Hendersonville Utility District (HUD) serves one of the most populous suburbs of Nashville, Tennessee.
Bluebonnet Rural Water Corporation (BRWC), a subsidiary of Bluebonnet Electric Cooperative, serves approximately 1,094 water meters in northeast Washington County, TX, but had a water storage problem not unfamiliar to even the largest water utilities in Texas.
National Lead Poisoning Prevention Week marks a time when EPA and our federal partners promote education and awareness activities that focus on lead and how to prevent its negative health effects. This year, we focus on the theme, “Lead-Free Kids for a Healthy Future.” It’s through our joint efforts that we have been able to make significant strides in reducing exposure to lead over the past several decades.
Researchers examine the feasibility of treating hexavalent chromium — the carcinogen made famous by the movie “Erin Brockovich” — with strong base anion exchange (SBA-IX).
In an effort to reduce reliance on dwindling surface and groundwater supplies in Texas, the Colorado River Municipal Water District (CRMWD) constructed a new Raw Water Production Facility (RWPF) in Big Spring. Big Spring is a 27,000-member community located in West Texas approximately 300 miles west of Dallas. This RWPF treats secondary wastewater to a standard that allows it to be re-introduced directly into the raw water supply for the water treatment plants of Big Spring, Odessa, and other communities in the region.
A processing plant in Minnesota faced operational challenges due to ceramic dust from the manufacturing process passing through their clarifier, even with flocculent addition.
In the fall of 2015, a small village on the border of Vermont in New York State, tested positive for Perfluorinated Compounds (PFCs), specifically Perfluorooctanoic Acid (PFOA), in the municipal drinking water. The influent levels of PFOA in the water were above 600 ng/L, and thus considered harmful to village residents. Realizing that PFOA was on the U.S. EPA Contaminant Candidate List, the Village solicited the services of engineering firm CT Male Associates to investigate treatment options and provide a treatment system.
A water quality audit revealed that two of the largest drinking water plants in the City of Montreal were out of compliance with Quebec’s latest water quality rules. Both drinking water facilities were located in heavily populated areas; consequently, plant modifications had to be accomplished within their existing infrastructure footprints.
The 34 MGD Otay Water Treatment Plant in San Diego, California serves a population of approximately 200,000. It is a conventional treatment plant that uses coagulation, flocculation, sedimentation, filtration and disinfection. The plant receives raw water from two different sources — imported water from the Colorado River and runoff water from three local reservoirs.
The City of Salem uses a slow sand filtration water treatment process, which uses naturally occurring biological activity to clean drinking water. The water treatment facility treats an average of 30 MGD throughout most of the year, with a peak of 50 MGD in the summer.
For decades, a Winnipeg utility used a multiple point-chlorination process to treat raw water drawn from remote Shoal Lake. Concerns eventually arose about the potential presence of chlorine-resistant pathogens–Crytosporidium and Giardia–and residual disinfection byproducts, which coincided with encroaching development near the lake. The Clari-DAF system was selected and now removes 70 percent of the organics at the Winnipeg plant, which also improves filtration and extends the intervals between filter backwashes.
What would happen if there was an emergency in the U.S. that caused radioactive material to contaminate drinking water supplies? What steps could your utilities and government take?
A water utility in the Midwest USA uses Monochloramine treatment in their two surface water treatment plants to disinfect raw water and establish residual disinfectant prior to discharge to their distribution system.
The design team for the intermediate ozone system at Buckingham Water Treatment Plant, Quebec, had limited space available for ozone contacting for the plant’s 1.3 – 7.4 MGD flow, so a standard fine bubble diffusion basin for ozone disinfection was not an option.
The removal of contaminants from public drinking water systems in the US is mandated by the Environmental Protection Agency’s (EPA) National Primary Drinking Water Regulations. These are legally enforceable standards that protect public health by limiting the levels of contaminants in drinking water. Similar regulations are managed by agencies worldwide to protect their citizens from drinking water contamination.
There are a plethora of drinking water contaminant removal technologies that public and private water systems use to comply with the EPA’s drinking water regulations. These include reverse osmosis, membrane, nanofiltration, ultrafiltration, chlorine disinfection, UV disinfection and Ozone-based disinfection practices.
The EPA’s list of drinking water contaminants is organized into six types of contaminants and lists each contaminant along with its Maximum Contaminant Level (MCL), some of the potential health effects from long-term exposure above the MCL and the probable source of the drinking water contaminant.
The six types of contaminants are microorganisms, disinfectants, disinfection byproducts, inorganic chemicals, organic chemicals and radionuclides.
Examples of microbiological, organic contaminants are Cryptosporidium and Giardia lamblia. Both of these microorganic pathogens are found in human or animal fecal waste and cause gastrointestinal illness, such as diarrhea and vomiting.
A common disinfectant used in municipal drinking water treatment to disinfect microorganisms is chlorine. The EPA’s primary drinking water regulations require drinking water treatment plants to maintain a maximum disinfectant residual level (MDRL) for chlorine of 4.0 milligrams per liter (mg/L). Some of the detrimental health effects of chlorine above the MCL are eye irritation and stomach discomfort.
Similarly, byproducts from the chlorine-based disinfection methods used by public water systems to remove contaminants can be contaminants in their own right if not removed from the drinking water prior to it being released into the distribution system. Examples of disinfection byproducts include bromate, chlorite and total trihalomethanes (TTHMs). Not removed from drinking water, these disinfection byproducts can increase risk of cancer and cause central nervous system issues.
Chemical contamination of drinking water can be caused by inorganic chemicals such as arsenic, barium lead, mercury and cadmium or organic chemicals such as benzene, dichloroethane and other carbon-derived compounds. These chemicals get into source water through a variety of natural and industrial processes. Arsenic for example is present in source water through the erosion of natural deposits. Many of the chemical contaminants are derived from industrial wastewater such as discharges from petroleum refineries, steel or pulp mills or the corrosion of asbestos cement water mains or galvanized pipes.
Radium and uranium are examples of radionuclides. Radium 226 and Radium 228 must be removed to a level of 5 picocuries/liter (PCI/L) and Uranium to a level of 30 micrograms/liter (30 ug/L).