Wednesday, May 22, 2024

Direct and Indirect Use of Water in Data Center Industry

Data centers directly and indirectly use water; however, they also have significant impacts on watersheds and the hydrologic cycle replacing natural open space with 7-8 football fields of building surrounded by cleared, compacted and paved land. Data centers also deliver contaminants into our waters.

We all know that data centers use huge amounts of electricity to power their millions upon millions of chips. One data center can require 50 times the electricity of a typical office building, according to the U.S. Department of Energy. That electricity has a water footprint.

The electric power sector uses a large amount of water, primarily for cooling (though there is hydroelectric use. In Virginia we use hydroelectric for power storage. The Bath County Pumped Storage Station uses two reservoirs to create a hydroelectric power storage battery which is reportedly the largest battery in the world with a maximum generation capacity of 3,003 MW and a total storage capacity of 24,000 MWh.

The most significant use of water is in power generation. Thermoelectric power plants (including natural gas, nuclear, and coal plants) boil water to create steam, which spins a turbine to generate electricity. The steam leaving the turbine must be cooled back into water to be used to generate more electricity. Plants withdraw water from nearby rivers, lakes, or oceans and pass that water through the steam leaving the turbine. That process cools and condenses the steam back into water, but a certain amount evaporates. In 2021, 73% of the utility-scale electricity generated in the United States came from thermoelectric power plants.

The electric sector’s water-withdrawal intensity—the amount of water withdrawn per unit of electricity generated—depends on the power generation mix and technology used. It has been falling as we move away from coal since natural gas uses less water. Nationally, water used in power generation was 11,595 gal/MWh in 2021.

While the Virginia power mix has been migrating away from coal and towards natural gas, nuclear and renewables, Virginia does not generate enough power to supply our current and growing need for power. The shortfall in power is supplied by PJM generation coming predominantly from West Virginia and Pennsylvania. 

Dominion Energy in Virginia predicts that by 2035 the data center industry in Virginia will require 11,000 megawatts from them, nearly quadruple what it needed in 2022, or enough to power 8.8 million homes. Northern Virginia Electric Cooperative recently told PJM that the more than 50 data centers it serves account for 59% percent of its energy demand. It expects to need to serve about 110 more data centers by July 2028.

Data centers also use large amounts of water directly for cooling systems, which ensure that the heat produced by these massive facilities is controlled.Data Centers are cooled using either air conditioning (electricity) or evaporative cooling (water). Evaporative cooling is more efficient and effective. 

In a water-cooled system, water-cooled chillers and cooling towers located on top of the data center roofs produce chilled water, which is delivered to computer room air conditioners for cooling the entire building. Some of this water can be recycled through the system more than once.

So, how much water do data centers use,. The industry treats it as a trade secret. In 2021, when Prince William County looked at water consumption for its 25 operational data centers at the time it found that water use varied by season and ranged from about 0.2 to 0.5 gallons per square foot per day. Of course, the total square footage of the data centers was not disclosed. The data centers that Prince William looked at were all relatively small 100,00-250,000 square feet- nothing like the hyper centers being built now. Today, data centers seem to start at a million square feet and move up from there with multiple building campuses.  How water use scales up in multi-story data centers is unknown. The heat island effect is likely to increase water needs for cooling.

Loudoun County has a larger data set. Loudoun County built a reclaimed water system to supply data centers more cheaply with water. However the expansion of data centers required more than that system could provide. The water from the Broad Run Waste Water Treatment plant was inadequate to serve all data centers.

from Loudoun Water ICPRB presentation data centers that they know about

According to Loudoun County, Data center water use will have grown to an average 4 million gallons a day of potable water and 4 million gallons a day of reclaimed water by the end of this year- since in northern Virginia we drink the reclaimed water from UOSA and returned upstream to the Potomac, that is enough water to supply 100,000 people. 

As reflected in the Loudoun Water data, some of the data centers do reuse water by recirculating the same water through their cooling systems multiple times while replenishing what evaporates. According to Google, this practice saves up to 50% of water when compared with “once-through” cooling systems. However, eventually this reused water needs to be replaced with new water, due to mineral scale formation which could damage the cooling equipment or once the conductivity of the water is too high which could damage the IT equipment.

The need for new water results from the build-up of calcium, magnesium, iron, silica, and salt which become concentrated by evaporative cooling cycles. The amount of water data centers consume also fluctuates based on seasonal weather conditions. Facilities typically use less water during the winter months and more during the summer months as can be seen in the potable water data from Loudoun County.

Data center wastewater is largely comprised of blowdown; the portion of cooling water removed from circulation and replaced with freshwater to prevent excessive concentration of undesirable components like salt can the concentrated impurities. In general data centers recycle their water until the concentration of dissolved solids (which is essentially salts) is roughly five times the supplied water. This blowdown is sent to the waste water treatment plant which is not designed to remove salts. This exacerbates the problem of salinization that is a  growing problem in our region and water resources.

