Manganese is an element that occurs naturally in water, soil, air and food, and can be found in ground and surface waters. Manganese is one of the most abundant metals in the earth’s crust and is a component of over 250 minerals. It is an essential nutrient for animals and plants, and is important in both growth and nervous system functioning. Manganese is also used in steel production and in fertilizers, batteries, fireworks, and in wastewater and drinking water treatment chemicals.

Manganese is regulated by a 0.05 milligrams per liter (mg/L) or parts per million (ppm) secondary Maximum Contaminant Level (MCL), a standard established to address issues of aesthetics. The State Water Resources Control Board Division of Drinking Water also established a notification level of 0.5 mg/L for manganese. At relatively low concentrations (0.02 mg/L or greater), manganese can cause discolored water (usually black or dark red/brown) and staining of laundry and plumbing fixtures. At higher levels (0.1 mg/L or greater), manganese can create a metallic taste in water.

Manganese is one of the metals to be monitored as part of the United States Environmental Protection Agency’s (USEPA) fourth Unregulated Contaminant Monitoring Rule (UCMR4). USEPA will use the data from the UCMR4 to determine future regulations to protect public health.

Golden State Water routinely monitors and tests for more than 230 contaminants, including manganese, to ensure the water delivered to customers meets all state and federal drinking water standards. Golden State Water makes water quality information available via annual Consumer Confidence Reports (CCR).

Water quality test results are directly submitted by the State certified laboratory to the State of California’s Division of Drinking Water (DDW) and recorded on the State’s website for full transparency. Click here to view test results on the DDW website.

As your water provider, we continually invest in water infrastructure, treatment and testing and take great pride in providing you with high-quality, reliable water.

Frequently Asked Questions

Q:  Has manganese been found in my drinking water?
A:  In 2017, manganese was detected in treated drinking water in seven of our 37 water systems. In five of these systems, the highest levels of manganese detected were above the current secondary MCL. Only one system had a manganese result above the state notification level of 0.5 mg/L. Our water systems are in compliance with the secondary MCL based on an average of monitoring results; however, we occasionally see short-term elevated levels of manganese in some systems. In our Clearlake system, for example, the highest level of manganese reported was caused by a large bloom and die-off of algae in the lake that resulted in low dissolved oxygen and subsequent release of manganese from lake sediments into the water.

Some of Golden State Water’s groundwater sources consistently contain manganese levels above the secondary MCL. Water from these wells is treated to remove manganese to levels below the secondary MCL. Click here to see the most recent results for manganese levels detected in our treated drinking water.

Q:   How is manganese removed from contaminated source waters?
A:  Manganese can be removed or controlled using a variety of treatment techniques. Each technique has advantages and disadvantages depending on the level of manganese present, chemical form, and other water quality parameters. Chemical oxidation and particle removal, filter media oxidation, biological treatment, ion exchange, and sequestration are common manganese control techniques. Even if most of the manganese is removed from the source water, substantial manganese accumulation in pipes can still occur in the distribution system. Stabilizing water chemistry and flushing pipes may help prevent and remove pipe scales.

Resources for Additional Information

State Water Resources Control Board