Denver Water wants to double the amount of recycled water used in the city. The health department is not sure it’s safe

Strain on the Colorado River, treatment budgets, could be eased by using recycled water for growing dope, flushing toilets

Gazette Introductory Note. This is a truncated version of a much longer article that we’re reprinting to illustrate the increasing reuse of water by cities as well as the legal intricacies of water recycling.  The full article is here.

Water is asking for state permission to expand the uses of recycled water to include flushing toilets in commercial buildings, washing cows and pigs at the National Western Stock Show, and irrigating crops such as marijuana.

This could increase the 80 or so big customers in metro Denver who already tap a 70-mile network of underground purple pipes carrying recycled water, cleaned to meet the drinking water standards that applied in the 1980s.

But state health officials aren’t sure it’s safe to allow wider use.

A  Denver Water plan calls for at least doubling the amount of recycled water the utility provides, beyond the current 2.6 billion gallons a year to more than 5.6 billion gallons by 2020.

Using more recycled water could save money because stripping away contaminants to meet current drinking water standards increasingly requires costly, energy-intensive treatment. And reusing water reduces Denver’s need to siphon more H2O out of the over-tapped Colorado River.

Denver’s marijuana sector, alone, could make a big difference. Dope growers have emerged as significant guzzlers, feeding plants an estimated 146 million gallons a year of drinking water. That’s more than the 98 million gallons that metro Denver brewers use to make beer.

“This is where the world is going,” Denver Water chief executive Jim Lochhead said.  “Utilities are exploring this concept of ‘one water,’ the right water quality for the right purpose, and making the most efficient use of water.”

Rising temperatures from climate change and exhaustion of the river compel new approaches, he said.

“The demands on our system are going to increase simply because it is going to be warmer. People and plants are going to be using more water,” Lochhead said.  “The prospects of a major new diversion project on the Colorado River are difficult at best.”

The Colorado Department of Public Health and Environment has raised multiple concerns.

State water quality staffers are reviewing  “adequate control of pathogens,” including the potential for bacteria to grow in the purple pipes, an agency spokeswoman said. That’s because irrigation of crops for human consumption could mean more people are exposed to bacteria. They’re also evaluating the potential for salts to build up in soils and groundwater. And they’re looking at issues around build-up of “antibiotic resistant genes” that recycled water could accelerate. (Bacteria that develop resistance to antibiotics can reproduce and pass on that resistance, creating many more antibiotic resistant bacteria.)

“We’re as much about water conservation as anyone else,” director Larry Wolk said. “If there’s reuse potential for that kind of water that doesn’t pose any type of health risk or has an acceptable health risk, then it is something we definitely should consider.”

“We won’t know until that technical assessment is complete if it is an acceptable risk or not. Just because it was OK in 1980 doesn’t necessarily mean it is OK today , because we know a lot more, after nearly 40 years, than we knew then,”Wolk said.

“But we are all about reuse,” Wolk said, “whether it is produced water, recycled water, graywater, if there is an acceptable health risk.”

A CDPHE meeting is scheduled for next week to launch a rulemaking process that will run through August 2018. Health officials said they want to hear from all sides and said any new uses of recycled water won’t hurt people or the environment.

State rules currently allow use of recycled water for car washing, landscape irrigation, industrial systems and putting out fires.

For years, Denver Water crews have been capturing wastewater, treating it and sending it back through the city. It is water initially diverted from the Colorado River and moved through tunnels under the Continental Divide. (Denver Water legally is limited to a one-time use of its other water that originates here in South Platte River Basin, because downriver agricultural producers have rights to use Denver’s  “return flows.”) The purple-pipe water is classified as nonpotable, but utility officials emphasized it meets the standards of water people were drinking in the 1980s.

The 80 current users of recycled water include irrigators and industrial plants, nine schools, 34 parks, five golf courses and the Denver Zoo.

Source: Denver Post.

Pure Water Gazette Fair Use Statement

Well Water Contaminants that Can Affect Your Health

Adapted from a Vermont Health Dept. Bulletin

You have probably heard about the big three contaminants that could be in your well water: arsenic, lead and E. coli bacteria. But what about lesser-known contaminants, such as manganese and nitrates?

They can have harmful health effects too, and testing is the only way to know if they’re in your drinking water.

Manganese is a naturally-occurring metal found in rocks and soil that can dissolve from bedrock and enter groundwater. We get manganese from the foods we eat, and small amounts are also added to most vitamin supplements and baby formulas.

