Closure of the POTW Pathway for Landfill Leachate
For decades, hauling landfill leachate to publicly owned treatment works (POTWs) has been the default disposal strategy across North America. That model is now rapidly changing, not because the EPA has finalized regulations, but because of a growing unease among municipal wastewater operators that they are inheriting a liability they cannot afford to carry. Across the U.S., wastewater plants are tightening acceptance policies for landfill leachate, with many reducing volumes, imposing new conditions, or refusing loads outright. What was once a steady revenue stream for POTWs is now viewed as a high-risk influent category, particularly as PFAS moves from an emerging contaminant to a regulated one. One of the clearest examples comes from Vermont, where the Montpelier wastewater treatment plant is the last remaining facility in the state accepting leachate. Even there, acceptance is no longer unconditional. The city now requires that leachate be pretreated to remove approximately 80% of PFAS before it can be discharged and demands verification prior to shipment. This has transformed the plant from a passive receiver into an active compliance gatekeeper.
Similar pressures are emerging elsewhere. In New York, the Albany County Water Purification District continues to accept landfill leachate, but with increasing scrutiny and political pressure. Local officials and stakeholders have raised concerns about PFAS accumulation in biosolids and long-term liability, with calls to halt leachate acceptance until clearer controls are in place. This type of pressure, regulatory, public, and financial, often precedes restrictions or rejection.
Beyond individual facilities, industry-wide case studies confirm the trend. POTWs are increasingly imposing PFAS-related conditions, dramatically increasing tipping fees, or declining to accept leachate altogether. In some cases, operators report abrupt notifications that their leachate will no longer be accepted unless pretreated, effectively shutting down traditional disposal pathways. What is notable is that most of these actions are not yet federally mandated. Instead, they reflect a proactive risk management response by POTWs. Typical municipal wastewater treatment plants are not effective at removing PFAS; the compounds pass through to effluent or concentrate in biosolids. As drinking water standards tighten and biosolids disposal becomes more constrained, POTWs are increasingly held accountable for contaminants leaving their systems. In that context, accepting landfill leachate rich in PFAS becomes a direct liability exposure. The safest solution, from the POTW perspective, is to limit or eliminate the source.
The implications for landfill operators are immediate and consequential. The traditional model: collect, haul, and discharge, cannot be relied upon going forward. Access to POTWs is becoming uncertain, more expensive, and contingent on meeting pretreatment requirements that many landfills are not currently equipped to achieve. In effect, the responsibility for PFAS management is shifting upstream. Landfills that once depended on municipal systems to “finish the job” are now being forced to consider on-site treatment as a baseline operational requirement rather than a future contingency. The door to POTW discharge is not yet closed, but it is narrowing quickly. Those who plan for that reality now will retain operational control. Those who do not risk finding themselves with leachate and nowhere left to send it.
What Oysters Can Teach Us About Membranes: Lessons in Non‑Fouling Filtration
Walk along any healthy shoreline and you’ll find millions of quiet water-treatment plants at work. Oysters, clams, and mussels sit motionless, pulling enormous volumes of water across their gills, extracting what they need, and releasing the rest, day after day, without fouling, plugging, or chemical cleaning. A single oyster can filter 50 gallons per day. A mussel bed can filter an entire bay’s water in a matter of days. These efficient filters that never need cleaning can improve water clarity, reduce phytoplankton blooms, and enhance light penetration for seagrasses. They do this using a filtration strategy that predates modern engineering by hundreds of millions of years, and it’s worth asking: what can our membrane systems learn from them?
At first glance, biological filtration and membrane filtration seem similar. Both rely on selective separation of particles from water. But the similarity ends quickly. Most engineered membranes depend on static pore sizes. If a particle is larger, it’s rejected; if smaller, it passes. Fouling is an unavoidable consequence. The membrane face becomes a graveyard of everything the process doesn’t want, and operators are left fighting buildup with back-pulses, chemicals, pressure, and downtime.
Biological organisms take a very different approach. Bivalve mollusks do not rely on rigid, size-based sieving alone. Their gill structures operate under smooth, laminar flow and are coated with living mucus layers that are constantly renewed. More importantly, they choose. Particles are not merely trapped because they are large enough, they are evaluated. Nutritious plankton is transported inward. Inert silt and irritants are rejected and expelled as pseudofeces before they ever clog the system. This selectivity is not engineered by specification sheets; it is the result of evolutionary optimization to capture only what is worth the energy to consume.
