Mississippi River’s 1926 dead zone holds lessons for Gulf of Mexico today

by Matt Sepic and Elizabeth   Dunbar, Minnesota Public Radio

Gazette Introductory Note: We always believe that environmental problems were never worse.  The fact is, they usually were worse at one time.  Sceptics and naysayers notwithstanding, modern sewage treatment and laws like the Clean Water Act and the Clean Air Act have made our environment much better and healthier than in was in the “good old days.” — Hardly Waite.

ST. PAUL, Minn. — Here in the land of 10,000 lakes, zebra mussels and Asian carp have generally topped the list of recent marine environmental concerns. But in the 1920s, before wastewater treatment plants were built, there were far bigger problems.

A 1926 survey of the Mississippi River between Minneapolis and Hastings turned up three fish.

“Not three species of fish,” said Rebecca Flood, an assistant commissioner at the Minnesota Pollution Control Agency. “Three fish.”

Back then there was so much sewage in the Mississippi River that algae took over and just about everything else died off. The river in the Twin Cities is much cleaner today, and the fish are back. But there’s a similar, even larger problem festering now just past the river’s southern end, in the Gulf of Mexico.

This time, the pollution that feeds the algae for the most part is fertilizer from Midwestern farms — including Minnesota’s. Just as in 1926, oxygen levels have plummeted. The fish population, the ecosystem in general, and the industries that depend on it are all in peril.

Scientists call that part of the Gulf a hypoxic zone. It’s also known as the dead zone. And its the size of Connecticut and Rhode Island put together.

Flood says Minnesota can do a better job of reducing runoff into waterways that drain into the Mississippi and contribute to the dead zone. The MPCA is developing guidelines with the goal of cutting phosphorous runoff into the Mississippi River watershed 35 percent by 2025, and nitrogen runoff by 20 percent. Part of the strategy will be to work with farmers to help them reduce the amount of fertilizer they use — and money they spend.

“My experience with individual farmers is that they’re pretty cautious and stingy about wasting money, and this is a waste of money to have our fertilizers going down to the Gulf of Mexico,” she said.

Details of Minnesota’s nutrient reduction plan will be available for public comment in early October. The proposal is just one of many being drawn up by the 12 states that are part of a task force that’s trying to shrink the dead zone. But reducing nutrient runoff from farms isn’t as easy as reducing fertilizer, says Bill Northey, co-chair of the task force that met in Minneapolis Tuesday. He’s an Iowa farmer, and his state’s agriculture commissioner.

“When we’re talking about nitrogen, we’re talking about soil organic matter. It’s in the crop residue that’s there from last year. As our water goes through those soils it’ll pick up nitrogen — sometimes from the fertilizer, sometimes from the residue, sometimes from the organic matter,” he said. “We have to manage all of that to try to reduce the amount of nitrogen that’s leaving those farms.”

In 2008 the task force set a goal of reducing the dead zone to 5,000 square kilometers — an ambitious goal that so far has proved elusive. The zone measured roughly 15,000 square kilometers, or roughly 5,875 square miles, this year.

Nancy Stoner, the EPA’s acting assistant administrator for water, admits the agency can’t claim success.

“It’s a very difficult goal, and even if we put in all the practices by 2015 that are necessary to reduce the dead zone, there’s a lag time,” she said. “That’s one of the challenges we have: to continue to make progress, to continue to motivate people.”

And motivating people is about all the EPA says it can do. The task force recommendations do not carry the force of law. The EPA has said setting nutrient rules would be too complex, and it can better fight water pollution by working with states.

But Ann Alexander, an attorney with the Natural Resources Defense Council, says the dead zone will continue to be a problem until the EPA steps up to the plate.

“I imagine there is a lot of nervousness on their part given the intensity of the opposition that they’re getting from many different quarters,” she said. “They’re getting opposition from agriculture, from manufacturing industries, from sewage treatment authorities.

The NRDC has sued the EPA in an effort to force the agency to act. Last week, a federal judge gave the EPA six months to decide whether to set nitrogen and phosphorous pollution standards — or explain why they’re not needed.