Nitrogen, also a natural element, can be found in water in the form of nitrate. Nitrate contamination of water usually comes from fertilized agricultural fields, septic system failures, or manure piles that are too close to wells.

Manganese and nitrates are required for health,  but we typically get all that we need from our diet, so we don’t need extra manganese and nitrates in our water.

Exposure to high concentrations of manganese over many years has been linked to toxicity to the nervous system.

Babies who drink formula made with nitrate-contaminated water are at risk for blue baby syndrome, a condition where the baby’s blood is less able to carry oxygen. Affected babies develop a blue-gray color and need emergency medical help.

Infants are more susceptible to adverse health effects associated with high levels of manganese and nitrates in drinking water because their bodies are smaller and still developing.

Health Departments recommend that people with private wells or springs have their water tested every five years for manganese and nitrates. In fact, comprehensive tests that evaluate all significant well-water issues, not just nitrates and manganese, are recommended.

How Long Do Water Filters Last?

Probably you have seen an ad for a small, one-cartridge “ten stage” water filter that promises to remove chlorine, lead, pesticides, herbicides, VOCs, fluoride,  and “pharmaceuticals,” and to “last for 10,000 gallons.” This advertising claim is actually true. But at the same time, it is a big lie. A really big lie.

The intent is to imply that  the filter will remove fluoride, VOCs, and all the other heavy contaminants listed “for 10,000 gallons.” But what “lasts for 10,000 gallons” really means is that it won’t fall apart and that it may even be removing some chlorine after 10,000 gallons. While it may “remove fluoride” for the first few gallons, it really doesn’t contain enough fluoride media to last past the original cartridge rinse. The trick is in the words.  It’s true that it “removes fluoride” and that it “lasts for 10,000 gallons,” but it certainly doesn’t remove fluoride for 10,000 gallons.

Even single media filters, like carbon blocks, have greatly different capacities for various contaminants that they treat.  Filter carbon is a very effective treatment–the best, in most cases–for a large majority of water contaminants, but in almost every case carbon filters treat chlorine much longer than they effectively treat more difficult contaminants.

For example, the manufacturer of one superb carbon block filter states the capacity of its 2.5″ X 10″ cartridge for removing chlorine as 20,000 gallons @ 1 gallon per minute. For removal of VOCs, however, the claim is for only 500 gallons at the reduced flow rate of 0.5 gallons per minute.

It is a mistake to assume, in other words, that the filter will remove VOCs as long as it will treat chlorine. If chlorine removal and taste/odor improvement are the only goals, then the filter can be used to its full chlorine capacity; but if you really need serious removal of specific contaminants, you should find out the cartridge’s capacity for the specific item you’re targeting and change the cartridge accordingly.

You should also notice that flow rate matters–a lot–and that if you want a faster flow rate, you need a larger filter.

Study finds that refillable water bottles are fertile growing ground for bacteria

Reprinted from Toronto Sun.

Gazette Introductory Note: We recommend that as you read this you try to remember any recent accounts you’ve heard of outbreaks of illness resulting from the use of refillable water bottles. Remember that we live in an ocean of bacteria. It isn’t remarkable that water bottles are teeming with microorganisms; it would be remarkable if they weren’t. –Hardly Waite.

You need to keep hydrated at the gym so you chug water from a refillable water bottle.

You might want to think twice before doing that.

According to a study by Treadmill Reviews, reusable water bottles contain high levels of human-harming bacteria. Swabbing four different bottle styles, the study found the containers were crawling with more than 300,000 colony-forming bacteria units per square centimetre.

Conclusion: drinking from a refillable bottle may be worse than licking a dog’s toy, the U.K. Sun reported.

The study detected that the average water bottle had 313,499 CFU (colony-forming units of bacteria) compared to 2,937 CFU found on a dog’s toy.

Bottles with a slide-top spout contained the most germs with an average of 933,340 CFU.

Squeeze-top bottles are just as harmful with an average germ count of 161,971 CFC.

Screw-top lid bottles aren’t as bad with 159,060 CFU. Surprisingly, the least harmful were straw-top bottles with a fraction of an average compared to others at just 25.4 CFU.

While squeeze-tops weren’t as harmful as its slide-top counterparts, almost 99% of bacteria found on the bottle contained harmful traces of antibiotic-immune bacteria like E.coli, the study suggested.

Overall more than 60% of germs found on water bottles can make people sick.

The study’s researchers suggested using straw-tops or stainless steel bottles over plastic ones. Researchers also recommend not letting a half drunk bottle sit unattended for weeks.

