SECTION 252:626-9-7. Iron and manganese control

(a)   General. DEQ must approve treatment processes. When selecting treatment processes, local conditions must be evaluated using engineering investigations, including chemical analyses of representative samples of water to be treated. Include provisions for pH adjustment of the water to optimize the chemical reaction and to produce a non-corrosive finished water, containing not more than 0.3 ppm of iron and 0.05 ppm of manganese.

(1)   Removal by oxidation, detention, and filtration.

(A)   Oxidation. Provide oxidation through the use of chlorination, chlorine dioxide, potassium permanganate, aeration, ozonation or other approved method.

(B)   Detention.

(i)   Reaction. Provide a minimum detention time of 30 minutes following oxidation in order to insure that the oxidation reactions are as complete as possible. Design the detention basin as a holding tank with sufficient baffling to prevent short circuits. Provide drains for the basin.

(ii)   Sedimentation. Provide sedimentation basins when treating water with high iron or manganese content, or where chemical coagulation is used to reduce the load on the filters.

(C)   Filtration. Provide filtration.

(2)   Removal by the lime-soda softening process. See 252:626-9-10.

(3)   Removal by manganese green sand filtration.

(A)   Make provisions to apply the permanganate as far ahead of the filter as practical.

(B)   Provide an anthracite media cap of at least 6 inches over the manganese green sand.

(C)   Three gal/min/ft is the maximum filtration rate.

(D)   Normal wash rate is 8 to 10 gal/min/ft of filter area.

(E)   Provide air washing.

(F)   Provide sample taps:

(i)   prior to application of permanganate,

(ii)   immediately ahead of filtration,

(iii)   at a point between the anthracite media and the manganese green sand,

(iv)   halfway down the manganese green sand, and

(v)   at the filter effluent.

(4)   Sequestration by polyphosphates. Do not use sequestration by polyphosphates where the concentration of iron, manganese, or the combination of the two exceeds 1.0 mg/l. Do not exceed 10 mg/l of total phosphate as PO4. Where phosphate treatment is used, provide chlorination and maintain chlorine levels throughout the distribution system as required by OAC 252:631.

(A)   Feeding equipment must meet the requirements of 252:626-11.

(B)   Do not apply polyphosphates ahead of iron and manganese removal treatment.

(b)   Sampling and testing equipment.

(1)   Provide smooth-nosed sampling taps for control purposes. Locate taps on each raw water source, treatment unit influent and effluent.

(2)   Provide testing equipment with the capacity to accurately measure the iron content to a minimum of 0.1 mg/l and the manganese content to a minimum of 0.05 mg/l.

(3)   Public water supply systems that feed polyphosphate or orthophosphate shall have test equipment capable of accurately measuring phosphates from 0.1 to 20 mg/l.

[Source: Added at 18 Ok Reg 1612, eff 6-1-01; Amended at 31 Ok Reg 1301, eff 9-12-14]