In Loudoun the reclaimed water distribution system in Ashburn receives reclaimed water from Loudoun Water helping to save money.  Purchasing  reclaimed water is cheaper than purchasing an equal amount of potable drinking water. To provide the reclaimed/ recycled water, Loudoun uses the effluent water from the Board Run wastewater treatment facility near Ashburn. That water is ultimately returned to the Potomac River, saltier than it started upstream from the Leesburg, Fairfax Water and Washington Aqueduct intakes for their drinking water treatment plants.

from Loudoun Water presentation to ICPRB

Loudoun Water tracking potable water use for data centers requires the data centers to self identify, which does not always happen. The reclaimed system needs a direct hookup, so that is easier to track. Overall, there is believe to be 51 million square feet of data centers operating in Northern Virginia at the end of 2023. Combining all the estimates and allowing for air cooled facilities, that is enough water for between 150,000-375,000 people.  CBRE estimates that 3-4 times that amount of data centers are currently under construction. 

Prince William county believes that most data center water comes from potable water supplies. Though Amazon has a permit to withdraw upto 2.5 million gallons of water a day from groundwater wells it has in Manassas, most data centers in Virginia are not required to permit and monitor their water use.  In Prince William County the treated sewage from UOSA is already used by Fairfax Water (upto 40 millions gallons a day) to supplement water supply to the Occoquan Reservoir for our drinking water supply.

Though we do not generally think of it that way, a data center is an industrial use, not a commercial use in its need for square footage and power with a very large carbon footprint, diesel generators and fuel storage tanks treated under regulations as separate sources of above ground fuel storage and potential release. The actual buildout of the physical properties of data canters is also impacting the availability of and quality of water. Impacting to future sustainability and availability of water for our region.

Sunday, May 19, 2024

Perserve the Watershed

Data centers directly and indirectly use water; however, they also have significant impacts on watersheds and the hydrologic cycle. In Virginia, data centers have be built on Greenfields and end up replacing natural open space with 7-8 football fields of building surrounded by cleared, compacted and paved land.  One data center or even a few dozen are fine, but that's not what we are doing. Reportedly, we currently have 51 million square feet of data centers in Northern Virginia and we as a region are running headlong to more than quadruple that number. Beyond the power use, that will be the biggest impact of Data Center Alley's expansion into Montgomery county and south beyond Manassas, VA. they will directly use enough water as the existing population and reduce our water availability and quality at the same time. 

The impervious cover, compacted soils, pavement and loss of natural open spaces from these giant hyperscale data centers will increase , flooding and  runoff to creeks and rivers. The larger volume, velocity and duration of stormwater flows will act like sandpaper on stream banks, intensifying the erosion and sediment transport from the landscape and stream banks. This often causes channel erosion, clogged stream channels, and habitat damage and road flooding.

Land use changes that significantly increase impervious cover from roads, pavement and buildings does two things. It reduces the open area for rain and snow to seep into the ground and percolate into the groundwater and  the impervious surfaces cause stormwater velocity to increase preventing water from having enough time to percolate into the earth, increasing storm flooding and preventing recharge of groundwater from occurring. 

 Increased stormwater volumes, sediment loads and pollutant loads are a direct result of clearing the land of trees and vegetation, construction activities for buildings and roads. Slowly, this can reduce groundwater supply over time. Groundwater serves as the savings account for streams,  rivers and lakes. Increasing population density, increases in industrial water use and reducing recharge as we’ve been doing slowly reduces groundwater levels over time as the groundwater is used up. Groundwater changes are not abrupt and problems with water supply tend to happen very  slowly and are missed until it is critical and a drought unveils it. 

With natural open groundcover, 25% of rain infiltrates into the aquifer and only 10% ends up as runoff. As imperviousness increases, less water infiltrates and more and more runs off. In highly urbanized areas, over one-half of all rain becomes surface runoff a five fold increase, and deep infiltration is only a fraction of what it was naturally occurring.

In a series of studies from the 20th century in California found this pattern of degradation. The well known example is of Los Penasquitos Creek in San Diego County, watershed development grew from 9% to 37% urbanization between 1966-2000. From 1973-2000, the total annual urban runoff in the upper watershed increased by 4% per year, resulting in more than a 100% increase in runoff for the measured time period. The flood magnitude for the 1-2 year storm also increased by more than 5 times from 1965-2000.