Flow plays a critical role. The water motion across a bivalve’s gills is highly controlled, laminar, and continuously shearing at the surface. This shear prevents accumulation and keeps the filtration interface clean. In other words, bivalves are not passive filters, they are dynamic, self-cleaning systems where fouling is biologically incompatible with survival.
Traditional membrane systems struggle because they violate this principle. Low shear at the membrane surface allows particles to settle, adhere, and compact. Fouling is not an anomaly, it is the natural outcome. This is where newer high-shear membrane technologies begin to come close to the superiority of mollusk filtration.
By generating extremely high shear directly at the membrane surface, while maintaining largely laminar bulk flow, VSEP disrupts boundary layers and prevents solids from establishing a foothold. The membrane is no longer a static wall waiting to foul, but an active interface where shear continuously works against deposition. While VSEP cannot “decide” which particles are nutritious, it mimics one of biology’s most powerful anti-fouling tools: sustained, localized shear where filtration actually occurs.
Nature reminds us that the most effective filtration systems are not those with the smallest pores, but those that manage flow, selectivity, and surface renewal. As membrane technology continues to evolve, the closer it comes to these biological principles, the more robust, and resilient, it becomes.
The Hidden Value of Coal Byproducts
Coal-fired power plants are often viewed primarily through an environmental lens. But there is much more to the story and coal plant benefits are often overlooked. First, these facilities transform what would otherwise be waste streams into valuable, marketable products. In many modern plants, very little is discarded. Instead, processes have evolved into surprisingly efficient, closed-loop systems that extract value at multiple stages. One of the most well-known byproducts of coal combustion is fly ash, a fine, powdery material carried with flue gas. Fly ash has become an important industrial commodity. It is widely used as a supplementary cementitious material in concrete. This not only provides a beneficial reuse pathway but also lowers the carbon footprint of construction materials.
Not often considered is the production of synthetic gypsum through flue gas desulfurization (FGD) systems. These systems are installed to remove sulfur dioxide (SO₂) from exhaust gases. The chemistry is elegant: limestone slurry reacts with SO₂ to form calcium sulfite, which is then oxidized to produce calcium sulfate dihydrate, chemically identical to natural gypsum. The result is a high-quality material that is directly suitable for manufacturing wallboard.
In fact, FGD gypsum now supplies roughly one-third of the raw material used in drywall production in markets like the United States. In some regions, it has become the dominant feedstock due to its proximity to manufacturing plants and consistent quality. Quality is a critical differentiator. FGD gypsum is typically very pure, as it is formed in a controlled chemical environment. By contrast, mined gypsum deposits can contain impurities such as clay, sand, and other minerals, requiring additional processing or limiting their applications. This consistency gives synthetic gypsum an advantage in wallboard manufacturing, where uniformity is essential.
Also, coal-fired plants retain certain operational strengths. Unlike natural gas, which can be offline during extreme cold events, coal can be stored on site in large quantities. This makes coal plants uniquely capable of delivering dispatchable power during winter storms, providing a layer of grid resilience that is underappreciated. What makes these plants particularly interesting is how integrated and efficient they have become. With technologies like VSEP, wastewater streams from FGD and related processes can be treated and recycled. This allows plants to recover and reuse water, further minimizing environmental impact. When combined with the beneficial use of fly ash and gypsum, the result is a system where every output stream is repurposed.
Rather than viewing coal combustion just as a source of emissions, modern engineering demonstrates how process integration can convert byproducts into valuable resources. While coal combustion has a carbon footprint, gypsum mining does also and gypsum produced from FGD water helps to offset the impact of mining. It is interesting to think that the drywall in your home may have come from flue gases in a power plant. In this light, coal-fired power plants, while evolving under environmental pressures, also represent a compelling example of industrial symbiosis, where nothing is wasted and every stream has a purpose.
