Zeolite Filter in Guatemala May Be the World’s Oldest
“About 2000 years ago at the Maya city of Tikal in northern Guatemala the residents had a sophisticated water filter system. Special X-ray analysis and radiocarbon ages showed that drinking water in the Corriental reservoir — an important source of drinking water — was filtered through a mixture of zeolite and crystalline quartz. These minerals are used in modern water filtration.” The Hindu
An article from Scientific Reports describes “researchers’ findings from Tikal, Guatemala, where zeolite was found in one of the largest storage facilities of Maya drinking water in use during the Late Preclassic to Late Classic cultural periods (~ 2200–1100 yr. B.P.). The apparent zeolite filtration system at Tikal’s Corriental reservoir is the oldest known example of water purification in the Western Hemisphere and the oldest known use of zeolite for decontaminating drinking water in the world.”
Scientific Reports describes the filtration system as composed of clinoptilolite (the zeolite species most p0pular in today’s filters), mordenite and sand-sized quartz crystals, held together as a filter by stone walls, woven reeds, or palm fibers. University of Cincinnati scientists who examined the filtration system say that it produced exceptionally clean water, reduced microbial contamination, and “would have protected the ancient Maya from harmful cyanobacteria and other toxins that might otherwise have made people who drank from the reservoir sick.”
Natural zeolite has become an indispensable tool in modern water treatment. For residential treatment, zeolite, especially the variety known as clinoptilolite, has largely replaced the old residential “multi-media” sediment filters, which consisted of layered materials like sand, garnet, and anthracite. Zeolite (furnished under a variety of brand names) replaces multi-media with a single substance which is lighter, easier to maintain, easier to backwash, and in general more effective. It supports high service flow rates and needs less backwash water to maintain. Natural zeolite can be adapted to a number of uses, including reduction of iron, hardness, and ammonia.
Fully automatic modern zeolite backwashing filter (made with natural clinoptilolite) filters down to 3 to 5 microns and supports high residential flow rates.
Hydrogen Peroxide for Water Treatment: Treating Hydrogen Sulfide and Iron with Hydrogen Peroxide Injection
Water Treatment Grade 7% Hydrogen Peroxide
Hydrogen peroxide (H2O2) is one of the most powerful oxidizers available for water treatment. Although it can be used to control bacteria, it’s main use is as pretreatment for filters removing iron and hydrogen sulfide.
Less hydrogen peroxide than chlorine is required to treat iron and hydrogen sulfide. When hydrogen peroxide reacts, oxygen is liberated and an oxidant potential 28 times greater than chlorine is produced. It is this large charge of liberated oxygen that makes hydrogen peroxide work so well.
Seven percent hydrogen peroxide (70,000 ppm) is the standard water treatment strength. At this strength liquid hydrogen peroxide can be transported through normal shipping methods and is not considered hazardous.
Thirty-five percent hydrogen peroxide (350,000 parts per million) is sometimes used. It is a hazardous material and must be handled with great care. It usually requires dilution with distilled water for residential use. For this reason, for most home applications 7% hydrogen peroxide is the product of choice.
A Filter Is Required
Like air, ozone, and chlorine, hydrogen peroxide prepares contaminants to be removed by a filter. The oxidizing agent is only half of the treatment. The filter that follows is necessary to remove the precipitated contaminants. Carbon is in most cases the filter medium of choice after hydrogen peroxide treatment. Manganese dioxide media like Birm, Katalox and Pyrolox can be destroyed by hydrogen peroxide. Carbon, both standard and catalytic, works well for both hydrogen sulfide and iron removal. Carbon also breaks down the residual peroxide, so there is usually no peroxide left in the service water. Mixed media filters, zeolite filters, and redox filters (KDF) have also been used successfully.
If the water is very clean and no iron is present, a carbon block filter alone can be used following H2O2 injection, but in most cases–in all cases, if iron is present–a backwashing filter is required. The backwashing process can also clear the system of gas pockets which can form, so backwashing filters are preferred in most cases, even if only odor is being treated.
Stability and Storage
Hydrogen peroxide is exceptionally stable, having around a 1% per year decomposition rate. Heat and sunlight can increase the rate of decomposition. Dilution of the peroxide should be done only with the best water possible. Distilled water is preferred. H2O2 reacts with impurities in the water and loses strength in the process.
