07-06-2020 Council Work Session Packet

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Feasibility Study Water Treatment Plant City of Lino Lakes, MN WSB Project No. 015822-000 Page 10 3.2.6 Secondary Drinking Water Contaminants In addition to Primary Drinking Water Contaminants, EPA has established National Secondary Drinking Water Regulations that set non-mandatory water quality standards for 15 contaminants. EPA does not enforce these "secondary maximum contaminant levels" or "SMCLs." They are established only as guidelines to assist public water systems in managing their drinking water for aesthetic considerations, such as taste, color and odor. These contaminants are not considered to present a risk to human health at the SMCL. Since these contaminants are not health threatening at the SMCL, and public water systems only need test for them on a voluntary basis. EPA believes that if these contaminants are present in your water at levels above these standards, the contaminants may cause the water to appear cloudy or colored, or to taste or smell bad. This may cause a great number of people to stop using water from their public water system even though the water is actually safe to drink. Secondary standards are set to give public water systems some guidance on removing these chemicals to levels that are below what most people will find to be noticeable. There are a wide variety of problems related to secondary contaminants. These problems can be grouped into three categories: Aesthetic effects -- undesirable tastes or odors; Cosmetic effects -- effects which do not damage the body but are still undesirable; and Technical effects -- damage to water equipment or reduced effectiveness of treatment for other contaminants. Aesthetic Effects Odor and Taste are useful indicators of water quality even though odor-free water is not necessarily safe to drink. Odor is also an indicator of the effectiveness of different kinds of treatment. However, present methods of measuring taste and odor are still fairly subjective and the task of identifying an unacceptable level for each chemical in different waters requires more study. Also, some contaminant odors are noticeable even when present in extremely small amounts. It is usually very expensive and often impossible to identify, much less remove, the odor-producing substance. Standards related to odor and taste include: Chloride, Copper, Foaming Agents, Iron, Manganese pH, Sulfate, Threshold Odor Number (TON), Total Dissolved Solids, and Zinc. Color may be indicative of dissolved organic material, inadequate treatment, high disinfectant demand and the potential for the production of excess amounts of disinfectant by-products. Inorganic contaminants such as metals are also common causes of color. In general, the point of consumer complaint is variable over a range from 5 to 30 color units, though most people find color objectionable over 15 color units. Rapid changes in color levels may provoke more citizen complaints than a relatively high, constant color level. Standards related to color include: Aluminum, Color, Copper, Foaming Agents, Iron, Manganese, and Total Dissolved Solids. Foaming is usually caused by detergents and similar substances when water has been agitated or aerated as in many faucets. An off-taste described as oily, fishy, or perfume- like is commonly associated with foaming. However, these tastes and odors may be due to the breakdown of waste products rather than the detergents themselves. Standards related to foaming include Foaming Agents. Cosmetic Effects Skin discoloration is a cosmetic effect related to silver ingestion. This effect, called argyria, does not impair body function, and has never been found to be caused by drinking water in the United States. A standard has been set, however, because silver is used as an antibacterial agent in many home water treatment devices, and so presents a potential problem which deserves attention. The standard related to this effect includes Silver.