Fly Ash Leachate Treatment
If you are running a power plant of any kind, when water hits your property, you own it. A power plant will generate various effluents including cooling tower blowdown, scrubber water, boiler blowdown, and even stormwater. Coal-fired power plants also generate a liquid leachate that comes from rainwater that percolates through piles of stored fly ash residue which is left over from combustion of the coal. Like stormwater, the fly ash leachate needs to be properly stored and eventually treated prior to discharge.
Storage ponds for fly ash leachate can be enormous and represent a big liability if something bad should happen. There have been many cases of accidental releases to the environment caused by Mother Nature or by aging infrastructure. In 2008, a berm failure caused a one billion gallon spill of fly ash leachate that cost $1 billion in remediation costs. In 2007, the EPA evaluated 17 fly ash leachate ponds in Wyoming at five power plants and found that 11 of these were 30 years old and 4 of them were at least 40 years old. It also found that 4 of these fly ash leachate ponds had no lining increasing the risk of groundwater contamination. In 2009, the EPA listed 44 fly ash leachate ponds that were high risk where accidental spills could occur. In total, journalists have identified 1500 fly ash leachate ponds in the United States with some of them as large as 1500 acres.
There really is no need to store all this water. Someday it will need to be treated anyway, especially when a coal-fired power plant closes. Since it has to be treated anyway someday, it would be better to treat this fly ash leachate as it is generated instead of storing it in large risky ponds that could end up being a big expense. Elimination of these storage ponds would also mean that the land area could be used for other more productive purposes.
The VSEP RO fly ash treatment system has been used many times at power plants and has also been used for treating flue gas scrubber water and cooling tower blowdown. The dissolved solids concentration in fly ash leachate can vary a great deal and the metals and pollutants will vary depending on the type of coal being used, but, in all cases, the VSEP is able to achieve very high recovery rates meaning that a much smaller evaporator can be used for final solids disposal. The VSEP is far less expensive to operate compared to an evaporator, so maximizing this recovery with a membrane system is very important.
New Logic was contacted to treat about 50 gpm of fly ash leachate with high recovery and producing < 200 mg/L sulfate. This fly ash leachate was fairly dilute with about 1% total solids and conductivity of about 10,000 µS. VSEP filtered this water with no pretreatment. The VSEP fly ash leachate treatment system was operated at 500 psi using a reverse osmosis (RO) membrane and achieved an average permeate flux rate of 28 gallons per square foot per day (GFD). The system recovered 93% of the volume as clean water permeate for discharge. While the fly ash leachate feed to the system measured 10,000 µS, the final treated VSEP permeate had a conductivity of only 365 µS and sulfates well below the requested limit. The final VSEP concentrate after a nearly 20x concentration had very high turbidity and precipitated suspended solids. New Logic has a new industry webpage dedicated to this application which can be found here: https://www.vsep.com/industries/fly-ash-leachate-treatment
The Challenge of Farming on Malta
Malta, located in the Mediterranean just south of Sicily is the 10th smallest country, but 9th with the highest population density. Malta produces only about 20% of its food needs and like many island countries, it has limited freshwater supplies. Malta faces many environmental problems including waste management, water scarcity, and habitat degradation due to urbanization. A study by Yale University of 180 countries ranked Malta last in general wastewater management. The island lacks any rivers or natural lakes. Groundwater and seawater desalination are used to provide drinking water. Overuse of groundwater for years has led to depletion and seawater intrusion raising the salinity of the available aquifer. The island has about 500,000 people living in just 316 square kilometers, which is about 1,500 people for every square kilometer. That doesn’t leave much room for farming or ranching. Pig farms are highly concentrated and disposal of the liquid manure is problematic.
Pig farming on the island is important for the economy and the government supports this industry. Since there is not enough land available for application, the typical method of disposal is to discharge pig waste to the local sewer. This is a violation of EU regulations and there has been some movement to change this practice. Also, in this case water is scarce and valuable. 85% of the island’s drinking water comes from seawater desalination which is energy intensive. The island imports all of its fuel to make power and this is expensive as well. So there is a need to treat the pig waste and also to recycle water. This makes it unique when it comes to manure projects that New Logic has done. Water is not normally considered as a benefit after the separation.
