Section 860. Chemical application

Only chemicals authorized in the construction permit or subsequently authorized by the division and in compliance with National Sanitation Foundation Standards 60 and 61 shall be used to treat drinking water or as an additive to drinking water.

A. Plans and specifications shall be submitted for review and approval, as provided for in Part I, and shall include:

1. Descriptions of feed equipment, including maximum and minimum feed ranges;

2. Location of feeders, piping layout, and points of application;

3. Storage and handling facilities;

4. Specifications for chemicals to be used;

5. Operating and control procedures; and

6. Descriptions of testing equipment and procedures.

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

1. Assure maximum efficiency of treatment;

2. Provide maximum protection to the consumer;

3. Provide maximum safety to operators;

4. Assure satisfactory mixing of the chemicals with the water;

5. Provide maximum flexibility of operation through various points of application, when appropriate;

6. Prevent backflow or back-siphonage between multiple points of feed through common manifolds; and

7. Provide for the application of pH-affecting chemicals to the raw water prior to the addition of the coagulant in turbidity removal processes.

C. Feed equipment.

1. Where chemical feed is necessary for the treatment of the supply, such as chlorination, coagulation or other essential processes:

a. A minimum of two feeders shall be provided; and

b. A standby unit or combination of units of sufficient capacity shall be available to replace the largest unit during shutdowns.

2. Feeders shall be of such design and capacity to meet the following requirements:

a. Feeders shall be able to supply at all times the necessary amounts of chemical at an accurate rate throughout the range of feed;

b. Proportioning of chemical feed to the rate of flow shall be provided where the water flow is not constant;

c. Positive displacement type solution feed pumps, or gravity feed through rotometers, shall be used to feed liquid chemicals, but should not normally be used to feed chemical slurries; and

d. Chemical solutions shall be prevented from being siphoned into the water supply by:

(1) Providing vacuum relief,

(2) Providing a suitable air gap, or

(3) Other approved devices or piping arrangements;

e. The service water supply shall be protected from contamination by chemical solutions by:

(1) Equipping the supply line with backflow or back-siphonage prevention devices or

(2) Providing an air gap between supply line and solution tank;

f. Chemical contact materials and surfaces shall be resistant to the aggressiveness of the chemical solution;

g. Dry chemical feeders shall:

(1) Measure chemicals volumetrically or gravimetrically;

(2) Provide effective solution of the chemical in the solution pot;

(3) Preferably provide gravity feed from solution pots; and

(4) Completely enclose chemicals to prevent emission of dust to the operation room;

h. No direct connection may exist between any sewer and a drain or overflow from the feeder or solution chamber or tank; and

i. A separate chemical waste tank should be considered.

3. Chemical feed equipment:

a. Shall be located near points of application to minimize length of feed lines;

b. Shall be readily accessible for servicing and repair, and observation of operation; and

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

4. Control:

a. Feeders may be manually or automatically controlled with the automatic control reverting to manual control as necessary;

b. The feeders shall be manually started following shutdown, unless otherwise approved by the division; and

c. Automatic chemical dose or residual analyzers may be approved for use and shall provide alarms for critical values, and recording charts.

5. Solution tanks. All solution tanks shall be manufactured of materials suitable as a food contact surface:

a. Means shall be provided to maintain uniform strength of solution, consistent with the nature of the chemical solution. Continuous agitation is necessary to maintain slurries in suspension;

b. Two solution tanks of specific capacity may be required for a chemical to assure continuity of chemical application during servicing;

c. Each tank exceeding 30 gallons in capacity or fixed in place shall be provided with a drain.

(1) No direct connection between any tank or drain and a sewer shall be permitted.

(2) All drains shall terminate at least two pipe diameters, but not less than two inches, above the rim of the receiving sump, conduit, or waste receptacle;

d. Means shall be provided to indicate the solution level in the tank;

e. Make-up water shall enter the tank above the rim at a distance of two pipe diameters but not less than two inches;

f. Chemical solutions shall be kept covered.

(1) Polyphosphate solutions shall be disinfected by carrying a chlorine residual when added to unchlorinated water.

(2) Large tanks with access openings shall have such openings curbed and fitted with tight covers;

g. Subsurface locations for solution tanks shall:

(1) Be free from sources of possible contamination;

(2) Assure positive drainage for groundwaters, accumulated water, chemical spills, and overflows; and

h. Overflow pipes, when provided, shall:

(1) Be turned downward, with end screened;

(2) Have free discharge;

(3) Be located where noticeable; and

(4) Be directed so as not to contaminate the water or be a hazard to operating personnel.

6. Weighing scales:

a. Shall be provided for weighing cylinders at all plants utilizing chlorine gas; for large plants, indicating and recording type are desirable;

b. Shall be required for fluoride solution feed in conjunction with a loss of weight recorder;

c. Should be required for volumetric dry chemical feeders; and

d. Shall be accurate to measure increments of 0.5% of load.