If using 35% peroxide, the 35-percent solution should be diluted to 7%. To do this, add 5 parts distilled, reverse osmosis, or deionized water to 1 part 35% hydrogen peroxide. Seven percent hydrogen peroxide is usually fed without dilution although it can be diluted if the injection system will not feed it in small enough quantities.
Practical Treatment Limits
H2S2 can be used to treat up to 10 ppm iron.
There is virtually no limit for hydrogen sulfide. It is not uncommon to oxidize up to 70 ppm hydrogen sulfide with peroxide.
Dosage: Simple But Not So Simple
Figuring the dosage needed for your application could not be simpler.
Here’s the formula:
Well pump output rate in gallons per minute, multiplied by
Required dosage in parts per million, multiplied by
1440—the number of minutes in a day—divided by
Solution Strength in parts per million, which equals
Needed Metering Pump Output in gallons per day (GPD).
Just joking about the “could not be simpler” part. Actually, dosage calculations are impossible and only work in college chemistry classes. In the real world, there will always be parts of the equation that you don’t know. However, working the formula helps you make an educated guess so you will know which size pump to buy and it will give you a starting place. Understand that in the end, there will always need to be some trial and error, some adjustment to your settings, then more trial and error. The information and calculator on this page may help, but don’t expect the calculator to give you a pat answer.
Other Considerations in Sizing and Setup
Use 0.4 ppm peroxide for each ppm of iron. Hydrogen sulfide treatment is pH dependent. Use 1 ppm hydrogen peroxide for each ppm of hydrogen sulfide at pH 7.0. The more alkaline the pH, the greater the dosage required. Adjust dosage accordingly for higher pH. Some trial and error will be necessary.
Warm water also causes oxygen to dissipate more quickly, so a higher dosage may be necessary as water temperatures increase.
Dosage is determined by the same formula as with other oxidants: gpm x 1,440 x dosage/ % concentration of H2O2= chemical feed rate needed.
Never mix H2O2 with alkaline chemicals such as soda ash, limestone, or ammonia. This will cause the rapid decomposition of the hydrogen peroxide and might even result in a violent reaction.
If an alkaline chemical like soda ash is need to raise pH, feed hydrogen peroxide with one pump and soda ash with a separate pump.
Contact Time Required
One of the great advantages of using hydrogen peroxide rather than chlorine is that its reaction rate is much faster. Therefore, it is common to use hydrogen peroxide without a retention tank. A retention tank between the injection pump and the filter is a necessary part of the system with chlorine; with hydrogen peroxide, the reaction rate is so fast that a retention tank is usually not needed.
As stated, a holding tank is usually not needed with hydrogen peroxide. Inject the peroxide with a peristaltic pump. (Conventional pumps can be used, but they often require modification.) If 7% peroxide is fed undiluted, a very low delivery rate pump (< 3 gpd, for example) is usually best in theory, but since hydrogen peroxide dosage needs don’t always follow theory, a higher dosage rate pump often works best. If no holding tank is used, a static mixer at the injection point is recommended. Injection is always before the well’s pressure tank. The filter, of course, follows the pressure tank. A softener, if used, must be downstream of the filter. Injecting hydrogen peroxide directly in front of the softener with no filter is not a good idea.
Reference: Scott Crawford, “Residential Use of Hydrogen Peroxide for Treating Iron and Hydrogen Sulfide,” Water Conditioning and Purification, December, 2009.
New Study Finds Cause-And-Effect Between PFAS Consumption, Reproductive Issues
By Peter Chawaga
New research has underscored the pervasive health effects that can stem from one of the country’s most notorious drinking water contaminants — and it might become key in legal battles between consumers and the industrial operations responsible for introducing them into water systems.
The study looked at the health of residents of a Minneapolis suburb whose water contained elevated levels of per- and polyfluoroalkyl substances (PFAS), also known as “forever chemicals,” before the installation of a municipal water supply filtration facility in 2006, and compared it with health outcomes for the residents after the filtration facility was installed. It found that expecting mothers and newborns experienced some alarming consequences when exposed to PFAS in drinking water.
“Oakdale residents who drank water polluted with toxic ‘forever chemicals’ experienced elevated rates of infertility, premature births and low birthweight babies due to the contaminants, according to a multiyear review of health records,” the Star Tribune reported. “The authors of the peer-reviewed research … say it’s the first to establish a causal link between the chemicals and reproductive impacts.”
The research found that babies in this suburb were 35 percent more likely to weigh less than five-and-a-half pounds at birth, 45 percent more likely to be born before 32 weeks, and that the general fertility rate was as much as 25 percent lower than in communities whose water wasn’t contaminated with PFAS. These health outcomes trended closer to the norm once the filtration facility was installed.