Bottles should also be hand washed with a weak bleach solution or cleaned via dishwasher.

Pure Water Gazette Fair Use Statement

Rinsing Water Filter Cartridges: Getting the Air Out

by Gene Franks

When water filter owners ask how long they should rinse the filter cartridges in new water treatment units, or in units they are replacing the the filter cartridges in, they usually expect a simple answer and that’s what they usually get.  Actually, though, the answer can be quite complicated and in most cases there is not a pat answer.

We’re concentrating on carbon filters here, which are by far the most common in residential treatment units, but the same principles apply in varying degrees to other media, like calcite, ion exchange resins, or activated alumina.


If you have a carbon filter, you’ve probably noticed that a big blast of black stuff comes out of the faucet when you start up a new cartridge. This is called “carbon fines.” It’s just manufacturing left-overs,  small pieces of carbon that have to be washed out.  Some filters, you may also have noticed, put out virtually no fines. This is because the manufacturer has gone to the trouble to clean the carbon up well (often washing it with acid) to keep the “fines” from going into your RO membrane or your refrigerator.

The assumption is that when the fines have subsided and the water is running more or less clear, the cartridge is ready to use. Not so.  There are other considerations.  For example, brand new carbon filters can contain residuals of contaminants (like arsenic), and even NSF Standard 42 cartridges, which are certified to be safe, sometimes are labelled with the admonition to “place the cartridge in an appropriate housing and rinse for a minimum of 20 minutes before use.” Anyone who has tested a reverse osmosis unit after a cartridge change knows that you do not get a valid TDS (total dissolved solids) reading of membrane performance after the cartridge change.  This is because the new carbon postfilter, for up to a week after the cartridge change, is putting out “solids” that the meter can see but the human eye cannot. To be clear, the same “TDS throw” occurs in all new carbon filters, not just RO postfilters; it’s just that only RO units are routinely tested for TDS performance.

AirairWhat air inside a carbon block cartridge looks like

A fact that water treatment professionals are aware of but that water filter users seldom consider is that new carbon filters are mostly air. What makes carbon such an amazingly effective filter medium, in fact, is not only what is there but what is not there. It’s the countless tiny air-filled pores inside the carbon particles that provide enormous amounts of surface area for chemical contaminants to cling to that make carbon so effective.   The so-called “40-40-20” rule has it that most carbon filters are 40% air-filled space between carbon particles, 40% air-filled inner pores, and 20% actual solid carbon. In fact, depending on the type of product and the manufacturing method, most carbon filters are said to be 70% to 90% air.

When a new cartridge is put into service, it can take days for the air to work out completely. That’s why users sometimes experience cloudy water (if air is causing the cloudiness, the water in a glass will clear from bottom to top) and why there sometimes appears be a scummy substance at the top of a glass of water from a new filter. The scum is air trapped under the “skin” at the top of the water column.  Both the cloudy color and the scum will go away with time, and it’s nothing to worry about.

Diminished Performance Because of Air

While fines and trapped air are aesthetic problems with filter startup that goes away fairly quickly, there is actually diminished performance from a new filter cartridge or carbon bed in a large filter caused by trapped air that lasts longer.   I sometimes tell customers with new products that the water will taste and look better after a week or so,  when the new filters have had a chance to “mellow in.”  Mellowing in is a low tech way of saying that everything will work better when water has had a chance to push the air out of the millions of tiny crevices within the carbon, thus allowing the water to come into intimate contact with the carbon itself.

Large industrial filters have to be soaked for long periods after rebedding to drive the air out the carbon.  Hot water, which speeds the process up, is also used.  Henry Norwicki et al. in a recent Water Conditioning and Purification article actually recommend a 72 hour soak for small filter cartridges:

There are two ways to replace the nano-spaced concentrated air: 72 hours submerged soaking in tap water or using hot water to remove trapped air. Water forms larger conglomerates by hydrogen bonding of water molecules. Conglomerates of hot water are smaller and can better penetrate adsorption spaces than larger, cold-water conglomerates. Replacing filter soaking water with fresh water and turning the filter vertically upside down is also beneficial. Draining helps remove air bubbles. When air in nanospaces is replaced by water, bubbles go into bulk volume between media particles. Simple draining removes these bulk water bubbles. Water inside particles, however, is not removed by draining. Soaking for 72 clock hours is necessary and extra time is acceptable.

