanks and pipelines for liquid chemicals shall be specified for use with individual chemicals and not used for different chemicals.

c. Chemicals shall be stored in covered or unopened shipping containers, unless the chemical is transferred into an approved storage unit.

d. Liquid chemical storage tanks must

1. have a liquid level indicator, and

2. have an overflow and a receiving basin capable of receiving accidental spills or overflows without uncontrolled discharge.


5.1.10 Solution tanks

a. A means which is consistent with the nature of the chemical solution shall be provided in a solution tank to maintain a uniform strength of solution. Continuous agitation shall be provided to maintain slurries in suspension.

b. Two solution tanks of adequate volume may be required for a chemical to assure continuity of supply in servicing a solution tank.

c. Means shall be provided to measure the solution level in the tank.

d. Chemical solutions shall be kept covered. Large tanks with access openings shall have such openings curbed and fitted with overhanging covers.

e. Subsurface locations for solution tanks shall

1. be free from sources of possible contamination, and

2. assure positive drainage for groundwaters, accumulated water, chemical spills and overflows.

f. Overflow pipes, when provided, should

1. be turned downward, with the end screened,

2. have a free fall discharge, and

3. be located where noticeable.

g. Acid storage tanks must be vented to the outside atmosphere, but not through vents in common with day tanks.

h. Each tank shall be provided with a valved drain, protected against backflow in accordance with Sections 5.1.5 and 5.1.6.

i. Solution tanks shall be located and protective curbings provided so that chemicals from equipment failure, spillage or accidental drainage shall not enter the water in conduits, treatment or storage basins.


5.1.11 Day tanks

a. Day tanks shall be provided where bulk storage of liquid chemical is provided.

b. Day tanks shall meet all the requirements of Section 5.1.10.

c. Day tanks should hold no more than a 30 hour supply.

d. Day tanks shall be scale-mounted, or have a calibrated gauge painted or mounted on the side if liquid level can be observed in a gauge tube or through translucent sidewalls of the tank. In opaque tanks, a gauge rod extending above a reference point at the top of the tank, attached to a float may be used. The ratio of the area of the tank to its height must be such that unit readings are meaningful in relation to the total amount of chemical fed during a day.

e. Hand pumps may be provided for transfer from a carboy or drum. A tip rack may be used to permit withdrawal into a bucket from a spigot. Where motor-driven transfer pumps are provided, a liquid level limit switch and an over-flow from the day tank, must be provided.

f. A means which is consistent with the nature of the chemical solution shall be provided to maintain uniform strength of solution in a day tank. Continuous agitation shall be provided to maintain chemical slurries in suspension.

g. Tanks and tank refilling line entry points shall be properly labeled to designate the chemical contained.


5.1.12 Feed lines

a. should be as short as possible, and

1. of durable, corrosion-resistant material,

2. easily accessible throughout the entire length,

3. protected against freezing, and

4. readily cleanable;

b. should slope upward from the chemical source to the feeder when conveying gases;

c. shall be designed consistent with scale-forming or solids depositing properties of the water, chemical, solution or mixtures conveyed; and

d. should be color coded.


5.1.13 Handling

a. Carts, elevators and other appropriate means shall be provided for lifting chemical containers to minimize excessive lifting by operators.

b. Provisions shall be made for disposing of empty bags, drums or barrels by an approved procedure which will minimize exposure to dusts.

c. Provision must be made for the proper transfer of dry chemicals from shipping containers to storage bins or hoppers, in such a way as to minimize the quantity of dust which may enter the room in which the equipment is installed. Control should be provided by use of

1. vacuum pneumatic equipment or closed conveyor systems,

2. facilities for emptying shipping containers in special enclosures, and/or

3. exhaust fans and dust filters which put the hoppers or bins under negative pressure.

d. Provision shall be made for measuring quantities of chemicals used to prepare feed solutions.


5.1.14 Housing

a. Floor surfaces shall be smooth and impervious, slip-proof and well drained with 3 inches per 10 feet minimum slope.

b. Vents from feeders, storage facilities and equipment exhaust shall discharge to the outside atmosphere above grade and remote from air intakes.


5.2 CHEMICALS

5.2.1 Shipping containers

Chemical shipping containers shall be fully labeled to include

a. chemical name, purity and concentration, and

b. supplier name and address.

5.2.2 Specifications

Chemicals and water contact materials shall meet ANSI/AWWA quality standards and ANSI/NSF standard 60 or 61 safety specifications.

5.2.3 Assay

Provisions may be required for assay of chemicals delivered.


5.3 OPERATOR SAFETY

5.3.1 Ventilation

Special provisions shall be made for ventilation of chlorine feed and storage rooms.

5.3.2 Respiratory protection equipment

Respiratory protection equipment, meeting the requirements of the National Institute for Occupational Safety and Health (NIOSH) shall be available where chlorine gas is handled, and shall be stored at a convenient location, but not inside any room where chlorine is used or stored. The units shall use compressed air, have at least a 30 minute capacity, and be compatible with or exactly the same as units used by the fire department responsible for the plant.