In 2018, in conjunction with the government of Malta, New Logic supplied pilot test equipment to a pig farm to demonstrate VSEP’s ability to make clean water from the pig waste. Disposal of the manure is a problem and it must be stored at the pig farm until it can be hauled to a sewer discharge point.
A Klass filter was used to remove solids larger than 100 microns. The resulting feed to the VSEP pilot unit had a conductivity of 24,600 µS. The VSEP pilot machine used a RO membrane to filter this effluent and removed 63% of the volume as RO permeate with a conductivity of 3,470 µS. A conventional spiral RO pilot was used to polish the VSEP permeate resulting in final treated water with 352 µS. Additional analytic testing was done and showed that with the two passes with RO, ammonia was reduced from 1,900 mg/L to 10 mg/L and potassium was reduced from 2,050 mg/L to < 10 mg/L. The same problem occurs for cow farms. After the pig manure was tested, a quick test on cow manure was completed showing water recovery of 77%. The farmer and the government observers considered the pilot a success and were amazed by the clean water that could be produced.
VSEP Used for Enzyme Extraction
Phosphorus is an essential mineral that plays a vital role in the body. It is a key component of bones, teeth, DNA, and RNA. Phosphorus is also essential for energy production, as it forms part of adenosine triphosphate (ATP), which is the primary energy carrier in cells. The recommended daily intake for humans is 700 mg per day. Phosphorus is found in meat and dairy products and in nuts and grains. However, phosphorus found in plants is in a form that is less absorbable. For this reason, herbivores like cows may not get sufficient amounts of this nutrient.
Plants store phosphorus in the form of phytic acid which contains six phosphate groups. When plants are consumed, this form of phosphorus is not digestible and would be excreted. Plants contain an enzyme, phytase, that will hydrolyze phytic acid to liberate the phosphorus so that it can be used as a nutrient. Phytase is added to animal feed as a supplement to help cow and livestock digest their food to make better use of the nutrients. This can also help to reduce the environmental impact of too much phosphorus in the manure.
Phytase is normally produced using microbiological fermentation and this can be expensive. One alternative method that was explored using VSEP was filtration of plant juice from Alfalfa. The liquid is extracted from the plant fiber, but this will have low concentrations of phytase and volume reduction would improve the economics of processing. The molecular weight of Phytase is estimated to be about 50,000 Daltons (Da). So work has been done using a 10,000 Da ultrafiltration membrane. Previous work was done using conventional UF membranes, but this juice starting at about 10% solids contains proteins and other organic materials making it viscous and prone to fouling of membranes.
More recent work was done using the dynamic VSEP membrane that employs torsional oscillation of the membrane to limit fouling and blocking of the membrane. The test work found that the VSEP performed well and was able to concentrate the juice to 20% solids which was near the point it was a semi-liquid. The report found that VSEP with a 10k Da UF membrane had a much more stable flow rate compared to more open membranes when used in a conventional system.
The Landfill PFAS Dilemma
The fluorinated chemicals known as PFAS are only recently getting attention. They have been used for decades and have now migrated throughout the environment and can be found everywhere. You are likely ingesting PFAS that come from your tea bags. PFAS has been detected in rainwater. By ingesting PFAS, this will end up in your blood and can take years to be purged. The health effects are not fully understood. Landfills accept waste and in the process receive all sorts of leachable PFAS materials. This ends up in the leachate collected at the liner of the landfill cell which is pumped out. This has historically been discharged to local municipal sewage treatment plants where it is diluted with municipal sewage and then discharged into the environment. The EPA is currently crafting new rules for treatment of leachate that specifically target PFAS chemicals. Landfills will be required to install on-site treatment equipment.
The PFAS problem extends beyond just leachate. The risk of contamination of groundwater, surface water, and nearby waterways represents a new and unknown liability for landfill operators. Virtually all landfills will have PFAS in their leachate. One landfill in North Carolina was receiving PFAS contaminated sludge from a Chemours facility in Fayetteville. In June 2023, the North Carolina Department of Environment mandated PFAS testing for all state landfills. Following testing at this landfill, elevated levels of PFAS were found in the leachate, groundwater, and surface water. Elevated levels were also found in surface waters downstream of the landfill indicating that the chemicals were migrating offsite. The landfill intercepts groundwater before it goes through the facility and then had been discharging this water into nearby waterways. Testing confirmed that this water was contaminated and discharge of this water was sending PFAS offsite.
