DEPARTMENT OF HEALTH - The following is excerpted from wsdm_appendix_B-1.DOC.

Secondary Contaminant Treatment Requirements and Options

This document helps to define the conditions under which departmental requirements for secondary contaminant treatment (primarily Iron and Manganese treatment) are determined. It further addresses considerations regarding treatment requirements that may be imposed on a water system. The term, treatment, shall mean either the removal of a secondary contaminant from the source water or the rendering of a contaminant such that its aesthetic impact is reduced or eliminated (most often referred to as "sequestering" for iron and manganese treatment).

The State Board of Health Drinking Water Regulations, in WAC 246-290-320(1)(c), states "when a secondary MCL violation occurs, the purveyor shall notify the Department and take corrective action as directed by the Department." This document establishes the conditions by which the Department may determine that treatment for secondary contaminants is, or is not, required. For existing community and non-community systems that have added new water sources containing secondary contaminants at or above MCL levels, treatment shall be required such that the existing distribution system water quality is not further impaired. Sources for newly developed community and non-community water systems with a confirmed secondary contaminant MCL exceedance will be required to be treated before they will be approved for service. Treatment by sequestering can only be considered if the combined iron and manganese levels are no more than 1.0 mg/l, and the manganese level is no more than 0.1 mg/l as Mn. If sequestering is considered for new sources, pilot testing to determine the appropriate treatment chemical dosage and treatment process requirements will be necessary. (Please refer to item III of this policy for specific treatment considerations).

Since secondary standards are based on aesthetic, not health related, considerations, the basis for departmental decisions for sources in existence prior to the date of this policy shall be the degree of customer acceptance of the water quality and the customers' willingness to bear the costs of meeting the secondary standards.

The Department will determine that a secondary contaminant problem may exist through evidence provided through either customer complaints or by review of information provided by a purveyor. It will require action by the purveyor when (by receipt of individual complaints or by group petitions) five or more specific complaints associated with a secondary contaminant have been received from different customers in any twelve-month period. The complaints may be individually received by the department or may be registered by a petition signed by five, or more, customers. When a problem is determined to be significant, the following requirements are applicable:

I. IRON AND MANGANESE (Fe/Mn)

Compliance with the secondary standards for Fe/Mn is not required for public water systems in existence prior to January 15, 1992, unless the iron and/or manganese is creating a 'significant' problem as defined previously. If a system has a 'significant' problem, it will be required to take the following actions:

1. The water supplier shall prepare an engineering report with recommended corrective actions necessary to bring the system into compliance with the Fe/Mn standards. The report shall evaluate all reasonable alternatives and shall determine the costs associated with each alternative. The study shall be prepared by a professional engineer registered in the state of Washington.
2. The results of the study conducted by the water supplier shall be made available to the customer at an appropriately noticed public meeting, or by document distribution.
3. The public water supply system shall prepare a proposed survey of the regularly billed customers which provides for questionnaires to be sent to each service connection to determine the customer preference regarding the quality of the water and the cost of compliance. The questionnaire shall be as objective as possible and shall be based on the engineering report. The estimated costs (both capital and operational) to the consumer shall be based on the most cost-effective alternative presented in the engineering report. This alternative must also be acceptable to the Department.
4. The proposed survey questionnaire and the engineering report shall be submitted to the Department for review and approval prior to its distribution. Upon approval of the survey questionnaire, the water supplier shall distribute it to the consumers. The results of customer response to the questionnaire shall be tabulated by the water system for submission to the Department.
5. Public water systems that do not serve regularly billed customers similar to a community, will be reviewed and evaluated in a manner determined to be appropriate by the Department.

Special Allowances for Standby or Emergency Sources

Systems may use existing untreated sources which exceed the MCLs for secondary constituents for standby service or to meet peak demands, without the need for an engineering report or customer survey, provided that:

1. The monthly production from such sources is metered and is not used for more than five consecutive days or a total of fifteen days per year (use for any part of a day constitutes a day's use); and
2. Secondary constituents do not generally exceed twice the MCL anywhere in the distribution system; and
3. Public notification is made, with the notification being prior to use, whenever possible.