Source: MPRNews.

Pure Water Gazette Fair Use Statement

Arsenic in our Drinking Water

by Deborah Blum

 The baby with the runny nose, the infant with a stubborn cough — respiratory infections in small children are a familiar family travail. Now scientists suspect that these ailments — and many others far more severe — may be linked in part to a toxic element common in drinking water.

The element is naturally occurring arsenic, which swirls in a dark, metalloid shimmer in soil and rock across much of the United States and in many other countries. It seeps into groundwater, but because the contamination tends to be minor in this country, for many years its presence was mostly noted and dismissed by public health researchers.

They’ve changed their minds. Long famed for its homicidal toxicity at high doses, a number of studies suggest that arsenic is an astonishingly versatile poison, able to do damage even at low doses. Chronic low-dose exposure has been implicated not only in respiratory problems in children and adults, but in cardiovascular disease, diabetes and cancers of the skin, bladder and lung.

Trace amounts in the body interfere with tumor-suppressing glucocorticoid hormones, studies show, which is one reason that arsenic exposure has been linked to a range of malignancies. Arsenic also interferes with the normal function of immune cells. It damages lung cells and causes inflammation of cells in the heart.

Researchers first became aware of these problems in so-called hot spot countries like Bangladesh, where arsenic levels in water can top 1 part per million. Decades ago, public health agencies there sought to replace microbe-contaminated surface water with well water. Only later did geological surveys reveal significant aquifer contamination from bedrock arsenic.

Scientists now report health risks at lower and lower levels of exposure in that country. In July, researchers at the University of Chicago found that residents of Bangladesh chronically exposed to arsenic at a mere 19 parts per billion showed signs of reduced lung function. At levels of 120 p.p.b. or higher, their ability to take in oxygen resembled that of long-term smokers.

“Bangladesh is unfortunately a living laboratory for the health effects of arsenic,” said Habibul Ahsan, the lead author of the study and director of the Center for Cancer Epidemiology and Prevention at the University of Chicago.

Dr. Ahsan, a native of Bangladesh, is one of the organizers of a long-term study of arsenic and health in that country, which now has 30,000 people enrolled. In 2010, he reported that 24 percent of all deaths from chronic disease in his study population could be attributed to drinking arsenic-contaminated well water.

“We need to take arsenic exposure very seriously,” Dr. Ahsan said.

That seems to be today’s watchword. Researchers have begun a widespread re-evaluation of arsenic as a public health threat not only in water, but in the food supply. The Food and Drug Administration recently set a limit of 10 p.p.b. for arsenic in apple juice, and the agency is now evaluating the risks posed by foods like rice, which tend to pick up arsenic from the soil. At the request of the Environmental Protection Agency, the National Academy of Sciences has begun an intensive review of arsenic risks. The academy study group is chaired by Joseph Graziano, a professor of environmental health sciences at Columbia University who researches the link between arsenic in drinking water and cognitive deficits in children.

Researchers also are taking a much closer look at drinking water, from Southwestern states like Nevada, where wells sometimes contain arsenic at more than 500 p.p.b., to the upper Midwest and New England, where a belt of arsenic-infused bedrock taints aquifers in stretches from the coast of Maine to a point midway through Massachusetts. Water in parts of the Central Valley of California, America’s breadbasket, has been found to be tainted with arsenic as well.

While municipal water suppliers are required to meet the E.P.A.’s safety standard of 10 p.p.b. for arsenic in drinking water, no such regulation exists for private wells. Nationwide, researchers say, about 13 million people get drinking water from private wells with arsenic levels above the federal standard.

And studies here are beginning to show a pattern of harm not unlike that seen in Bangladesh. One study of private wells in Michigan, tainted with arsenic in the 10 to 100 p.p.b. range, found increased mortality rateslinked to everything from diabetes to heart disease. Another focusing on cardiovascular disease in small communities is due to be published next week.

At Dartmouth College, the New Hampshire Birth Cohort Study is following women through pregnancy into parenthood, comparing the health of children in families drinking from private wells with those who rely on municipal water supplies.

