Solutions
Generating safe, clean water compliant with all regulatory requirements
Rescue Engineers is dedicated to solving water quality challenges from a variety of contaminants that are subject to agency regulations. Our solutions help our clients meet or exceed all state and federal regulations on contaminant levels so that they can generate drinking water that is clean and completely safe for public consumption.
Contaminants
Arsenic
Source: Arsenic is a naturally occurring mineral in rocks and soil and thus can dissolve into groundwater. The level of waterborne arsenic, however, can be exacerbated by discharge from the industrial processing of various consumer products as well as agricultural waste products.
Health Impact: Arsenic is a known human carcinogen and may cause non-cancerous diseases in various soft tissues such as the bladder, lungs, and kidneys.
Treatment: California restricts arsenic in water to no more than 10 ppb (0.010 mg/L). As(III) can be easily converted to As(V) using chemical oxidants such as chlorine, potassium permanganate, and ozone, which are known to improve arsenic removal (Ghurye and Clifford, 2001 and 2004). The dosage of oxidants will depend on the concentrations of other substances in the source water, such as iron, manganese, sulfide, and dissolved organic matter.
Hexavalent Chromium
Source: Chromium is found naturally in rocks, minerals, and soil and thus can leech into groundwater. Industrially, chromium is used in anti-corrosion coatings, metal plating, and wood preservatives and industrial discharges can affect groundwater.
Health Impact: Chromium is a known human carcinogen via inhalation while ingestion from drinking water may lead to cancer and liver damage.
Treatment: California restricts hexavalent chromium in water to no more than 10 ppb (0.010 mg/L). Chromium is treated via a three-stage process:
- Reduction: Reducing agent, ferrous iron (Fe(II)) or stannous tin (Sn(II), is added to the raw water. The agent reacts with Cr(VI), converting it to Cr(III).
- Coagulation: Chlorine is added to oxidize excess ferrous iron (Fe(II) to ferric iron (Fe(III). Anionic polymer serves as a filter aid to build up the ferric iron particle size for filtration.
- Filtration: The particles are removed through a filter media. Treated water passes through.
Iron & Manganese
Source: Iron occurs naturally in the Earth’s crust and can especially be found in well and spring water. Manganese occurs naturally in rocks and soils and can leech into groundwater.
Health Impact: Iron and manganese are not health risks at typical levels. Iron can cause a metallic taste, reddish discoloration, and strong odor. At high levels, manganese may affect the nervous system, particularly in infants and small children (possibly resulting in learning and memory issues).
Treatment: California sets an enforceable Secondary Maximum Contaminant Level (SMCL) at 0.05 mg/L for manganese and at 0.3 mg/L for iron to manage the aesthetic issues.
Iron ions Fe2+ and Fe3+ readily combine with oxygen and sulfur containing compounds to form oxides, hydroxides carbonates, and sulfides. Iron is most commonly found in nature in the form of oxides. Media iron concentration in rivers has been reported to be 0.7 mg/L while concentration in drinking water is normally less than 0.3mg/L.
Manganese (Mn) is found throughout the environment and is needed for normal physiological functions in humans and animals. Generally found in a dissolved state and remains stable over time. The presence of iron and manganese promotes growth of iron-reducing bacteria (Crenothrix, Gallinonella, Leptothrix and Spehaerotilus).
Turbidity
Source: Turbidity is a measure of water clarity that indicates the amount of particulate matter in suspension. Turbidity can be caused by a variety of natural processes including soil erosion, stormwater runoff, growth of microscopic organisms like algae, and the decay of organic matter.
Health Impact: Turbidity can reduce the effect of disinfectants on pathogens like bacteria and viruses. Pollutants like heavy metals, pesticides, and bacterial nutrients can be carried by suspended particulates.
Treatment: California sets specific limits on how much turbidity can increase from its natural level measured in Nephelometric Turbidity Units (NTU).
Turbidity can be treated with filtration, coagulation and flocculation (the addition of chemicals that cause suspended particulates to clump together into larger, heavier “flocs” that can then be precipitated out or filtered), sedimentation (allowing gravity to settle turbid particles), and membrane filtration (e.g., reverse osmosis and ultrafiltration).