Reducing LNG Dependence: Why Local Biogas Matters for South Korea
South Korea is one of the world’s largest importers of liquefied natural gas (LNG). In fact, Korea imports nearly all of its fossil fuels, including natural gas, relying on seaborne LNG deliveries to power its industries, generate electricity, and heat homes. This dependence has made Korea a top-three LNG importer globally, alongside Japan and China, underscoring both the scale of its energy demand and its exposure to global supply chains. While LNG has been a reliable energy source for decades, recent geopolitical instability, sanctions, and shipping disruptions have highlighted the vulnerabilities inherent in long-distance fuel supply chains. Conflicts affecting major gas-producing regions, combined with volatility in shipping, have underscored the need for countries like South Korea to diversify and localize their energy strategies. Disruptions can have immediate consequences for energy security and economic stability.
This is where biogas presents a compelling opportunity. Produced from organic waste streams such as livestock manure, food waste, and industrial byproducts, biogas offers a renewable, locally generated methane source that can directly offset imported natural gas. For heavily import-dependent nations, this approach delivers not only environmental benefits but also enhanced energy resilience. By transforming waste into energy, countries can reduce exposure to international fuel markets. South Korea is particularly well-positioned to expand its biogas footprint. With high population density, substantial food waste generation, and advanced infrastructure, the country already possesses the raw inputs and logistics needed for scalable anaerobic digestion projects. Government support for circular economy initiatives and low-carbon energy further strengthens the case for domestic gas production through biogas.
However, the success of biogas depends not only on gas production but also on effective management of the effluent. New Logic has been at the forefront of this segment, providing anaerobic digester effluent treatment systems using its VSEP reverse osmosis technology for decades in Korea and elsewhere. These systems enable high-efficiency effluent treatment, helping operators meet stringent discharge requirements while maximizing water reuse.
An of this expertise in action is New Logic’s collaboration with Tium Eco & Energy in South Korea. Five years ago, New Logic installed a biogas effluent treatment system for one of Tium’s projects. That installation demonstrated the effectiveness of combining anaerobic digestion with advanced membrane treatment to create a sustainable, closed-loop solution. Building on that success, New Logic has engaged with the CEO of Tium Eco & Energy to negotiate the deployment of a second VSEP system for a new biogas project currently under development. Importantly, this project is backed by the Korean government, reflecting national-level recognition of the role biogas can play in strengthening domestic energy production and reducing reliance on imported LNG.
As South Korea navigates an increasingly uncertain global energy landscape, local solutions like biogas are no longer just environmentally attractive, they are strategically essential. By investing in technologies that convert waste into reliable energy and ensure efficient resource recovery, the country can move toward a more resilient, self-sufficient energy future.
The Vanishing Lakes of the Southwest
When I was a kid, summer meant piling into the car and heading north with my family to Lake Pillsbury in Lake County, California. It was one of those places that felt timeless, cool mornings on the water, the hum of a small fishing boat, campfires burning low as the sun dropped behind the hills. For many families, Lake Pillsbury wasn’t just a reservoir. It was a destination, a place to get away from the city, a piece of California. Now, it may be gone.
The hydroelectric Scott Dam built in 1922 created Lake Pillsbury at the headwaters of the Eel River. Under current proposals by the owner PG&E to remove the dam, the lake would be drained and the Eel River would once again flow freely through the valley with no retention and no lake. The suggested goal is to restore the Eel river to its natural condition and reopen hundreds of miles of habitat to salmon and steelhead, and create what could become the longest free‑flowing river system in the state. In April, a buyer for the project emerged and so the plan is still not final.
The Scott Dam has created a lake habitat but has blocked natural fish migration. Removing the dam recreates new cold-water spawning habitat for salmon and steelhead fish. But the story doesn’t end there. Because Lake Pillsbury is not just a dammed river, it has become an ecosystem in its own right. Over the last hundred years, lake trout fisheries have developed. Amphibians, birds, and mammals have adapted to the lake environment. Waterfowl use it as habitat. Campgrounds, marinas, and local communities depend on it. Vacation homes have been built around the lake. Remove the dam, and that lake-based ecosystem disappears along with it.
Lake Pillsbury also plays a functional role in flood control and water management. It stores winter runoff, water that falls during California’s increasingly intense rainy season, and releases it gradually in the summer months. That stored water provides irrigation water for local agriculture and supports both the Eel River downstream and the Russian River system serving 600,000 people through a diversion tunnel. Without the dam, that storage capacity is lost. Water that once could be held back for dry months instead flows out to the ocean in real time. The proposed removal of lower Cape Horn Dam complicates things further. Today, that facility diverts tens of thousands of acre‑feet of water each year from the Eel River into the Russian River watershed, supporting agriculture and ecosystems downstream. This action would reduce California’s stored water capacity.