In a study published in July in Environmental Research, researchers measured arsenic exposure during pregnancy and then tracked respiratory infections in infants up to four months of age. The higher the arsenic exposure in the mother, the scientists found, the greater the number of respiratory infections in their infants, especially ones that required a visit to the doctor or prescription medicine.

The results describe a pattern similar to that seen in Bangladesh, where scientists have found a greater than 50 percent increase in severe lower respiratory infections among infants of mothers with high levels of arsenic, compared with those with the least exposure.

“We were surprised to find the connection so visible at the lower exposures seen here,” said Margaret Karagas, a Dartmouth epidemiologist and the senior author of the study. The Dartmouth pregnancy cohort study has also found a link between low-level exposure to arsenic and low birth weight in infants.

“If people have private wells, they need to have them tested for arsenic,” she said. “You want to know what’s in your water.” Meanwhile, Dr. Karagas and other experts are looking at the ways that arsenic in the food supply might add to an individual’s cumulative exposure.

“We need to start looking at all the sources,” Dr. Ahsan said.

Source: New York Times Health/Science.

Pure Water Gazette Fair Use Statement

More information: Arsenic. 

Ultraviolet Can Be Used to Reduce Chlorine and Chloramines

As a footnote to a recent article we published about removing chloramines with ultraviolet, here is a quote from water treatment expert David Bauman, writing in Water Technology:
Ultraviolet (UV) treatment is another dechlorination alternative.

UV is often promoted as a pretreatment method for reverse osmosis (RO), to reduce chlorine that could degrade certain RO membranes.

An advantage of UV, as with certain activated carbons, is that it can reduce both free chlorine and combined chlorine compounds (chloramines). At the right wavelengths, the UV light dissociates chlorine in water to form hydrochloric acid. Or, to phrase it in a less negative way, hydrogen and chloride ions are formed.

Different peak wavelengths have been published for dissociation of free chlorine, so a UV manufacturer would have to be consulted. Manufacturers say that up to 15 parts per million (ppm) of free chlorine can be removed.

The UV dosage required for dechlorination depends on total chlorine level, ratio of free versus combined chlorine, background level of organics, and the desired reduction level.

To our knowledge, there are no residential UV systems yet on the market for chloramine reduction.

Water harvesting helps Kenya’s women cope with failing rains

by James Karuga

NGURUBANI, Kenya (Thomson Reuters Foundation) – When Rose Wanjiku first moved to her home in Central Kenya province 14 years ago, the region received four months of rain every year. The rains began in April and again in October, and were sufficient for a small-scale farmer such as herself to grow staples like maize and beans to feed her family and sell the surplus at local markets.

Today the Ngurubani area gets only two months of rain a year. Because of the growing scarcity, Wanjiku has resorted to irrigating her crops with water pumped from the Thiba River when rains fail in mid-season. Even though the river is just a stone’s throw away from her house and fields, the water pump means extra expenses for her household.

“Farming has become very expensive for us these days. We hardly make profits,” said her husband Munene. His wife added that the river water cannot be used for household purposes because it is too muddy.

To counter the water shortages, Wanjiku, 45, has begun harvesting rainwater. Her roof is fitted with gutters and through a loan fromSMEP, a Kenyan microfinance programme, she has bought a 2,300-litre (600-gallon) water tank to store the harvested water.

Rainwater gathered since April has been sustaining her household until the rains are due to begin again next month.

Wanjiku began making loan payments of 1,000 Kenyan shillings (around $11) a month in February, and aims to clear the loan by November.

The frustrations of poor rainfall also have taken a toll on Margaret Njeri Muthee, 38, another farmer and secretary of the 12-member Wendani Women’s Group, which also counts Wanjiku as a member.

Njeri recalls that when she first moved to Ngurubani 15 years ago, rains were regular and she was able to harvest up to two 90kg bags of beans per acre of land.  Today she gets half a bag of beans at most.

“The weather has really changed here – there is a chill I never saw before, destroying our staples,” Njeri said. Because of the unpredictable weather and poor crop yields, Njeri now rears pigs, in addition to chickens and cattle.