31 private wells were tested. Six of these, located near the landfill showed elevated levels and these homes have been receiving bottled water for drinking. Other homes further out have had detectable levels as well. The boundary of the plume has not yet been confirmed. The landfill has been required to install treatment equipment for this intercepted groundwater and achieve a 50% reduction in PFAS within 2 weeks and 90% reduction by April 14th. They are also required to get a discharge permit and comply with state water quality standards.
This illustrates the challenge landfills will have with the new PFAS regulations. They need to not only consider the treatment of the leachate, but any water above or below ground that exists on the landfill property. The EPA is also considering whether to classify PFAS as a hazardous substance like asbestos which would entail a whole new set of requirements for the landfill. This is a new area of liability that came out of nowhere for landfill operators.
VSEP – The Solubility Rule Breaker
Agitation influences nucleation because it alters the physical and chemical environment where nuclei form. This nucleation can be solids precipitating when the solubility limit is reached. There are many people in the industry who are experts in conventional spiral membrane systems. They know that solubility limits cannot be exceeded or scale will form on the membrane due to crystallization of sparingly soluble salts. Crossflow is used to create agitation or shear in these systems, but it is not enough to prevent scaling. People have learned this rule and many mistakenly apply it to all membranes. However, the effects of agitation can completely negate this rule. VSEP uses this to allow for RO filtration of supersaturated solutions where the VSEP is actually working like a membrane crystallizer.
This can be difficult for people to picture and many membrane experts still can’t see how VSEP can do this. One perfect example is a pot of boiling water. The air bubbles propagate from a nucleation site on the wall of the pot. But as soon as you start to stir this pot, the air bubbles will stop forming. Another example is how ice will form at the banks of a creek, but not in the center where the water is flowing. Agitation can be measured by something called the rate of shear. The unit of measuring this is referred to as inverse seconds-1. This is simply a measurement of how quickly adjacent layers of a fluid are moving relative to each other. It is like a velocity gradient where fluid layers are sliding past each other at different rates.
The greater the shear, the more inhibited nucleation will be:
Low Shear < 10 inverse seconds-1 – Minimal disruption of clusters, nucleation occurs freely in localized supersaturated zones.
Moderate Shear 10-100 inverse seconds-1 – Breaks up weak nuclei, promotes uniform supersaturation, results in fewer nucleation sites and larger crystals.
High Shear 100-1000 inverse seconds-1 – Aggressive cluster breakup, inhibits nucleation almost entirely, favors crystal growth on existing seed crystals, causes secondary nucleation on fragmented crystals.
The VSEP system generates 75,000 inverse seconds-1 of shear, far greater than any other kind of membrane technique for generating agitation or shear. In the VSEP, the rate of shear is the highest at the membrane surface and so it does not offer nucleation sites. Away from the membrane in the bulk flow where the rate of shear has decayed, clusters of crystals and suspended solids offer very attractive nucleation sites and this is where precipitation will occur since the thermodynamics are much more favorable.
In a calm supersaturated solution with no shear, crystallization would happen quickly as in the boiling pot. When shear is present, fewer nucleation sites are available and precipitation takes longer. Calcium sulfate and silica can take minutes or even hours to crystallize under optimum conditions. Since the incredible shear of the VSEP delays and inhibits immediate crystal formation and because the fluid passes through the VSEP filter in less than 2 minutes, VSEP is able to operate freely with very concentrated brines and is not susceptible to scaling of the membrane.
Energy Diversity – Why it Matters
The world is changing fast. It has been 140 years since electricity was first commercialized, 75 years since the first commercial computer, and only 30 years since the internet was widely available. In a very short time, all of civilization now depends on the flow of electrons through copper wires. During the Christmas weekend in 2022, an extratropical cyclone known as Storm Elliott created frigid winter temperatures and resulted in record electricity demand. 60 people died from storm-related causes.
