Current through August 31, 2023
Iron and manganese control, as used herein, refers solely to
treatment processes designed specifically for this purpose. The treatment
process used will depend upon the character of the raw water. The selection of
one (1) or more treatment processes must meet specific local conditions as
determined by engineering investigations, including chemical analyses of
representative samples of water to be treated, and receive the approval of the
Department. The Department may require a pilot plant study in order to gather
all information pertinent to the design. See Subsection
501.19 for general information
on conducting pilot studies. (3-24-22)
01.
Removal by Oxidation, Detention and
Filtration. (3-24-22)
a. Oxidation may
be by aeration or by chemical oxidation with chlorine, potassium permanganate,
ozone or chlorine dioxide. (3-24-22)
b. Detention time: (3-24-22)
i. A minimum detention time of thirty (30)
minutes shall be provided following aeration to ensure that the oxidation
reactions are as complete as possible. This minimum detention may be omitted
only where a pilot plant study indicates no need for detention. The detention
basin may be designed as a holding tank without provisions for sludge
collection but with sufficient baffling to prevent short circuiting.
(3-24-22)
ii. Sedimentation basins
shall be provided when treating water with high iron or manganese content, or
where chemical coagulation is used to reduce the load on the filters.
Provisions for sludge removal shall be made. (3-24-22)
c. Filtration. Rapid rate pressure filters
are normally used for iron and manganese removal. Pressure filters shall not be
used in the filtration of surface or other polluted waters or following
lime-soda softening. (3-24-22)
i. The rate of
filtration shall not exceed three (3) gallons per minute per square foot of
filter area except where in-plant testing as approved by the Department has
demonstrated satisfactory results at higher rates. (3-24-22)
ii. The filters shall be designed to provide
for: (3-24-22)
(1) Loss of head gauges on the
inlet and outlet pipes of each battery of filters. (3-24-22)
(2) An easily readable meter or flow
indicator on each battery of filters. (3-24-22)
(3) Filtration and backwashing of each filter
individually with an arrangement of piping as simple as possible to accomplish
these purposes. (3-24-22)
(4)
Minimum side wall shell height of five (5) feet. A corresponding reduction in
side wall height is acceptable where proprietary bottoms permit reduction of
the gravel depth. (3-24-22)
(5) The
top of the wash water collectors to be at least eighteen (18) inches above the
surface of the media, (3-24-22)
(6)
The underdrain system to efficiently collect the filtered water and to
uniformly distribute the backwash water at a rate not less than fifteen (15)
gallons per minute per square foot of filter area. (3-24-22)
(7) Backwash flow indicators and controls
that are easily readable while operating the control valves.
(3-24-22)
(8) An air release valve
on the highest point of each filter. (3-24-22)
(9) An accessible manhole to facilitate
inspection and repairs for filters thirty-six (36) inches or more in diameter.
Sufficient handholds shall be provided for filters less than thirty-six (36)
inches in diameter. (3-24-22)
(10)
A means to observe the wastewater during backwashing and construction to
prevent cross connection. (3-24-22)
02.
Removal by Manganese Coated Media
Filtration. This process consists of a continuous or batch feed of
potassium permanganate to the influent of a manganese coated media filter.
(3-24-22)
a. Other oxidizing agents or
processes such as chlorination or aeration may be used prior to the
permanganate feed to reduce the cost of the chemical. (3-24-22)
b. An anthracite media cap of at least six
(6) inches or more as required by the Department shall be provided over
manganese coated media. (3-24-22)
c. Normal filtration rate shall be three (3)
gallons per minute per square foot. (3-24-22)
d. Normal wash rate shall be eight (8) to ten
(10) gallons per minute per square foot with manganese greensand and fifteen
(15) to twenty (20) gallons per minute with manganese coated media.
(3-24-22)
e. Sample taps shall be
provided prior to application of permanganate, immediately ahead of filtration,
at points between the anthracite media, and at the filter effluent. The sample
taps shall satisfy the requirements of Subsection
501.09.
(3-24-22)
03.
Removal by Ion Exchange. This process is not acceptable where
either the raw water or wash water contains dissolved oxygen or other oxidants.
(3-24-22)
04.
Biological
Removal. Biofiltration to remove manganese, iron, or a combination of
manganese and iron requires on-site piloting testing to establish
effectiveness. The final filter design shall be based on the on-site pilot
plant studies. (3-24-22)
05.
Sequestration by Polyphosphates. This process shall not be used
when iron, manganese or a combination thereof exceeds one point zero (1.0)
mg/l. The total phosphate applied shall not exceed ten (10) mg/l as
PO4. Where phosphate treatment is used, satisfactory
chlorine residuals shall be maintained in the distribution system. Possible
adverse affects on corrosion must be addressed when phosphate addition is
proposed for iron sequestering. (3-24-22)
a.
Stock phosphate solution must be kept covered and disinfected by carrying
approximately ten (10) mg/l free chlorine residual unless it is demonstrated to
the satisfaction of the Department that the phosphate solution is not able to
support bacterial growth and the phosphate solution is being fed from the
covered shipping container or an approved disinfected tank. Phosphate solutions
having a pH of two point zero (2.0) or less may also be exempted from this
requirement by the Department. (3-24-22)
b. Polyphosphates shall not be applied ahead
of iron and manganese removal treatment. The point of application shall be
prior to any aeration, oxidation or disinfection if no iron or manganese
removal treatment is provided. (3-24-22)
06.
Sequestration by Sodium
Silicates. Sodium silicate sequestration of iron and manganese is
allowed only for ground water supplies prior to air contact. On-site pilot
studies are required to determine the suitability of sodium silicate for the
particular water and the minimum feed needed. Rapid oxidation of the metal ions
such as by chlorine or chlorine dioxide must accompany or closely precede the
sodium silicate addition. (3-24-22)
a. Sodium
silicate addition is applicable to waters containing up to two (2) mg/l of
iron, manganese or combination thereof. (3-24-22)
b. Chlorine residuals shall be maintained
throughout the distribution system to prevent biological breakdown of the
sequestered iron. (3-24-22)
c. The
amount of silicate added shall be limited to twenty (20) mg/l as
SiO2, but the amount of added and naturally occurring
silicate shall not exceed sixty (60) mg/l as SiO2.
(3-24-22)
d. Sodium silicate shall
not be applied ahead of iron or manganese removal treatment.
(3-24-22)
07.
Sampling Taps. Smooth-nosed sampling taps shall be provided for
control purposes. Taps shall be located on each raw water source, each
treatment unit influent and each treatment unit effluent. The sample taps shall
satisfy the requirements of Subsection
501.09. (3-24-22)