“I’m tired of farming maize and beans,” she added.

As a result of increasingly short rainfall, Njeri was spending 400 shillings (nearly $5) every week to pay for a donkey-drawn cart to fetch water from the Thiba River, over a kilometre away from her home. But now she, too, has a water tank, bought on credit from SMEP.

Njeri and Wanjiku are among over 7,000 Kenyan recipients of an ongoing water credit scheme accessed through microfinance institutions such as SMEP. The scheme enables households to buy tanks to capture and store clean rainwater that runs from rooftops along the gutters.

Widespread Water Stress

UNESCO reports that 17 million of Kenya’s 41 million inhabitants lack access to safe water.

Of the loan recipients, 92 percent are women. According to Patrick Alubbe, East Africa regional director of Water.Org, a nongovernmental organisation, it is the women in households who must spend hours searching for water, and this makes them appreciate the scheme, as it saves them time.

SMEP has given 821 water-related loans so far, with repayment rates of more than 90 percent, according to Fridah Njeru, SMEP’s senior programmes coordinator.

Kenya has 29,000 beneficiaries of water-related loans countrywide, with some funds going to building latrines or fix sewer systems to improve sanitation. The scheme also operates in Uganda, Bangladesh and India.

With a tank to harvest rainwater, Wanjiku says she no longer needs to wait for mud in collected river water to settle at the bottom of her containers so that she can use it at home.

Kenya’s average annual rainfall is 630 mm, which qualities it as a water-scarce country, according to a study published by the U.N. Food and Agriculture Organization. However, a study by the Southern and Eastern Africa Rainwater Network notes that large groundwater aquifers represents a valuable water resource not directly related to or dependent on rainfall patterns.

Experts are pointing to aquifers as the country’s next important source of water. This comes following the recent discovery of aquifers in the drought-hit Turkana region in Kenya’s north, where rainfall does not exceed 450mm annually.

The aquifers are reported to hold 250 billion cubic metres – enough to supply Kenya’s needs for 70 years at the current rate of consumption of 3 billion cubic metres a year.

Source: Reuters.

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Warning raised about ’emerging contaminants’

by Cynthia McCormick

A new study by the Silent Spring Institute in Newton (MA) shows that sewage treatment plants aren’t any better at removing a new class of contaminants from treated water than septic systems.

Researchers found that antibiotics and chlorinated flame retardants, for instance, pass through both systems relatively unscathed.

The results weren’t surprising because wastewater treatment systems are made to remove pathogens and solid waste, not the chemicals contained in medicine, herbicides, plasticizers and other products, Silent Spring Institute research scientist Laurel Schaider said.

But the study shows that systemsbeing developed to protect the Cape’s coastal waters from nutrient overloading and algae blooms should also take steps to protect drinking water from what scientists call “emerging contaminants,” she said.

Many of the chemicals are considered hormone disrupters that act like estrogen, which has caused breast cancer cells to grow in a laboratory setting.

For the report — available at www.silentspring.org — the Newton-based research institution analyzed 16 already existing studies of wastewater and septic system treatments, including two originating on Cape Cod.

In recent years, Silent Spring has released studies showing the presence of dozens of emerging contaminants in public and private wells on the Cape. The Cape now has “a critical moment” in deciding the future direction of wastewater treatment and how it affects drinking water, Schaider said.

“It is a concern, and the county will be looking at how best to deal with the issue,” Tom Cambareri, water resources program manager for the Cape Cod Commission, said. “We’re evaluating all possible alternatives.”

Bacteria break down some chemicals and use them as a food source, removing them from the water supply, Schaider said. Both sewage treatment systems and septic systems do a good job removing chemicals such as caffeine and acetaminophen, for instance, she said.

Other chemicals such as the antibiotic sulfamethoxazole and TCEP, a chlorinated flame retardant, pass through both systems largely unchanged, Schaider said.

Next, Silent Spring will look at whether ecological toilets of the type being evaluated for use in Falmouth remove the contaminants from treated water, Schaider said.

Source: South Coast Today.

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 Acidic Water

by Pure Water Annie

 Gazette technical wizard Pure Water Annie offers a nutshell view of treating acid water.