“The research team said the study is the first to establish a cause-and-effect relationship between the filtration of drinking water containing high amounts of PFAS and better reproductive outcomes,” the Environmental Working Group explained. “Almost all previous studies have examined only the association between PFAS exposure and birth outcomes, not a direct cause and effect.”
Elevated levels of PFAS have been found in drinking water throughout the U.S. There are no federal limits on PFAS discharge, nor are there strict limits on PFAS levels in drinking water, though the U.S. EPA does maintain health advisories. A handful of states have taken their own action to reduce the presence of PFAS in source and drinking water.
As communities across the country look to hold industrial polluters responsible for the cost of removing PFAS from source water, the study may provide some critical legal ammunition. For instance, there are multiple lawsuits seeking damages from 3M and DuPont, two manufacturers of the chemicals.
“I think it will be used in litigation that has been filed and is going to be filed, not just here but in other countries as well,” former Minnesota Attorney General Lori Swanson, who has successfully sued 3M for $850 million in environmental damages in the past, told the Star Tribune.
Though the results of the study are jarring, they may prove to be useful data points in the fight to rid drinking water of these particularly insidious contaminants. If so, that might be one small silver lining to come from this Minnesota suburb’s struggles.
With Hundreds Of Thousands Of Sites, Abandoned Mines Pose Significant Water Quality Threat
By Peter Chawaga
“It will take 500 years for the Bureau of Land Management to complete an inventory of abandoned hard rock mines and features on its land.”
In August 2015, an accidental wastewater spill from Colorado’s Gold King Mine released a flood of contaminants into source water across three states. Though the U.S. EPA settled with the State of Utah earlier this month regarding the contamination there, it’s clear that the agency has a lot more work to do to protect other areas of the country from similar disasters.
The primary issue is that there is no comprehensive inventory of mining sites that might be poised to release untreated wastewater containing lead, copper, silver, manganese, cadmium, iron, zinc, or mercury into source water.
“A 2020 report by the U.S. Government Accountability Office explored the breadth of the problem, uncovering some sobering statistics that should give one pause,” according to an AP News report on the extent of the potential water contamination problem posed by the country’s abandoned mines. “The Bureau of Land Management estimates that based on current staffing and resources, it will take 500 years for the agency to complete an inventory of abandoned hard rock mines and features on its land.”
The EPA currently estimates that there are about 500,000 abandoned mine sites on federally protected sites across the country. It has been working on some of these sites for more than two decades and the costs associated with this work are incredibly high.
“EPA spent $2.9 billion through fiscal years 2008 through 2017 to identify, clean up and monitor hazards at abandoned hard rock mines,” per AP. “13 Western states …. spent a collective $117 million in nonfederal funds during the same period.”
With so much work needed to even fully map the issue on a federal level, some states have been working to address abandoned mine contamination within their own borders. The Utah Division of Water Quality (UDWQ), for instance, plans to launch an inventory of discharging mines in its state.
“After the Gold King Mine spill happened, we got a lot of inquiries if this were problematic in Utah,” said Steve Fluke, administrator over a program within the UDWQ mining division, according to The Denver Post. “I would not want to say they are ticking time bombs waiting for a Gold King Mine incident, but they need to be looked into.”
With such a monumental task facing EPA and its mandate to protect the country’s source water quality, it’s likely that other states will make similar efforts. But no matter which agencies take up the issue, it’s going to be a time-consuming and expensive effort.
The Viqua IHS22-D4: The ideal Sediment, Carbon, and UV Unit for Large Homes
The Viqua IHS22-D4. An Ideal Whole Home Treatment
The IHS22-D4 Unit from Viqua features Viqua’s compact but powerful D4 UV system–twice as strong as it needs to be even at 12 gpm flow rate– plus a 5 micron sediment filter and Viqua’s highly effective carbon block filter for chlorine, general chemicals, lead, and taste/odor improvement.
Features & Specs
Disinfection Flow Rates
12 GPM (45 lpm) (2.7 m3/hr)
9 GPM (34 lpm) (2.0 m3/hr)
25 1/5″ x 12″ x 28″ (64 cm x 30 cm x 70 cm)
Shipping Weight lbs (kg)
35 lbs (15.9 kg)
This unit is our part #UV894, and the price is $995, shipped free to any lower-48 US address. It is not on our main website, but can be ordered any time by phone: 940 382 3814. Approximate annual upkeep for filters and UV lamp replacement is $230. Normal lamp replacement interval is one year, and the unit reminds you when it’s time to replace the lamp.
