The U.S. Environmental Protection Agency’s (EPA) Water Infrastructure Resiliency and Finance Center, in collaboration with the...
Consumer concerns about drinking water contaminants and aesthetics partially explains the increased demands for alternatives to tap water such as bottled water or water from a vending machine. Media hype about contaminants and aggressive marketing by some bottled water companies also plays a role.
Today, there are three basic types of water vending machines. The majority are self-contained, freestanding floor models located either inside or in front of a grocery store, convenience store or other retail outlet. The second type are water vending machines installed on counter tops, usually adjacent to soft drink, coffee and other beverage dispensing equipment. The last type are water vending machines designed so that the treatment components are located in a remote area of a facility (often a storeroom), while a smaller dispensing unit is located on a counter top or free standing in the sales area of the store.
The trend in water vending over the last five years is to locate equipment inside stores. Vending from indoor locations benefits the consumer and the retailer.
Most water vending machines provide one or more levels of purification, in terms of water treatment. Filtration-only machines provide the most basic level of treatment. These machines are essentially designed to reduce the taste, odor and turbidity of the source water, which is always from an approved water system. Other machines may contain additional treatment devices to reduce high concentrations of total dissolved solids (TDS) to more acceptable levels or to produce "purified water," which among other requirements must have a TDS concentration no greater than 10 mg/L.
Pre-filtration. Depending on the quality of the source water, a vending machine will begin the treatment process with a mechanical filter to remove sediment and residue. This usually is followed by activated carbon filtration and often a second mechanical filter to remove carbon fines extracted from the carbon filter. This pre-filtration process normally uses filters with media core sizes ranging from 1 to 20 microns.
Activated carbon filtration.
Activated carbon filtration is effective in adsorbing a wide variety of organic compounds, including ones that can impart taste, odor and color, or that may be potentially carcinogenic such as THMs or other volatile organics. The carbon media may be in block or granular form; the longer the contact time the greater the contamination reduction. When a carbon adsorption capacity is exhausted the filter must be replaced or the medium regenerated. Carbon filters also may be used to remove or reduce chlorine that can otherwise damage reverse osmosis (RO) membranes.
Reverse osmosis. RO equipment normally follows pre-filtration in the treatment sequence. The unit receives feed water under pressure at one end of its semipermeable membrane. The water essentially is forced through the membrane one drop at a time. As the water passes through the membrane, contaminants are left behind in the "reject" water that either can be returned to the RO membrane for further treatment or, more frequently, is discharged to waste. RO systems are effective in reducing TDS; metals such as arsenic, cadmium, copper, lead and sodium; nitrates; asbestos; radium; Giardia cysts; and bacteria. The effectiveness of the membrane depends on age, the type of contaminants and the concentration of solids in the feed water.
Disinfection. Disinfection is the last step in the treatment process before water is dispensed and usually is accomplished by exposing the water to ultraviolet (UV) radiation. A UV lamp is similar to a fluorescent lamp except that it uses a low pressure mercury vapor to produce the desired UV wavelength (253.7 nanometers). Since most materials do not efficiently transmit UV light, a special quartz glass is used to encase the lamps. UV light destroys microorganisms by scrambling their DNA structure, which interferes with cell reproduction. Radiation dosage, exposure time and water quality must be considered for effective germicidal treatment.
One other important factor to consider when operating water-vending machines is the laws regarding their operation. Twenty-two states now have some type of regulation concerning water vending machines. Unfortunately, regulations vary by state because there are no federal regulations pertaining to vended water beyond the water quality standards prescribed by the Safe Drinking Water Act (SDWA).
Water vending is regulated primarily as a non-community, non-transient public water supply. This means for the most part, SDWA standards apply but since water vending machines are required to be connected to a public water supply that meets SDWA requirements, the machines are considered "consecutive treatment" and are exempt from SDWA water quality monitoring requirements.
With the proliferation of vending machines in operation and the variety of regulations monitoring their operation, quality control of the water produced by the operator is essential. While local and state health authorities have primary responsibility for enacting and enforcing minimum public health and safety standards for installing, operating and maintaining these machines, national standards for their design and construction also are important.
Many regulatory agencies rely on the "Standard for the Sanitary Design and Construction of Food and Beverage Vending Machines" developed by the Automatic Merchandising Health-Industry Council, an advisory group to the National Automatic Merchandising Association. The Standard was last revised in January 2000 and includes a section for water vending machines added in 1984. When a vending machine meets the standard requirements, an independent public health consultant who conducted the evaluation issues a Letter of Compliance. Re-evaluations are conducted annually to assure machines continue to be manufactured in compliance with the standard.
A listing of machines certified by the NAMA Evaluation Program can be found on the NAMA website www.vending.org under the Technical Services section.
About the Author
Larry M. Eils is the senior director of technical services for the National Automatic Merchandising Association (NAMA), located in Chicago. NAMA is the trade association representing the food and beverage vending, office coffee service and food management industries. Mr. Eils is responsible for informing and educating vending operators, machine manufacturers, suppliers and regulatory officials on matters of health, safety and technical issues relating to the food and beverage vending industry. He also oversees the NAMA Vending Machine Evaluation program, the Technician Training program, the NAMA Vending Technology Standards Committee and Route Driver Certification program.
Surprisingly, water vending machines are not a new phenomenon. As early as 215 B.C. sacrificial water was vended from a tabletop dispenser. However, it was more than 2,000 years later in 1908 before another water vending machine appeared on the scene. This time the consumer purchased a small individual paper cup from a dispenser and filled it with drinking water from an adjacent reservoir. This was the invention of the "Dixie Cup," whose manufacturers believed it would not sell unless the customer was able to immediately use it.
It was not until 1976 that the first practical water vending machine was designed and placed into use, and it was not until the early 1980s that water vending became a viable industry. Vending machines offer retail outlets significant advantages over bottled water by the reduced need to order, store and stock valuable shelf space with bulky and low profit-generating bottled water.