Total Dissolved Solids: A Matter of More Than Just Good Taste


The following discussion of Total Dissolved Solids views TDS mainly from the municipal water supplier’s point of view. 

Everyone wants good-tasting water, but most water treatment plants (WTPs) are hostages to the composition of their local source water supplies. One of the components involved in taste is total dissolved solids (TDS), which can affect both the acceptability of finished water taste and its likelihood to corrode or clog pipes and fixtures. Here’s how to quantify the problem and what to do about it if it is excessive.

TDS: Good, Bad, Or Indifferent?

Water chemistry can be a complex subject based on the qualities of the source water and the objective of where it needs to be. TDS includes all conductive ions in a solution – both positively charged ions and negatively charged anions – able to pass through a 2-micron filter. TDS presents itself in multiple forms – e.g., magnesium, calcium, sodium, potassium, sulfates, chlorides, nitrates, etc. These components’ effects on drinking water treatment depend on the degree of their presence (measured in mg/L or ppm) and their impact on water aesthetics (taste and clarity). For example, TDS at elevated levels can be a concern in terms of excessive mineral deposits on water treatment and water distribution infrastructure. In and of itself, however, TDS is not considered to be a health hazard and is only regulated as a secondary drinking water standard. The U.S. EPA Guideline for TDS is 500 ppm.

Aside from the potential for corrosion, another practical matter of TDS concern for water treatment providers is the aesthetics of taste. An often-cited guideline, resulting from a study reported by William Bruvold and Henry J. Ongerth in the April 1969 AWWA Journal, classifies the correlation between TDS and taste-test results as follows:

The Luck Of The Draw

To a degree, water utilities are victims of their source water’s geography. For example, in the U.S. the Ohio, Mississippi, and Missouri river drainages all have naturally higher levels of TDS. But TDS levels can also vary within a water source based on seasonal conditions, weather events, and other external causes. These might include soil contamination, stormwater-induced runoff (urban or agricultural), or point-source pollution from sewage treatment or industrial plants.

Of the many dissolved solids potentially found in water, calcium and magnesium – in proper amounts – are key ingredients in a great-tasting glass of water. (By comparison, TDS levels in bottled mineral water typically range from 350 to 600 ppm.) Too much of a good thing, however, can lead to a metallic, bitter, or salty taste and to mineral deposits on water distribution infrastructure and consumer faucets. Other TDS salts, minerals, or organic components can also introduce undesirable tastes, especially at higher levels. While many of the ions that make up TDS are not considered health hazards, some naturally occurring toxic ions such as lead, arsenic, and cadmium can be included in TDS sample readings.

Measuring TDS Accurately

Using the behavior of electricity as a means of reflecting water chemistry is a common thread in water quality testing. For TDS detection and measurement, changes in conductivity are used to identify higher or lower concentrations of TDS in surface water. Readings can vary with gentle springtime rains that dilute TDS levels in the water or by heavy summer downpours that raise conductivity as a result of sudden heavy runoff from mineral-rich soils.

Because WTPs can be affected by water sources coming from miles away from the plant intakes, hand-held portable instruments provide a convenient means of taking accurate and reliable readings at remote locations in addition to the plant intake.

Some extremely compact instruments even include the ability to interface with smartphone apps, enabling users to collect, view, and transmit field readings easily. Readings can be completed in as little as 10 to 20 seconds, with conductivity and TDS resolution of 0.1 for measurements of 1 to 99 ppm and repeatability of + one count for readings < 1,000 ppm.

Be sure to calibrate all TDS instrumentation using the appropriate standard solutions traceable to the National Institute of Standards and Technology (NIST) and having appropriate conductivity/ppm values.

Figures 1 and 2. Compact handheld instruments and smartphone applications make the capture and management of TDS data easier, wherever readings are required.

TDS: What To Do Once You Identify It

Depending on the nature of the solids and dissolved solids in the source water, there are a variety of methods for removing them. The following chart shows the relative performance levels of various filtering media in removing particles and dissolved solids.

Reverse Osmosis.  Reverse osmosis (RO) is the most complete and reliable solution for removing salts and other TDS from drinking water. While it does a good job of removing all particles as well as undesirable dissolved solids, it can be very expensive. Unfortunately, it will remove all of the calcium and magnesium that can give drinking water its taste, so RO-water is often filtered back through a mineral bed of calcium and magnesium to restore those elements.