When the impervious cover in a watershed exceeds 5%-20% the impacts are:

  • Excessive stream channel erosion from  both the streambed and stream banks.
  • Reduced groundwater recharge
  • Increased size and frequency of 1-2 year floods
  • Decreased movement of groundwater to surface water, perennial streams will become ephemeral 
  • Loss of streambank tree cover
  • Increased contaminants in water 

When generally wooded and open rural areas are cleared, graded and compacted and developed for data centers, we begin the destruction of parts of our watershed.  This must be limited to preserve our source of drinking water. We have no replacement. Otherwise, the development will increase stormwater runoff i in quantity and velocity washing away stream banks, flooding roads and buildings carrying fertilizers, oil and grease, and road salt to the streams and rivers and our reservoirs.

The consequences of this change are a decrease in the volume of water that percolates into the ground, and a resulting increase in volume of stormwater and decrease in quality of surface water. These hydrological changes have significant implications for the quantity of fresh, clean water that is available for use by humans, fish and wildlife. If taken to a high enough extent of development, to survive in the region we will need to build more reservioirs and increase the water treatment lines to drink essentially storm flood waters.

Data centers are part of our modern world. What we need to do is manage our watershed to minimize the damage to our essential water resources. Let’s talk about what we need to do to manage the impacts from data centers. Data center companies are more than cautious about sharing any information they don’t have to. Many are not even collecting data at all.

We cannot plan for the future of Virginia without planning and managing our water resources.  Climate is changing, data centers are adding extra pressure in their direct water use to regions already challenged with meeting public, agricultural, and industrial needs. We have not had a drought of any significance in in more than 15 years. What will we find when the drought comes? We need to make sure our region will have a sustainable source of quality drinking water. To do this, data is essential. We need to know and track how much water data centers use and what is happening to our water resources and land cover. Here are some simple suggestions for just understanding what we are doing. 

  • All groundwater wells (other than domestic individual supply) need to be permitted with monthly volume limits and required reporting.
  • An adequate number of groundwater monitoring wells need to be added to the open access USGS network.   
  • To fight inland salinization, data centers need to remove the salt from blow down and waste water and control the use of road salt on their sites.
  • Above ground fuel storage tanks will have adequate secondary containment to prevent release of fuel to the environment.
  • Generators need to be permitted as a single source.
  • Mature trees need to be preserved. Natural open space (Woodland buffers) need to be increased in size to 500 foot to avoid the edge effect and so that they can provide environmental services including stormwater management and groundwater recharge. 
  • Virginia needs to manage the amount of impervious surfaces in watersheds keeping it between 5-10% and avoiding fragmented open space.


Wednesday, May 15, 2024

Wells of Virginia -2023 Annual Report

Private drinking water wells serve more than a fifth of Virginia’s population or 1.7 million residents.   Virginia created the Virginia Household Water Quality Program (VAHWQP) to provide affordable water testing and education about private water wells to those residents of the Commonwealth. Extension Offices hold drinking water clinics and provide information to assist private well owners in understanding and maintaining their wells. 

The quality and safety of private wells are not regulated under Federal nor, in most cases, state law. In Virginia regulations control only construction and the absence of bacteria at the time of a well’s completion. The U.S. Environmental Protection Agency Safe Drinking Water Act does not regulate individual households. As a result, individual homeowners are responsible for maintaining their own water supply and ensuring the quality of the water for their family.

The Virginia Household Water Quality Program was, originally created in 1989, was relaunched in 2007 with a USDA grant. In 2011 the program was expanded under another USDA grant to subsidize testing, quantify bacteria, add metals, and begin research out of Virginia Tech. Now the program is self-sustaining with clinics held in 91 of the 96 counties in 2021. The analysis is done by the Virginia Tech laboratory and research utilizing the data is being pursued by graduate students.

In all the Virginia Household Water Quality Program clinics the water samples are analyzed for: iron, manganese, nitrate, lead, arsenic, fluoride, sulfate, pH, total dissolved solids, hardness, sodium, copper, total coliform bacteria and E. Coli bacteria, and last year cost $65 in Prince William County. These are mostly naturally occurring contaminants and common sources of contamination: a poorly sealed well or a nearby leaking septic system, or indications of plumbing system corrosion. Though not an exhaustive list of potential contaminants, these are the most common contaminants that effect drinking water wells.

from VHWQP 2023 annual report

Though about 600,000 of Virginia households with 1,600,000 residents or 19% of the Virginia population have private wells, only around 3,611 households chose to participate in the Virginia Household Water Quality Program clinic in 2023 and may not be representative of all private drinking water wells in the Commonwealth. Nonetheless, the data collected over the past 17 years is the one of the largest databases on private drinking water wells available. Well water quality is driven by geology, well construction and condition, nearby sources of contamination, and, within the home, water treatment devices and composition of plumbing materials.  