In February 2023, Energy Ventures Analysis prepared a report on the grid functions during Storm Elliott. It summarized how power companies dealt with the record load demand and how the grid functioned during the frigid winter storm. Cold weather can affect power production. During the frigid storm, natural gas production in Appalachia dropped by 25% due to well freeze-offs and equipment failures. In the Southeast, natural gas demand for home heating surged. Then gas pipeline pressure became too low to safely operate power plants and this caused many to shut down.
As the power demand surged during the storm, every bit of spare capacity was needed. Gas-fired power plants struggled to keep operating. The one source of energy that was able to ramp up was coal-fired power to meet demand. Coal plants store the fuel source on-site and electricity production can be ramped up at any time without concern about the availability of fuel.
As natural gas demand in Kentucky spiked during Winter Storm Elliott, pressure along one of the primary natural gas supply pipelines, Texas Eastern, dropped unexpectedly. 900 MW of LG&E/KU natural gas-fired generation suddenly came offline, resulting in rolling blackouts for over 53,000 LG&E/KU customers. This was the first time in LG&E/KU history that the utility had to implement rolling blackouts for its customers.
Power generation that can be increased to match demand is known as dispatchable power. Power from installed wind and solar plants cannot be increased on demand. Gas or oil-fired power plants can produce dispatchable power as long as there is fuel available. Over the last decade, dispatchable power from coal plants has been taken offline and is being replaced with power sources that cannot be increased. The planned removal of 82 GW of coal power by the end of the decade means there is not enough power for another Storm Elliott event.
With modern technology, coal can be a clean source of energy and there are compelling reasons to keep this source in the energy mix. Modern coal-fired power plants now use flue gas scrubbers to remove pollutants from their air emissions. The wastewater from air scrubbing can be cleaned effectively to make it cleaner than water it would be discharged to. The EPA tightly regulates this kind of effluent and has listed the VSEP vibratory membrane RO filtration system as a best available technology for treatment of flue gas desulfurization (FGD) effluent. The VSEP system employs torsional oscillation of the membrane which allows for high concentration levels exceeding the solubility limits of calcium sulfate. At the same time, the RO membrane produces a filtrate with very low levels of arsenic, mercury, and selenium, well below the EPA effluent limits.
Putting Off Today What You Might Not Do Tomorrow
There are only a few places in the world where Phosphate ore can be found that is viable for mining. These places include Morocco, Jordan, and Florida. The wet-process manufacture of phosphoric acid from this ore to make fertilizer requires a large volume of process water. After processing, the water is stored in very large ponds known as phosphogypsum stacks, known as gyp stacks. Careful water balance management must be used to operate the system at par or with a negative water balance. However, during rainy periods there is a risk of an uncontrolled discharge of the untreated process water. Leaks and issues with these decades-old storage ponds have occurred several times. Ocean dumping of the raw wastewater has been done during emergencies.
Before mine closure, something will need to be done with this water. For now, the plan is to just store it indefinitely. The volume of water that will need treatment is in the billions of gallons. The pond water also has a very low pH and contains a mixture of regulated inorganic chemicals that cannot be discharged without treatment. In addition, trace levels of radium and other radioactive nuclei mean alternative uses other than disposal are not practical and have not been approved by the EPA.
In 2004, New Logic demonstrated its VSEP technology under the direction of the Florida Institute of Phosphate Research, (FIPR), an industry organization. There were several objectives in looking at the VSEP as a treatment option including:
- Water balance management
- Solution for plant closures
- Emergency remediation
- Phosphorus recovery
A long-term pilot study was set up near Lakeland, Florida to measure the VSEP performance. The pond water used for testing had a pH of 3 and had 9400 mg/L of total dissolved solids. The water had a slight yellow color and some turbidity, but was pretty clear. After extensive testing, the VSEP system with a RO membrane installed recovered an average of 65% of the volume as clean water and produced a very dark thick concentrate material with a lot of precipitated solids. Because of the vibration of the membrane and the resulting shear at the membrane surface, VSEP can be used as a crystallizer and will actually precipitate solids without scaling or fouling during filtration.
