03-07-2022 Council Work Session Packet

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1. INTRODUCTION 1.1 Purpose of Study WSB was authorized to complete this water treatment pilot study as the first step to verify the effectiveness of a full-scale gravity biological filtration water treatment plant to remove ammonia, iron, and manganese from the City's water. Conducting this pilot study was recommended in the City's Water Treatment Plant Feasibility Study completed in June 2020. The MDH considers biological filtration to be an efficient and effective treatment method to remove ammonia, iron, manganese, and other contaminants in public drinking water supplies. The purpose of the pilot study is to provide the City with critical information that is required to design and construct a water treatment plant if the City decides to address the high manganese levels in its drinking water. It was decided to conduct the pilot study with groundwater pumped by Well 6 because it contains the highest levels of manganese and iron in comparison to the City's other wells. 1.1 Effects of Iron Iron in drinking water is regulated by the Secondary Drinking Water Standards (SDWS) set by the U.S. Environmental Protection Agency (EPA). Unlike with the Primary Drinking Water Standards, the SDWS are not enforced since they are not considered to be a health risk. The SDWS are guidelines to assist public water systems in managing their drinking water for aesthetic considerations. The SDWS for iron is 0.30 mg/L. Iron concentrations above the SDWS can stain household fixtures and clothing, cause water discoloration, coat pipes within water distribution systems, and cause unpleasant taste and odors. Dissolved iron can be treated by oxidizing it to its insoluble form and removing it by filtration. Iron is usually oxidized with aeration, chlorine, or a combination of the two. 1.2 Effects of Manganese Manganese is a common, naturally occurring mineral found in rocks, soil, groundwater, and surface water. The SDWS include a recommended limit for manganese since manganese causes physical and aesthetic effects on drinking water such as staining, taste, and color. Manganese in water can stain laundry, cause scaling on plumbing, and cause water to look, smell, or taste bad. Additionally, manganese can create a brownish -black or black stain on toilets, showers, bathtubs, and sinks. The SDWS recommended limit for manganese in drinking water is 0.05 mg/L. The EPA is in the process of determining if a Maximum Contaminant Level (MCL) should be established for manganese due to updated research on its health effects. As such, the EPA included manganese in the Fourth Unregulated Contaminant Monitoring Rule (UCMR4), which requires all public drinking water systems serving over 10,000 people and randomly selected small systems to monitor for manganese. The EPA will also consider the health effects of manganese in their regulatory determination and evaluate potential risks to adults, children, and infants. The MDH, in conjunction with studies conducted by others, has determined that children and adults who drink water with high levels of manganese for an extended period of time may experience problems with memory, attention, and motor skills. These side effects are more acute in infants (babies under the age of one), as they may result in long term learning and behavioral problems. Therefore, the MDH has established a maximum recommended manganese concentration in drinking water of 0.10 mg/L for infants and 0.30 mg/L for adults and children. Similar to iron, dissolved manganese can be treated in drinking water by oxidizing it to its insoluble form and removing it by filtration. Manganese is usually oxidized with potassium or sodium permanganate. However, manganese can also be removed biologically from water using naturally occurring microorganisms. Water Treatment Pilot Study Report Biological Removal of Ammonia, Iron and Manganese at Well House No. 6 City of Lino Lakes, MN WSB Project No. 0 18601 -000 Page 2