7. Feed lines:

a. Shall be as short as possible in length of run and be:

(1) Of durable, corrosion resistant material;

(2) Easily accessible throughout entire length;

(3) Protected against freezing; and

(4) Readily cleanable.

b. Shall slope upward from chemical source to feeder, when conveying gases;

c. Shall introduce corrosive chemicals in such manner as to minimize potential for corrosion;

d. Shall be designed consistent with scale forming solids depositing properties of the water, chemical solution, or mixture conveyed;

e. Shall not carry chlorine gas beyond the chlorine feeder room unless the chlorine is under vacuum; and

f. Shall be designed so that liquid alum does not mix with water prior to the point of application.

8. Service water supply:

a. Water used for dissolving dry chemicals, diluting liquid chemicals, or operating chemical feeders shall be:

(1) Only from a safe, approved source;

(2) Protected from contamination by appropriate means;

(3) Ample in supply and adequate in pressure;

(4) Provided with means for measurement when preparing specific solution concentrations by dilution; and

(5) Properly treated for hardness when necessary.

b. Where a booster pump is required, duplicate equipment shall be provided and, when necessary, standby power.

c. Backflow prevention shall be achieved by appropriate means such as:

(1) An air gap between fill pipe and overflow rim of solution or dissolving tank equivalent to two pipe diameters but not less than two inches;

(2) An approved reduced pressure zone backflow preventer, consistent with the degree of hazard, aggressiveness of chemical solution, back pressure sustained, and available means for maintaining and testing the device; or

(3) A satisfactory vacuum relief device.

D. Chemicals.

1. Quality.

a. Chemical containers shall be fully labeled to include:

(1) Chemical name, purity and concentration;

(2) Supplier name and address;

(3) Precautions in handling; and

(4) Requirements of Virginia Department of Labor and Industry, Virginia Occupational Safety and Health Standards for General Industry, section 1910.1200(f).

b. Chemicals shall meet American Water Works Association standards, where applicable, and be stamped or certified accordingly.

c. Provisions may be required for assay of the chemicals delivered where the quality is in doubt.

d. Chemicals having a distinguishing color may be used, providing the coloring material is not toxic in concentrations used and will not impart taste, odor, or color to the water supply.

2. Storage.

a. Space shall be provided where at least 30 days of chemical supply can be stored in dry storage conditions at a location that is convenient for efficient handling unless local suppliers and conditions indicate lesser storage is adequate.

b. Cylinders of chlorine gas shall be:

(1) Isolated from operating areas;

(2) Restrained in position to prevent upset; and

(3) Stored in rooms separate from ammonia storage.

c. Liquid chemical storage tanks shall:

(1) Have a liquid level indicator; and

(2) Have an overflow and a receiving basin or drain capable of receiving accidental spills or overflows.

d. Special precautions shall be taken with:

(1) Sodium chlorite, to eliminate any danger of explosion; and

(2) Activated carbon, which is a potentially combustible material, requiring isolated, fireproof storage and explosion proof electrical outlets, lights, and motors in areas of dry handling.

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

f. Solution storage or day tanks supplying feeders directly should have sufficient capacity for one day of operation.

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

3. Handling.

a. Provisions shall be made for measuring quantities of chemicals used to prepare feed solutions.

b. Storage tanks and pipelines for liquid chemicals shall be specific to the chemicals and not for alternates.

c. Chemicals that are incompatible shall not be fed, stored, or handled together.

d. Provisions shall 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 shall be provided by use of:

(1) Vacuum pneumatic equipment or closed conveyor systems;

(2) Facilities for emptying shipping containers in special enclosures; or

(3) Exhaust fans and dust filters which put the hoppers or bins under negative pressure.

e. Precautions shall be taken with electrical equipment to prevent explosions, particularly in the use of sodium chlorite and activated carbon.

f. Acids shall:

(1) Be kept in closed, acid resistant shipping containers or storage units; and

(2) 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.

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

h. Provisions shall be made for disposing of empty containers by an approved procedure which will minimize exposure to the chemical.

E. Housing.

1. Structures, rooms, and areas accommodating chemical feed equipment shall provide convenient access for servicing, repair, and observation of operation.

2. Floor surfaces shall be smooth and impervious, slip-proof and well drained with a slope of ⅛ inch per foot, minimum.

3. Open basins, tanks, and conduits shall be protected from chemical spills or accidental drainage.

F. Operator safety.

1. Gases from feeders, storage, and equipment exhausts shall be conveyed to the outside atmosphere, above grade and remote from air intakes.

2. See 12VAC5-590-1000 for special provisions for handling and storing chlorine.

3. A plastic bottle of hydrochloric acid (muriatic acid in commercial form) shall be available for ammonia leak detection where ammonia gas is used or stored.

4. At least one pair of rubber gloves with long gauntlets, a dust respirator of a type approved by the Virginia Occupational Safety and Health Standards for General Industry, Section 1910.134 for toxic dusts, and an apron or other protective clothing shall be provided for each operator in any shift who will handle dry chemicals.

5. Rubber gloves, clothing protection, and goggles shall be provided for each operator preparing chemical solutions.

6. Facilities shall be provided for washing of the face, gloves, and protective equipment.

7. See 12VAC5-590-1000 E.

Historical Notes

Derived from VR355-18-009.02 § 3.23, eff. August 1, 1991; amended, Volume 09, Issue 17, eff. June 23, 1993.

Statutory Authority

§§ 32.1-12 and 32.1-170 of the Code of Virginia.