OSA WATER WORKS 

WATER QUALITY

Biological Water Quality, Chlorine, and Ultraviolet Distinfection.

For potable water supply the most important water quality issue is biological water quality.  Waterborne pathogens include viruses, bacteria, and protozoa, all of which originate in the gastrointestinal tract of a warm-blooded animal.  In areas that are subject to human contamination, the list of pathogens and resultant infirmities is legion, including such terrible conditions as:  cholera, hepatitis, typhus, typhoid fever, amoebic and bacterial dysentery, diarrhea, shistosomiasis, and others.  In native waters originating in streams and springs in the Costa Rican rain forest, the only pathogens are those that circulate through animals.  In practice, this gets down to one bad actor, giardia lamblia, a protozoan that is responsible for giardiasis, or beaver fever as it is colloquially known.

In order to protect municipal water supplies against the large number of potentially deadly waterborne diseases, water engineers use chlorine as a disinfectant.  Conventional practice is to dissolve enough chlorine in water so that a chlorine "residual"  remains in the water to actively attack pathogens while the water is in the distribution system.  Chlorine is so toxic that if it is present in even the slightest amount, no microbe can survive its oxidative toxicity.  Chlorine can be detected by very simple colorimetric means, unlike the detection of microbes, which is very complicated and imprecise.  This means that it is possible to have a 100% guarantee of safe drinking water based on so simple a process as a chlorine check. 

Chlorine is a carcinogen and its reaction with some organic compounds produce even more carcinogenic metabolites.  So, chlorine is not something that you want in your water.  However, the lives saved by its use as a disinfectant outweigh the lives lost through unintended cancers by many many orders of magnitude, so chlorination of public water supplies is a standard engineering practice to ensure the potability of water and is a net positive and nearly universal in Costa Rica.  However, homeowners can install a granular activated carbon filtration system in their homes to remove chlorine prior to use.  This way the water is protected by chlorine until its delivery to the home and the danger of carcinogenicity is eliminated by removing chlorine at its point of use, representing the best available water quality management practice.   A GAC home treatment system to remove chlorine costs $450 for a 5 gpm system and $700 for a 10-gpm system and have annual cartridge replacement costs of $150-300.

For individual homes where the threat is not from human-borne pathogens but from natural pathogens in the wild, ultraviolet disinfection is a better way to achieve disinfection.  It deactivates microorganisms during passage through a reaction chamber illuminated with ultraviolet light.  While UV disinfection does not leave a residual to keep on protecting following the UV chamber, these systems are for home use, so it is essentially point of use.  UV-disinfection modules come packaged together with partuclate and GAC filtration modules in the Pura-III home purification system, which is ideal for most home installations in Costa Rica.  The units cost $1150 FOB San Jose and annual replacement cartridges and bulbs are around $300.

Water hardness.

Water hardness is a problem that is widespread for deep wells that typically penetrate aquifers in volcanic rocks with an abundance of calcium and magnesium.  There is nothing in itself intrinsically wrong with hard water.  It is certainly not toxic.  But it causes scale to precipitate in pipes and valves and particularly inside domestic appliances that change the temperature of water, most notably ice makers, espresso machines, boilers, irons, and similar devices.  High hardness water also requires a greater amount of detergent to achieve comparable "sudsiness," and it results in objectionable rings around drains and toilet bowls.  While softening cartridges are available and can be used inside filter housings, these do not work as reliably as ion exchange water softeners.  If hardness is high enough to require treatment at all, it is best to not mess around with cartridges and to opt instead for a full water softener.  I offer the XXXX water softening unit for $975 FOB San Jose.  This unit requires rock salt for regeneration and is fully automated.  For protection of individual machines like ice makers, a cartridge softener for $350 is normally adequate so long as it is on a regular replacement cycle.

Iron, Manganese, and Sulfur.

For high iron, manganese, and sulfur, chlorination systems tend to be the only viable option other than development of a different water supply altogether.  These come from deep wells when the homeowner is unlucky and are often the source of continual discontent until the investment is made in a robust water treatment system capable of removing the objectionable contaminants.

The first step in evaluating water treatment needs is representative sampling and chemical and biological analysis to determine the basic mineral makeup of the water and any contaminants that may be present.  Generally speaking, springs are the highest water quality source for rural homeowners.  Typically, a well installed spring water supply requires no water treatment of any kind, not even a sediment filter.  All rainfall capture and stream water systems require particulate, GAC, and ultraviolet disinfection, making the Pura-III system ideal for these cases.  Near surface wells often have bacterial contamination but rarely have mineral problems like water hardness, iron, manganese, and sulfur.  Deep wells are nearly always free of biologic contaminants but commonly have mineral water quality issues that may or may not require treatment for optimal home use.  And all municipal water supply comes with chlorine, which the homeowner may prefer to remove prior to ingestion.  So, while some generalizations are possible, nothing will ultimately take the place of a chemical analysis to know what the water has in it.

For question on water quality, you can contact me by filling out the questionnaire or  just write me an email.  It is usually possible for you to collect samples and submit them to a laboratory and gather all the information necessary to make excellent water treatment decisions without incurring any consulting costs so that the equipment and its installation is often the only actual expense required to ensure that your water supply provides you with the degree of water quality that you decide is appropriate.

Organic Compounds.

For synthetic organic compounds present as dilute contaminants in ground water, granular activated carbon adsorption is the technology of choice for removal of these contaminants.  While synthetic organic contaminants are not uncommon in the ground water of industrialized societies from spills and seepage from industrial facilities, contamination in Costa Rican aquifers is rare.  So, this is an unusual circumstance.  GAC filtration is also helpful for removal of naturally occurring organic compounds that result from the decay of organic matter and which can introduce taste and odor to water.  This happens in still water and is common in swamps.  Organic compounds can also result from longterm water storage, particularly in rainfall capture systems.  Consequently GAC filtration is a necessary component of rainfall capture water purification systems to ensure the highest possible quality water.