Acidic water is, by definition, any water with a pH of less than 7.0.

Water that is low in pH can have undesirable effects on plumbing fixtures and piping. Green staining of fixtures is a common indication of acidic water. Copper pipe can be ruined by water low in pH.

Low pH is also an issue in water treatment. Sometimes it is necessary to raise the pH of acidic water in order for other treatment strategies to apply. For example, oxidizing iron to prepare it for filtration is difficult if the pH of the water is low, so raising the pH of the water is often the first step in removing iron from well water.

Almost all water treatment issues involve pH in some way. Water constituents change in nature as pH changes, so many treatments can be applied only if pH is within the desired range.

Although the sales strategy of a class of drinking water products called “ionizers” is based on raising the pH of acidic water, there is no evidence that drinking water low in pH has any negative effect on health. Taste, of course, can be an issue if the pH is very low.

Treating Acidic Water

The pH value of water decreases as the amount of carbon dioxide, CO2, increases, and pH increases as the amount of bicarbonate alkalinity increases. The ratio of carbon dioxide and bicarbonate alkalinity within the ranges of 3.6 to 8.4 is an indication of the pH value of the water.

Acidic water can be corrected by several water treatment strategies. A common treatment is injection of soda ash, and a more aggressive treatment is the injection of caustic soda (sodium hydroxide). This is usually accomplished by injecting a solution of the soda ash or caustic soda directly into the water pipe.

A second strategy is to run the water through a bed of calcite (the most common treatment mineral) or corosex. As the low pH water passes through the bed, the mineral dissolves into the water and raises its pH.

Calcite treatment raises the pH by adding calcium carbonate to the water. This has the sometimes undesirable effect of increasing the hardness of the water slightly. Calcite and corosex are most commonly used in backwashing filters, but calcite alone can be used with simple upflow filters if the water is reasonably clean. Calcite is also commonly used in cartridge form as a postfiltration treatment for undersink reverse osmosis units. RO lowers pH, and calcite filters are used to bring the pH back to neutral.

Go here for more information about calcite filters or soda ash feeders.

Also, more about pH and water.

Dwindling Water Supplies Make Every Drop Count

 Drought and chronic water shortages played a significant role in sparking Syria’s civil war and in unrest throughout much of the Middle East, water experts now believe.

Around the world, water demand already exceeds supply in regions with more than 40 percent of the world’s population. That may climb to 60 percent in the coming decade, a new study has found.

“Water-scarce regions can’t grow enough food to feed their own people,” said co-author Manzoor Qadir of United Nations University’s Canadian-based Institute for Water, Environment and Health (UNU-INWEH).

About 70 percent of the world’s freshwater – and up to 95 percent in some countries – is used for irrigation. There is intense competition for freshwater between municipal, industrial, and agricultural uses. Increasingly, agriculture has been losing out, particularly in water-stressed regions, Qadir told IPS.

Between 2006 and 2011, up to 60 percent of Syria’s land experienced its worst ever drought and a series of crop failures. In 2009, the U.N. reportedthat over 800,000 Syrians lost their livelihoods and fled to cities as result of the drought.

The entire Mediterranean region is undergoing a prolonged drought that has been linked to climate change, according to a recent U.S. study. If climate-altering carbon emissions continue at current rates, droughts in the region will worsen and lengthen.

Drought In Sri Lanka

As water supplies fall, many regions are using urban wastewater, a very valuable resource if it is treated properly, says the study “Global, regional, and country level need for data on wastewater generation, treatment, and use“, published Sep. 5 in the journal Agricultural Water Management.

This is the first study to look at how wastewater is used in 181 countries. One of the key findings is that only 55 countries have good data. Synthesising what data there are, researchers found that high-income countries treat 70 percent of their wastewater while middle-income countries treat 28 to 38 percent. Just eight percent of wastewater generated in low-income countries undergoes any kind of treatment.

“From the earliest of times, most wastewater has truly been wasted. However, it is a vast resource if we reclaim it properly, which includes the separation of municipal from industrial wastewater,” said UNU-INWEH Director Zafar Adeel.