The Viqua illustration above shows an ideal UV installation with pretreatment, individual optional by-pass assemblies for the all components, and the UV unit itself. It also shows an optional solenoid and temperature management valve, which would not be needed for most residential installations.
UV always needs at least one pretreatment item, a 5-micron or tighter sediment filter somewhere in front of the UV unit to assure that there are no particles in the water to shade pathogens from the germicidal light.
Additional pretreatment depends on the quality of the water. Water to be treated should have less than seven grains per gallon hardness, less than 0.3 ppm iron and less than .05 ppm manganese. The carbon filter shown in the diagram is optional and might be included to improve taste, remove extraneous chemicals, remove a small amount of odor, or even to remove chlorine or chloramine if city water is being treated. Carbon will not address iron, manganese, and hardness. The softener in the picture will treat hardness and small amounts of iron and manganese. If iron and manganese are excessive, separate treatment will be needed.
The UV Itself
UV units are sized mainly by gallons per minute treatment capacity. Typical “whole house” residential sizes are 10 to 18 gpm. The UV unit pictured above is a free-standing unit, but systems are also sold that have the sediment and/or carbon stage(s) built on the same frames as the UV chamber. See picture below. Most residential UV units are 115V systems that plug directly into a wall outlet.
The Viqua 12 gpm unit above has sediment filter and lead-removal carbon block built onto the same frame as the UV chamber.
The first step in regulating microplastics in water is defining microplastics
Microplastics are becoming a persistent water quality problem but they are not currently regulated. Microplastics can enter drinking water supplies through sources like surface runoff, atmospheric deposition and sewer overflows, according to the World Health Organization. The health effects aren’t well understood, but studies have found small plastic particles can migrate from animals’ digestive systems into other organs.
Before a contaminant can be regulated, it must first be defined. California recently approved the nation’s first definition of microplastics. Definition is the first step in requiring local suppliers to test drinking water for small plastic particles that could hurt human health. Other states are expected to take their cue from California.
Although chemical companies lobbied against the definition, the California regulatory board stuck to its original proposed definition: “solid polymeric materials to which chemical additives or other substances may have been added, which are particles which have at least three dimensions that are greater than 1 nanometer and less than 5,000 micrometers.” The definition excludes naturally derived polymers that haven’t been chemically modified, which can include “bioplastics” made from starch and other biomass.
This probably means that eventually drinking water agencies in California will have to test their supplies for plastic particles smaller than 5 millimeters and report their findings.
Regulation of plastics in water is uncharted territory, but California has now taken the first step.
Article adapted from Debra Kahn, “California becomes first state to define ‘microplastics’ in water.” from June of 2020. Politico.
Gazette Introductory Note: It isn’t uncommon when a “recent scientific analysis” discovers something that has been common knowledge for decades. In this case, what has just been discovered is that raising cattle for food is an environmental disaster. In addition to the twenty-fold waste of water (as compared with direct human consumption of plants), there is an equally significant amount of water pollution that goes with animal agriculture. When your city water supplier puts the familiar list of water saving tips (like, don’t run water continually while you brush your teeth) in with your utility bill, the list almost never includes real water saving tips like “stop eating pigs and cows.”
Persistent water stress throughout much of the U.S. is linked to multiple causes, including climate change that is warming temperatures and growing populations that put additional strain on available source water. And now, a recent scientific analysis is pointing the finger at another culprit: the cattle industry.
A scientific study published in Nature suggests that cattle are one of the major drivers of water shortages, primarily because of the water required to grow the crops that feed them.
“Across the U.S., cattle-feed crops, which end up as beef and dairy products, account for 23% of all water consumption,” The Guardian reported in a summary of the study. “In the Colorado River Basin, it is over half.”
The Colorado River Basin services some 40 million people in seven states, and is so overdrawn that it rarely reaches the ocean as it once did regularly, per the report. But it is far from alone as a drought-stricken water source in the country. Lake Mead, as another example, hasn’t been full since 1983 and has been reduced by nearly two-thirds over the last 20 years — and almost 75 percent of that decline has been caused by cattle-feed irrigation, the study found.
“It takes a lot of water to make a double-cheeseburger,” according to The Guardian, as it framed the impact in a way many Americans may better understand. “One calculation puts it at 450 gallons per quarter-pounder. The study also found that most of the water-intensive beef and dairy products are being consumed in western cities.”
