12 Va. Admin. Code § 5-590-860 - Chemical application

A. Plans and specifications shall be submitted for evaluation and approval, as required in Part I (12VAC5-590-200 through 12VAC5-590-220), 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. Chemical storage and handling facilities;

4. Specifications for chemicals to be used;

5. Operating and control features; 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 backsiphonage between multiple points of feed through common manifolds; and

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

C. Feed equipment.

1. Where chemical feed is necessary for the treatment of the source water, such as chlorination, coagulation, or other essential processes, a standby feeder or combination of feeders shall be available to provide the required chemical dose with the largest feeder out of service.

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

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

b. Proportioning of chemical feed to the rate of flow shall be provided where the water flow is not constant or where specifically required by the department.

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

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

e. Dry chemical feeders shall:

(1) Measure chemicals volumetrically or gravimetrically;

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

(3) Provide gravity feed from solution pots; and

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

f. No direct connection shall exist between any sewer and a drain or overflow from the feeder or solution chamber or tank.

g. 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 within a protective curbing so that chemicals resulting from equipment failure, spillage, or accidental drainage shall not enter the water in conduits or treatment or storage basins.

4. Control.

a. Feeders shall be capable of both manual and automatic control with the automatic control reverting to manual control as necessary;

b. Feeders shall be manually started following shutdown, unless otherwise approved by the department; and

c. Automatic chemical dose controls with residual analyzers shall provide alarms for critical values and shall include indicating and recording equipment.

5. Solution tanks. All solution tanks shall be manufactured of materials suitable for food contact or that meet the requirements of 12VAC5-590-810.

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

b. Solution tanks shall be of sufficient number and capacity to assure continuous chemical application during tank servicing, and the access openings shall be curbed and fitted with tight covers.

c. Each tank exceeding 30 gallons in capacity or fixed in place shall be provided with a drain unless other means of dewatering the tank are provided.

(1) Direct connection between any tank or drain and a sewer is prohibited.

(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. Process 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.

g. Buried or subsurface chemical storage or solution tanks are prohibited.

h. Overflow pipes, when provided, shall:

(1) Be turned downward, and when located outside, be provided with an appropriately sized screened end to prevent entry of insects and small animals;

(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 water treatment plants utilizing chlorine gas; for large water treatment plants, indicating and recording type are desirable;

b. Shall be provided for fluorosilicic acid feed systems in conjunction with a loss-of-weight recorder;

c. Shall be considered 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 the 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 a 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.

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

8. Process water.

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

(1) 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, a spare pump shall be provided.

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

(1) An air gap between the fill pipe and overflow rim of the solution or dissolving tank, and 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, location, and available means for maintaining and testing the device; or

(3) A satisfactory vacuum relief device.

D. Chemicals.

1. Storage.

a. Space shall be provided where at least 30 days of chemical supply can be stored, based on the average dose and average annual water treatment plant flow rate. Storage shall be at a location that is convenient for efficient handling and safety. Lesser storage capacity may be approved if the owner can demonstrate that the local suppliers or other conditions will provide an uninterrupted source of chemicals.

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 sodium chlorite to eliminate any danger of explosion.

e. Activated carbon. The following special precautions shall be taken in areas where activated carbon is stored, handled, and fed.

(1) Isolated, cool, and dry areas free from sources of ignition shall be provided for activated carbon storage;

(2) Electrical equipment, devices, and materials shall comply with applicable codes;

(3) Ventilation in areas associated with the storage, handling, and feeding of activated carbon shall be localized so as not to cause dust or material to be drawn into other areas; and

(4) Activated carbon shall not be stored with strong oxidants such as ozone, liquid chlorine (i.e., compressed chlorine gas), and permanganate.

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

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

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

2. 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 to mitigate the quantity of dust that 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 that put the hoppers or bins under negative pressure.

e. Precautions shall be taken with electrical equipment to prevent explosions and other hazards.

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 a 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 mitigate excessive lifting by operators.

h. Provisions shall be made for disposing of empty containers by an approved procedure that will mitigate 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.

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

F. Operator safety. Safety provisions shall protect people at the waterworks from chemical exposures in accordance with VOSH laws and regulations.

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 and 12VAC5-590-1001 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 that complies with VOSH laws and regulations 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. Facilities such as emergency eye wash and showers shall be provided for washing of the face, gloves, and protective equipment.

Notes

12 Va. Admin. Code § 5-590-860

Derived from VR355-18-009.02 § 3.23, eff. August 1, 1991; amended, Virginia Register Volume 9, Issue 17, eff. June 23, 1993; Amended, Virginia Register Volume 37, Issue 20, eff. 6/23/2021.

Statutory Authority: §§ 32.1-12 and 32.1-170 of the Code of Virginia.