The volume of wastewater potentially available worldwide each year is equivalent to 14 months of outflow from the Mississippi River into the Gulf of Mexico, Adeel told IPS.

In poor, water-scarce countries, wastewater is widely used to irrigate foodlands – some estimate as much as 300 million hectares producing 10 percent of the world’s food, the study says.

However, there is little data to confirm this. It is often a country’s ‘dirty little secret’ that much of the food consumed in urban areas is grown using untreated wastewater.

Wastewater is valuable because it has very high level of nutrients, including potash, nitrogen and phosphorus, eliminating the need and cost of fertilisers. However, untreated wastewater can transmit diseases such as cholera. Chile experienced cholera outbreaks and banned the use of untreated wastewater in 1992.

“Disease outbreaks from using wastewater do happen but it is rarely cited as the cause,” said Qadir.

One reason is that few studies have been done. A few years ago Qadir and colleagues discovered higher rates of waterborne diseases like gastroenteritis in children in the Mediterranean who were eating food grown using untreated wastewater.

In the 1990s, fruit and vegetable exports from Jordan were banned for similar reasons. Jordan has since implemented an aggressive campaign to rehabilitate and improve wastewater treatment plants and introduced enforceable standards.

“Israel uses nearly every drop of its wastewater with specific uses determined by the quality”, Qadir said.

Many homes in California have separate grey and black water collection systems. Grey water from showers and dishwashing is reused to water lawns and gardens, the report said.

People are generally reluctant to eat food grown using wastewater but it is perfectly safe if treated properly, Qadir stressed.

“Unfortunately, water treatment is not seen as a priority in many countries.”

Source: Inter Press Service

Pure Water Gazette Fair Use Statement

Choosing a Countertop or Undersink Drinking Water Filter

by Gene Franks

Standard vs . Proprietary

If you purchase a water filter with a “proprietary” design, you won’t have to choose a filter cartridge for it because the filter manufacturer has chosen it for you. In other words, if you purchase an Aquasana, you have only one cartridge choice: the standard Aquasana. If you purchase a Multi-Pure filter, Multi-Pure has already decided which cartridge you will use: the standard Multi-Pure.

Aquasana and Multi-Pure provide you exactly the same cartridge whether you have city water with chlorine or with chloramines or whether your city fluoridates its water or not. If your well water has a rotten egg odor, if it has sand, or silt, or iron, or nitrates, or bacteria, with Multi-Pure and Aquasana it’s all the same: you’ll get the same filter cartridge you would get if you lived in Cleveland or Tucson.

Proprietary Countertop.  Price: $260. Replacement Cartridge Price: $70.  Cartridge Styles Available: 1. 

Standard Sized Countertop.  Price: $77. (With Lifetime Guarantee). Standard Cartridge Replacement Price: $21. Cartridge Styles Available:  Countless.  

If, however, you purchase a water filter that uses a standard-sized 9.75” X 2.5”cartridge, you have literally hundreds of excellent filter cartridges to choose from. Moreover, if you bought your filter from Sterling Springs, you can replace the cartridge with one purchased from Pure Water Products. Or vice versa.

Standard sizes got to be standard for a reason. They are a convenient and practical size that offers good performance in a compact package.

The variety of filter cartridges available in the standard 9.75” X 2.5” format is amazing. Every major filter cartridge manufacturer provides filter cartridges in this size.

In addition, with standard-sized units you have the option of multiple cartridges. Standard-sized housings can be easily joined to form multi-canister units. Multiple housings, of course, allow cartridges to be mixed and matched to created a total filtration unit with much more capacity and treatment range than is possible with a one-size-fits-all proprietary unit.

Here are some examples of the excellent cartridges available for standard sized-filters:

MatriKX CTO Plus carbon block, rated for 20,000 gallons of chlorine reduction, it’s a great filter for chlorine, chloramines, VOCs, chemicals in general, plus excellent taste/odor performance. A very tight nominal 0.6 micron filter.