For those who are concerned about rising source-water scarcity, it’s clear that new solutions and changes to old behavior are needed. The researcher behind the study proposed that leaving farmland idle without irrigation, a practice known as “fallowing,” may be needed.
“[The researcher] noted that the strategy should be temporary and rotational, and that ranchers should be compensated because they lose income growing nothing,” per The Guardian. “Fallowing is at least twice as effective as other water-saving tactics, according to [the] analysis.”
Plant-based meat alternatives may also help with growing source-water scarcity, as consuming less beef and dairy may be the only real solution to this growing stress on the water supply. A meatless Beyond Burger generates 90 percent fewer greenhouse gas emissions and has almost no impact on water scarcity, according to the report summary.
Without wastewater treatment, diseases and infections would ravage our society.
by Trevor English
Wastewater treatment is often an overlooked necessity of civilization. Without proper sewer systems, wastewater treatment plants, and overall regulation, our cities would be ripe with disease and human waste everywhere.
Believe it or not, much of the modern wastewater management technology we consider standard in any 21st century home, things like toilets and sewer pipes, are actually relatively new in the grand scheme of history.
The history of wastewater treatment
That’s not to say that sewer systems haven’t been around for ages. After all, the ancient Romans had a complex system of sewers at the peak of their empire. Rather, the knowledge of how poorly managed wastewater can drastically impact the health of society is relatively new.
The Romans had a centralized sewage management system, although it was fairly rudimentary by today’s standards. Open and closed ditches and pipes would carry away excrement and trash, primarily using rainwater runoff. The contaminated water would then flow into large concrete tanks that let the sewage settle out before the water was allowed to flow into the nearby rivers. There was indoor plumbing, and public latrines were also built over the sewers.
In medieval Europe, closed sewers, stone conduits, or ditches were used to drain sewage away from residential areas, often in conjunction with septic tanks, but chamber pots were often dumped directly onto the streets. Between 1858 and 1859 the Thames in London was chock full of untreated wastewater, which combined with very hot weather to cause what became known as “the Great Stink“.
The 17th and 18th centuries saw a rapid expansion in waterworks and pumping systems, but the Industrial Revolution led to even more rapid growth of cities and pollution, which acted as a constant source for the outbreak of deadly diseases like cholera and typhoid.
As cities grew in the 19th century, increasing public health concerns led to the development of municipal sanitation programs and the construction of sewer systems in many cities. These systems often discharged sewage directly into rivers without treatment, but by the late 19th century, chemical treatments and sedimentation systems were in use in many cities.
The construction of centralized sewage treatment plants began between the late 19th and early 20th centuries. These systems passed sewage through a combination of physical, biological, and chemical processes to remove pollutants. Also beginning in the 1900s, new sewage-collection systems were designed to separate storm-water from domestic wastewater, to prevent treatment plants from becoming overloaded during heavy rains.
In the 1910s and 20s, engineers developed more sophisticated systems to treat drinking water before it was supplied to residents in cities.
In the 1910s and 20s, engineers developed more sophisticated systems to treat drinking water before it was supplied to residents in cities.
Stepping back for a moment and examining the timeline here, we can begin to understand just how recent effective wastewater treatment on a grand scale appeared. Roughly 150 years ago was the first few centralized instances of water treatment for cities. It would take decades for more rigid practices to emerge.
In 1972, the Clean Water Act was passed in the United States. Up until this point, sewage treatment for some cities still relied on chemical treatment and filtration, and the treated sewage was often dumped into rivers and streams. There was little in the way of pretreatment of industrial wastewater to prevent toxic chemicals from interfering with the biological processes used at sewage treatment plants.
After the passage of the Clean Water Act, cities started a process known as secondary treatment, which removes all the pollutant organic materials from the effluent. Wastewater with high concentrations of organic materials and nutrients being dumped into rivers was causing algal blooms and the bacteria growth, which created dead zones in rivers. The secondary treatment essentially eradicates the effluent of microorganisms and organics so that when it’s discharged, it has little effect on the surrounding environment.
To think, just 50 years ago many communities in the world were dumping mostly untreated sewage into rivers.
Wastewater treatment processes have really experienced their most rapid growth in the last 30 or so years, now with every planned municipality in the world having some form of a centralized wastewater management system. It’s all at a hefty cost too – on the scale of billions and billions of dollars.