Nanofiltration. Because nanofiltration can remove some salts (divalent ions), it can be used to reduce levels of TDS and soften water.

Ultrafiltration.  While ultrafiltration will remove larger particles, in order for it to have an impact on TDS removal, dissolved substances first need to be captured through coagulation with alum or iron salts or through activated carbon adsorption.

Source: Water Online, July 15, 2019

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More about TDS from this site.

Simple Chlorination Unit

Posted August 3rd, 2019

Simple and Effective All-In-One Chlorine Treatment


chlorinationallinonewithlabelsOur compact residential chlorination system needs no electricity. The simple chlorine pump operates on water pressure, and it needs no expensive metering devices because the rate of flow through the water pipe determines the rate of chlorine injection. No over-sized retention tank is required because the system uses an advanced design compact tank that outperforms much larger conventional retention tanks.

The system consists of a sediment filter, a Dosatron NSF certified 14 gallon per minute water driven injection pump, a 15 gallon solution tank, and the advanced  12″ X 60″APW (Nelsen) compact retention tank.  The system has everything needed to treat bacteria, iron, manganese, or hydrogen sulfide odor.

A filter appropriate to the targeted contaminant must be added after the retention tank. The filter is not included. The equipment shown on this page is pre-treatment for filtration.

The compact all-in-one chlorination system is designed for use in standard residential applications, but it can be easily adapted to other uses.  It is especially good for part-time residences like summer homes or hunting cabins because the retention tank has a bottom drain that makes winterization easy. It’s also perfect for remote locations like workshops, barns, or remote apartments. The fact that no power is needed, of course, makes it ideal for off-grid homes.

Unlike electric pumps, the water-powered system can be installed anywhere in the water line without regard to the well’s pressure tank or electrical system.

The complete chlorination system, without filter, is currently priced at only $1095.

The Cost of Agricultural Nutrient Runoff

by Michael Curley


The following excerpt, published in the June 2019 issue of Water Finance and Management magazine,  recognizes the top polluter of US water today, agricultural runoff, and shows why it’s such a hard problem to solve.


Water quality is a major problem throughout the United States. But it’s not nearly as bad as it used to be. In 1969, the Cuyahoga River in Cleveland was so polluted that is actually caught fire! That made headlines all across the country and galvanized the U.S. Congress into passing the Clean Water Act (CWA) in 1072 over the veto of President Nixon. The CWA contained a funding provision called the construction grant program to be administered by the U.S. Environmental Protection Agency (EPA). Over the next 15 years, EPA handed out over $70 billion of funds to local governments or authorities for sewer projects. The construction grant program required a local match. So, between federal grants and the local matching funds, the US spent well over $100 billion controlling urban water pollution between 1972 and 1987.


By 1987, EPA had tired of watching abuses in its grant program and Ronald Reagan, who was no friend of grants to begin with, was president. So, the CWA was amended to replace the construction grant program with a loan program called the Clean Water State Revolving Fund (CWSRF).


In 1972, when the CWA was first passed, urban sewage was the No. 1 source of water pollution…Since 1987, the CWSRF has provided more than $135 billion of financial assistance for almost 40,000 clean water projects.

Between the $100 billion construction grant program and the $135 billion spent by the CWSRF and the hundreds of billions of dollars more that has come from the municipal bond market, we have pretty much won the war on urban sewage. It is no longer the No. 1 water pollution problem.



Now the No. 1 source of water pollution in the United States is agricultural runoff. But in terms of attacking this problem, we have an “equipment” issue. The “equipment” is the payment method. Both the municipal bond market and the CWSRF – the two major sources of funds for water pollution abatement – are ill suited to making, say, a $50,000 loan to a farmer for a Best Management Practice (BMP) that would reduce agricultural runoff.



There is a second problem, which is worse: who pays? When the CWSRFs lend money to wastewater authorities, these agencies usually have tens of thousands of ratepayers over whom they can spread the cost. An upgrade to their treatment plant might cost $10 million. But they could borrow 100 percent of this money from their CWSRF” at a low interest rate and spread the cost across their users for a small fee.



Contrast this with a farmer who can build a constructed wetland on 2 acres of his land that he doesn’t need for crops. This would certainly make a major reduction in the runoff from his farm. The wetland might cost $100,000. The farmer could also borrow from the CWSRF under the same terms,” but the farmer would have to pay for the entire amount.