MatriKX VOC. A tight 0.6 micron coconut shell carbon block. Designed for overall performance on chlorine and chemicalsd, but is especially good at VOC reduction.It’s a great taste/odor enhancer as well.

MatriKX PB1. A great one-cartridge drinking water filter, it is a tight 0.5 micron carbon block (too tight for use in reverse osmosis units) with lead reduction and cyst removal capability.

Doulton Super Sterasyl Imperial. An oversized-Doulton ceramic cartridge with a carbon core, this is one of several Doulton cartridges made to fit standard housings. Its strong point is removal of bacteria and cysts, but it’s also a good all-around chemical filter. While Doulton undersink and countertop units command a premium price, the regular-sized cartridges can fit into any standard housing.

Pentek ChlorPlus 10. A tough Pentek carbon block made with specialty carbon aimed toward removal of chloramines from city water, the cartridge has excellent all around carbon performance for taste/odor and chemical reduction.

In addition to carbon cartridges, there are many standard-sized “media” cartridges that treat nitrates, fluoride, arsenic, iron, rotten-egg odor, low pH, scale buildup, hardness, high TDS and more.

Another important consideration in deciding between standard vs. proprietary units is pricing. Standard sizing, of course, means competition, which keeps pricing fair. It is not uncommon for a high quality 9.75” X 2.5” carbon block cartridge to cost ¼ the price of a propriety cartridge.

Nominal vs. Absolute

If you’re puzzled by what filter makers mean when they call their filters “absolute” or “nominal,” technical wizard Pure Water Annie will clear the matter up for you. 

Water filtration devices are rated by the sizes of particles that will pass through them. The ratings are normally expressed in microns.

Micron ratings are applied to all types of filtration devices, including even granular filters. It is said, for example, that a sand filter is roughly a 10 micron filter, meaning that it filters out particles ten microns and larger in girth. Carbon block filters are also assigned micron sizes, but micron ratings are most meaningful in comparing sediment filters.

The micron is a standard measure of size that is used by filter makers. The diameter of a human hair is about 90 microns. Sediment filters are used to catch particles 1/300 of that.

Most sediment filters are given ratings by their manufacturers that describe their effectiveness at removing particles down to a specified size. The most common of these are”nominal” and “absolute.”

Nominal, according to the Water Quality Association (WQA), means that the filter will filter out at least 85% of the particles of the size it is rated for. In other words, a filter that is rated as a 1 micron nominal can be expected to pick out 85% of the particles that are 1 micron or larger from the water that passes through it.

Absolute, theoretically, means that the filter will reject virtually all of the particles of the given size. The usual expectation is a 3-log rejection–or 99.9%. Absolute ratings are usually used for the tightest filters and for purposes where efficiency really matters. For example, if a filter maker promises removal of E. coli, more or less 85% efficiency isn’t good enough. If you’re going to trust your life to the filter, you expect an absolute 3-log or 4-log rating at the very least.

The problem with the absolute vs. nominal system is that there is really no universal standard that assures uniformity. Some makers of filters for non-critical applications, for example, might consider 70% rejection suitable for a nominal filter. Definitions vary from one manufacturer to another, and there is really no way for the end user to verify the claim. 

For most common filtration issues filters rated as “nominal” are used.  For example, a nominal 5 micron sediment filter is a standard size used in much residential water treatment.

Keep in mind that tighter is not always better.  The lower the micron rating of a filter, the more it restricts flow.  An absolute 1 micron filter is normally not a good choice for a residential sediment filter because there will be too much pressure loss.  If you put in a filter to remove sand, a filter with a low micron rating is not only unnecessary, but it will also become clogged much faster than a looser filter.

Reference:  The Pure Water Occasional.

Eastern rivers ‘on Rolaids’ raise concerns

Study links rising alkalinity to acid rain, urbanization

 by Timothy B. Wheeler

 Baltimore Sun

Fresh water isn’t what it used to be. New research has found that human activity has caused subtle but significant changes in the basic makeup of rivers in Maryland and elsewhere, with potential consequences for public water use and the health of aquatic ecosystems.