Overall, the statewide sampling last year found that just under 38% of the wells have coliform bacteria present, and almost 5% have E. coli bacteria. Though 23% of wells were found to have acidic water (low pH) about 7% of homes have first flush lead levels above the EPA safe drinking water standard maximum contaminant level for lead and 8% for copper. Lead and copper leach into water primarily because of corrosion of plumbing and well components but can also result from flaking of scale from brass fittings and well components unrelated to corrosion. Copper and lead predominately come from the pipes and lead containing components in wells. Over time older pipes and fixtures corrode or simply wear away and the lead and other corrosion material (like rust) is carried to the drinking water. Time and water do cause corrosion, but this can be aggravated by the pH of the water or other changes in water chemistry. The amount of lead corroded from metal plumbing including faucets with brass interiors generally increases with increasing water corrosiveness.

About 34% of households have elevated sodium exceeding the EPA Safe Drinking Water Act limit. This could be a result saltwater infiltration from natural or man-made sources (like road salt) or could indicate that water softeners are adding too much sodium to the water. Of the 3,611 participants in 2023, 40% report that they NEVER tested their water before and 30% had tested only once (presumably at purchase). About 46% of participants have participated in the VAHWQP clinic before.  Virginia Tech recommends annual testing of well water to make sure it is safe to drink, and you have the appropriate treatment system(s).


Sunday, May 12, 2024

The Wells of Prince William 2024

Earlier this month the well owners who participated in the 2024 Prince William County Well Water Clinic received their results by email. Below you can see the summary of what was found in the 84-water analyses performed. VA Tech tested for the naturally occurring contaminants and common sources of contamination: a poorly sealed well or a nearby leaking septic system, or indications of plumbing system corrosion. These are the most common contaminants that affect our drinking water wells. 

To determine if treatment is necessary, water test results should be compared to a standard-usually the U.S.EPA Safe Drinking Water Act (SDW) limits. Though private wells are not regulated by the U.S. Environmental Protection Agency (EPA) or the Safe Drinking Water Act, the SDW act has primary and secondary drinking water standards that we use for comparison. Primary standards are ones that can impact health and from the tested substances include coliform bacteria, E. coli bacteria, nitrate, lead, and arsenic. Secondary standards impact taste or the perceived quality of the water.

Just because your water appears clear does not mean it is safe to drink. The 2024 Prince William County water clinic found that 27.4% of the wells tested present for coliform bacteria. This is higher than last year. Coliform bacteria are not a health threat itself; it is used to indicate other bacteria that may be present and identify that a well is not properly sealed from surface bacteria. The federal standard for coliform bacteria is zero, but the federal standard allows that up to 5% of samples can test positive for coliform during a month.

One of the bacteria contaminated wells tested positive for E coli. Fecal coliform and E. coli are bacteria whose presence indicates that the water is contaminated with human or animal wastes. Disease-causing microbes (pathogens) in these wastes can cause diarrhea, cramps, nausea, headaches, or other symptoms. These pathogens may pose a special health risk for infants, young children, and those with compromised immune systems. However, people can drink water contaminated with fecal bacteria and not notice.

If your well is contaminated with coliform but not fecal coliform or E. coli, then you have a nuisance bacteria problem, and the source may be infiltration from the surface from rain or snow melt. Typical causes are improperly sealed well cap, well repairs performed without disinfecting or adequately disinfecting the well, failed grouting or surface drainage to the well. Very low levels of coliform (1-5 MPN) may appear in an older well during extremely wet springs.

If your well was found to have coliform bacteria present you should shock chlorinate the well (according to the procedure from VA Tech), repack the soil around the well pipe to flow away from the well and replace the well cap. Then after at least two weeks and the next big rainstorm retest the well for coliform. If coliform bacteria is still present then a long-term treatment should be implemented: using UV light, ozonation, or chlorine for continuous disinfection. These systems can cost up to $2,000 installed (maybe more with recent price increases).

If you have fecal coliform in the well or E. coli, your well is being impacted by human or animal waste and you are drinking dilute sewage. If there is not a nearby animal waste composting facility, then you are probably drinking water from a failed septic system- yours or your nearest neighbors or in some areas a leaking sewer line. To solve this problem you need to fix or replace the septic system that is causing the contamination, replace the well or install a disinfection and micro filtration or reverse osmosis system. Giardia or Cryptosporidium are two microscopic parasites that can be found in groundwater that has been impacted by surface water or sewage. Both parasites produce cysts that cause illness and sometimes death. Chlorine can work against Giardia but not Cryptosporidium. Ultraviolet (UV) light works against both Giardia and Cryptosporidium so it is the preferred method of treating this problem.