Now, however, we can flush our toilets and shower without really having to worry about what’s happening to all that dirty water. It gets handled by trusty wastewater treatment plant operators before being discharged into local rivers and lakes. “Oh, and what happens to all the solids from wastewater?” you might wonder. Well in some cases, wastewater treatment plants will let it dry, package it up and sell it as fertilizer to help supplement the hefty costs of running a treatment plant.
In other cases, some plants will use the sludge to produce methane, which they will then burn for power or sell. Wastewater treatment today uses science and engineering, though it is still a little bit smelly. We suppose it comes with the territory.
Now that we understand just how recently our knowledge of sanitation when it comes to human waste has emerged, let’s take a closer look at exactly how wastewater treatment plants work.
How modern wastewater treatment works
When you flush a toilet, your waste flows through the sewers to a wastewater treatment plant that treats it. Sewer systems are a topic all their own, so we’ll mainly focus on how your wastewater goes from one of the dirtiest substances on the planet back into water that’s safe for the environment, and in theory, safe enough to drink. Some wastewater plants known as full-cycle reuse plants will even take wastewater and treat it all the way back to drinking water, which will then be pumped to city inhabitants. This may sound gross, but today’s level of engineering and chemistry allow full-cycle reuse plants to output drinking water chemically identical to what’s in your tap right now.
Before we dive into the specific process of wastewater treatment, let’s put things into a scale. New York City has an array of 14 wastewater treatment plants that handle 1.3 billion gallons of wastewater per day (4.9 billion liters). That is enough wastewater to fill the dead sea with sewage in 8 years, just from one large city.
So society produces a lot of waste. Let’s see what happens first when it arrives at a wastewater treatment plant.
Pre- and Primary Treatment
When wastewater arrives at a treatment facility, it first gets all the large chunks filtered out through a screen, a rather large one. These screens are generally called bar screens, and their main job is to make the sewage more homogenous so it can flow through pumps and pipes in the plant.
The waste removed from bar screens is sent off to the landfill, and the slightly less chunky sewage heads to the next step, the grit chamber.
Grit chambers are essentially just big pools that you definitely don’t want to swim in, they allow the larger particles in the sewage to settle out to the bottom. These larger particles, things like dirt, sand, and large food particles, are called grit. Again, this process aids in making the sewage more homogenous than when it came in. The grit is also trucked off to landfills.
After the sewage gets pretty homogenized in these first few processes, it moves onto the primary clarifiers.
Primary clarifiers function as giant settling basins that allow particles larger than 10 μm, referred to as suspended solids, to settle out to the bottom of the basin. A giant skimming arm also scrapes away fat and grease that rise along the surface of the water.
These primary clarifiers are based on a principle called settling velocity, essentially just the speed at which particles settle. Engineers make sure that the inflow of the water to the primary clarifier isn’t more than the settling velocity of the particles, which ensures that particles still settle out and the sewage keeps on flowing.
Upon leaving the primary clarifiers, the sewage is free of solids bigger than 10 μm and at this point, is mostly contaminated with organic matter. The sewage then moves on to aeration basins, beginning the secondary treatment processes.
Secondary wastewater treatment
Aeration basins are essentially bubbly hot tubs for sewage. They bubble up air through the bottom of the sewage, which invigorates the sewage with dissolved oxygen. Engineers also pump in activated sludge into aeration basins, which is essentially bacteria and waste from the next round of clarifiers. This activated sludge raises the oxygen content of the water and the bacteria go on a feeding frenzy, eating up all of the organic matter.
After the aeration basins, the sewage is going to look a lot clearer and it will head onto the secondary clarifiers. This is the final filtering process, where all the remaining particles settle out. The stuff that settles out is that activated sludge that we just mentioned, and a part of it is reused to make the aeration basins run smoothly. What isn’t used is left to dry out before it’s disposed of or used as fertilizer.
By the time the sewage leaves the secondary clarifiers, 85 percent of all organic matter has been removed and it will look fairly clear. It might also be safe to drink too, but you’re probably not going to want to. The final process before discharge is disinfection.
This process kills off all the bacteria still left in the water and makes sure there aren’t any diseases being discharged into rivers. This is typically done through chlorine, ozone, or ultraviolet disinfection (or a combination of these).
Ozone disinfection involves discharging electricity into the water to cause oxygen gas molecules to turn into ozone molecules, which oxidizes the bacteria, causing their cell walls to break, and kills them.