In a survey said to be the first of its kind, researchers say two-thirds of nearly 100 rivers and streams checked across the eastern United States, including the Patuxent and Potomac rivers, have become noticeably more alkaline over the past 25 to 60 years. It’s as if they’d been fed a steady dose of antacid medicine, “like rivers on Rolaids,” said Sujay S. Kaushal, a University of Maryland geologist and the study’s lead author.

Several years ago Kaushal and other colleagues documented a gradual increase in salt levels in streams in the Northeast, which at the time they attributed to runoff of road salt. But, Kaushal said, a closer look at stream sampling from the U.S. Geological Survey and other sources found the rising salinity also tied to the rivers’ increasing alkalinity.

“We weren’t expecting it to be this widespread,” he said. “These trends that we’re seeing in the Schuylkill River and Potomac River, these trends are troubling.”

Nor did the scientists expect to find that their leading suspect for changing river chemistry is an environmental menace thought vanquished long ago.

At first, they figured the rising alkalinity seen across the eastern United States came from landscape changes in a river’s watershed, such as mining or urban and suburban development. But the changes in river chemistry were so extensive that they figured something more, and more widespread, was going on.

They concluded it had to be acid rain.

Blamed for killing forests and rendering New England lakes lifeless in the 1970s, acid rain has been reduced dramatically in the decades since by government regulation of coal-burning power plants and motor vehicle exhaust, two leading sources of pollution that turned precipitation acidic.

They concluded it had to be acid rain.

Blamed for killing forests and rendering New England lakes lifeless in the 1970s, acid rain has been reduced dramatically in the decades since by government regulation of coal-burning power plants and motor vehicle exhaust, two leading sources of pollution that turned precipitation acidic.

Rainfall today is much less acidic than it used to be, experts say, but all sources of acid rain haven’t been muzzled. Rain in Maryland and elsewhere is still corrosive enough to dissolve limestone and other rocks.

“Despite the great progress we’ve made in controlling oxides of nitrogen and sulfur from smokestacks and tailpipes, the precipitation is still acidic, unhealthy for us and streams,” said Russell R. Dickerson, an atmospheric chemist at the University of Maryland.

The minerals released when rocks dissolve under acid rainfall tend to be alkaline, Kaushal explained. And those minerals aren’t just neutralizing the acidity in precipitation, but overwhelming it, he added.

The effect is pronounced in urban areas like Baltimore, he said, and even in streams like the Gwynns Falls, where there isn’t much natural limestone in the watershed. But there, he pointed out, “you have pavement, sidewalks and concrete,” with limestone often a major ingredient. They dissolve under acidic rain as well, in a process dubbed “chemical weathering.”

Baltimore’s streams also may get an extra dose of alkalinity antacid from its leaky sewers, Kaushal suggested, because wastewater can be alkaline.

“We think that acid rain is affecting all of them, coupled with mining and land use,” he said. “Basically when you have dissolving either of the limestone or concrete, that’s a kind of universal mechanism contributing to river alkalization.”

Just as some mysteries remain about how rivers’ chemistry is changing, the impacts also are uncertain, but could be problematic. Many streams in the Chesapeake Bay region are suffering from an overdose of nutrients. Increasing alkalinity coupled with an abundance of nitrogen, one of those nutrients, can generate ammonia in the water, which can kill fish. The changes also may accelerate algae growth, already a problem in bay waters.

With the rising salinity of rivers and streams, calcium concentrations are increasing as well, making the water “harder” for human usage, Kaushal said. That can complicate everything from showers to doing laundry, and can lead to “scaling” in water pipes, a buildup of calcium that constricts the flow.

William P. Stack, deputy program director of the Center for Watershed Protection, said he alerted Kaushal to the increasing chloride concentrations in Baltimore’s raw water supply several years ago when he was with the city Department of Public Works. Stack said he also noticed the city’s water was gradually getting harder. While the hardness is not a health threat, and can be treated to counter it, he said he still found it troubling.

“The broader concern is we’re picking up a signature in the ambient concentration or quality of our waters,” Stack said. “What else is going on that we’re not picking up? And do we really fully know what the ramifications are?”

Source: Baltimore Sun

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