The failing septic systems can often be identified by using tracer dyes. While continuous disinfection will work to protect you from fecal bacteria and E. coli, be aware that if your well is being impacted by a septic system, then the well water might also have present traces of all the chemicals and substances that get poured down the drain. Long term treatment for disinfection, and micro-filtration should be implemented: using UV light, ozonation, or chlorine for continuous disinfection, carbon filtration, and anything that is used for drinking should be further treated with a reverse osmosis systems or micro membrane system both work by using pressure to force water through a semi-permeable membrane. Large quantities of wastewater are produced by reverse osmosis systems and need to bypass the septic system or they will overwhelm that system creating more groundwater problems. Reverse osmosis systems produce water very slowly, a pressurized storage tank and special faucet needs to be installed so that water is available to meet the demand for drinking and cooking.

Nitrate can contaminate well water from fertilizer use; leaking from septic tanks, sewage and erosion of natural deposits. None of the wells in our group of 84 samples had nitrate levels above the MCL. The regulatory limit for nitrate in public drinking water supplies, 10 mg/L,  was set to protect against infant methemoglobinemia, but other health effects were not considered and are emerging as problems. Nitrate in a well tends to climb slowly over the years if the septic systems do not have at least 3 acres between them. Based on a study done years ago in Dutchess County NY at least 3 acres are necessary to naturally treat the nitrate.

Dr. Mary Ward of the Occupational and Environmental Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute has lead several important studies comparing all the research on the health impacts from exposure to nitrate in water. The first review was of studies published before 2005. In 2018 Dr. Ward was lead author on a review of more than 30 epidemiologic studies on drinking water nitrate and health outcomes. If your nitrate-N levels are climbing, you might want to read Dr. Ward’s work. Thre are AOSS systems designed to remove nitrate. These are very expensive (think new care expensive.)

This year they found 3.6% of homes had first draw lead levels above the SDWA maximum contaminant level of 0.015 Mg/L. After flushing the tap for at least one minute none of the homes had lead levels above the 0.15 mg/L level; however, many scientists do not believe that any level of lead is safe to drink over an extended period of time. AndOften homes that have elevated lead in the first draw, have lower pH values. Corrosive water is the primary risk for lead in well water. However, over time water with a neutral pH could dissolve the coating on galvanized iron,  in brass well components and plumbing fixtures.

Houses built before 1988 when the ban on lead went into effect and have low pH water typically have higher lead concentrations. Lead leaches into water primarily as a result of corrosion of plumbing and components in the well itself but can also result from flaking of scale from brass fittings and well components. Corrosion control techniques such as adjusting pH or alkalinity that are commonly used to neutralize aggressive water will not work in to reduce lead being leached from well components. For most instances, though, a neutralizing filter and lead removing activated carbon filters can be used to remove lead leaching from plumbing pipes, solder and fixtures. Recently, some home water treatment companies are offering home treatment systems that neutralize the water and add orthophosphate other phosphate solution to coat the piping to prevent further corrosion of metal pipes. It should work if maintained. This type of solution is used in public water supplies. I have no experience with this type of home system and am not aware of any testing.
Iron and manganese are naturally occurring elements commonly found in groundwater in this part of the country. 4.8% of the wells tested exceed the iron standard and 3.6% exceeded the manganese standard. At naturally occurring levels iron and manganese do not present a health hazard. However, their presence in well water can cause unpleasant taste, staining and accumulation of mineral solids that can clog water treatment equipment and plumbing and discolored water. The standard Secondary Maximum Contaminant Level (SMCL) for iron is 0.3 milligrams per liter (mg/L or ppm) and 0.05 mg/L for manganese. This level of iron and manganese can be detected by taste, smell, or appearance. In addition, some types of bacteria react with soluble forms of iron and manganese and form persistent bacterial contamination in a well, water system and any treatment systems. These organisms change the iron and manganese from a soluble form into a less black or reddish brown gelatinous material (slime). Masses of mucous, iron, and/or manganese can clog plumbing and water treatment equipment.

All systems of removing iron and manganese essentially involve oxidation of the soluble form or killing and removal of the iron bacteria. When the total combined iron and manganese concentration is less than 15 mg/l, an oxidizing filter is the recommended solution. (Iron bacteria, hydrogen sulfide and tannins can also be removed with pre-chlorination.) An oxidizing filter supplies oxygen to convert ferrous iron into a solid form which can be filtered out of the water. Higher concentrations of iron and manganese can be treated with an aeration and filtration system. This system is not effective on water with iron/ manganese bacteria but is very effective on soluble iron and manganese, so you need to do further testing to determine what type of iron/manganese you have before you install a treatment system. Newer iron filters have an option to add an ozone generator to kill reducing bacteria.  Water softeners can remove low levels of iron and manganese and are widely sold for this purpose because they are very profitable but are now being banned in some locations due to rising sodium and chloride levels, what is known as inland salinization. Increasing salinization of our water resources is a growing problem in our region. Also, water softeners are easily clogged by iron bacteria.