There is no legal authority in the CWA to require the farmer to do anything. He can simply go on polluting.”



The author goes on to suggest two possible solutions to this problem including sponsorship by a government entity and adoption by a publicly owned treatment works system that can receive credits on pollution permits for assisting in the project.

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The Current Status of US and UK Regulation of PFAS.

(Excerpted from a Harvard School of Public Health article by Dr. Phillipe Grandjean.)


Q: Are governments in Europe and the U.S. taking any action to regulate PFASs?

A: The Council of EU Ministers recently concluded that the European Commission should generate a joint EU strategy on PFASs, treating all the many individual compounds as a group and recommending that they be approved only for essential uses. This means that two commonly used PFASs, such as PFOA and PFOS [perfluorooctane sulfonic acid], cannot be swapped out for other PFASs, except for uses considered “essential.” This is being done because the entire class of chemicals is suspected of having similar properties in regard to environmental dissemination and human health.

Individual EU agencies are currently working on more specific issues, such as lowering tolerable limits in drinking water and phasing out the use of PFASs in food wrappings.

In the U.S., older PFASs are being phased out but they are being substituted with similar PFASs that have not yet been tested in any detail and are therefore not regulated.

There are some legislative efforts underway in Congress to address the use of PFASs, and these are of course highly beneficial and appropriate. For example, one proposal would require a number of actions, including the stipulation that the EPA set nationwide drinking water regulations for PFOA and PFOS. But the proposal would give the EPA two more years to address what are termed “unreasonable risks” from these chemicals, which is generous, as EPA has been aware of the growing problems for a very long time. It’s also not clear if President Trump will approve these congressional proposals. He recently threatened to veto a bill that would phase out the military’s use of firefighting foams that contain PFASs and that has led to the contamination of vast groundwater reservoirs.

States continue to be impatient and have developed their own approaches to control what some call the PFAS “crisis.” Most recently, New Hampshire has announced new water limits for the four major PFASs, with limits for two of those, PFOS and PFOA, about five-fold lower than the EPA guidelines. At least six other states have also set limits below EPA guidelines.

TCE—How To Get Rid of It

The usual recommendation for TCE removal is carbon filtration, reverse osmosis, and packed tower aeration. Clearly, the best protection strategy for residential users is whole house carbon filtration and undersink reverse osmosis for drinking water. TCE is a “whole house” treatment issue because it can be either inhaled as a vapor, absorbed through the skin in bathing, or ingested in drinking water. Although a few states have set lower limits, the federal maximum acceptable limit for TCE is 5 parts per billion.

Who Much Nitrate Do Home RO Units Remove?

A standard rejection rate chart for thinfilm RO membranes that we use gives the rejection rate for nitrates as 93% to 96%. Other charts we’ve seen put the rate as low as 80%.  While nitrate is removed handily by small RO units, it isn’t what RO is best at.

Factors that affect performance negatively are low water pressure, low pH, and high sodium and sulfate levels.

If water pressure is low, adding a pressure boosting pump to the RO unit would enhance performance. Or, if very low nitrate levels are essential, you can add a nitrate-specific anion cartridge to your undersink RO unit which should assure virtual 100% nitrate reduction. A small nitrate cartridge operating as an RO post-filter will normally have more than enough capacity for a year of service between cartridge changes.

Nitrates are mainly a drinking water issue, so whole house treatment is usually unnecessary.

After at least 7 children diagnosed with cancer, parents eye chemical in city’s water

CBS News Report, January 19, 2019

Parents in one California community are fighting for answers after at least seven children were diagnosed with cancer in the past four years. Earlier this year, they fought to remove a cell phone tower from a local elementary school campus. Now, they’re focusing on a chemical in their drinking water supply that’s linked to cancer. And Ripon, California, is just one of dozens of cities across the country dealing with the possibly harmful chemical.

“Until we figure out what is happening in this town, we won’t stop,” said Kellie Prime, a mother whose son, Kyle, is one of at least seven kids in Ripon who have been diagnosed with cancer in recent years. Prime and another mother successfully had the cell phone tower removed, and have since shifted focus to the drinking water.

“My gut tells me that something is here that’s causing these issues,” Prime said.

Ripon was once home to a Nestle plant that used trichloroethylene, or TCE, to decaffeinate coffee until the 1970s.  Nestle discharged the plant’s wastewater into the city’s sewers. TCE was recently found in one of five city drinking water wells.

