Yellowish Water in the System
UPDATE JUNE 26, 2019
Update on Water Quality Issue in the System
We are currently experiencing some yellow water in our system again after having the water system run clear. The water has been and continues to be safe to drink within the Rancho Murieta Community Services District service area. This is confirmed with laboratory results from the certified laboratory, California Laboratory Services, that the District sends its samples to. Some areas of the District experienced little to no issues, however some areas have cleared up but occasionally are getting some lightly yellow colored water as pockets of the system work themselves out. We have also had a few days of slight manganese carry through our filtration process this week so the potential for color may exist for the next two days or so. This is the result of our filtration processes solids handling system, which recovers and returns water from the backwash water from the plant, from a sand filtered collection drain back to the front end of our filtration process, and this water contains high levels of manganese. To resolve that issue, we are currently sending the backwash into our sewer system instead of back into our water treatment process. As of this morning results with District lab equipment shows that the water quality results are very good with effluent manganese at 0.01 mg/l which is just at the detection limit for it.
Please click on the link below for the full update.Click here for the full update.
UPDATE JUNE 19, 2019
The Water Treatment system is now producing water with no detectable amount of manganese. In-house laboratory equipment and certified laboratory results show that there is no detectable amount of manganese in the water leaving Water Plant #2 since being brought online June 14, 2019. Water Plant #1 is having difficulty removing manganese to within acceptable levels and has been shut off until the manganese settles out in the Chesbro Reservoir.
Certified laboratory results also continue to show that the system water has no bacteriological issues detected and manganese levels below the public reporting limit of 0.5 mg/L.
UPDATE JUNE 17, 2019
Click on the link below to print out the Update Notice..Yellowish Water in the System Update - June 17, 2019
Water quality has improved. The District has made modifications to our water treatment process to help filter out the dissolved manganese that is the cause of the yellowish water. Staff worked to flush the water supply system throughout the weekend and today and are getting improved water quality results with little to no yellow water throughout most of the system. Staff is still in the process of flushing dead end areas and some areas with persisting yellow water. Summertime irrigation is also helping to use up the water and flush it out the system as well.
Your patience is greatly appreciated as we resolve this issue.
The District is looking into online monitoring equipment that may be able to help alert staff to potential issues with the water supply reservoir before they become a problem. We are also reviewing and updating our procedures that are in place to direct staff on how to deal with the issue on manganese in the Chesbro Reservoir which supplies the water treatment plant.
Public Notice - June 14, 2019
Click on the link below to print out the Notice.Public Notice on Yellowish Water in the System
In the process of filling our potable water reservoirs, pumping cold snowmelt water from the Cosumnes river into lake Chesbro, which supplies the drinking water plant, has caused it to “turn-over” stirring up sediment containing the minerals iron and manganese. The dissolved portion of this water containing these minerals was not being filtered out through our membrane treatment process, and when chlorine is added after filtration, it oxidizes the dissolved minerals in a slow reaction and causes them to precipitate (go from a dissolved form to a solid form) and appear in the water after our detection equipment. This has been corrected in the treatment plant by the addition of a pre-oxidant so it will be filtered out in the treatment process.
Is it Safe to Drink?
Yes. Our testing results showed that there was 0.086 mg/L of manganese in the Rio Oso tank feeding Units 3 & 4 and 0.071 mg/L of manganese in the VanVleck tank feeding the rest of the community, with no iron being detected. Manganese is considered a Secondary standard contaminant, meaning it is primarily an aesthetic concern. These levels are above the secondary standard level required by the State at 0.05 mg/L and we are working diligently to bring the levels down by producing better water and flushing the water distribution system to purge it of the lower quality water.
Sources of iron and manganese in drinking water
Iron and manganese are the 4th and 13th most common metallic elements found in the Earth’s crust, respectively. Water percolating through soil and rock can dissolve minerals containing iron and manganese and hold them in solution in varying amounts. Iron pipe & valve corrosion may be a source of iron in drinking water.
When water containing iron and manganese is exposed to air, or any oxidant such as chlorine, these elements are oxidized and precipitate out of solution. Upon oxidation, colored forms of iron and manganese become visible in water. In the case of iron, white, then yellow and finally red-brown solid particles form that settle out of the water. Iron oxide particles may not settle out and can impart the water with a red tint. Oxidized forms of manganese usually remain dissolved in water, giving it a black or yellowish tint. These abrupt changes in the chemical forms of iron and manganese are responsible for the staining properties of waters containing these elements. Iron will cause reddish-brown staining of laundry, porcelain, dishes, utensils and even glassware. Manganese causes a brownish-black stain. Soaps and detergents do not remove these stains and use of chlorine bleach may set the stains. Clothing or fixture stains may sometimes be washed away using white vinegar.
Deposits of iron and manganese can build up in pipelines, pressure tanks, water heaters and water softeners. This may reduce the available quantity and pressure of the water supply and therefore periodic flushing of water pipelines and hot water heaters is recommended.
Iron and manganese can affect the flavor and color of food and water, which affects both taste and appearance. Most commercially available filter systems such as Brita or Pur Filters, cartridge filters in refrigerators, and tap mounted units, will remove iron and manganese.
Removal in treatment
The District operates an aeration system in the Chesbro reservoir in an effort to oxidize iron and manganese out of solution, changing it from a dissolved form of the mineral to a solid, so it may be filtered out in its treatment process. However, this is only partially affective as it occurs by the water plant pipeline intake and not the entire reservoir. Additionally, if needed, the District feeds drinking water approved oxidant Potassium Permanganate (NSF 60) at a low dose into its water plant intake to oxidize Iron &/or Manganese into a solid form for them to be filtered out.
Why wasn’t this detected before it became a problem?
The water treatment equipment that continually measures the clarity of the water has shown, and continues to show, very clear, clean water being produced. The issue is that the dissolved form of the mineral has not been visible until it has reacted with the chlorine that is added to the water for disinfection purposes. The oxidation reaction of chlorine with manganese is reported by the American Water Works Association handbook for Iron & Manganese removal as being between 2-3 hours. This is why it has only showed up in our water distribution system and brought to our attention via consumer complaints. Also, staff was in the process of routinely flushing the distribution system and early complaints were thought to be the result of the stirring up iron from opening and closing valves. We are working to change our monitoring systems to be able to deal with it proactively in the future.
Potential health effects of iron and manganese in drinking water
Iron and manganese in drinking water are not considered health hazards by the EPA. In addition, iron and manganese are needed in low doses for human health. Grains, beans, nuts and teas in particular are rich in manganese. It is an essential trace mineral for the body to function, however excess manganese exposure has potential health implications. See website links below.
EPA’s website regarding Iron and Manganese standards
State’s website regarding Manganese