Chemical oxidation can be used to remove high levels of dissolved or oxidized iron and manganese as well as treat the presence of iron/manganese (or even sulfur which was found in one well exceeding the EPA MCL) bacteria. The system consists of a small pump that puts an oxidizing agent into the water before the pressure tank. The water will need about 20 minutes for oxidation to take place so treating before a holding tank or pressure tank is a must. After the solid particles have formed the water is filtered. The best oxidizing agents are chlorine or hydrogen peroxide. If chlorine is used, an activated carbon filter is often used to finish the water and remove the chlorine taste. The holding tank or pressure tank will have to be cleaned regularly to remove any settled particles.

The pH of water is a measure of the acidity or alkalinity. The pH is a logarithmic scale from 0 – 14 with 1 being very acidic and 14 very alkaline. Drinking water should be between 6.5 and 8.5. For reference and to put this into perspective, coffee has a pH of around 5 and salt water has a pH of around 9. Corrosive water, sometimes also called aggressive water is typically water with a low pH. (Alkaline water can also be corrosive.) Low pH water can corrode metal plumbing fixtures causing lead and copper to leach into the water and causing pitting and leaks in the plumbing system. The presence of lead or copper in water is most commonly leaching from the plumbing system or well rather than the groundwater. Acidic water is easily treated using an acid neutralizing filter. Typically, these neutralizing filters use a granular marble, calcium carbonate or lime. If the water is very acidic a mixing tank using soda ash, sodium carbonate or sodium hydroxide can be used. The acid neutralizing filters will increase the hardness of the water because of the addition of calcium carbonate. 16.7% of the wells tested were found to have acidic water this year. One well had too high a pH. This is usually from over treating with a water softener, but can be an expression of other pollution.

Water that contains high levels of dissolved minerals is commonly referred to as hard. Groundwater very slowly wears away at the rocks and minerals picking up small amounts of calcium and magnesium ions. Water containing approximately 120 mg/L can begin to have a noticeable impact and is considered hard. Concentrations above 180 mg/L are considered very hard. Hard water can be just a minor annoyance with spotting and the buildup of lime scale, but once water reaches the very hard level 180 mg/L or 10.5 grains per gallon, it can become problematic. Overall, 17.9% of homes tested had very hard water. (It is to be noted that 53.6% of homes reported having a water softener.)

Two methods are commercially available (and certified) to treat hard water. A water softener and a water system that work through a process called template assisted crystallization (TAC), have been certified by DVGW-W512 and are available in whole house units. In template assisted crystallization, water flows through a tank of TAC media. When the hard water comes into contact with the media, the magnesium and calcium ions are caught by the nucleation sites. As more calcium and magnesium ions build up within the sites, small micro-crystals form and flow through your plumbing. They do not attach themselves to your water pipes as scale.

The ubiquitous water softening system is an ion exchange system consisting of a mineral tank and a brine tank. The mineral tank holds small beads of resin that have a negative electrical charge. The calcium and magnesium ions (along with small amounts of other minerals) are positively charged and are attracted to the negatively charged beads. This attraction makes the minerals stick to the beads as the hard water passes through the mineral tank. Sodium from salt is used to charge the resin beads. The brine tank is flushed out when the resin beads are recharged carrying the salty solution to the environment. Inland salinization of surface waters and groundwater is an emerging environmental concern. Research has shown that salinization has affected over a third of the drainage area of the contiguous United States even in areas without road salt. At the present time the EPA guidance level for sodium in drinking water is 20 mg/L. Given the number of homes with elevated sodium and our local geology, it is probably a reflection of the number of homes with water softeners-50.0% of the wells tested had elevated sodium.

One of wells was found that had arsenic exceeding the EPA MCL for drinking water of 10 ppm. While arsenic is a naturally occurring element found in soil and groundwater it is not typically found at significantly elevated levels in this geology. Arsenic is best removed by water treatment methods such as reverse osmosis, ultra-filtration, distillation, or as a last choice ion exchange (water softeners). Typically, these methods are used to treat water at only one faucet. Though anionic exchange systems (water softeners) are whole house systems, they may not be the best choice.

Wednesday, May 8, 2024

Dogs Know Words

It will come as no surprise to any dog owner that research scientists have found that pet dogs know the words for many objects. The understanding of object words had not been previously demonstrated as a general capacity in any non-human species,  despite many pet owners reporting the fact.  It has now been demonstrated.

This image is from Science News a great magazine where I read about this study

In non-verbal humans object word knowledge is typically tested using the semantic violation paradigm, where words are presented either with their matching image or another object (a mismatch).  Such mismatch elicits an N400 effect, a well-established neural correlate of semantic processing that can be measured with an EEG. Most famously this technique is used to test preverbal infants.  

Pet dogs live in our human environment and are surrounded by speech. They learn. In 2020 Gabor et al found similarities between humans and dogs in the neural processing of speech. Scientists developed a methodology of studying brain mechanics in dogs that is non-invasive using EEG much they way they study brain activity in infants.