California authorities have estimated that 9 million acre feet (MAF) of additional water supply needs to be added by 2040. Probably not accounted for are the vast reductions in lakes and reservoirs in the Southwest. The volumes of the major lakes have had huge declines including Lake Powell reduced by 77%, Lake Mead by 67%, Walker Lake by 90%, Salt Lake by 70%, and the Salton Sea by 50%. Aquifers face a similar dire situation. The Central Valley aquifer system has lost 60 MAF of volume since 1960. It is estimated by satellite images that the aquifer is losing 7.5 MAF per year during drought conditions. Yet despite these water losses, California is planning to add only 9 MAF of new water source without building any reservoirs. 9 MAF is the size of two Lake Shastas.
California is moving toward removing man’s footprint on rivers reducing water storage at the same time it is acknowledging a growing need for additional water storage. Dam removal restores natural ecosystems that have been changed. It also eliminates lake ecosystems that people, wildlife, and economies have come to depend on. That change will mean renewal for some species, loss for others, and adjustment for the communities in between. It is not a simple story.
Sarajevo’s Landfill Moves Toward EU‑Level Leachate Management
Across Southeastern Europe, the push toward European Union environmental compliance is reshaping how legacy landfills handle one of their most difficult challenges: leachate. Nowhere is that transition more visible than at the Smiljevići landfill in Sarajevo, where operators are working to move from basic containment toward modern treatment solutions. Under EU-aligned environmental frameworks, landfills are expected to collect, treat, and safely discharge leachate, rather than relying on natural dilution. Bosnia and Herzegovina has formally adopted this direction, with landfill projects emphasizing that leachate must be treated prior to discharge to meet environmental standards.
It is important to recognize that the Sarajevo landfill is not an uncontrolled dump. The site incorporates several modern landfill management features, including: compacted and layered waste placement, daily cover practices, surface water diversion, and engineered leachate collection and drainage systems. These systems reduce infiltration and direct leachate into a network of collectors rather than allowing it to freely migrate into soil and groundwater.
However, while collection infrastructure is in place, full-scale treatment has not historically kept pace. Studies of the site consistently highlight that leachate management has been a long-standing unresolved issue, with no stable, comprehensive treatment plant operating at full scale. Effluent is ultimately discharged into the local stream network, where dilution and biodegradation provide the primary “treatment”. Local environmental studies note that nearby streams have been expected to absorb biodegradable loads, underscoring the reliance on receiving-water assimilation rather than engineered treatment. This approach, common in many developing regions, falls short of EU expectations for controlled, high-quality discharge.
Recognizing the gap, Sarajevo has begun moving toward compliance. A membrane bioreactor (MBR) pilot plant has been installed and tested on-site, demonstrating the feasibility of biological treatment combined with membrane separation. MBR technology offers strong removal of organic matter and ammonia, but it can be capital‑intensive and operationally complex, particularly for variable landfill leachate streams.
In parallel with these efforts, New Logic has proposed a more robust membrane solution based on its VSEP reverse osmosis technology. The proposed system includes six VSEP modules to treat 350 m³/day with 80% volume reduction. By mechanically vibrating the membrane surface to minimize fouling, VSEP is designed to handle the high solids, scaling, and variability challenges typical of landfill leachate. Compared with a full MBR installation, the VSEP approach is projected to deliver lower overall lifecycle costs, while producing a high-quality permeate suitable for compliant discharge. The situation in Sarajevo reflects a broader reality: many landfills in developing or transition economies are technically “controlled,” yet still lack sustainable leachate treatment and disposal systems. Collection infrastructure is often in place, but complete treatment, especially that meeting EU standards, are still under development.
