Pure Water Occasional, April 17, 2022
 
Happy Spring from Pure Water Products, the Pure Water Gazette, and the Pure Water Occasional.
 
In this Eastertime issue there are articles about mercury, VOCs, city water chloramine filtration, chlorine burns,  chloride, and ultraviolet installation. 
 
Mercury is removed handily from water by standard residential reverse osmosis or carbon filtration. Coal-fired power plants are by far the main source of mercury contamination in our water supplies.
 
VOCs or Volatile Organic Compounds are many and diverse. The Calgon article below makes the whole VOC issue a lot less confusing. Activated Carbon is the standard treatment for VOCs,  but residential users need larger filters that are changed more frequently if there is persisent VOC contamination.
 
Whole house residential chloramine filters range from simple cartridges to fully automatic electronic backwashing tanks. The article  below reports a residential user's relatively inexpensive, low maintenance backwashing filter that does not require electricity or even a permanent drain connection. 
 
"Chlorine burns" are common, necessary, and hardly ever understood by city water customers. The article below puts them in perspective.
 
Chloride is a frequently misunderstood natural component of all water. The article tells you all you need to know about it.
 
When installing ultraviolet units, it's important to get everything in the right order. 
 
 
 
Thank you for reading.   And sincere thanks from Pure Water Products for your continuing support.  We consider our greatest asset to be the many faithful customers who have kept us going over the years. We really appreciate your business!
 
Thanks for reading!

For article archives and water news, please visit the Pure Water Gazette.
 
Mercury
 
 
Mercury is a neurotoxin that harms the lungs, the kidneys, the immune system, the heart and the brain.  The young and the unborn  are most at risk and severe developmental problems can result from mercury poisoning. Mercury can be a water contaminant, but eating poisoned fish is the main cause of mercury poisoning in humans.
 
For mercury contaminated water, the EPA-recommended treatments that are available to residential users are activated carbon filtration, reverse osmosis, and distillation. Mercury exists as an organic contaminant (that’s what poisons fish) and an inorganic pollutant.  It is the inorganic form that contaminates drinking water.
 
According to a 2012 report from the NRDC (Natural Resources Defense Council), over half of the Great Lakes region’s noxious mercury pollution can be attributed to the 25 worst coal-fired power plants in the Great Lakes area.   Nationwide, over half of mercury pollution comes from coal-fired power plants.
 
Reference: Your Bass Guy
 

 

VOCs For Non-Scientists: Understanding, Detecting, Removing

Below is a straightforward explanation of the highly problematic group of water contaminants known as VOCs. The article is from the Calgon Carbon Corporation, a leading supplier of water treatment media. It is focused toward operators of large water treatment plants, but the information applies to residential water users as well.

Volatile organic compounds (VOCs) are a large class of substances that may be found in various water sources. Many water quality managers and operators at water treatment plants (WTPs) know which substances are considered VOCs but not all understand the chemistry behind the designation. What follows is a straightforward guide to understanding VOCs, specifically, what qualifies a compound as a VOC, how to detect them, and how to treat and remove them from the water system.
 
What Is A VOC?

As the name implies, a VOC is defined primarily by two things. The first is that the chemical is volatile, which means that it easily changes state from liquid to gas with a relatively small amount of energy. Most VOCs have a comparatively low molecular weight, which is one of the reasons for this volatility. The other key defining factor is that it is organic, meaning the molecule is composed primarily of carbon atoms.
 
Most VOCs are manmade products, although a few, such as acetone, are also naturally occurring. That means nearly all VOCs end up in the water supply via industrial processes, chemical spills, or other human activity.

Nearly all VOCs are manmade.

Half come from industrial processes, 45% from motor vehicles, and 5% from consumer solvents.

VOCs in water are analyzed by using the U.S. EPA method 524.2. This process involves purging potential contaminants from a water sample using inert gas then desorbing them into a capillary gas chromatography column connected to a mass spectrometer.
 
Federally regulated VOCs are listed under the Safe Drinking Water Act (SDWA). Of course, each individual state may have its own list of regulated VOCs beyond those in the SDWA.
 
VOC Levels

For regulated VOCs, the EPA and state agencies set two levels for each chemical: a maximum contaminant level (MCL) and a maximum contaminant level goal (MCLG). The MCL is the largest permissible concentration of the chemical in water, while the MCLG is the concentration at which there is no known or expected health risk.
 
