What is Grey Water?

On islands the waste that is produced from washing machines, sinks, dishwashers and other appliances is known as grey water or sullage. Grey water comprises about 50-80% of water used in the home and it differs from black water which is primarily composed of chemicals and biological contaminates such as feces. Many island owners use a septic system that collects and treats both black and grey water. Other island owners choose to keep there black and grey water separate, instead opting to treat their grey water and return it back to the natural environment.

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Ultraviolet water purification lamps produce UV-C or “germicidal UV.” UV light is capable of killing microorganisms such as bacteria, viruses, molds, algae, yeast, and oocysts like cryptosporidium and giardia. Ultraviolet purification is considered the most effective technology for eliminating biological contaminates in a water supply available to homeowners. There are no known organisms immune to its effect and it’s generally regarded as being able to kill more than 99.99% of bacteria. Next to bacterial eradication the biggest advantage of UV purification is that it does not introduce any chemicals into the water, it does not alter the taste, it produces no byproducts and it does not alter the pH or any other properties of the water. In addition the system is energy efficient requiring the same amount of power as a 60W light bulb. The downside of UV filtration is that it has no effect on chlorine, heavy metals, smell or other chemical contaminates. UV lamps (bulbs) need to be replaced on a yearly basis. It is important to remember that UV light is not visible therefore the lamp may be producing light but not necessarily UV light. Therefore, after one year there is no guarantee that the lamp is producing sufficient UV to kill microorganisms. UV lamps cost between $450 and $700 depending on the type of system and replacement bulbs cost approximately $80.

Image obtained via: http://www.breathepureair.com/biozone_bulbs.html

Carbon Filtering

Carbon filters have been used for several hundred years and are considered one of the oldest means of water purification. Carbon filtering is a method of filtering that uses a piece of carbon to remove contaminants and impurities. Each piece of carbon is designed to provide a large amount of surface area, in order to allow contaminants the most possible exposure to the filter. Carbon used for water filtration is generally activated with a positive charge. This is done so as to attract negatively charged water contaminants. Carbon filters are most effective at removing chlorine, sediment, and volatile organic compounds (VOCs) from water. They are not generally effective at removing minerals, salts, and dissolved inorganic compounds. Thus they are often used in combination with reverse osmosis systems which remove these types of impurities. Most often it is used in combination with a reverse osmosis system.

Advantages/Disadvantages

Carbon filtrations systems are the most effect means of removing organic compounds, chlorine and radon. In addition, carbon filtration is a very cost effective means of water purification. It is crucial that a schedule of filter replacement is followed due to the tendency for bacteria to build up on the carbon thus reducing its efficiency.

Cost of Carbon Filtration

Carbon filtration systems typically cost between $300 and $400 but can cost more depending on the type of system. Replacement cartridges can cost between $20 and $75 depending on the type of system used.

Water purification is often a necessity on private islands. Treatment can reduce common contaminates, such as sediment, calcium, iron, magnesium, sulfate, nitrates, arsenic, lead, bacteria and viruses. Water treatment can produce cleaner, safer, better tasting, and better smelling water, better suited for household use.

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