A. Basis for Departmental Decisions

1. 1. If the customer survey adequately demonstrates that the majority of the consumers (over 50 percent) that respond to the survey questionnaire do not wish to pay the costs necessary to attain compliance with the Fe/Mn standards, the water supplier may submit a written application requesting the Department to allow operation without treatment. The Department will then issue a letter which states that treatment for Iron and/or Manganese will not be required. This allowance will be effective for a five-year period beginning from the date of the letter.
   
   NOTE: Although it would be desirable for all system customers to respond to the survey, it is not expected that 100% response will occur. The Department considers that validation of the survey would require at least 50% of the total current customer base responding to the survey. The purveyor must pursue this level of response to the extent that an additional survey questionnaire must be sent to all customers not responding to the initial survey if less than 50% of all customers did not respond. If, after the second survey, it remains that less than 50% of the customers responded, the Department will use a simple majority for the responses received to determine the requirement for treatment.
   
   Whenever the survey shows clearly that greater than 50 percent of all possible customers have stated either a willingness or unwillingness to pay for treatment, this information can be immediately presented to the state without waiting for additional customer responses.
2. 2. At the end of the five-year period, the Department may re-evaluate the system's status. The water supplier may be required to conduct a new survey if the Department determines that substantial changes have occurred (i.e., large increase in new customers, significant changes in the quality of the water, etc.) which would warrant a re-survey of customers. Regardless of the five-year period covered by the Department's decision, the water supplier shall be required to re-survey its customers if the Department receives a petition signed by at least 25 percent of the water system's billed customers requesting a new survey. This will only be required, however, if a survey has not been conducted within the past 24 months.

B. Procedures for Enforcement

All public water systems which are determined to be in violation of the standard for Fe/Mn may be issued a directive or, if needed, a departmental order to come into compliance with the standards, unless the criteria and procedures previously presented in this document are followed and the Department has determined that treatment is not warranted.

II. OTHER SECONDARY CONTAMINANTS

The Department will pursue action regarding secondary contaminants other than Iron or Manganese in a manner similar to that presented for Iron and Manganese. However, the degree of problem significance may be variable. Depending on the constituent in question and the numbers and types of customer complaints, the Department will determine, on a case-by-case basis, the most appropriate course of action.

III. TREATMENT CONSIDERATIONS

Iron/Manganese Removal

When removal of iron and/or manganese is required, the most common method for removal employs oxidation followed by sedimentation and/or filtration. Oxidation may be affected by aeration, chlorination (chlorine or chlorine dioxide), or with use of potassium permanganate. Treatment is most effective at higher pH levels, usually in excess of pH 7.5. The best oxidant for manganese removal is potassium permanganate, which has been shown to be effective over wide ranges of pH.

Ion Exchange technologies can also be used for Fe/Mn removal. With these methods special care must be taken to insure that the iron and/or manganese is not oxidized before application through the exchange media. Fouling of the exchange bed can occur if the iron or manganese is not maintained in a chemically reduced state.

Lime Softening processes can be used for iron/manganese removal, but this practice is normally used adjunct to water softening, which is not common in Washington State.

Treatment Waste Disposal

Wastes (i.e., brine discharges or filter backwash wastewater) associated with treatment applications must be disposed of properly. The Washington Department of Ecology should be contacted to determine the disposal requirements.

Iron/Manganese Sequestering

When sequestering (also called stabilization, chelation, or dispersion) is used as treatment method, certain limitations need to be recognized. Sequestering is not considered appropriate whenever the combined iron/manganese level is in excess of 1.0 milligram per liter (mg/L), with the manganese level being no more than 0.1 mg/l as Mn. In no case shall sequestering be considered for combined iron/manganese levels above 1.0 mg/L, or when manganese levels are reported above 0.1 mg/l.

Addition of sequestering agents such as the polyphosphates (hexametaphosphate, trisodium phosphate) must be done prior to any oxidation influence. Concentrations of polyphosphate cannot exceed 10 mg/L as PO. The polyphosphate must be listed as acceptable for drinking water uses by the National Sanitation Foundation or the Underwriter's Laboratory before it may be applied in practice.