When Rain Becomes Regulated Water: Why Stormwater Treatment Matters
On the surface, stormwater seems simple. Rain falls, flows across land, and eventually makes its way to a stream or river. But at industrial facilities, that same rain can pick up oils, metals, sediment, and other contaminants. Once that happens, stormwater is no longer just rain, it becomes a regulated effluent under federal law. Stormwater is governed by the Clean Water Act through the National Pollutant Discharge Elimination System (NPDES). Importantly, the regulation does not focus on the water itself, but on what the water contacts and where it ultimately flows. When rain or snowmelt comes into contact with industrial materials, such as raw materials, fuels, or waste, it is defined as “stormwater associated with industrial activity” and must be managed.
The rules apply to a wide range of industries including manufacturing, mining, landfills, recycling facilities, transportation yards, and power plants. These facilities typically operate under a general stormwater permit, which requires the development of a Stormwater Pollution Prevention Plan (SWPPP), implementation of best management practices, and, in many cases, monitoring and reporting.
For many people, the surprising part is that regulation applies even if a facility does not generate traditional wastewater. A well-known example is the Red Dog Mine in Alaska. The site does not produce any wastewater, yet it must manage the water that falls on its property. Once precipitation contacts the ground, the facility effectively “owns” that water and is responsible for ensuring it is properly discharged. Another common misconception is that facilities connected to city storm drains are exempt. In reality, the opposite is true. Discharges to municipal separate storm sewer systems (MS4s) are also regulated, and both the municipality and the industrial site must meet permit conditions.
In many cases, permit requirements can be met through prevention, covering materials, improving housekeeping, and minimizing exposure. However, for operations such as landfills or power plants, stormwater often becomes too contaminated for simple controls. When pollutant levels exceed regulatory benchmarks, treatment becomes necessary. This is where advanced technologies such as reverse osmosis come into play. VSEP (Vibratory Shear Enhanced Processing) membrane systems have been deployed at power plants and landfill sites where stormwater is collected alongside leachate or wastewater. These applications demand robust treatment capable of removing dissolved solids, metals, and other contaminants to meet stringent discharge or reuse requirements.
By treating stormwater through high-efficiency membrane systems, facilities can achieve consistent compliance while reducing overall water volumes. In many cases, this approach supports zero liquid discharge (ZLD) strategies or enables water reuse, turning a regulatory burden into an operational advantage. Stormwater regulation may begin with something as simple as rainfall, but its implications are far-reaching. As industries continue to operate under tighter environmental standards, technologies that can reliably manage and treat complex water streams will play an increasingly important role.
Today we Take Water Safety for Granted
In an age when a glass of water can be analyzed in minutes for bacteria, metals, and contaminants, it is easy to forget how uncertain and dangerous drinking water once was. For the pioneers who crossed the United States in the 1800s, water was one of the greatest threats along the trail. Wagon routes like the Oregon and California Trails often followed rivers, but even then, safety was never guaranteed. The same streams that sustained wagon trains also served as washing areas, livestock watering spots, and, tragically, informal waste disposal sites. Thousands of people and animals moved along these routes each season. By the time a later group reached the same water, it could be heavily contaminated, though it might still appear clear and inviting.
Pioneers relied heavily on guides or previous accounts in maps, but, when they encountered unfamiliar water sources, they relied on simple, sensory judgments. Clear, flowing water was usually preferred over cloudy or stagnant pools. If a stream ran over gravel and looked fresh, it was considered safer. They sniffed for foul odors and sometimes tasted cautiously. Surroundings mattered as well: lush vegetation suggested reliable groundwater, while white, crusty soil, common in parts of the Great Basin, warned of alkaline water that could sicken both people and livestock. But even clean looking water could be deadly.
Animals were sometimes used as indicators. If wildlife drank from a source, pioneers often assumed it might be safe. Unfortunately, this was a dangerous assumption. Animals can tolerate pathogens that humans cannot, and contaminated water could still attract thirsty herds. Some pioneers attempted basic water treatment. Muddy water might be left to settle so sediment would sink to the bottom, or strained through cloth. On occasion, water was boiled, but usually as part of cooking or coffee preparation rather than as a systematic health measure. Germ theory was not widely understood until later in the century, so these efforts were inconsistent at best.
