Section 930.20 Treatment
Plant
A non-community water system,
semi-private water system, or a private water system which obtains water from a
surface source, shall treat water by utilizing a water treatment plant with
either slow sand filtration or cartridge filtration, and disinfection.
a) General
1) Raw Water Quality. The turbidity of the source water shall
not exceed 50 nephelometric turbidity units. Cartridge filtration shall not be
used to treat water obtained from rivers.
2) Intake. A means must be provided to withdraw raw water from
the surface source. Intakes shall not incorporate a submerged sand and gravel
filter. The intake must be located at a point of deepest water in the pond and
must be capable of being raised or lowered for cleaning. A coarse meshed screen
with openings not greater than ¼ inch shall be placed over the end of the
intake pipe to prevent entrance of fish, dead leaves, and other debris. The
intake pipe must be constructed such that it is flexible, will not break when
raised, and shall be approved for use as potable water piping in accordance
with the Illinois Plumbing Code (77 Ill. Adm. Code 890, Section 890.Appendix A
Plumbing Materials, Equipment, Use Restrictions and Applicable Standards) or
Table A Approved Materials for Water Service Pipe of this Part. The intake
pipe must be kept below any ice, it must be buried in a trench through shallow
water, and it must be placed below the frost line at all points.
b) Slow Sand Filtration. The treatment plant shall include the
following principal units.
1) Raw Water Pump. A pump shall be required to deliver water
from the intake to the filter at a rate which is greater than the filtration
rate. The pump must be self-priming or so installed that it will not lose its
prime.
A) The pump shall be driven by an electric motor, controlled by a
sensing system on top of the filter, and set to start and stop the raw water
pump automatically. The system shall be set to allow 10 inch-12 inch
fluctuation in the water level in the filter to prevent frequent cycling of the
pump.
B) The raw water pump will not be required when the elevation of
the filter is below the elevation of the intake pipe. Elevation difference
between the pond and the filter must be sufficient to produce the flow rate
needed at times of low pond water levels in accordance with the rates set forth
in Section 930.30 of this Part. There must be no possibility of flooding the
treatment plant by high water which may occur below the pond.
2) Filter Sand. The filter must be designed so that the raw
water flows downward by gravity through the filter media.
A) Filter Sand. The filter media shall be a layer of sand at
least three feet in depth. The sand shall have an effective size of .25-.35 mm
with an ideal size of .30 mm and a uniformity coefficient of 1.4-1.8 with an
ideal uniformity coefficient of 1.6. The sand shall be supported by a bed of
gravel one foot in depth. A perforated pipe must be installed at the bottom of
the filter which will allow water to flow to a water storage tank.
B) Filtration Rate. The maximum permissible filtration rate shall
be 2 gallons per minute for each 25 square feet of sand surface area. The
amount of water needed per day shall be calculated using Table B.
C) Construction. The filter must be constructed of concrete or a
material which will not corrode or deteriorate and the walls and bottom shall
be watertight. Examples of materials which will corrode or deteriorate include
wood, tin, or steel. The minimum height of the filter shall be 8 feet in order
to provide for a 3 foot depth of water above the sand, and a minimum of 1 foot
from water level to the top of the filter during operation.
D) Underdrain Pipe. A perforated underdrain pipe, 1¼ inches
inside diameter or larger, shall be installed horizontally at 2 inches above
the bottom of the filter tank. One end of the pipe shall be capped within the
filter to prevent the entrance of gravel. The other end shall pass through the
filter wall, and a valve shall be installed to regulate the flow of water
leaving the filter. See Illustration A. Forty -50 holes in the underdrain
pipe shall be drilled in 2 rows at a 90o angle to each other on the
bottom side of the pipe. The holes shall be ¼ inch in diameter and shall be
uniformly spaced. One separate underdrain pipe shall be installed for each 75
square feet of filter area.
E) Gravel. Clean, washed gravel shall be placed in three graded
layers in the filter, the coarsest gravel being on the bottom. The bottom
layer shall be placed to a depth of 6 inches, and shall consist of stones ½-¾
inches in diameter. The top of the pipe shall be 2 inches below the top of
this layer. The second or middle layer shall be 3 inches in depth and shall
consist of stones ¼-½ inches in diameter. The third or top layer shall be 3
inches in depth and consist of stones ⅛-¼ inches in diameter.
