Unconventionally Mining Phosphorus from Wastewater

By Michael Schmid of Renewable Nutrients

Conventional wastewater treatment facilities have evolved to become extremely proficient in the practice of sequestering nutrients, particularly phosphorus and nitrogen, present within their incoming municipal and industrial waste streams. Many facilities, and perhaps the case could be made to suggest “most” of the 16,000+ treatment plants in the United States, employ a form of chemical precipitation that serves to bind dissolved phosphorus to a metal salt or rare earth elements (e.g. – ferric chloride, alum or cerium chloride). This precipitations segregates the phosphorus such that it travels with the solids portion of the treatment process and thereby delivers to receiving waters a final liquid effluent that is low in phosphorus (or at least within a mandated tolerance for the nutrient).

The common practice of dosing an incoming waste stream with metal salts does have its disadvantages, however. In many cases, it can be rather costly just from a chemical consumption perspective, which is driven by the amount of daily incoming total phosphorus that needs to be isolated and removed from the liquid stream. The addition of metal salts also adds to the facility’s overall sludge content, creating more solids material that must be treated, digested, dewatered and ultimately disposed, and compounding the operational cost drivers that have to be controlled and managed. Finally, from an environmental standpoint, it simply cannot be beneficial long-term to landfill or even land apply biosolids that are artificially saturated with metals (and phosphorus), so beyond the daily cost of operations, there may very well prove to be a heavy cost to the environment.

Fortunately, many treatment facilities have recognized the operational and environmental costs associated with dosing metal salts and are employing alternatives. One emerging technology for managing incoming phosphorus, which has gained wide acceptance especially by progressive treatment plant operators, is bio-P. Here, phosphorus is captured and removed from the incoming liquid stream biologically by phosphorus accumulating organisms (PAOs). While bio-P can be very efficient at removing phosphorus and isolating it to the solids stream, the PAOs tend to release the nutrient from within their cell walls during and after anaerobic digestion. Unfortunately, this released phosphorus typically follows the liquid portion of the solid stream through dewatering, producing a high-P liquid side stream that is nearly always routed back to the plant’s head works, and must ultimately be re-treated again and again by the bio-P process. This side stream is commonly referred to as a “recycle stream,” and in many cases can exhibit phosphorus levels as high as or even exceeding 500ppm. Recycling this phosphorus-laden stream serves to limit the capacity and effectiveness of any bio-P process, yet it also yields a single, concentrated point or “reserve” from which phosphorus can be mined, recovered, and even re-used beneficially.

While academics and scientists have studied, debated, and preached about nutrient (and specifically phosphorus) recovery from waste streams for many years, putting the concept to practice is a relatively recent phenomenon. There are several new technologies on the market today that can assist a treatment facility in removing and recovering phosphorus from its waste streams, but one emerging technology that has proved particularly effective at recovering phosphorus from side streams or recycle flows is Quick Wash® – a concept originally developed by the USDA and commercialized by Renewable Nutrients.

 

 

Quick Wash is versatile enough that it can recover phosphorus from both liquid and solid streams, but given a bio-P operation (also sometimes referred to as Enhanced Biological Phosphorus Removal – EBPR), one area in particular where it can be effectively deployed is downstream of dewatering to treat the liquid side stream (or recycle stream). In the illustration above, the Quick Wash system receives the recycle flow and extracts nearly all of the phosphorus that is not already in solution. The system then precipitates out the phosphorus by introducing lime and forming calcium phosphate. The calcium phosphate is filtered using a liquid/solid separation apparatus and can be used beneficially as a phosphate fertilizer, an animal feed additive, or as a supply of raw material where calcium and phosphorus are required. The final liquid effluent from the Quick Wash system is routed back to the facility head works as a clean, very low-P or even no-P stream. So Quick Wash not only recovers phosphorus and produces a valuable byproduct, but it eliminates the recycle flow of phosphorus and yields greater capacity and efficiency in a bio-P operation. This increased capacity gives a facility the flexibility to increase its incoming waste stream flow without the addition of major infrastructure upgrades.

Progressive wastewater treatment facilities that operate bio-P combined with anaerobic digestion are producing an untapped, yet readily available phosphorus reserve in the form of phosphorus-rich recycle streams. Recycling released phosphorus from the solid stream back into the liquid stream only serves to add to a facility’s daily phosphorus load and create a scenario in which its bio-P operation is unable to operate at its intended capacity. The phosphorus-rich recycle streams of such facilities present an opportunity for technologies not only to extract and recover phosphorus and re-purpose it for beneficial re-use, but also to eliminate the constant recycling and re-treating of phosphorus within a treatment plant. Given a finite or limited worldwide phosphate rock supply, and the need for phosphorus as a life-sustaining nutrient important to preserving global food security, it only makes sense to “tap” the phosphorus reserve created in treatment plant recycle streams. Thanks to technologies, such as Quick Wash, phosphorus recovery may soon be standard operating procedure and wastewater treatment plants may very well be able to truly own and live-out the moniker “Water Resource Recovery Facility.”

 

Opinions expressed here do not necessarily reflect those of the Sustainable Phosphorus Alliance.