The city of Ripon said TCE levels reached 90% of the EPA maximum allowed in drinking water last summer.  The well was turned off four months later.  The city says the water “meets all established drinking water standards,” and Nestle said that for more than 30 years, the company has “implemented… cleanup and water protection measures to ensure… levels… do not exceed California standards.”

But University of California San Francisco scientist Veena Singla said that when it comes to chemicals like TCE, there are no safe levels of exposure.

“Drinking water standards and guidelines that we have now are many decades old, and they don’t account for the latest science that shows pregnant women and children are more susceptible to TCE,” Singla said.

Millions of pounds of TCE are used every year for manufacturing and degreasing. The chemical can migrate from industrial sites into surrounding communities through the soil and water, and can even turn into a clear, odorless vapor that moves up into the homes above.

“We know it can cause cancer by any route of exposure,” Singla said. “So what that means is whether you breathe it in, whether you drink it in contaminated water… we’re concerned about all those exposures.”

When asked if she thinks TCE exposure could have caused her son’s cancer, Prime said that “I think it needs to be looked into, for sure.”

Last year, CBS News visited Franklin, Indiana, where dozens of kids were diagnosed with cancer. A non-profit found high levels of toxins, including TCE vapor, in homes near an old manufacturing site. Clean up and testing under the EPA is ongoing.

“We used our kids as the canary in the coal mine in our town,” said Kari Rhinehart, who lost her daughter to brain cancer.

In White Bear Township, Minnesota, community members diagnosed with cancer and their loved ones were outraged after learning a company that makes fishing sinkers and battery terminal posts admitted TCE had been leaking into the air for years, at points reaching seven times what was allowed.

In Ripon, families are calling for additional vapor testing. “We have a lot more questions than we do answers — so until we get those answers to those questions, we are very concerned,” Prime said.

Regulators say potential health effects from TCE depend on the amount and length of exposure, and it can be difficult to trace the cause of any one cancer diagnosis.  But Prime says after seeing her son’s battle firsthand, she’ll do anything to prevent other parents from experiencing the same pain.

“It was hell… it was life-altering,” Prime said. “He’s sick every day, losing weight, losing his hair.”

Her son is now in remission – but Prime is determined to keep pushing forward. She said she’s motivated by “the fight these kids have in them.”

“We have to show them that we will fight for them,” she said.

The regional water board has asked Nestle to do additional vapor testing to ensure TCE levels are within new, stricter guidelines set by the state.  Nestle says the work plan has been submitted and approved by the water board.

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This year marks the 20th Anniversary of the removal of the 160 year old Edwards Dam on the Kennebek River.


Edwards Dam was a hydroelectric dam on the Kennebec River in the U.S. state of Maine. It was located in Augusta, Maine, about 40 miles (64 km) upstream from the Atlantic Ocean. Built in 1837 of timber and concrete, it was 917 feet (280 m) long and 24 feet (7.3 m) high. It is most famous for its removal in 1999, the first removal of a hydroelectric dam by the government against the wishes of the dam owner. 

Twenty years ago, the annual run of alewives (a migratory fish essential to the marine food web) up Maine’s Kennebec River was zero. Today, it’s five million — thanks to the removal of Edwards Dam and additional restoration measures upstream. The Kennebec and its web of life have rebounded in many ways since Edwards Dam came down in 1999.

The removal of Edwards Dam was significant because it was the first time the federal government ordered a dam removed because its costs outweighed its benefits. The restoration of the Kennebec sparked a movement for free-flowing rivers in the U.S. and around the world.

According to the dam removal database maintained by American Rivers, 1,605 dams have been removed in the U.S. since 1912. Most of these (1,199) have occurred since the removal of Edwards Dam in 1999. The year with the most dam removals was 2018 (99 dams removed). 2017 was the second most productive year, with 91 dams removed.

The lesson from the Kennebec after twenty years? Dam removal works.   The Natural Resources Council of Maine report that since Edwards Dam was removed on July 1, 1999, tens of millions of alewives, blueback herring, striped bass, shad, and other sea-run fish have traveled up the Kennebec River, past the former Edwards Dam, which blocked upstream passage since 1837.  Abundant osprey, bald eagles, sturgeon and other wildlife have also returned.

