General Information on Drinking Water

With today's awareness of the many unwanted substances in various water supplies, a line of specialized devices are being marketed to treat small quantities of water just for drinking and cooking purposes. This awareness has been heightened by the wide media coverage given to chemical spills, toxic waste dumps, the under-treatment of community waters and improper sewage disposal; all of which seem to cause short or long term effects on potable water sources. Together, these factors tend to create an air of doubt at times as to the quality of the water we consume. Bottled water, sold in supermarkets as well as home delivery, has met a good deal of the need for safer drinking water when doubts persist in the mind of the homemaker as to the local water quality. This product is also used for aesthetic quality reasons or to satisfy dietetic needs. Two grades of "bottled water" are available. First is the very low mineral content grade produced by either (a) distillation/ozonation process or (b) reverse osmosis process. This grade meets the need of those on a low sodium regimen. The second grade which may represent the bulk of bottled water sales is the "spring water" type which may be unmodified well water, charcoal-filtered and ozonated. Or, this grade can include a municipal water source which has been selectively processed for pleasant taste and is odor free. But, for homeowners or businesses that prefer or must have their own supply of higher quality water, a specialized line of water treating devices have been produced by Glacier International Inc. These devices use the commercially proven water treatment practices that have been redesigned in miniature for use on very small flow rates with limited daily output. As a general rule, these devices are placed on a separate cold water line at a special bench or kitchen sink faucet. Included in this product grouping are distillers, reverse osmosis systems, filters, cartridge units and sediment/carbon adsorption filters with replaceable elements.

Disposable Cartridge Filters

Perhaps the most widely used item for improving drinking water quality in the home is the replaceable cartridge type filter. (Figure 1) The filter element usually contains a wound fabric or layers of paper-like material which screens out turbidity and particulates from the water stream. Some replacement elements also contain a layer of fine activated carbon laminated on paper to perform some taste and odor removal function. Other cartridges are made with solid porous activated carbon elements which offer the dual function of sediment removal as well as adsorption of excess chlorine. These small filter units are a "do-it-yourself" item quite reasonably priced. These small carbon filters can also improve the quality of ice cubes in automatic dispensing refrigerators or cube makers.(Refer to Figure 1)  

      There is a limited life to the filter elements and, for best performance, the cartridges should be replaced as often as every three months. (Carbon can act as a harbor for non-pathogenic organic species, so it is wise to replace these cartridges at regular intervals.) Where there is a high residual chlorine content in the tap water, this pre treatment is very important to make good tasting coffee, tea, as well as orange juice and other fruit juices. Like any water processing device, disposable cartridge filters can only function effectively when properly maintained by replacing the cartridge at set intervals and carefully cleaning the housing with warm water and detergent with a few ounces of laundry bleach for disinfection.

Distillers

A second product line to provide a better quality of drinking water and home cooking water is the small distiller, which produces minute-mineral content water. This equipment, like its larger commercial model, both disinfects the  water and removes most impurities producing what is commonly accepted as "Safe Mineral-Free Water". Home distillers are of various designs, ranging from counter-top single-batch versions to those which can be centrally located with the stored distilled water piped to several locations in the home. Automatic home distillers, which maintain a supply of processed water from a reservoir, find wide usage in North American homes. The home requirement for distilled water is from three to ten gallons per day depending on the variety of uses. Based on the earth's solar evaporation technology, today's state-of-the-art domestic distillers use recent designs and materials to reach greater efficiency levels. The basic process is that of heating water in a chamber until it boils producing a steam vapor. Dissolved solids and unwanted contaminant liquids with higher boiling points than water ideally remain behind in the chamber while those liquids which boil at lower temperatures are largely vented as vapors. The cooled steam condenses into minute-mineral content water which collects in a reservoir for use upon demand. All distillation systems requiring electrical energy and home distillation units use 110-120 volt a.c. current. The daily product water capacity of home distillers ranges from three to 12 U.S. gallons per day. Power consumption of these systems varies from three to five kilowatt hours of electricity per gallon of distilled water produced.

Drinking Water Via Reverse Osmosis (RO)

The phenomena of osmosis was originally discovered by a French scientist in 1748 who observed that water would diffuse spontaneously through a pig bladder membrane into a parallel chamber of alcohol. This interesting concept, osmosis and its counterpart, reverse osmosis, for the next 200 years was not much more than a laboratory topic because natural membranes were scarce and unreliable. In the mid-1950s, the work of Dr. S. Sourirajan at UCLA and others advanced the RO technology to the point where artificial membranes could be manufactured. During this era, considerable work was done for the U.S. Office of Saline Water into methods of desalination with serious research emphasis on reverse osmosis. The movement of water from soils into plants roots is an example of osmosis at work in nature. When a semi-permeable membrane, like a living cell wall, separates two solutions having different solids concentrations, the pure water will flow from the least concentrated solution through the membrane and into the solution containing the higher solids concentration. The flow will stop when the osmotic pressure on both sides of the membrane equalize. This process occurs continuously in the organs of living things as an example of how water is transported in nature.(Refer to Figure 3).

Reverse Osmosis is just what its title implies; it is the reverse of naturally occurring osmosis. By applying artificial pressure to the water solution of higher solids concentration, the flow of liquid is reversed. (Refer to Figure 4)

The membrane will, under these conditions, only allow the water molecule to pass through the highly concentrated salts solids on the opposite side of the semi-permeable membrane. During the mid 1970s, RO became a practical drinking water process as new "low pressure" systems were designed to function on line pressure of 35 psi or higher. For the most part, drinking water RO systems are installed on a separate (Figure 5) single tap. The apparatus is usually located under the sink in homes and clinical offices. The standard components, as illustrated, consist of 1 or 2 pre filters, RO module membrane cylinder, drain for (brine) reject water, a small storage tank and a post carbon filter. 

Because only small daily quantities are needed for this purpose, the RO device produces an average of two to 12 U.S. gallons of low-mineral (low TDS) water in a 24 hour time span. The filters in these systems should be changed every 6 to 12 months and the membrane changed every 1 to 2 years.

Disinfection By Distillation

The distiller process described in technical detail earlier in this chapter is yet another means of obtaining small volumes of "safe drinking water". This sterilization process is among the easiest to operate by homemakers and requires only conventional 110 - 120 volt a.c. electric current for counter top models. No chemicals are used. Just heat to disinfect the product water, which at the same time demineralizes the water. The distillation process is perhaps the most readily understood method among lay people for disinfection in general, and consumers at large, so it appeals to many as a viable mode of treatment. One limiting factor of this process is the extra time needed to produce one gallon of processed water when compared to ultraviolet, ozonation, and chlorination.