We’re a long way from recommending that customers soak filter cartridges for 72 hours before using them, but it helps to know what’s going on inside the filter and be a bit forgiving if water is cloudy and doesn’t taste as good as you would expect with brand new filter cartridges.

Enlargement of granular carbon shows countless pores that adsorb contaminants. The surface area of the pores is exceptional. A single pound of activated carbon has more surface area in its pores than 100 football fields. When the carbon is new, these pores are filled with air that must eventually work its way out.

Enlargement of granular carbon shows countless pores that adsorb contaminants. The surface area of the pores is exceptional. A single pound of activated carbon has more surface area in its pores than 100 football fields. When the carbon is new, these pores are filled with air that must eventually work its way out.

New Technologies That Save Water Should Be Taken with a Grain of Salt

Many water saving products work well, and yet  . . .

Vortech Tanks

Enpress, the tank manufacturer, makes the following advertising claim for its popular “Vortech” brand mineral tanks for backwashing filters and water softeners:

It’s proven – we have saved over 14 billion gallons of water and counting with our Vortech® and Mid-Vortech® distributor plate technologies since they were introduced 10 years ago!

The manufacturer is, of course, basing its “proof” on the assumption that everyone who uses the tank is taking advantage of the superior backwash flow performance of the tank as compared with conventional mineral tanks with gravel underbedding. While the manufacturer’s tests show that backwashing filters built in Vortech tanks can be backwashed with up to 30% less water, it’s safe to say that only a relatively small percentage of products using Vortech tanks are actually using 30% less water as compared with similar products that use standard mineral tanks.

The reason is that Vortech tanks don’t have magic properties that makes them automatically save 30% of the backwash water. To save water, they have to be set up by the installer to have either a shorter backwash/rinse cycle or to have a more restrictive backwash flow control device installed so that fewer gallons go out the drain line. We (at Pure Water Products) use Vortech tanks on all our filters, but we take a more conservative 20% reduction in regeneration water.  (Or first concern is to make sure the filter works properly. We we want to be sure it doesn’t fail because it’s starved for water.) If everyone used Vortech tanks with our setup, therefore, Enpress would have to say that they have saved 9 billion rather than 14 billion gallons.

When I asked one of our large suppliers for their setup formula for Vortech units, I was told that they set use the same setup for Vortech as for standard tank units. Although they advertise Vortech tanks as water savers, the Vortech units they make use exactly the same amount of water as their standard units. My guess is that this is the rule rather than the exception.

High Efficiency Softener Resin

The same is true for the extra efficient softener resins. Resin that can be regenerated with 4 pounds of salt per cubic foot of resin only saves salt if the installer sets it up that way. Resin itself doesn’t automatically save salt. In fact, softeners in general are among the products that are often advertised as salt and water efficient yet are set up exactly like standard models. The most sophisticated water softener does not automatically save water if it is not set up properly at installation.

Water Saving Reverse Osmosis Membranes

High efficiency RO membranes, like the new Pentair GRO units, are great water savers and they perform as advertised.  But, they only save water if they are set up correctly. The membrane itself does not automatically save water: it has to be paired with a drain line flow restrictor that matches the membrane. It is the flow restrictor that actually governs how much water goes out the drain line, not the membrane. If you buy a GRO membrane from Amazon and put it on your RO unit, it will only save water if you pair it with a properly sized flow restrictor.

There is a new RO unit just on the market that boasts “3 gallons of drinking water to 1 gallon of concentrate.” We haven’t seen it or seen an explanation of how it works. We’ve had excellent performance from the Pentair GRO with its 1 to 1–one gallon of RO permeate water for one gallon to drain–ratio, but 3 to 1 seems to good to be true.

The Permeate Pump

The RO “Permeate Pump” is now a recognized water saver, and if you install it properly your revere osmosis unit will definitely fill its tank faster and shut off faster and therefore run less water to drain. The pump can be installed with or without a shutoff valve and there is disagreement about which way is better.  The good thing is they save water either way, and it’s easy to tell if you have it installed right: if it makes a thumping sound, you got it right.

Advanced tanks, water saving membranes, and high efficiency resins are all significant water savers, but you should not think you’re saving water just because you own them.  Most products of this type work only if  you set them up right.


Posted June 27th, 2017

Perfluoroalkyls in a nutshell

What are PFCs?

PFCs are a family of man-made compounds that are not naturally occurring in the environment. Perfluoroalkyls repel oil, grease, and water, and as a result were used as protective coatings in cookware, carpet, clothing, paper, and cardboard packaging, as well as in fire-fighting foams. They are very stable compounds that are resilient to breakdown in the environment. The most common perfluoroalkyl compounds are perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA).