Even with caution, disease was widespread. Waterborne illnesses such as dysentery, often called “the flux”, caused severe dehydration and weakness. Cholera, one of the most feared diseases on the trail, could strike suddenly, leading to vomiting, diarrhea, and death within hours. Typhoid fever also appeared in some wagon trains. Under harsh conditions, far from medical care, these diseases spread quickly, especially when groups camped close together and relied on the same contaminated sources. Historians estimate that roughly 300,000 to 500,000 pioneers made the journey west over several decades. Of those, about 20,000 to 30,000 died along the trails, with waterborne illness accounting for a significant share, particularly during cholera outbreaks in the late 1840s and early 1850s. One person out of 15 never made it to the destination. In some wagon trains, deaths from disease far exceeded those from accidents or conflicts.
Today, by contrast, modern water testing can detect microscopic pathogens, chemical contaminants, and toxins with precision unimaginable to those travelers. Municipal treatment systems remove and disinfect threats before water reaches the tap. Looking back, the courage of the pioneers is undeniable. Every drink of water carried risk. Their story underscores just how fortunate we are to live in a time when science has transformed something as simple as a drink of water.
Protecting Groundwater and Supporting Sustainable Winemaking
Across California’s wine regions, land application of winery process water has long been a practical solution for wastewater management. Applied correctly, it supports vineyard irrigation and reduces surface water discharge. Applied poorly, it can allow nitrogen and salinity to migrate through soils and into underlying aquifers, threatening drinking water sources. Recognizing these risks, the California State Water Resources Control Board adopted statewide General Waste Discharge Requirements (WDRs) for Winery Process Water in 2021. Known as the Winery Order (Order WQ 2021‑0002‑DWQ), the regulation is a major shift in how winery wastewater is regulated, monitored, and managed.
The Winery Order was designed to address a persistent problem. Nitrogen is highly mobile in soil. When winery wastewater is land applied, especially after only partial biological treatment, nitrogen can convert to nitrate and leach downward, eventually reaching groundwater used for domestic drinking water. Elevated nitrate levels pose health risks. To prevent this, the 2021 Order establishes a uniform statewide framework that replaces a patchwork of regional permits. Requirements are based on annual process water volume, ranging from 10,000 gallons per year to 15 million gallons per year. Standardized discharge specifications are created for surface impoundments (ponds), land application areas, and subsurface disposal systems. There are expanded monitoring and reporting requirements including nitrogen loading calculations. This includes a clear emphasis on nitrogen, salinity (TDS), and biochemical oxygen demand (BOD) as the primary constituents of concern. For many wineries, these requirements reveal a hard truth: existing methods of truth treatment may no longer be sufficient.
Aerobic digesters, facultative ponds, and other biological treatment systems are widely used in the wine industry. While effective at reducing BOD, these systems often leave behind nitrogen, dissolved solids, and residual organics that exert oxygen demand. Under the Winery Order, land application is no longer just about spreading water, it’s about demonstrating protection of groundwater quality over the long term. That means controlling mass loading, not just meeting basic operational practices. For wineries operating near sensitive aquifers or facing limited land area, compliance using biological treatment alone can become operationally complex, land‑intensive, and uncertain.
This is where Vibratory Shear Enhanced Processing VSEP® RO membranes offers a fundamentally different approach. Unlike conventional membrane systems, VSEP uses high‑frequency vibration to keep membrane surfaces clean, allowing it to process challenging winery wastewater streams without the fouling limitations that often plague spiral RO systems. When applied after primary screening, a VSEP‑RO system can remove dissolved nitrogen compounds, reduce salinity, and produce high‑quality filtrate suitable for irrigation. In many cases, generate water clean enough for process reuse or other non‑potable applications
Rather than relying on soil to finish the treatment process, membrane separation achieves compliance before land application. This dramatically reduces nitrogen loading rates, minimizes groundwater risk, and simplifies compliance demonstrations under the Winery Order.
Mile-High and Dry This Year
For generations, Denver’s water has come from high in the Rocky Mountains, where winter snow melts into the rivers and reservoirs that sustain the metro area through the long, dry summer. This year, that story has taken a troubling turn. After an unusually warm and dry winter, the mountain snowpack Denver depends on has fallen to historic lows, forcing Denver Water to enact mandatory rationing measures for the first time in more than a decade.