This non-invasive canine neuroscience technique was developed and perfected in a laboratory at Eötvös Loránd University in Budapest. There are videos you can watch online of dogs participating in some of their research narrated by the lead scientist of this study, Marianna Boros. The dogs seem perfectly happy (tails waging) and are not restrained so they could walk away. They do have a couple of electrodes stuck to their fur. It looks harmless in the videos.

Now researchers in Budapest have tested word knowledge and found that all pet dogs tested in a small group know the words for things. Every dog I’ve ever had knew what a leash, Kong and ball were, and many, many more things. However, this is the first neuroscientific evidence that animals can understand word meaning the same way humans do.  Now if they could just test cats…but I’m afraid the two skills necessary-lying on a mat and staying awake are beyond pet cats.


Sunday, May 5, 2024

My Well Test Results

The Virginia Tech Extension Virginia Household Water Quality Program finally emailed the water test results from the water clinic. This is what I saw when I opened my attachment:


Coliform bacteria was found present. Total coliform bacteria is called an indicator bacteria. They are  found on the ground surface and in surface water, generally do not cause disease. They are indicators of the possible presence of disease bacteria, and if found, point to the need for additional testing  for E. coli ,which was not found. Total coliform (and E. coli bacteria) results also include “MPN”, or “most probable number”, which is a statistical estimation of how many bacteria were found in 100 mL of sample. This number can range from < 1 (Absent)  to greater than  2,419, which is represented as “>2419” or “too numerous to count”. The MPN can give an idea of the extent of contamination of a water supply, but, ideally, no bacteria should be present. My MPN was 1.01.

My well tested positive with an MPN of 1.01/100 mg/L indicating that there is a very small amount of bacteria (about 1 per 100 ml of water). This could be an accidental cross contamination, a result of all the rain,  or it could be in the source water, plumbing or on the faucet. I have no water treatment devices in my house so that was out.

Standard protocol if a well tests PRESENT for coliform is:

  1. Retest using proper sampling procedure and verify that E coli is tested for.
  2. If the sample still tests positive for total coliform then treat the system with chlorine
  3. Retest the water after the chlorine has left the system in about two to three weeks (make sure that the water tests negative for chlorine).
  4. If your well water still tests positive for total coliform: Carefully check the well and water system for points of contamination. Make sure you have a sound and secure sanitary well cap and that the soil around the well is packed to drain water away from the well.
  5. Then treat the well and plumbing system again making sure to disinfect any treatment equipment, replace filters, with chlorine for 12-24 hours to disinfect system (the 12-24 hours is essential). Then flush the chlorine from the system- not to your septic system. Make sure that this is done correctly.
  6. Retest the water after the chlorine has left the system in about two weeks. If coliform bacteria is “ABSENT” you’re done. If not, then it is time to install a long term disinfection system. (UV light or continuous chlorination)

If the MPN is above 50-100 I would skip retesting and simply jump right to fixing the problem: methodically shock chlorinate the well (according to the procedure from VA Tech), repack the soil around the well pipe to flow away from the well and check and disinfect the well cap and replace as necessary. That is a lot of work for contamination that may have happened in taking or processing the sample.

Though I hate to think that I was the source of human error, taking a sample at 4:30 am I certainly could have been. The aerator or  lab, too, could have been the source of cross contamination.

There could be other sources of minor Coliform contamination and these are beginning to worry me. From Penn State Extension we also know “Time of year and weather conditions can affect the occurrence and amount of coliform bacteria in wells. “....Since coliform bacteria like to live near the surface of the earth and prefer warm temperatures, it is reasonable that bacteria would be more likely to occur in groundwater wells during warmer, wetter weather conditions when surface water is recharging groundwater aquifers. Thus, the highest number of bacteria will be found by testing your well shortly after several weeks of rainy weather, while the fewest bacteria will be found when testing during dry, cold conditions in the winter. These variations in bacteria with season and weather conditions need to be considered when testing your water supply for bacteria.”

This failed test had been taken during a two week period where we had several days of rain. Our geology is fractured rock with very little overburden...still 1.01 MPN spoke more of accidental cross contamination, but this is the second time in 4 years that I got this result. I always worry that with a fractured rock system we a susceptible to contamination. Over the weekend I went out and got a sample bottle from a certified laboratory and will carefully clean the spouts and take  another sample this week. If it is positive, I will chlorinate this month, if negative, I will think about it, maybe test the well for coliform bacteria quarterly and track it more closely. It is, after all, my family’s water supply.

Wednesday, May 1, 2024

Occoquan Overlay

To protect the Occoquan Reservoir that provides drinking water to the eastern portion of Prince William County, the county has created an overlay district in the lower Occoquan Watershed. Now that the overlay district is being added to the Comprehensive Plan, there are attempts to exempt the largest undeveloped parcels from the protections. The whole point of the ORPA is to prevent more intense development and protect the drinking water supply for eastern Prince William.