Chlorine treatment kills the bacteria in a similar manner but is a liquid chemical added to the water, and the treatment plant operators will generally remove the chlorine before releasing the effluent so the chlorine doesn’t damage the environment.
Lastly, engineers can also use ultraviolet light to scramble the DNA of the bacteria, making it impossible for them to reproduce. All three of these processes have different pros and cons and are used fairly interchangeably across the world.
In most cases, after disinfection, the water is released into rivers and streams. In regions where water is scarce, sometimes the treated wastewater will head back for another round of treatment to be made into drinking water. Chemically, this is very safe and could probably be used in many more places around the world if it wasn’t for the stigma surrounding the closed-loop process of turning wastewater back into drinking water.
The entire process takes around 24 to 36 hours for a molecule of water to make it through the treatment plant.
And that’s the magic of wastewater treatment. It’s an essential process that allows us to live our lives without having to think about our own waste. Be sure to thank all the wastewater treatment plant operators around you, because they have to deal with what you don’t want to, 24/7.
Gazette Introductory Note: Now that we’re about half a year into the COVID-19 era, we’ve had truckloads of opinions and advice from the experts and the non-experts, the wise and the foolish, the Democrats and the Republicans, the holy and the unholy, the vaxxers and the anti-vaxxers–in short, from just about everyone. So, the views of a water treatment professional are in order. Below is an article by Mr. Peter Cartwright, a highly respected water treatment veteran. Mr. Cartwright’s article appeared in the July 2020 issue of Water Conditioning and Purification magazine.
There’s so much we don’t know about the virus behind this pandemic, but we are learning a little more each day. To the microbiologists, this virus is known as SARS-CoV-2, closely related to SARS-CoV-1, the virus that caused the SARS outbreak in 2002-3. Most of the current scientific information and recommendations are based on what we learned in dealing with the SARS virus, but there are significant differences. The normal incubation period is two to 14 days after infection; however, during this time, these people may be contagious without even knowing they are infected.
What are its effects?
In addition to the well-known symptoms of fever, coughing and loss of breath, the CDC has recently added chills, muscle pain, headache, sore throat and loss of taste and/or smell. Additionally, medical personnel are now reporting blood clots and issues with kidneys, heart, intestines, liver and the brain. Doctors also suspect a link between COVID-19 and a rare inflammatory condition, Kawasaki Disease.
So where did this particular virus come from? Virologists estimate that about 1.7 million viruses are lurking on this planet, 75 percent of which are in wildlife. Many of the dangerous ones (SARS, MERS, Ebola, rabies, etc.) have been identified in bats and are readily transmitted to humans, possibly through another vector such as snakes. There is lack of agreement on the specific source of this one.
Is it waterborne?
COVID-19 is spread through respiration from the lungs. Diseases such as salmonellosis and cryptosporidiosis result from eating or drinking but the experts do not feel that COVID-19 can be spread that way. In other words, we catch this disease from inhaling, not from eating or drinking. The World Health Organization (WHO) issued a March 19 Interim Guidance wherein they state: ”Although persistence in drinking water is possible, there is no evidence from surrogate human coronaviruses that they are present in surface or groundwater sources or transmitted through contaminated drinking water. The COVID-19 virus is an enveloped virus, with a fragile outer membrane. Generally, enveloped viruses are less stable in the environment and are more susceptible to oxidants, such as chlorine.”
The virtually ubiquitous practice of chlorinating municipal drinking-water supplies in the US has reinforced the conclusion that this virus will not survive in drinking water. This document goes on to state: “Heat, high or low pH, sunlight, and common disinfectants (such as chlorine) all facilitate die off.” In centralized water treatment applications, WHO specifies a free-chlorineconcentration of equal or greater than 0.5 mg/L, at least 30 minutes contact time and pH < 8.0. For non-centralized applications, in addition to chemical treatment (0.5 percent sodium hypochlorite or equivalent disinfectant), they recommend “…boiling or using high-performing ultrafiltration or nanomembrane filters, solar irradiation and, in non-turbid waters, UV irradiation.” Based on this, POU RO technology should be effective. All of these assume careful, hygienic handling practice.
This WHO document also states: “There is no evidence that the COVID-19 virus has been transmitted via sewerage systems with or without wastewatertreatment.” As with other pathogenic viruses, it may be present in sewage, but does not appear to present a greater operational hazard to wastewater plant workers wearing the necessary protective equipment.
So how is it spread?