PFOS and PFOA compounds were produced in large quantities in the United States and have contaminated air, water, and soil at locations where they were produced or used. As a result, PFOA and PFOS are found in air and dust; surface and groundwater; and soil and sediment. The highest levels of PFOS and PFOA are typically at or near a facility that produced or used the compounds. Since they are found in air and dust, they appear in remote locations where flooding and groundwater migrate them through the soil.

Health Effects of PFCs

The most common exposure to PFOS and PFOA is through ingestion, with drinking water supplies being the primary route for exposure. Typically, populations near facilities where PFOS and PFOA was manufactured or used have the highest levels of these compounds in their drinking water. Health advisories by the EPA indicate that exposure to PFOS and PFOA over certain levels may result in adverse health effects, including developmental effects to fetuses during pregnancy or to breastfed infants (e.g., low birth weight, accelerated puberty, skeletal variations), cancer (e.g., testicular, kidney), liver effects (e.g., tissue damage), immune effects (e.g., antibody production and immunity), thyroid effects and other effects (e.g., cholesterol changes). As a result the EPA has established a combined lifetime exposure of 70 parts per trillion for PFOS and PFOA.

Water Treatment?

The best and most commonly applied water treatment for PFCs in general is the old standby, granular activated carbon.

Quick Reference Table for Water Contaminant Treatment



Acidic Water Soda ash injection; Sodium Hydroxide injection; Calcite
Acrylamide Carbon (with moderate probability of success)
Alachlor Carbon
Alpha particles Reverse Osmosis; distillation
Alum (Aluminum Sulfate) Reverse Osmosis; distillation
Aluminum Water softener; Reverse Osmosis; distillation; electrodialysis
Ametryn Reverse Osmosis, carbon, and UV used together
Ammonia Water softener with previous removal of calcium and magnesium; deionization; natural zeolite, chlorination
Antimony Reverse Osmosis; coagulation/filtration
Arsenic Ion exchange; Reverse Osmosis; distillation
Asbestos Reverse Osmosis
Atrazine Carbon
Barium Ion exchange; Reverse Osmosis; lime softening; electrodialysis
Benzene Adsorption with carbon; ozone
Benzo(a)pyrene (PAHs) Carbon
Beta particles and photon emitters Ion exchange-mixed bed; Reverse Osmosis; distillation
Cyanotoxins UV; Reverse Osmosis; nanofiltration;  carbon; chlorination
Total Coliforms (including fecal coliform and E. Coli) UV; chlorine/chloramine disinfection; ultrafiltration; Reverse Osmosis; ozone
Beryllium Activated alumina; coagulation/filtration; ion exchange; lime softening; Reverse Osmosis
Alkalinity Aeration; acid injection; anion exchange
Bisphenol A (BPA) No recommended treatment
Boron (Borate) Reverse Osmosis; ion exchange; increasing pH
Bromates (Potassium Bromate and Sodium Bromate) Prevention by pH alteration; anion exchange; ammonia impregnated carbon
Brackish Water Reverse Osmosis; distillation
Bromine (Bromide) Reverse Osmosis; carbon; UV; dialysis
Cadmium Reverse Osmosis; cation exchange; dialysis
Carbaryl (Sevin) Carbon; coagulation; ozone
Calcium Ion exchange; Reverse Osmosis; deionizers; dialysis; distillation; ultrafiltration
Carbofuran Carbon
Carbon dioxide Aeration; deionization; raising pH with Soda Ash injection
Carbon tetrachloride Air stripping;  carbon; coconut shell carbon; Reverse Osmosis
Chloral hydrate Carbon
Chloramines Carbon; catalytic carbon; ascorbic acid, UV
Chlordane Carbon
Chloride Reverse Osmosis; electrodialysis; distillation;  anion exchanger
Chlorine Carbon; KDF
Chlorine dioxide Carbon (possible success)
Chlorite Carbon (possible success)
Chloroacetones No recommended treatment
Chlorobenzene Carbon; Carbon with packed tower aeration
Chloropicrin Chemical oxidation
Chlorpyrifos Coagulation; carbon; ozone
Chromium Reverse Osmosis; distillation; strong base anion exchange regenerated with caustic soda
Color Carbon; anion exchange after water softener; iron/manganese removal methods