According to American Rivers, “On a basic level, dam removals matter for the specific rivers and ecosystems that are restored to health. But looking at the bigger picture, dam removals also matter in terms of our relationship with all rivers – because with every individual act of restoration we’re creating a new and compelling picture of what the future can look like. We’re spotlighting the benefits that healthy, free-flowing rivers can naturally provide. We’re demonstrating the power of local citizens to drive positive change. And we’re proving that communities can reclaim their rivers and their stories.”


Toxic algae blooms force Mississippi to close all mainland beaches

Mississippi authorities are telling people to stay out of the water because the toxic algae can cause rashes, stomach cramps, vomiting, and diarrhea

By Ben Kesslen and Associated Press


Mississippi closed all mainland beaches on the state’s coastline during the Fourth of July weekend due to toxic bacteria sweeping the state’s Gulf Coast.

The Mississippi Department of Environmental Quality (MDEQ) has been closing beaches due to blue-green algae blooms since June.

By Sunday, the spread of the noxious bacteria forced the department to close the state’s last open mainland beach.

Blue-green algae blooms can cause rashes, stomach cramps, vomiting and diarrhea, and state officials also advised against eating fish or seafood from areas affected by the algae.

Beaches on the state’s barrier island remain open, according to the National Park Service, but are being closely monitored. MDEQ said people and pets are welcome to sit on the beach, but are not to go in the water.

The blue-green algae, also known as Cyanobacteria, live in water and are the most common type of algae to bloom. The algae often have a distinct musty smell and sometimes look like paint floating on water, according to the National Oceanic and Atmospheric Administration (NOAA).

NOAA says the blooms are happening because of Mississippi River flooding that ravaged the Midwest and Southeast all spring.

To ease the flood waters and prevent the water from reaching New Orleans, authorities opened the Bonnet Carre Spillway, which diverted some of the water to the Mississippi Gulf.

Another contributing factor to the algae blooms: climate change.

Larry Brand, a marine biology and ecology professor at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science, told NBC News that while blooms are mainly caused by excess nutrients, “algae also like higher temperatures.”

“As the earth gets warmer, you can get more and more blooms,” Brand said.

The extreme weather that climate changes causes often leads to massive rain storms and floods, which Brand says moves fertilizers from soil into bodies of water. As this becomes more common, so too might algae blooms.

And there’s no real way to stop a bloom once it happens in a large body of water.

“You’re going to have to wait for the tides to flush it away,” Brand said.

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Recycled Filter Carbon

Residential water filters and reverse osmosis units normally use filter carbon in some form, and the carbon used in residential units is normally new carbon. There is no program that we know of that recycles filter carbon from small household filter cartridges for reuse as filter carbon. Over the years some vendors have advertised recycling of spent filter cartridges, but these programs were, in our view,  more about marketing than recycling, designed to appeal to environmentally conscious customers and to promote cartridge replacement sales. Recycling of small cartridge carbon is simply not economically feasible.

However, carbon recycling does happen, and in a big way, with large industrial and municipal filter applications.

Here’s an interesting account of how carbon recycling works, from the Calgon Corporation, a major provider of filter carbon.

What should treatment operators know about the differences between virgin and reactivated GAC when evaluating options for PFC removal?

Although virgin and reactivated GAC may be of the same starting material and same activity level, they are two distinct products. Virgin GAC is an activated carbon product that has not been used in a previous application, so its quality and performance are consistent. Reactivated GAC is a product whose capacity was exhausted (spent) in a previous application and has undergone a high-temperature thermal process to destroy adsorbed material (remove contaminants) and restore a majority of the adsorptive capacity that allows the product to be reused in appropriate applications. The reactivation process alters the pore structure and can impact performance/quality, but can still provide a cost-effective treatment solution.

Within the term “reactivated GAC” it is also important to distinguish between a custom-reactivated GAC and a pool reactivated GAC. A custom-reactivated GAC is a product that has been previously used and spent in a specific customer’s application, removed from service, segregated from other spent GAC, reactivated, and returned to the same customer for reuse. In a pool reactivated product, spent carbons from a variety of customers’ applications are co-mingled, reactivated, and used for a variety of non-potable applications. The quality of a custom-reactivated product is generally higher than the quality of a pool-reactivated product, but is highly dependent on the application in which it was used, the reactivation conditions, and the initial carbon product. Custom reactivation is most economical for quantities above 20,000 pounds. It is vital to select a virgin material that can withstand multiple cycles of treatment and reactivation. A reagglomerated, bituminous, coal-based product has been shown to be a superior base product for reactivated GAC.