VOC Types And Properties

Not all VOCs behave the same. There are three sub-classifications of VOCs based on their boiling points:
 
  1. VVOCs (very volatile organic compounds). With boiling points of <0°C to 50-100°C, many of these exist solely in a gaseous state. Examples include butane, propane, and trichloromethane.
  2. VOCs (volatile organic compounds). Although the term VOC is often used to describe chemicals from all three subcategories, technically it applies only to those with boiling points in the 50-100°C to 240-260°C range. Some examples are ethanol, acetone, and vinyl chloride.
  3. SVOCs (semi-volatile organic compounds). The least volatile subclass is defined by boiling points from 240-260°C to 380-400°C.  Phthalates, many pesticides (including DDT), and nitrobenzene are some such examples.
VOCs can be further categorized as either hydrophobic (repel water) or hydrophilic (attract water). Hydrophobic VOCs (e.g., benzene) usually have smaller molecular weights and do not dissolve easily in water, which makes them relatively easier to move to a gaseous state. By contrast, hydrophilic VOCs (e.g., acetone) tend to have higher molecular weights and are more easily dissolved in water, which makes them relatively harder to move into a gaseous state.
 
Removing VOCs From Water

There are two primary methods for removing VOCs from source water.
 
Air Stripping. The process of forcing air through water works well on VOCs with lower boiling points (especially VVOCs) and/or those that are hydrophobic. This includes chemicals such as vinyl chloride, methyl chloride, chlorofluorocarbons, and methane.
 
Activated Carbon. Higher-molecular-weight VOCs won’t be as responsive to air stripping. For these chemicals, a granular activated carbon (GAC) filter is a more effective solution. The activated carbon can adsorb most VOCs, including those that are more difficult to remove via air stripping. Because VOCs diffuse quickly through the carbon bed, however, it is important to ensure the carbon has a high iodine number. Usually, about 1,000 to 1,100 is ideal to reduce the number of changeouts.
 
Establishing A Buffer For VOCs

It’s rare for water treatment plants to discover new VOCs in their source water. Most water systems are well established, and the challenge is less about tackling a previously unencountered chemistry but rather struggling to meet established and new MCLs.
 
That said, chemical spills can happen anywhere. For example, a city that pulls from a riverway with heavy boat traffic is always susceptible to some type of spill, as anything that is on a boat can end up in the water. Even chemical spills on land, such as a tipped gas tanker, can result in VOCs in groundwater. A GAC system that is in place for everyday VOCs will act as a buffer, ready to adsorb new contaminants should they enter the source water.
 
 
 
 
 
 

 
Simple and Effective Chloramine Filter for City Water Residential Application
 
 
Pictured above is a city residential catalytic carbon filter for treatment of chloramine and random chemical contaminants. It was designed and installed by the home owner.  Here are details:
 
Media tank is a 12″ X 52″ inch Vortech (saves water during backwash and requires no gravel underbed).
 
The tank contains two cubic feet of Centaur catalytic carbon, a specialty carbon designed for chloramine reduction.
 
The control valve is a Fleck 2510 manual (non-electric) filter valve. It has a three-position control for service, backwash, and rinse. The manual valve costs considerably less than the standard electric timer. A stainless steel bypass is included for easy maintenance.
 
Clear-housing sediment filters are installed both before and after the large filter.
 
The drain (needed for backwash and rinse cycles) is half-inch flexible tubing.
 
Plumbing parts used by the installer are a mixture of standard hardware-store  PEX, Shark-Bite, and John Guest components.
 
Discussion: This is a very functional filter that will provide excellent water for general household use for many years with little upkeep and minimum expense.  Inclusion of the before and after sediment filters assures that the carbon will stay clean and that any carbon particles (fines) that escape the filter will not make it to home plumbing lines and appliances.
 
The manual control valve is ideal for this application. The purpose of the backwash in city water filters is mainly to resettle the carbon bed and eliminate channels.  With normal residential use, probably once a month is more than adequate for backwash/rinse, which is a five or six minute job that uses just a few gallons of water. (This filter, built with a Vortech tank, needs only 5 gallons per minute to backwash the media bed.)
 
 

 

What Are Chlorine Burns?

Once a year, usually in spring,  water suppliers that normally disinfect their product with chloramine, a mixture of chlorine and ammonia, perform a cleaning procedure known as a “chlorine burn.”  The purpose is simply to clean out the pipes, ridding the distribution system of film and debris that has built up.
 
 
The clean-out is accomplished by simply switching disinfectants from chloramine to straight chlorine for a time, and usually increasing the dosage a bit to speed things along. Compared with chlorine, chloramine is a rather weak disinfectant.  Its weak performance allows sludge and scum, bacterial film, to build up in pipe walls and crevices.  The yearly purge, or “burn,” with straight chlorine cleans things out.
 