Copper POE applications and plumbing fixtures protected by cation exchange, pH control, and film-creating compounds such as polyphosphates; POU treatment: Reverse Osmosis, distillation, and carbon
Corrosion Increasing pH; Reverse Osmosis to reduce chlorides; carbon filtration to reduce chloramines/chlorine; lowering temperature of hot water heater; sediment filtration; decrease flow rate
Cryptosporidium Carbon; Reverse Osmosis; nanofiltration; UV; ozone; distillation
Cyanazine (Bladex) Carbon
Cyanide Reverse Osmosis; electrodialysis; chlorination, retention, and filtration; Carbon  with packed tower aeration
1,2-Dichloropropane Carbon with packed tower aeration; carbon
1,3-Dichloropropene/ 1,3-Dichloropropane Carbon; hydrolosis
1,4-Dioxane Biological activated carbon; UV or ozone with hydrogen peroxide
2,4-D (2,4-dichlorophenoxyacetic acid) Carbon
Dalapon Carbon
DBCP (1,2-Dibromo-3-chloropropane) Carbon and packed tower aeration;  carbon
DDT (Dichlorodiphenyltrichlorethane) Carbon; coagulation
DEHA [Di(2-ethylhexyl) adipate] Carbon
DEHP [Di(2-ethylhexyl) phthalate] Carbon
Diazinon (Spectracide) Hydrolosis
Dichloroacetic Acid (DCA) Prevention through pre-filtration to remove organic matter or pH adjustment prior to treatment
o-Dichlorobenzene Carbon with packed tower aeration; Carbon
p-Dichlorobenzene Carbon with packed tower aeration; carbon
1,2-Dichloroethane GAC with packed tower aeration; activated carbon
1,1-Dichloroethylene GAC with packed tower aeration; activated carbon
cis-1,2-Dichloroethylene GAC with packed tower aeration; reduction by Reverse Osmosis
trans-1,2-Dichloroethylene GAC with packed tower aeration; reduction by Reverse Osmosis
Dichloromethane (DCM) GAC with packed tower aeration
Dicofol Hydrolosis; possible treatment with activated carbon
Diflubenzuron Activated carbon
Dimethoate Chlorination and GAC
Dinoseb GAC
Dioxin (2,3,7,8-TCDD) GAC
Diquat GAC
Diuron (DCMU) Activated carbon
Edetic Acid (EDTA) Ozone with activated carbon
Endocrine disruptors (EDCs) Nanofiltration; Reverse Osmosis; activated carbon; distillation; ozone; advanced oxidization
Endosulfan Activated carbon
Endothall GAC
Endrin GAC
Epichlorohydrin (ECH) No recommended treatment; limited usage
Ethylbenzene GAC
Ethylene dibromide GAC
Fenitrothion Hydroloysis
Flouride Reverse Osmosis; distillation; filtration through activated alumina
Formaldehyde GAC
Foaming agents Coagulation/flocculation; sedimentation; filtration; activated carbon
Giardia lamblia Filtration of 1 micron size or below; UV; Reverse Osmosis; ozone; shock chlorination
Glyphosate (Roundup) GAC
Haloacetic acids (HAA5) Pre-filtering prior to disinfection treatment; activated carbon; Reverse Osmosis
Hardness Water softener; Reverse Osmosis; lime softening; polyphosphates; siliphos
Heptachlor GAC
Heptachlor epoxide GAC
Heterotrophic plate count (HPC) N/A
Hexachlorobenzene (HCB) GAC
Hexachlorobutadiene (HCBD) GAC
Hexachlorocyclopentadiene GAC with packed tower aeration
Hydrogen Sulfide Oxidizing with gas: chlorine, aeration, hydrogen peroxide, ozone, potassium permanganate followed by filtration of oxidant and elemental sulphur; open tank aeration; carbon for small amounts; changing sacrifical anode of hot water heater
Iodine-131 Reverse Osmosis
Iron Ferrous Iron removal: Water softener; oxidation with air, ozone, potassium permanganate, chlorine, or hydrogen peroxide; filtration with Filox, Birm, and Greensand; Ferric Iron removal: filtration with wound string filter; backwashing filter; Heme Iron removal: scavenger anion resin; oxidation with chlorine followed by mechanical filtration
Iron Bacteria Chlorination
Lead Reverse Osmosis; water softeners; removing the source; corrosion control methods in pipes including pH and alkalinity adjustment; calcium adjustment; silica or phosphate-based corrosion inhibition
Legionella Heat and flow-rate management; UV; ultrafiltration
Lindane GAC
Magnesium Water softener; Reverse Osmosis
Malalthion and Malaoxon Activated carbon
Manganese Ion exchange; oxidation/filtration; chemical feeding then filtering through greensand, carbon, or filter ag
