Secondary drinking water contaminants are regulated to prevent taste, odor, color and other aesthetic drinking water quality problems. These contaminants include iron, manganese, sulfate, organic material, hydrogen sulfide and hardness.

Iron

Iron can be a major nuisance in a private water supply. It stains laundry and fixtures, promotes the growth of iron bacteria slimes in plumbing and gives water a bitter, metallic taste. Iron can be present in the water in two forms— soluble and oxidized. As each form can require a different type of treatment device, you need to determine which form is present in your water so that the proper treatment device can be selected. Trained personnel in the water treatment field can help you with this. The secondary drinking water standard for total iron is 0.3 mg/L.

Soluble iron, also called clear water iron or reduced iron, is easily recognized because the water is clear when first drawn, but soon becomes filled with red rust if left standing. Soluble iron causes reddishbrown stains on plumbing fixtures, porcelain, cooking utensils and laundry.

Soluble iron, usually up to 3.0 mg/L, can be removed by an ion exchange treatment device. A manganese greensand oxidizing filter will be effective for concentrations up to 10.0 mg/L. For concentrations above 10.0 mg/L, chlorination followed by filtration is usually needed.

Oxidized iron, frequently referred to as red water iron, is formed when water containing soluble iron reacts with air. The iron found in surface water is usually oxidized. Water containing oxidized iron will show rust particles or black specks suspended in the water. Red water iron, like clear water iron, causes reddish-brown stains on clothes, porcelain and cooking utensils. Oxidized iron can be removed by mechanical filtration or chlorination.

Small particles of oxidized iron that do not settle out are referred to as colloidal iron. These small particles cannot be removed by ordinary filtration.

Colloidal iron, like other forms of iron, causes reddishbrown stains on laundry, plumbing fixtures and cooking utensils. Colloidal iron may be found in water from shallow wells, but is seldom found in deep well supplies. The presence of colloidal iron can be shown by the use of filter paper. In some cases, the addition of alkalinity to the water may allow the colloidal particles to agglomerate into settleable, filterable particles that can be removed by mechanical filtration.

Colloidal iron can be removed by chlorination.

Manganese

Manganese causes dark brown to black stains on plumbing fixtures and will cause laundry to be stained black. Manganese can cause an unpleasant taste and appearance in coffee, tea and other beverages. Manganese can be removed with a water softener. The secondary drinking water standard for manganese is 0.05 mg/L.

Sulfate

Water containing high concentrations of sulfates will have a laxative effect and a bitter taste.

The secondary drinking water standard for sulfates is 250 mg/L. Sulfates can be removed by ion exchange and reverse osmosis.

Organic Material

One source of color in water is from small amounts of organic material from the decomposition of fallen leaves, algae and other plant matter. This decaying vegetation produces humic acids also referred to as tannins. The color in the water may not be visible in a glass of water but will be evident when viewed against a white background in a sink or bath tub. These materials are found in surface water and are normally harmless. Phenols produced by this organic decomposition may result in objectionable taste and odor even when present in small amounts. Activated carbon filters can remove most organic material.

Hydrogen Sulfide

Hydrogen sulfide is a gas produced by the decomposition of underground organic deposits. It readily dissolves in water and gives it a characteristic rotten egg odor and obnoxious taste.

Hydrogen sulfide is very corrosive and will rapidly tarnish silver causing it to turn black. In some cases, hydrogen sulfide may be present in the hot water, but not the cold. In this situation, a chemical reaction is occurring in the water heater between the magnesium anode of the water heater and sulfate in the water.

Removal of the magnesium anode will usually eliminate the problem. Treatment to reduce hydrogen sulfide includes manganese greensand filtration or chlorination followed by filtration and aeration.

Hardness

Hardness is caused by dissolved minerals, primarily calcium and magnesium, which are picked up by water as it travels through rocks and soils. Hardness is a common problem where ground water is used as a water supply. The highest concentrations of these minerals come from wells in limestone rock. High concentrations can result in mineral deposits in water heaters and pipes, and film on sinks and bathtubs. Hardness also requires increased soap usage in dishwashers and washing machines. A major problem caused by hardness is reduced efficiency of water heaters resulting in premature replacement. The following table shows a rating system commonly used to describe the hardness of water.

Lab results frequently will refer to minerals in water as grains per gallon (gpg). One grain per gallon of calcium for example is equal to 17.12 mg/L as CaCO3. Thus multiply grains per gallon by 17.12 to obtain the equivalent value in milligrams per liter.

Hardness usually is treated using ion exchange water softeners. The level of hardness at which treatment is used to soften the water varies, depending on consumer preference. Reducing the hardness of the water too much may make the water corrosive to the plumbing system and can in some instances result in increased lead concentrations.

Chlorine

Chlorine is used to kill and prevent the regrowth of harmful microorganisms in water supply systems. However, high levels of chlorine can result in taste and odor problems. Chlorine also can combine with other drinking water contaminants to form chloramines, which can create noticeable taste and odor problems.

Activated carbon filters are effective in removing taste and odor problems associated with chlorine.

Hard Water Levels

Grains Parts Per Million Per Gallon (mg/L as CaCO3) Rating

less than 1.0 less than 17.1 soft

1.0 – 3.5 17.1 – 60 slightly hard

3.5 – 7.0 60 – 120 moderately hard

7.0 – 10.5 120 – 180 hard

over 10.5 over 180 very hard