 
Chloramine is substituted for chlorine as the regular disinfectant in an increasing number of city water systems. The switch from chlorine to chloramine has been going on over a number of years as suppliers seek ways to stay in compliance with EPA standards for DBPs,  disinfection by-products, that are produced as a consequence of chlorination. Some DBPs are known carcinogens, and EPA requires suppliers to monitor them.  Chloramine, a weaker disinfectant, does not produce the specific DBPs that the EPA regulates.
 
Are chlorine burns a good idea?  Good or bad, they are necessary, since without a periodic cleanout, buildup in pipes would create significant problems for the water system. 
 
The practice does call into question, however, the wisdom of using chloramine rather than chlorine in the first place, since, as many argue, the burn and subsequent purging of pipes creates elevated levels of disinfection by-products in the system and higher than normal chlorine discharge into lakes and streams. In other words, for a short time we get concentrated doses of disinfectants and byproducts, which may be worse than what we would have with chlorine as the regular disinfectant.
 
The moral for residential city water users: With a good carbon filtration system in your home, you won’t even know when the burn takes place.  The elevated chlorine levels, murky water, and dislodged sediment that your neighbors are complaining about, you won’t even notice. If your city uses chloramine, you should use equipment that is designed for chloramine treatment. Any filter that removes chloramine also removes the chlorine used during the annual burn.
 
 

Chloride

Chloride, one of the most prevalent anions found in water, combines most commonly with the cations sodium, calcium, and magnesium.
 
Chloride levels in most waters range from 10 to 100 mg/L,  and sea water contains over 30,000 mg/L chloride in combination with sodium, as NaCl.
 
Chloride is an essential electrolyte that helps to maintain pH, transmit nerve impulses and regulate cellular fluids.
 
Chloride in water is more a plumbing issue than a health issue.
 
Chloride, when concentrated, can cause corrosion of metal piping, so when treating water high in chloride plastic is usually preferred to stainless steel for reverse osmosis membrane housings. Iron is leached into water from metal pipes when high levels of chloride are present. Chloride is the main cause of pitting of stainless steel. Chloride combines with hydrogen to produce hydrochloric acid.
 
The suggested MCL for chloride is 250 ppm. Above this level water often has an unpleasant salty taste.
 
Reverse osmosis removes around 95% of chloride, and electrodialysis and distillation are also effective. In industrial settings, strong base anion exchangers can be used.
 
In practical terms for most residential users, in city water chloride is not a problem.  For well owners with high chlorides, undersink reverse osmosis takes care of drinking water.  If water is so high in chlorides that it is unusable for irrigation, whole house reverse osmosis is an option.
 
 
 

Planning and Installing Residential UV Units

 
The Viqua manufacturer’s illustration above shows an ideal UV installation with pretreatment, individual optional by-pass assemblies for the all components, and the UV unit itself. It also shows an optional solenoid and temperature management valve, which would not be needed for most residential installations.  Most residential UV installations are not this elaborate, and they don’t need to be.
UV is normally installed as the final item in a treatment system. Pretreatment needed depends entirely on the quality of the water.
Pretreatment

UV always needs at least one pretreatment item, a 5-micron or tighter sediment filter somewhere in front of the UV unit to assure that there are no particles in the water to shade pathogens from the germicidal light.
 
Additional pretreatment depends on the quality of the water.  Water to be treated should have less than seven grains per gallon hardness, less than 0.3 ppm iron and less than .05 ppm manganese. The carbon filter shown in the diagram is optional and might be included to improve taste, remove extraneous chemicals, treat a small amount of odor, or even to remove chlorine or chloramine if city water is being treated. (Disinfectants like chlorine are not removed to protect the UV unit, which is not adversely affected by chlorine or chloramine,  but to improve the quality of the water entering the home.) Carbon will not address iron, manganese, and hardness. The softener in the picture will treat hardness and small amounts of iron and manganese. If iron and manganese are excessive, separate treatment will be needed.
 
The UV Itself

UV units are sized mainly by gallons per minute treatment capacity. Typical “whole house” residential sizes are 10 to 18 gpm. The UV unit pictured above is a free-standing unit, but systems are also sold that have the sediment and/or carbon stage(s) built on the same frames as the UV chamber. See picture below. Most residential UV units are 115V systems that plug directly into a wall outlet.
 
 
The Viqua 12 gpm unit above has a sediment filter and a lead-removal carbon block built onto the same frame as the UV chamber.
 
 
 
 
 
 
 
 
 
 
Places to visit for additional information:

 
 
 
 
 
 
 
Thanks for reading and be sure to check out the next Occasional!
Pure Water Products, LLC, 523A N. Elm St., Denton, TX, www.purewaterproducts.com. Call us at 888 382 3814.
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