Since polyphosphate is a bacterial nutrient and can lead to bacterial growth in distribution lines, disinfection must be applied following the sequestering treatment.

To prevent oxidation of the iron or manganese before they are stabilized, the polyphosphate should be added into, or near, the well on the suction side of the pump to minimize oxidation by aeration. The application point for the disinfectant should be more than 10 feet downstream of the pump discharge. A greater distance may be required by manufacturer's recommendations.

Sequestering agents are effective in cold water, but lose their capability in heated or boiled water. It must be recognized that this form of treatment may not resolve customer concerns for hot water portions of domestic service.

If it is determined that sequestering, after a year from its initiation as evidenced by complaints of the water system customers, is ineffective in eliminating a secondary contaminant problem, then removal treatment must be instituted.

Pilot Testing for Sequestering - Laboratory Bench Scale Tests

When sequestering is considered for iron/manganese control the following process can be used to determine the dosage of sequestering agent needed for proper operation:

1. Treat a series of samples with a standard chlorine solution to determine the chlorine dose required to produce the desired chlorine residual.
2. Prepare a standard sequestering agent solution by dissolving 1.0 gram of agent in a liter of distilled water in a volumetric flask.
3. Treat a separate series of samples with varying amounts of the sequestering agent. One milliliter (ml) of the standard agent solution, prepared as per item 2 previously, is equivalent to a 0.1 % solution. One ml of this stock solution in one liter of sample is equivalent to 8.34 pounds of sequestering agent per million gallons. Stir the various dosages to insure good mixing in the series of samples; and continue to stir while adding the previously determined chlorine dosage so as to minimize creation of localized high chlorine concentrations.
4. The series of treated samples are to be observed against a white background to note the degree of discoloration. The proper dose of sequestering agent is that which delays noticeable discoloration for a period of four days.
   
   (NOTE: Samples for the above bench test should be freshly collected and should be kept away from direct sunlight to avoid heating. The samples should be maintained at room temperature for the duration of the test.)

Notification Required

Whenever sequestering treatment is used for management of iron and/or manganese problems in a water system, the customers must be notified that this form of control is being used and that they may still experience problems with the hot water portion of their home plumbing. In addition, customers located in more remote portions of the water distribution system must be informed that iron/manganese may still pose a problem if their water is not routinely flushed through their lines. The form, method of delivery, and frequency for this notification will be determined in consultation with the Division of Drinking Water authority regarding secondary contaminants.

IV. DISTRIBUTION SYSTEM RELATED PROBLEMS

Occasionally, complaints regarding aesthetic concerns may occur which are not directly attributable to source water levels of iron and/or manganese. The water quality may be such that corrosion of the system distribution piping may lead to high iron levels at consumer taps. Or, for some systems there may be problems associated with lengthy dead-end lines which are not routinely flushed. For existing systems, the nature of any consumer complaints must be examined to determine if the problem is water source or distribution system related. The water purveyor will be responsible for development of a report, to be submitted for department review, which identifies the nature of the problem. If corrosion of the distribution system is determined to be the problem, any treatment options examined to remediate the aesthetic concern must address ways to mitigate problems associated with water corrosivity. NOTE: Sequestering is not considered appropriate for distribution system related problems for either primary or secondary contaminants.

REFERENCES

• "Water Treatment Principles and Design" by James M. Montgomery, Consulting Engineers, Inc., John Wiley and Sons, New York, et al. 1985.
• "Handbook of Public Water Systems" by Culp/Wesner/Culp, Van Nostrand Reinhold Company, New York, 1986.
• "Water Supply, Treatment and Distribution" by Rodger Walker, Prentice Hall, Inc, New Jersey, 1978.
• "Water Treatment Plant Design", 2nd Ed., ASCE, AWWA, McGraw-Hill Publishing Company, New York, et al., 1990.
• "Water Treatment Plant Operation", Volume II, California State University, Sacramento, for the California Department of Health Services and the U.S. Environmental Protection Agency.