Protecting the recharge of groundwater within the Occoquan watershed serves to protect all of the water resources in the watershed. Today, the Occoquan watershed is often described as the most urbanized watershed in the nation. Certainly, there are far more urbanized areas in the United States, but they do no longer have functioning watersheds. We need to effectively protect ours and our source of drinking water.

from NVRC

As the US Geological Survey points out: “Nearly all surface-water features (streams, lakes, reservoirs, wetlands, and estuaries) interact with ground water. These interactions take many forms. In many situations, surface-water bodies gain water and solutes from ground-water systems and in others the surface-water body is a source of ground-water recharge and causes changes in ground-water quality. As a result, withdrawal of water from streams can deplete ground water or conversely, pumpage of ground water can deplete water in streams, lakes, or wetlands.”

Ground water flow and storage, often viewed as static reservoirs, are dynamic and continually changing in response to human and climatic stress [Alley et al., 2002Gleeson et al., 2010]. Increase or decrease in precipitation patterns impacts available surface and groundwater. Man’s hand in changing the land surface also impacts water resources.

Land use changes that increase impervious cover more than 5-10% from roads, pavement and buildings does two things. It reduces the open area for rain and snow to seep into the ground and percolate into the groundwater and the impervious surfaces cause stormwater velocity to increase preventing water from having enough time to percolate into the earth, increasing storm flooding and preventing recharge of groundwater from occurring. 

Slowly, this can reduce water supply over time. As groundwater levels fall, perennial steams that feed the rivers become ephemeral. The groundwater becomes disconnected from the surface water network. Once the hydrology is destroyed by development, it cannot be easily restored, if at all. Though there have been a few attempts we have not succeeded in restoring a watershed. According to the NVRC in 2015 impervious surfaces in this lower Occoquan area was already at 11%.

from NVRC

Protecting the Occoquan Reservoir requires protecting all the water resource in a region because all water in the watershed is connected. Precipitation moves into the water table (the hyporheic zone) down to groundwater or into rivers and streams. Disrupting the balance of water flow can have dire consequences. The available supply of fresh water is continually renewed by the hydrologic cycle and in the case of the Occoquan Reservoir the actions of mankind. The need for water is constant and grows with population, wealth and business activity. There is also a seasonality to water- we use more in summer.

There has been a six-fold increase in population from when the statistics were first collected in the early 1970’s. Ironically, the defining study of water quality issues within the Occoquan Reservoir (Metcalf and Eddy, Inc., 1970) which led to the development of a management plan for the Occoquan included one recommendation to “provide highest treatment technically achievable; discharge reclaimed water to the Occoquan Watershed; and limit basin population to 100,000.”

The quantity and quality of ground water in Prince William County varies across the county depending on the geologic and hydrogeologic group you are in. Generally speaking, the groundwater in the county is recharged in elevated areas and discharges to streams and estuaries. However, the paths and duration of groundwater flow are different between consolidated rocks and unconsolidated material. 

In the area of the proposed ORPA is beyond the Culpeper Basin in the Piedmont region. This area of the ORPA is primarily hydrogeologic group D composed of igneous rock formations with areas of hydrogeologic group E that transition at the bounds of the ORPA to group E and then to the Coastal Plain.

Hydrogeologic group D is located within the Piedmont formation and consists of three igneous plutons in the eastern part of Prince William County: the Goldvein, Lake Jackson, and Occoquan Plutons. Rocks within hydrogeologic group D tend to have moderate water-bearing potential and ground-water storage is predominantly in the overburden, which is the soils above the bedrock. Wells in this area are most susceptible to drought and tend to be slightly acidic. The igneous rocks have subhorizontal sheeting and near vertical joints overlain by thick overburden. Groundwater wells in the area tend to have yields range from 1.2 to 100 gal/min which has resulted in the development of homes with wells in the area due to the thickness of the water storing overburden.

Hydrogeologic group E is also in the Piedmont formation in the eastern part of the county, and consists of metasedimentary, metavolcanic, and other metamorphic rocks. Rocks within hydrogeologic group E tend to have poor water-bearing potential, and thin- to thick cover of overburden. Similar to the rocks of hydrogeologic group D, ground-water storage tends to be predominantly in the overburden. Some of the poorest yielding wells in Prince William County are located in this hydrogeologic group and can be as low a 0.25 gallons per minute, but can also reach upto 70 gallons per minute-, but tending towards the low end because of the thinness of the overburden beyond the limits of what is the proposed ORPA. Homes and businesses in this area have depended on public water supply due to the limitations on well development and that water comes from the Occoquan Reservoir.