The bad news is that the COVID-19 virus appears to be transmitted through the air in tiny droplets, typically larger than 5µ. Although the virus itself is extremely small, measuring about 0.1µ, it is readily carried in respiratory droplets. When someone coughs or sneezes, huge quantities of droplets are released. What may not be so obvious is that we spray droplets even by talking (also breathing?). These droplets may be suspended for a long time (hours?) and travel significant distances by air movement. The six-foot rule is just an educated guess and some experts feel it should be much farther, perhaps up to 12 feet.
This underscores the value of face masks. It is suggested that N95 masks be reserved for medical and other personnel in direct contact with infected people. This is good advice, as these masks are manufactured to ensure filtration of at least 95 percent of particles as small as 0.3 microns. The good news is that most droplets containing the virus are much larger than this and, depending on the particular face-mask construction, should be effective at removing these droplets. Even home-made masks constructed from old T-shirts or other cloth will help prevent the wearer from infecting people nearby.
The second pathway of COVID-19 exposure is from surfaces. Experts estimate that the virus is infectious for as much as three hours in droplets, four hours on copper surfaces, 24 hours on cardboard and three days on plastic or stainless steel. Note the antimicrobial credit given to copper, which also includes brass. It also appears to be able to survive on the soles of shoes for up to five days. The SARS-CoV-2 virus will not survive for any length of time outdoors, thanks to the excellent disinfecting properties of UV radiation from sunlight. It appears that UV radiation in the 200 to 222-nm wavelength will effectively inactivate (kill) the virus without harm to human skin. It is also readily inactivated by wiping surfaces with bleach solutions (four teaspoons per one quart of water).
The virus can readily enter the body through mucous membranes around the eyes, nose and throat. It is critically important that we keep the virus particles off our hands (which is why we are inundated with advice regarding hand-washing) and to avoid touching your face. If you think of this virus as sitting on everything you touch, that should be motivation to constantly wash. The experts tell us that the optimum procedure is with soap and water (for 20 seconds) and that hand sanitizer (minimum alcohol concentration of 60 percent) should be used only if soap and water are not available.
Facts and fallacies
As with anything so dominant in the news and on social media today, there is a plethora of misinformation circulating. The list below presents some of these along with the truth as provided by respectable authorities.
The virus that causes COVID-19 is more deadly than any other pathogen. The data so far indicate the fatality rate at one to three percent; SARS was 11 percent and MERS was 34 percent.
Getting COVID-19 is a death sentence. 80 percent of those infected have mild symptoms and get well.
This disease is less deadly than the flu. COVID-19 appears to be more deadly than the seasonal flu.
The virus that causes COVID-19 is the most infectious pathogen. Pathogens that cause measles, polio, diphtheria and whooping cough are more contagious.
Pneumonia and flu vaccinations will protect you from COVID-19. No, they won’t.
Antibiotics will work. These are only for bacterial infections and will not work on viruses.
Sipping water every 15 minutes will prevent infection. Absolutely will not work.
Taking garlic, ibuprofen, echinacea, vitamin C, zinc, elderberry juice, green tea, steroids and other home remedies. There is no evidence that any of these will prevent infection or lessen the symptoms.
Either cold or hot weather will kill it. No evidence to support this.
Hot baths will prevent infection. No.
It can be transmitted through mosquito bites. No evidence to support this.
If you cannot hold your breath for 10 seconds without coughing, you have COVID-19. This is not true.
Wash your hands with antibacterial soap. While hand washing with soap is absolutely the best way to remove the virus from your skin, the antibacterial ingredient is considered ineffective and is actually a significant pollutant in water supplies.
And the future?
Unfortunately, without much more testing, it will be virtually impossible for the experts to gain the critical knowledge necessary to trace this pandemic and make informed decisions about when and how we can return to some semblance of normalcy. Will recovered patients be immune to reinfection? For how long? Will blood plasma containing antibodies from these people help those with COVID-19 disease recover more quickly? When flu season comes this fall, will COVID-19 come back with a vengeance? Unanswered questions.
At the time of this writing, there is an antiviral drug, Remdesivir, which has shown promise in small studies and has been approved for treatment in hospital settings. Another one, Leronlimab also appears promising in limited trials. Meanwhile, there are at least 70 drugs under development globally, including vaccines from Oxford University and China, as well as those under development by Bointech/Pfizer and Moderna. In the meantime, we owe it to ourselves and loved ones to maintain a healthy lifestyle and outlook, both physically and mentally. The byword today is stay safe—we will get through this if we all work together!