Denver Water, which provides drinking water to approximately 1.5 million people, relies heavily on snowmelt from two major watersheds: the South Platte River Basin and the Colorado River Basin. As of late March, snowpack in these basins stood at just 42% and 55% of normal, respectively, both ranking among the worst levels ever recorded in Denver Water’s monitoring history. Normally, snowpack continues to accumulate into April before gradually melting and refilling reservoirs. This year, however, snowpack peaked early and has already begun melting away, leaving water managers little hope for a late-season recovery.
Reservoirs are currently about 80% full, below the seasonal average of 85%, and officials warn that without aggressive conservation, supplies could fall to levels that threaten long-term reliability. In response, the Denver Board of Water Commissioners declared a Stage 1 drought on March 25, with mandatory water-use restrictions. The goal is reduce overall water consumption by 20% through at least April of next year. This marks the first time since 2013 that Denver has implemented drought restrictions beyond standard summer watering rules. Because outdoor irrigation accounts for the largest share of residential water use, the most visible restrictions focus on lawns and landscapes.
Residential customers may water outdoors no more than two days per week. Homes with even-numbered addresses: Sunday and Thursday. Homes with odd-numbered addresses: Wednesday and Saturday Commercial, multifamily, HOA, and government properties are limited to Tuesdays and Fridays. Watering is prohibited between 10 a.m. and 6 p.m., when evaporation rates are highest. Water must not run into streets, sidewalks, or alleys. Leaking sprinkler systems must be repaired within 10 days. Customers who violate watering-day rules may face warnings or fines, reinforcing that these measures are mandatory, not voluntary.
The restrictions go beyond yards and gardens. Under Stage 1 rules, restaurants may serve water only upon request, a step designed to reduce waste from unused glasses, hotels are encouraged to reduce towel and linen washing frequency, commercial vehicle washing is limited. Residents are urged to take shorter showers, run full loads of laundry, and fix household leaks promptly. Denver Water emphasizes that these measures are small individually but significant when adopted across an entire city. Water managers stress that Denver has weathered droughts before and has significantly reduced per-capita water use over the past several decades. Still, this year’s snowpack collapse is a reminder of the region’s vulnerability.
Unlocking the Hidden Value of Lignin with VSEP
In the pulp and paper industry, black liquor has long been viewed primarily as a fuel source, especially in mills equipped with recovery boilers. Embedded within this stream is lignin, a material with growing industrial value across a wide range of applications. Lignin is the substance that gives plants their rigidity, binding cellulose fibers together to provide structural strength. During the pulping process, lignin is separated from cellulose and ends up dissolved in black liquor along with inorganic chemicals such as sodium hydroxide and sodium salts. While large mills typically burn this mixture to recover energy and chemicals, smaller or specialty mills can lack recovery boilers, leaving them with a challenging waste stream and limited options for value recovery.
This is where VSEP (Vibratory Shear Enhanced Processing) nanofiltration (NF) offers a compelling opportunity. VSEP NF systems can selectively separate black liquor into two valuable fractions: a permeate rich in caustic water that can be reused in the process, and a concentrate enriched in lignin. Even in cases where caustic recovery has limited economic impact, the lignin concentrate itself can represent a significant revenue opportunity. At lower purity levels, lignin can be used as a fuel or as an additive in asphalt and concrete, where it acts as a binder or dispersant. These applications tolerate higher ash content and residual salts, requiring minimal processing. However, as purity increases, so does the value. Purified lignin can be used in phenolic resins for plywood and insulation, as a partial replacement for petroleum-based chemicals, or as a dispersant in agricultural and industrial formulations. At higher purity levels, where ash, carbohydrates, and inorganic salts are minimized, lignin becomes a feedstock for advanced materials. These include carbon fiber precursors, activated carbon, and bio-based polyols used in polyurethane foams and coatings. In these markets, consistent molecular weight distribution and low impurity levels are essential, and product values can reach into the thousands of dollars per ton.
VSEP systems enable this value progression by not only concentrating lignin, but also by downstream purification through diafiltration or washing. After initial concentration, water can be introduced to wash the lignin, removing dissolved salts, residual caustic, and low-molecular-weight impurities. Multiple washing stages can be applied, depending on the target application and required purity level. This flexible approach allows operators to tailor lignin quality to specific market needs.