VSEP Pilot Testing
Pilot testing is a very important part of the decision-making process when it comes to full-scale implementation. Not all equipment can be effectively pilot tested. Companies that make evaporation technology might have a pilot unit available, but it will be large and expensive to rent. Often they will suggest a “boil-down” test where a small amount of liquid is supplied to their lab and boiled to remove water to see how the material behaves. Then projections are made from this work.
Biological treatment systems are very hard to pilot test. These do not scale up well and it can take 30 days or more for bacteria colonies to get established and then show some results. Chemical treatment systems are also done at a small scale and will not scale-up proportionally. Spiral membrane companies often just rely on computer simulations and stick to pretty clean water applications.
For these reasons, pilot testing is fraught with risk, which is exactly what the client is trying to avoid by pilot testing. However, VSEP can be used very effectively during pilot testing. After 38 years of conducting thousands of pilot tests, New Logic has vast experience in properly conducting a test to simulate full-scale operation. Unlike other technologies, a membrane will scale-up accurately. If one square foot of membrane can produce 20 gallons of filtrate per day, then you can be sure that 1000 square feet will produce 1,000x the volume produced in the pilot. Membrane separation can also accurately be reproduced. If the membrane is rejecting 90% of the ammonia, you can be sure a larger amount of membrane will do the same.
New Logic has an excellent record of system sizing based on pilot testing. New Logic also has a fleet of pilot machines that can be rented and deployed quickly. These machines for rent include the LP VSEP which is used most of the time for onsite pilot studies. But, full-scale systems are also available for larger flow rates. There are five different size VSEP units that can be used for pilot testing. These will range in flow rates from 0.5 gpm to 40 gpm. No matter what flow rate is used for pilot testing, the gallons per square foot per day is reproducible and can accurately be used for estimating full-scale system sizing.
Before shipping, the pilot unit is fitted with the optimum membrane. The pilot shipment will include all of the necessary hoses and supplies to run the test. Pilot machines can be equipped to accept any three-phase voltage that is available. New Logic will also dispatch a field engineer to get the equipment commissioned and then to complete training of onsite staff for operation. Typically 4-8 weeks is enough time to collect all the data needed.
VSEP can Solve the Nitrogen Problem
Farming and ranching are relatively new in California compared to other places in the world. There has only been about 150 years of this activity in the Central Valley of California. And it has been only recently since addition of modern fertilizers to the soil. In parts of Belgium, manure has been land applied for many hundreds of years, and the soil is overfertilized causing many issues with greenhouse gases and water quality. When Nitrogen is applied to the land, some of it can be converted to nitrous oxide (laughing gas) which is a greenhouse gas. Some nitrogen will end up in the drinking water aquifer and some will run off as nitrates into surface water. To limit this, the EU developed the Nitrate Directive which limits land application of nitrogen to 170 kg/hectare (375 lbs/ 2.5 acres) per year. If you are a pig farmer or dairy operator, this limits the amount of manure that you can land apply and would limit the number of animals a farm can possess.
In California, Wisconsin, and elsewhere, only now are the effects of too much nitrogen being seen. There are no limits that I am aware of for nitrogen application, but people are aware of the issue and are taking action to mitigate this. The California Central Valley Water Board is collaborating with businesses, government, and community organizations to address the Nitrate and salinity issues. Dairies and livestock farmers are aware of the problem and the potential liability.
Many residents in rural areas rely on well water for drinking water. A program is offered in the California valley to provide free well water testing in 15 groundwater basins. Since this began, 3,200 wells have been tested and 2,000 households were found to be affected. As a result, more than 4.3 million gallons of replacement drinking water has been provided at bottle-filling stations throughout the valley. While the valley relies on agriculture for its economy, people also need to have safe water for drinking.
Dairy farms are adopting new technologies and methods including lined manure lagoons and better manure management practices. Hauling and land applying manure can be expensive, especially if there are long distances involved. Many dairies are using anaerobic digestion to treat the liquid manure and make biogas. However, this will not remove nitrogen.