MCPA (4-(2-methyl-4-chlorophenoxy)acetic acid) GAC; ozone
Mercury Activated carbon; Reverse Osmosis; distillation; ion exchange; sulfide precipitation; starch xanthate
Methane Atmospheric aeration
Methanol (Methyl Alchohol) Ozonation with UV
Methoxychlor GAC
Methyl Tertiary-Butyl Ether (MTBE) Coconut shell carbon; reduction through carbon block filtration
Metolachlor (S-Metolachlor) GAC
Molinate GAC
Monochloracetic Acid (MCAA or Chloroacetic Acid) No recommended treatment; formation during water disinfection may be prevented with pre-filtration to remove organic matter, or pH adjustment
Mutagen X and MX Analogues Activated carbon
Naphthalene Activated carbon
NDMA (N-Nitrosodimethylanime) Reverse Osmosis removes 50%
Nickel Strong acid cation exchanger; reduction through activated carbon and RO
Nitrite (measured as Nitrogen) Ion exchange; Reverse Osmosis; electrodialysis; distillation and blending
Nitrate (measured as Nitrogen) Ion exchange; Reverse Osmosis; electrodialysis; distillation and blending
Nitrilotriacetic Acid (NTA) Activated carbon
Norovirus Reverse Osmosis; nanofiltration; ultrafiltration; chemical oxidation; UV; distillation
Odor Activated carbon; oxidation/reduction; chlorine dioxide; ozone; hydrogen peroxide
Oryzalin Activated carbon
Oxamyl (Vydate) GAC
2-Phenylphenol (OPP) Activated carbon
Paraquat dichloride Activated carbon
Parathion (Ethyl Parthion) Activated carbon; hydrolysis
Pendimethalin GAC
Pentachlorophenol GAC
Perchlorate Reverse Osmosis; anion exchange; carbon adsorption; distillatin
Perfluorinated Chemicals (PFCs) Activated carbon; Reverse Osmosis
Permethrin Activated carbon
Pesticides Activated carbon; Ultrafiltration; Reverse Osmosis
pH Raising pH: feeding soda ash, caustic soda, sodium bicarbonate, or potassium hydroxide; calcite; corosex; Lowering pH: feeding sulfuric, hydrochloric acids, phosphoric acid, acetic acid, citric acid, vinegar into water
Pharmaceuticals and Personal Care Products (PPCPs) Chlorine; ozone; activated carbon; Reverse Osmosis
Phosphates Alum; sodium aluminate; ferric chloride; precipitated with lime to hydroxyapatite at pH of 10 or more and then filtered
Picloram GAC
Pirimiphos-methyl Activated carbon
Polychlorinated biphenyls (PCBs) GAC
Polynuclear Aromatic Hydrocarbons (PAHs) GAC
Propanil Activated carbon
Pyriproxyfen GAC
Tetrachloroethene/Perchloroethylene (PCE) GAC with packed tower aeration
Radon Point-of-entry devices: GAC, Aeration systems
1,2,3-Trichloropropane (TCP) GAC
2,4,6-Trichlorophenol (Dowicide 2S) GAC
Temephos Adsorption with activated carbon
Terbuthylazine (TBA) GAC
Tetrachloroethanes Activated carbon
Thallium Activated alumina; ion exchange
Toluene GAC with packed tower aeration
Total Dissolved Solids (TDS) Reverse Osmosis, Distillation, Deionization.
Toxaphene GAC
Trichloroacetic Acid (TCA) No recommended treatment; can be reduced during chlorination with coagulation and pH regulation
1,2,4-Trichlorobenzene (TCB) GAC with packed tower aeration
1,1,1-Trichloroethane GAC with packed tower aeration; activated carbon
1,1,2-Trichloroethane GAC with packed tower aeration; activated carbon
Trichloroethene (TCE) Activated carbon adsorption; reverse osmosis (70-80 % removal); air stripping
Tritium No known treatment
Turbidity Depends on amount and nature of particles present; Likely use of sediment filters
Uranium Reverse Osmosis; anion exchange; activated alumina; electrodialysis; enhanced coagulation/filtration
Selenium Reverse osmosis; anion exchange; distillation
Silica Ion exchange with strong base anion resin; coagulation/filtration; reverse osmosis; ultrafiltration; lime softening/precipitation in large flows
Silver Reverse Osmosis; distillation; strong acid cation exchange for reduction
2,4,5-TP (Silvex) GAC
Simazine GAC
Spinosad DT (Spinosyns A and D) Activated carbon
Styrene GAC with packed tower aeration
Sulfate Reverse Osmosis; strong base anion exchanger
Vanadium Ion exchange
Vinyl chloride GAC with reverse osmosis; distillation; air stripping
Volatile Organic Chemicals (VOCs) Activated carbon; coconut shell carbon; reverse osmosis; aeration with activated carbon
Xylenes (total)

