Current through Register Vol. 49, No. 13, September 23, 2024
Subpart 1.
Feed equipment required.
If chemical feed such as chlorination, coagulation, or other
processes are necessary for the protection of the water supply, a minimum of
two feeders must be provided so a standby unit or combination of units is
available to replace the largest unit during shutdowns. Spare parts must be
available for all feeders to replace parts subject to wear and damage.
Subp. 2.
Design and
capacity.
The design of the facility must ensure that:
A. a separate feed system is provided for
each chemical;
B. feeders supply,
at all times, the necessary amounts of chemical at an accurate rate, throughout
the range of feed. To allow for changes in pumping or application rates, the
feeder must be designed to operate between 30 and 70 percent of the feeder
range on initial start-up. If this is not possible with stock chemical
solution, the chemical must be diluted;
C. proportioning of chemical feed to rate of
flow is provided;
D. positive
displacement-type solution feeders are used to feed liquid chemicals;
E. chemical solutions are prevented from
being siphoned into the water supply by assuring discharge at points of
positive pressure and by providing antisiphon devices, or through a suitable
air gap or other effective means approved by the commissioner;
F. the service water supply is protected from
contamination by chemical solutions either by equipping the supply line with
backflow or backsiphonage prevention devices, or by providing an air gap of two
pipe diameters, but not less than three inches, between the supply line and top
of the solution tank;
G. materials
and surfaces in contact with chemicals are resistant to the chemical
solution;
H. dry chemical feeders:
(1) measure chemicals volumetrically or
gravimetrically;
(2) effectively
dissolve the chemical in the solution pot;
(3) provide gravity feed from solution pots,
if possible; and
(4) completely
enclose chemicals to prevent emission of dust to the operating room;
and
I. no direct
connection exists between any sewer and a drain or overflow from the feeder or
solution chamber or tank.
Subp.
3.
Location of feed equipment.
Chemical feed equipment must be:
A. readily accessible for servicing, repair,
and observation of operation;
B.
located and have protective curbings to prevent chemicals from equipment
failure, spillage, or accidental drainage from entering the water in conduits,
and treatment or storage basins; and
C. located above grade.
Subp. 4.
Controls.
Feeders must be manually or automatically controlled if the
water supply pumps are manually controlled. Where pumps are automatically
controlled, the feeders must be automatically controlled. In all cases,
automatic control shall be capable of reverting to manual control when
necessary.
A. Feeders must be designed
and controlled to provide rates proportional to flow.
B. Automatic chemical feed rate control may
be used in combination with residual analyzers which have alarms for critical
values and recording charts.
Subp.
5.
Weighing scales.
Weighing scales:
A.
must be provided to weigh cylinders at all plants using chlorine gas;
B. are required for solution feed unless a
comparable means for determining use is approved by the commissioner;
C. are required for volumetric dry chemical
feeders; and
D. must be accurate
enough to measure increments of 0.5 percent of load.
Subp. 6.
Feed lines.
Feed lines must:
A. be
as short as possible in length of run; of durable, corrosion resistant
material; easily accessible throughout entire length; protected against
freezing; and readily cleanable;
B.
slope upward from chemical source to feeder when conveying gases;
C. introduce corrosive chemicals so as to
minimize the potential for corrosion;
D. be designed consistent with the
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; and
F. include an injection nozzle when
application is into a pipeline.
Subp.
7.
Service water supply.
Water used for dissolving dry chemicals, diluting liquid
chemicals, or operating chemical feeders must be from a safe, approved source
with appropriate backflow prevention provided. The commissioner may grant an
exception in cases where the finished water quality is not affected by addition
of the chemical mixed with untreated water.
Statutory Authority: MS s
144.383
