Ordering Information:
ORDER NUMBER:  91147
DATE AVAILABLE: Fall 2006

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PRINCIPAL INVESTIGATORS:
Paul M. Kohl and Steve J. Medlar

OBJECTIVES:
The objective of this project was first to evaluate the occurrence, chemistry, and treatment methods associated with manganese (Mn) in ground and surface waters. Building upon these findings, a further goal was to study problems associated with manganese in water distribution systems and measure Mn in specific distribution systems. Another objective was to estimate achievable, cost-effective target levels for manganese below the current drinking water advisory standard of 0.05 mg/L.

BACKGROUND:
Manganese in drinking water is an aesthetic problem, characterized by so-called “black water,” laundry spotting, and similar issues. The control of manganese in a water distribution system relates more to reducing consumer complaints than to protecting health. However, consumers often judge drinking water based on its appearance, odor, and color at the tap even if it is safe to consume. The control of manganese is complicated by its complex chemistry.

HIGHLIGHTS:
Mn problems have been an issue for so long there is a general feeling that there is nothing new to know about them. However, with changing water treatment processes Mn is once again becoming an issue. Most utilities that have Mn can control it via induced oxide-coated media effect (IOCME) but are unaware they can do so. It is not until that process is disrupted that utilities discover the effectiveness of a chlorinated filter for controlling Mn.

APPROACH:
The research team conducted a comprehensive literature review. This review dealt with the regulatory history, health effects, chemistry, and technology associated with Mn. A survey was used to determine the industry’s knowledge base as well as obtaining certain occurrence data. This data was a focused set. Certain utilities participated in distribution system sample analysis. These samples were taken along the length of the distribution system, including the near, middle, and far ends. The concentration of Mn was determined and speciation was conducted via filtration. Case studies were performed to test the limits of certain Mn control technology. Finally, a cost model was proposed to help quantify the cost of increased Mn control as compared to the benefit realized by consumer.

RESULTS/FINDINGS:

• Speciation of Mn (determining oxidation state) in bulk water via filtration was an effective method.
• There were no strong correlations between Mn occurrence data and other water quality parameters. This was true for Mn in source water and for Mn in distribution systems.
• Mn that is allowed to enter the distribution system will accumulate in it. If Mn was dissolved when entering the system, it was converted to insoluble Mn over the length of the system either accumulating on the walls or in sediment. It is released at various times but mostly when there is a hydraulic change in the system.
• IOCME is a major Mn control unit process. The loss of chlorine results in Mn passage. Also, low pH and low temperature reduce the effectiveness of IOCME.
• Mn is regulated as an aesthetic issue but this must be balanced with health effect information. Controlling Mn to below the secondary maximum contaminant level (SMCL) of 50 µg/L is wise and most utilities are capable of doing it.
• The overall cost to the utility is usually more than the benefit to the individual consumer. However, the benefits go beyond those assigned to the consumers, including reduced flushing and fewer complaints, and add to the value of more Mn control.

IMPACT:
The results from this research program indicate that problems associated with Mn are much more common than previously thought. Geographically, Mn can occur virtually throughout the world and be present in both ground and surface waters. Reliable treatment processes are available to economically reduce source water Mn to well below the present U.S. drinking water standard of 0.05 mg/L. The research suggests that a more appropriate target level for Mn to minimize consumer problems would be 0.02 mg/L. The surveys conducted during this study indicated that a standard of 0.05 mg/L Mn was not sufficiently low to ensure minimal consumer complaints. Most existing treatment plants designed to reduce Mn can be modified, usually with operating chemistry, to produce water with a manganese concentration considerably below the current standard.

MULTIMEDIA:
The report appendices are included on CD-ROM.

RESEARCH PARTNER:
USEPA

PARTICIPANTS:
The research team surveyed 242 utilities. Eleven utilities consented to do distribution system sampling and of those, two participated in case study testing. Since all the results were confidential only the following two case study utilities are identified in the report: Philadelphia Water Department and West Virginia American Water Works.