This has been what has driven New Logic’s VSEP business in Europe where the problem is much more acute. Only recently, people are realizing there is a problem in the United States and more needs to be done to even distribute the manure and nutrients so that over-fertilization does not occur. A typical VSEP RO system can volume reduce digested or raw manure by 70-80%. Hauling costs are reduced by a similar amount. For even more savings, drying the concentrate from the VSEP can result in a pelletized or bagged fertilizer product that can be sold.
Water Wars in Western States
The Colorado River is born in the high mountains of Colorado near Granby and travels south crossing the border into Mexico emptying into the Gulf of California near Baja. The river travels from Colorado through Utah, then Arizona and the Grand Canyon, and then makes the southern border of Nevada and California. The San Juan River comes out of New Mexico to feed the sort of mighty Colorado. Further north, the Green River and Big Sandy come down from Wyoming to merge into Colorado. The Colorado is the 5th longest river in the U.S. at nearly 1,500 miles long.
These seven states were originally allocated 15 million acre-feet (maf)/year from the Colorado River. This was split evenly between the four upper basin states: Colorado, Utah, Wyoming, and New Mexico, and the three lower basin states: California, Arizona, and Nevada. A separate agreement allocates 1.5 maf/yr to Mexico. The flow of the river has been declining in recent years and this is now causing problems. There are two large hydroelectric power systems on the river. One located at Lake Powell in Utah and one at Lake Mead in Nevada. Lake levels are approaching dangerous levels where hydroelectric power could be shut off.
The Bureau of Reclamation has established a 3-tier system of action based on lake levels at Powell and Mead. Tier one restrictions are in place since 2022 when the elevation of Lake Mead hit 1,055 feet. The upper basin states are required to divert water from other reservoirs to keep Lake Powell above 3,525 feet which is only 35 feet above minimum level to ensure hydropower. Lake Mead at 1,055 feet is about 100 feet above the minimum power pool level where no power can be made. This would black out Las Vegas. The dead pool level is where no water would flow out of the Hoover Dam and this level is 895 feet.
To prevent these power plants from becoming non-operational, restrictions are in place. The upper basin states do not have to cut water withdrawals but can make voluntary cuts and divert water from other reservoirs. Two of the three lower basin states, Nevada and Arizona have required cuts. California has no required cut in water consumption. Arizona has been required to make nearly all of the water reductions.
The federal government prefers that the states all agree on allocations. They have given them until February 14th to reach an agreement or the Bureau of Reclamation will set the rules. The states have been deadlocked for two years. Representatives of the states met in January to try to reach a plan. Nevada’s representative, John Entsminger, stated that every representative had the same message during the negotiations. They all talked about all the great things they are doing, how impossible it is to do more, and why other states should do more. So no agreement was reached and one may not be by February 14th.
The Colorado Rivers headwaters saw a weak snowpack last winter and the flow into the river was only 56% of normal last year. The current elevation of Lake Powell is only 3539 feet, dangerously close to the minimum 3525 required level. Lake levels drop in the summer when there is no rain and projections for 2026 are not good. There is a real concern that the hydroelectric power at Lake Powell could be shut down by October.
The Glen Canyon Dam at Lake Powell has installed power capacity of 1.32 GW. The Hoover Dam at Lake Mead has 2.08 GW of installed power which is enough to supply 1.3 million homes. The power output falls as the lake level drops. A 20-foot drop in Lake Mead would result in a 70% power capacity loss. As of January 4th, the snowpack in the western region is only 28% of normal which is the lowest level since 2001.
The states may not be able to agree on a fair allotment plan and the Bureau of Reclamation may need to step in and mandate more restrictions. The current population of California is nearly 40 million people who live in a desert. The population was half that much in 1970. The greater Los Angeles area that includes five counties has 21 million people. Many of them have backyard pools and nice green lawns in a place where only cactus used to grow. Arizona’s population is also increasing. Even if the Colorado River’s flow remained the same it will not be enough for expanding water needs. We use more water today than we did in 1928. A comprehensive solution needs to be completed. The solution may involve an all of the above strategy. One solution that has not received much notice is water recycling. Instead of using water once and throwing it away, treating wastewater prior to discharge and recycling clean water would be an excellent way to help solve the problem.
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