5.3.3 Chlorine leak detection

A bottle of ammonium hydroxide (56 per cent ammonia solution) shall be available for chlorine leak detection; where ton containers are used, a leak repair kit approved by the Chlorine Institute shall be provided. Continuous chlorine leak detection equipment is recommended. Where a leak detector is provided it shall be equipped with both an audible alarm and a warning light.

5.3.4 Protective equipment

a. At least one pair of rubber gloves, a dust respirator of a type certified by NIOSH for toxic dusts, an apron or other protective clothing and goggles or face mask shall be provided for each operator as required by the reviewing authority. A deluge shower and/or eyewashing device should be installed where strong acids and alkalis are used or stored.

b. A water holding tank that will allow water to come to room temperature must be installed in the water line feeding the deluge shower and eyewashing device. Other methods of water tempering will be considered on an individual basis.

c. Other protective equipment should be provided as necessary.


5.4 SPECIFIC CHEMICALS


5.4.1 Chlorine gas

a. Chlorine gas feed and storage shall be enclosed and separated from other operating areas. The chlorine room shall be

1. provided with a shatter resistant inspection window installed in an interior wall,

2. constructed in such a manner that all openings between the chlorine room and the remainder of the plant are sealed, and

3. provided with doors equipped with panic hardware, assuring ready means of exit and opening outward only to the building exterior.

b. Full and empty cylinders of chlorine gas should be

1. isolated from operating areas,

2. restrained in position to prevent upset,

3. stored in rooms separate from ammonia storage, and

4. stored in areas not in direct sunlight or exposed to excessive heat.

c. Where chlorine gas is used, the room shall be constructed to provide the following:

1. each room shall have a ventilating fan with a capacity which provides one complete air change per minute when the room is occupied,

2. the ventilating fan shall take suction near the floor as far as practical from the door and air inlet, with the point of discharge so located as not to contaminate air inlets to any rooms or structures,

3. air inlets should be through louvers near the ceiling,

4. louvers for chlorine room air intake and exhaust shall facilitate airtight closure,

5. separate switches for the fan and lights shall be located outside of the chlorine room and at the inspection window. Outside switches shall be protected from vandalism. A signal light indicating fan operation shall be provided at each entrance when the fan can be controlled from more than one point,

6. vents from feeders and storage shall discharge to the outside atmosphere, above grade,

7. the room location should be on the prevailing downwind side of the building away from entrances, windows, louvers, walkways, etc.,

8. floor drains are discouraged. Where provided, the floor drains shall discharge to the outside of the building and shall not be connected to other internal or external drainage systems.

9. where deemed necessary, provision shall be made to chemically neutralize chlorine gas before discharge from the water treatment plant building into the environment. Such equipment shall be designed as part of the chlorine gas storage and feed areas to automatically engage in the event of any measured chlorine release. The equipment shall be sized to treat the entire contents of the largest storage container on site.

d. Chlorinator rooms should be heated to 60 °F, and be protected from excessive heat. Cylinders and gas lines should be protected from temperatures above that of the feed equipment.

e. Pressurized chlorine feed lines shall not carry chlorine gas beyond the chlorinator room.


5.4.2 Acids and caustics

a. Acids and caustics shall be kept in closed corrosion-resistant shipping containers or storage units.

b. Acids and caustics shall not be handled in open vessels, but should be pumped in undiluted form from original containers through suitable hose, to the point of treatment or to a covered day tank.


5.4.3 Sodium chlorite for chlorine dioxide generation

Proposals for the storage and use of sodium chlorite must be approved by the reviewing authority prior to the preparation of final plans and specifications. Provisions shall be made for proper storage and handling of sodium chlorite to eliminate any danger of fire or explosion associated with its powerful oxidizing nature.

a. Storage

1. Sodium chlorite shall be stored by itself in a separate room and preferably shall be stored in an outside building detached from the water treatment facility. It must be stored away from organic materials because many materials will catch fire and burn violently when in contact with chlorite.

2. The storage structures shall be constructed of noncombustible materials.

3. If the storage structure must be located in an area where a fire may occur, water must be available to keep the sodium chlorite area cool enough to prevent heat induced explosive decomposition of chlorite.

b. Handling

1. Care should be taken to prevent spillage.

2. An emergency plan of operation should be available for the clean up of any spillage.

3. Storage drums must be thoroughly flushed prior to recycling or disposal.

c. Feeders

1. Positive displacement feeders shall be provided.

2. Tubing for conveying sodium chlorite or chlorine dioxide solutions shall be Type 1 PVC, polyethylene or materials recommended by the manufacturer.

3. Chemical feeders may be installed in chlorine rooms if sufficient space is provided or facilities meeting the requirements of subsection 5.4.1 shall be provided.

4. Feed lines shall be installed in a manner to prevent formation of gas pockets and shall terminate at a point of positive pressure.

5. Check valves shall be provided to prevent the backflow of chlorine into the sodium chlorite line.


| General | | Design | | Source | | Treatment | | Chemical Application | | Pumping Facilities | | Finished Water Storage | | Distribution Systems |
Appendix A Contents
Back to codes