San Jose Water Company (SJWC) provides drinking water for over a million people in the greater San Jose Metropolitan region and is a recognized leader in drinking water treatment and distribution system water quality management. With over 90 water storage facilities in service, planned maintenance and rehabilitation of capital assets is a key component of SJWC’s CIP program.
This municipality disinfects 1-1.5 million gallons per day of drinking water, and is currently transitioning from a small system serving <10,000 people to a large system serving >10,000 people. Chlorine gas was used as the primary disinfectant for the raw water entering the plant.
The manufacturing of soda ash from Trona is a multi-step process that results in the production of a waste liquor that contains significant levels of organic contamination.
Historically, Lyon County Utilities, Nevada, applied 12.5% bulk sodium hypochlorite for disinfection at each of their well sites. Always looking to improve system efficiency, Lyon County staff reexamined on‐site hypochlorite generation to determine if the use of the 0.8% sodium hypochlorite solution could mitigate the challenges associated with dosing high strength sodium hypochlorite.
A combination of growing demand, aging infrastructure and regulatory requirements acted as drivers for a new ozone system at the Miramar Water Treatment Plant in San Diego, CA.
Chatsworth Water Works Commission provides both water and wastewater services to the 5,000 residents of the cities of Chatsworth and Eton, GA.
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?
In April 2013, City Utilities started up three Microclor Model MC‐1500 skid systems, each rated at 1,500 pounds per day of free available chlorine.
Ensuring the quality and safety of drinking water across the U.S. EPA-monitored 155,000 public water systems has become a national issue.
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.
Our nation’s record of progress in advancing public health under the Safe Drinking Water Act is significant.
For Robert Stout, general manager of Mid-Arkansas Utilities (MAU), the primary water provider for a three-county rural area spanning 2,220 square miles, the reason to switch to a dry calcium hypochlorite feeding system was simple, “using chlorine gas was not only dangerous for us, it was a big hassle and time-consuming.”
The burden of the unavailability of replacement parts for the aging generators and the FBD basin high maintenance motivated the Orlando Utilities Commission's Southwest Water Treatment Plant to update and upgrade the plant’s ozone system.
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).