For smaller pulp and paper facilities without recovery boilers, this capability represents a strategic shift. Instead of managing black liquor solely as a disposal challenge, these mills can convert a waste stream into a valuable product portfolio. By leveraging VSEP NF and staged washing, lignin can move up the value chain—from low-value fuel to high-performance industrial material. In a market increasingly focused on sustainability and bio-based alternatives, lignin offers a path toward both environmental and economic gains. With the right separation technology, what was once waste can become a profitable resource.
Converting Sludge to Energy and Clean Water: The Rise of Centralized Biogas and Digestate Treatment
Municipal wastewater sludge is increasingly being redefined, not as a waste liability, but as a renewable energy resource. This shift is driven by the intrinsic biochemical composition of sludge and by advances in anaerobic digestion (AD) infrastructure that enable efficient methane recovery. For engineers evaluating this transition, it is important to understand both the material characteristics of sludge and the system-level constraints that historically limited its energy utilization.
Primary and secondary sludges generated at publicly owned treatment works (POTWs) consist largely of water (typically 92–99%) and a concentrated solids fraction containing microbial biomass, undigested organics, extracellular polymeric substances, lipids, proteins, and carbohydrates. Volatile solids typically comprise 60–80% of total solids, representing the biodegradable fraction. This organic matrix serves as an ideal substrate for anaerobic digestion, where hydrolytic, acidogenic, acetogenic, and methanogenic pathways sequentially convert complex organics into methane (CH₄) and carbon dioxide (CO₂). The methane yield is directly linked to volatile solids destruction and substrate availability.
However, raw sludge is unstable: it contains pathogens, generates odors, and continues to biologically degrade in an uncontrolled manner. Stabilization via anaerobic digestion is therefore essential, not only to reduce pathogens and volatile solids, but also to produce a predictable, energy-rich biogas stream. During digestion, volatile solids are typically reduced by 40–60%, while methane concentrations in biogas range from 55–70%, depending on feedstock composition and operating conditions.
Despite the widespread adoption of anaerobic digesters at medium-to-large POTWs, biogas utilization has historically been inefficient. Many facilities operate legacy digestion systems where biogas is either flared or used solely for low-grade thermal applications such as digester heating via boilers. This reflects a combination of factors: limited gas production from dilute sludge-only feedstocks, insufficient economies of scale to justify upgrading systems, and historically low energy prices. Additionally, plant operators have prioritized process stability over energy optimization, leading to conservative approaches to gas handling.
In contrast, centralized “hub-and-spoke” biogas facilities are reshaping the landscape. These facilities aggregate sludge from multiple POTWs and often co-digest it with higher-energy substrates such as food waste, fats, oils, and grease (FOG), and agricultural residues. This dramatically increases methane yield and makes energy recovery, particularly as renewable natural gas (RNG), economically viable.
VSEP has been installed for 33 biogas project, but, mostly where manure or food waste is the primary feedstock. Recently, VSEP was pilot tested at a facility southeast of Oslo, Norway. This project exemplifies this model: a regional digestion hub receiving hauled sludge and co-substrates to maximize gas production. Gas production is the profitable side, but the residual digestate and handling of this is an expense and a problem. The digestate in this case was relatively dilute at less than 1% total solids. The VSEP equipment was demonstrated for several weeks achieving 90% recovery with an average flux rate of 18.5 GFD (32 LMH). The VSEP RO filtrate was run through spiral RO polishing systems to reduce ammonia and COD to low levels for surface water discharge.
As digestion efficiency improves, attention is shifting to digestate management, particularly the liquid fraction. Post-digestion centrate contains elevated concentrations of ammonia, soluble COD, recalcitrant organics, PFAS, and dissolved metals. Advanced membrane systems, such as VSEP reverse osmosis, are increasingly deployed to address this bottleneck. In the Norway pilot, VSEP demonstrated the ability to produce a high-quality permeate suitable for discharge, effectively removing ammonia, COD, PFAS compounds, and heavy metals while concentrating residuals for further handling. RO membranes are uniquely able to remove all contaminants and not only some like other technologies. VSEP RO is uniquely able to filter this difficult effluent with only coarse solids removal ahead of it.
This evolution, from sludge disposal to integrated energy and resource recovery, signals a fundamental shift in wastewater engineering. As centralized digestion hubs expand and regulatory pressures intensify, high-performance digestate treatment technologies will become essential components of the overall system design.
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