GAC with packed tower aeration; activated carbon

What is DOC and How Is It Treated?

Dissolved organic carbon (DOC) is a general description of the organic material dissolved in water.

Organic carbon occurs as the result of decomposition of plant or animal material, and a small part of the organic carbon  may then dissolve into the water.

Organic material (including carbon) results from decomposition of plants or animals. Once this decomposed organic material contacts water it may partially dissolve.

DOC does not pose health risk itself but may become potentially harmful when in combination with other aspects of water. When water with high DOC is chlorinated, harmful byproducts called trihalomethanes may be produced. Trihalomethanes may have long-term effects on health. That is why DOC is a consideration when water is chlorinated.

Not only can Dissolved Organic Carbon promote the formation of trihalomethanes (THMs) in chlorinated water, it can also  interfere with the effectiveness of disinfection processes such as chlorination, ultraviolet and ozonation. DOC can also promote the growth of microorganisms by providing a food source. In addition, it can add taste, odor and color.

Organic content is usually higher in surface water than in well water.

Removal of dissolved organic carbon is more commonly done by municipalities and water suppliers than by homeowners. City water suppliers have treatment strategies to draw on that aren’t available to residential users. They are also in a better position to prevent the formation of DOC, which is usually easier than treating it.

Treatment methods effective in removing DOC from water include: coagulation/flocculation processes, biological filtration, granulated activated charcoal and distillation. For residential water treatment, GAC is the most common and the most practical treatment. Distillers can be used for drinking water only.

Usually treatment is recommended if concentrations of DOC are greater than 5 mg/L.  At that level, it is likely that chlorination will result in the formation of THMs in excess of EPA standards. Above 5 mg/L color of the finished water also becomes objectionable.  For concentrations of less than 2 mg/L, color is usually not an issue and THM creation will be small.

The best home treatment for DOC is carbon filtration.

Hard to believe, Garden Hose Day is again upon us

Moving National Garden Hose Day from August to June makes the holiday’s promoters look like geniuses.  Last year’s event, on its new June 21 date, exceeded expectations in terms of crowd sizes, enthusiasm and product sales.

Although Minneapolis has become the unofficial capitol of Garden Hose Day activities, communities large and small around the US are holding Garden Hose celebrations this year. The Garden Hose Tug, an enhanced variation of the good old fashioned Tug O’ War game, remains the main event in most Garden Hose Day celebrations, although garden hose crafts contests, in which contestants show objects they’ve created from garden hoses, are expected to run a close second in popularity at this year’s events.


Last year Cleveland added a canine division to the Garden Hose Tug. In the final round, the event winner, Little Arnold, on the left, bested Spot, his weightier opponent, in less than four minutes.

The common garden hose is one 0f life’s treasures that we take for granted.  When you think of it for what it is–a very inexpensive portable pipe that can bend around corners, roll up for storage,  and carry high volumes of water quickly over great distances–it deserves our admiration as one of civilization’s simple but awe-inspiring achievements. For simplicity, for efficiency, and for utility, the garden hose is right up there with the canoe, the bicycle and the clothes line in the list of man’s greatest creations. For gardening, car washing, filling pools–for more of our routine activities that we can recount–the humble garden hose saves time, money, and labor. But for many of us, the garden hose is of greatest importance because it evokes happy memories of childhood and summer days.

We urge you to go to a garden hose event in your neighborhood this year.


An attractive garden hose basket that is a popular item in Amazon garden hose stores. In addition to the almost limitless array of decorative hoses, there are special nozzles, colorful hose bibs, manual and electrically-powered hose dispenser/retractors,  hose splitters, hose repair kits, hose unions, hose protectors, and more.  Related items include lawn equipment, car wash paraphernalia,  clothing,  books about gardening, patio cooking, landscaping and washing cars, patio furniture, lawn sprinklers,  gardening tools–the list is endless. Yes, even X-rated products that include sex toys and clothing with suggestive phallic mottoes and pictures were on the market this year.