F) Filter Valves. The piping which carries the water from the
filter is to be valved as shown in Illustration B. The filter to waste pipe
shall discharge at least 6 inches above the floor drain to permit checking the
clarity of the filtered water and to measure the flow rate of filtered water. The
floor drain shall not be located over the filtered water storage tank nor shall
any portion of the waste drain piping pass through any part of the water
storage tank. The filtered water shall be stored in the storage tank and a
float valve shall be installed at the end of the filtered water pipe within the
storage tank to shut off the flow when the tank is filled to approximately 6
inches from the top. (See Illustration A for exact location.) Solenoid valves
controlled by a float switch may also be used. A manhole shall be installed in
the top of the storage tank. The manhole shall have a raised curb and be
provided with a cover of the overhanging type. The float valve is to be
located to one side of the manhole so that it may be reached for any adjustment,
without entering the storage tank. The floor drain which receives filtered
water and discharges to waste shall discharge at ground level, at least 15 feet
horizontally and downgrade from the plant and above any floodwater level. This
drain shall not be connected to any other drain or sewer.
G) Filtered Water Storage Tank. A watertight and pollution-proof
reservoir must be provided to receive the filtered water. Its capacity shall
be at least equal to the amount of water which will be used in one day. This
amount is obtained by using Table B. The top of the storage tank shall not be
higher than the bottom of the filter, and shall not be located where it can be
subject to flooding. Sources of pollution shall not be located closer to buried
water storage tanks than indicated in Section 920.50 of the Illinois Water Well
Construction Code (77 Ill. Adm. Code 920.50).
H) Filtered Water Pump and Pressure Tank. An electrically driven
pump shall be provided to remove water from the storage tank. The water
distribution system shall be designed to maintain a minimum positive pressure
of 20 pounds per square inch (p.s.i.) in all parts of the system at all times.
Water pipe shall conform to applicable specifications and standards of the
Illinois Plumbing Code (77 Ill. Adm. Code 890, Section 890.1150) for the type
of pipe to be used.
I) Filter
Building. A building or structure shall be provided to enclose the filter and
pumps. If the system is to be operated through the winter months, heating must
be provided to prevent freezing.
c) Cartridge
Filtration. The treatment plant shall include the following principal units.
1) Raw
Water Pump. The pump shall be driven by an electric motor and be controlled by
a pressure switch set to turn on the pump at a pressure of no less than 20
pounds per square inch. The pump shall be protected against excessive cycling
by the installation of a hydropneumatic tank. The volume of water that can be
drawn from the hydropneumatic tank between pump cycles shall be at least equal
to the volume of water pumped in 30 seconds. The hydropneumatic tank shall be
installed upstream of the filters and disinfection system.
2) Particulate
Reduction Filter. Particulate reduction shall be accomplished using a filter
certified to comply with ANSI/NSF Standard 42 − Drinking Water Treatment
units − Aesthetic Effects, for particulate reduction, class I or II and
be listed as such by an approved certification agency. The design flow rate in
the particular application in which the filter is utilized shall not exceed the
rated service flow rate for which the filter was certified. An official
certification label from the certifying agency shall be permanently affixed to
the filter. When treating turbid waters, an additional filter may be needed
prior to the particulate reduction filter.
3) Turbidity
Reduction and Cyst Reduction. Turbidity reduction and cyst reduction shall be
accomplished utilizing either separate filters for each process or one filter
for both processes. The turbidity and cyst reduction filters shall be located
downstream of the particulate reduction filter.
A) Turbidity
Reduction Filter. Turbidity reduction shall be accomplished using a filter
certified to comply with ANSI/NSF Standard 53 − Drinking Water Treatment
units − Health Effects, for turbidity reduction and be listed as such by
an approved certification agency. The design flow rate in the particular
application in which the filter is utilized shall not exceed the rated service
flow rate for which the filter was certified. An official certification label
from the certifying agency shall be permanently affixed to the filter.
