Water Purification Technology:
What is “Green” & What is Not
Stephen K. Wiman
What constitutes sustainable or “green” technology in water purification systems? For a water treatment solution to be considered green, it must meet the criteria of not adding anything to the water and not using any additional water in the process. This article covers green technologies currently available and the contaminants for which green purification technologies are, and are not, an option. In the marketplace, there is an abundance of “greenwashing” of conventional technology and often a failure to disclose all the parameters of a purification system touted as being environmentally responsible. But just as conventional water purification is (or certainly should be) based on water chemistry, so is green technology in water purification. If you don’t know what is in the water, you cannot possibly be successful in treatment.
Why should you be interested in green water purification?
Santa Fe has one of the lowest per-capita water uses in the US (101 gallons per capita per day; City of SF Water Conservation Office). But why not do your part to make it even lower by using green water purification techniques if applicable? The mix of Santa Fe municipal system water at any connection point is a combination of physical location (proximity to reservoirs and
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well fields) and seasonal levels of reservoir water. Water quality may vary locally and seasonally. The presence of naturally occurring contaminants makes water purification of interest to people with health-related water contaminant concerns and to those who experience infrastructure damage from contaminants (primarily hardness “scale,” iron and manganese staining) in both municipal and well (aquifer) water supplies. (See Table 1) There are some contaminants for which there is simply not a sustainable solution. Several technologies merit additional explanation.
GAC and Carbon Block Filters
The most effective method of removing chlorine is by using carbon filters (often improperly identified as “charcoal”). Some carbon filters are predominantly made from coal (look for “iodine content” as an indicator of the presence of coal), but the very best carbon filtration media is GAC (or granulated activated carbon) made from coconut shells, a renewable resource. Depending on the processing and particle size, the surface area of activated carbon can range from 500 to 1,400 square meters per gram. Several companies are now manufacturing GAC with sustainable technology by capturing the greenhouse gases from the ovens used to toast the coconut shells (to create the high volume of surface area) and by using the byproduct gases for other industrial applications. (See Figure 1)
Granulated activated carbon (GAC) is effective but it can provide a base for the growth of bacteria, has to be replaced (or wastefully backwashed) on a regular basis, and it becomes less effective through time because of channeling (erosion). An increasingly popular method of removing chlorine is by whole-house filtration using
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