B) Cyst
Reduction Filter. Cyst reduction shall be accomplished using a filter certified
to comply with ANSI/NSF Standard 53 − Drinking Water Treatment units −
Health Effects, for cyst reduction and be listed as such by an approved
certification agency. The design flow rate in the particular application in
which the filter is utilized shall not exceed the rated service flow rate for
which the filter was certified. An official certification label from the
certifying agency shall be permanently affixed to the filter.
4) Flow Control.
A flow control valve and a flow rate meter shall be installed downstream of the
filters. The flow rate meter shall have a range which will permit the
measurement of the rated service flow rate for the filters, and shall have an
accuracy of ± 10% over the full scale.
d) Disinfection.
1) A
disinfection system shall be installed with calcium or sodium hypochlorites or
gas chlorine or other disinfecting agents approved by the Department.
Proposals for the use of disinfecting agents other than those specifically
listed in this Section must be approved by the Department prior to preparation
of final plans and specifications. The Department will grant approval when all
available information establishes that the chemical to be used as a
disinfecting agent meets the following conditions: the residual levels created
by the use of the chemical will not jeopardize the health of the user of the
water, testing procedures for residual elements are recognized in
"Standard Methods for the Examination of Water and Wastewater" (1995
Edition − American Public Health Association) (see Section 930.15) and
the chemical will destroy bacteria in the water supply. Ultraviolet
disinfection may only be used in water treatment plants utilizing cartridge
filtration.
2) Chlorination.
Disinfection using chlorine shall include feeding equipment, a retention tank
and testing equipment.
A) Chlorination
Equipment. The chlorinator shall be designed to provide a free chlorine
residual of at least two milligrams per liter (mg/l) in the water. The
equipment shall be designed so that it will operate accurately over the desired
feeding range. Where flow is uniform, actuation of a constant volume feeder by
the pump circuit is required. Where flow is variable, automatic flow
proportioning is required.
i) Hypochlorinator.
Positive displacement pumps shall be provided to inject hypochlorite solution.
The pump shall be of variable flow type and shall be of sufficient capacity to
feed the required amount of disinfectant. If calcium hypochlorite is used, the
concentration of calcium hypochlorite in the solution shall not exceed 5
percent. The solution container shall have a minimum capacity equal to the
volume of solution required per day. The chlorine pump shall be controlled by
a float switch located in the filtered water storage tank. Chlorine shall be
pumped whenever water is flowing into the storage tank.
ii) Gas
Chlorinators. Any gas chlorination system shall meet the requirements of
Section 900.40(n)(5) of the Drinking Water Systems Code (77 Ill. Adm. Code
900.40(n)(5)).
B) Contact
Time and Point of Application. Chlorine shall be applied after the filter and
prior to the filtered water storage tank, and in a manner that will provide a
free chlorine residual of at least 2 milligrams per liter in the water after
thorough mixing and a contact time of at least 30 minutes at maximum flow
rates. The pipe carrying water from the filter shall terminate at or above
the water surface of the storage tank. Water shall be withdrawn from a solid
pipe at a point not more than 3 inches above the bottom of the water storage
tank.
C) Testing
Equipment. Chlorine residual test equipment capable of measuring free chlorine
residual shall be provided and shall be capable of measuring residuals to the
nearest 0.1 mg/L in the range below 0.5 mg/L, to the nearest 0.3 mg/L between
0.5 and 1.0 mg/L, and to the nearest 0.5 mg/L between 1.0 mg/L and 2.0 mg/L.
3) Ultraviolet
Disinfection. Where ultraviolet disinfection is used, it shall be accomplished
using an ultraviolet disinfection system certified to comply with ANSI/NSF
Standard 55 − Ultraviolet Microbiological Water Treatment Systems −
Class A Systems. The design flow rate for the ultraviolet disinfection
equipment shall be at least equal to the rated service flow rate for any of the
filters. The ultraviolet disinfection equipment shall be installed downstream
of the filters.
(Source: Amended at 27 Ill.
Reg. 15998, effective October 1, 2003)