About Renewable Nutrients

Renewable Nutrients is a private, North Carolina-based company that turns waste into sustainable and profitable resources. Through its patented Quick Wash® system, Renewable Nutrients enables waste treatment facilities and animal feeding operations to extract and recover phosphorus from biosolids and manure. The remaining biosolids or manure, which contain crop-friendly ratios of nitrogen-to-phosphorus, can be land-applied, thus minimizing the amount of waste trucked to disposal sites, and reducing or even eliminating the incidence of nutrient pollution from soil runoff. In addition, municipalities and farms can sell the recovered phosphorus on the open market, and engage in the trading or marketing of nutrient credits.

 

Phosphorus Extraction from Wastes: The Key to Phosphorus Problems?

By Nick Reckinger of FEECO International, Inc.

As one of the key nutrients in growth, phosphorus is critical to maintaining food security and life on Earth. This has scientists worried over the dwindling mineralogical reserves from which we mine this valuable nutrient source. Interestingly, the world faces a problem of too much phosphorus in other areas; excess phosphorus from nutrient runoff is contaminating waterways and causing toxic algal blooms and dead zones throughout the world.

As the world looks to feed a growing population, demand for this life-giving nutrient is not likely to waver. This has many looking at the opportunity to use this resource in a more sustainable way. Processing of organic wastes can help alleviate pressure on finite resources while diverting phosphorus from waste as runoff back into the soil where it belongs.

The Case for Recycling Phosphorus

Organic wastes are a renewable resource, so it’s easy to see why the potential to derive even a small portion of our phosphorus requirements from this growing category of wastes is so attractive. One recent study looked at three primary phosphorus waste streams (human food waste, human excreta, and animal manure) and concluded that it would take only 37% of the phosphorus available in these existing waste streams to support the yearly U.S. corn crop’s phosphorus requirements.

Recycling phosphorus from organic wastes would not only provide the world with a much needed renewable source of phosphorus, but it would also help to mitigate the environmental problems that result from phosphorus runoff. Dead zones, or hypoxic areas that kill off fish and other organisms in waterways as a result of insufficient oxygen, have largely been blamed on nutrient runoff, with agriculture being a major contributing source.

Although restoration is an option, it is costly, making the prevention of dead zones much more feasible. And while there are many contributing factors to runoff (proximity to waterways, soil type, distance to bedrock, etc.), minimizing the potential for runoff to occur through proper fertilizing techniques and nutrient management best practices will likely be a primary endeavor in protecting waterways.

Two materials in particular have seen a surge of interest for their nutrient recovery and reuse potential: biosolids and manure.

Biosolids

Biosolids, also commonly called wastewater treatment sludge, are the materials left over from the wastewater treatment process. While various methods exist for the disposal of biosolids, disposal methods such as landfilling or incineration usually disregard the valuable nutrient content that biosolids hold. Additionally, disposal is increasingly being seen as unsustainable from a long-term perspective. And with increasing regulation around land application, municipalities are in need of a workable solution.

Manure

Similarly, regulation around the land application of manure has also been increasing, putting a growing strain on farms dealing with the massive amounts of manure produced by the agricultural norm of large-scale farming operations. Farms are also limited in the distance they can haul their manure to land apply it, due to its high moisture content, which makes transportation a costly expense.

Simultaneously, farms are purchasing chemical fertilizers to provide much of their nutrient needs, while the value of the manure they land apply is not often fully realized due to runoff, resulting in an inefficient imbalance of nutrient resources for crop production.

Granulation: Key to Recycling Phosphorus?

Phosphorus recovery from organic wastes is still in its infancy as an industry, with much research under way, and still more to be done. As a fertilizer industry veteran, we have been among those on the forefront of this issue, having developed process solutions and systems around nutrient recovery from organic wastes for decades. We use our expertise in granulation to transform difficult to handle, moisture-laden materials into a dry, premium-grade granular product that exceeds the EPA’s 503 regulations for a Class A Biosolid. This, in combination with significantly reduced odor, eases many of the issues surrounding land application.

In addition to these benefits and reduced transportation costs, there is ample opportunity for customized formulations and nutrient blends through granulation. As such, granulation can serve as a means to producing a marketable product that can supplement the purchase of additional nutrients for both municipalities and large-scale farms, all while reducing waste management costs.

Reduced Runoff through Granulation

While granulation offers many benefits to the farmer and/or municipality, the granulation of organic wastes into fertilizer or soil amendment products ultimately aids in the runoff prevention effort; because granulation produces a dry product, there is less potential for runoff to occur. Unlike the moisture-rich raw materials, a dry product does not add moisture to the soil, which can increase the likelihood of runoff occurring.

Furthermore, a granular product makes following a nutrient management program much easier and more efficient. The N:P ratio is often imbalanced as a result of fertilizing to meet nitrogen demands and inadvertently over-applying phosphorus. Granular products allow the N:P ratio to be carefully controlled to suit the nutrient profile of the land where it will be applied, significantly reducing the opportunity for runoff to occur. Granules also allow for easier and more accurate dispensing; soil receives only what it needs, further reducing the chance for excess phosphorus to leach from the soil.

An Overview of the Granulation Process

The granulation process is different from one source material to the next, with necessary pre-conditioning methods also differing. However, in general, granulation works by taking the nutrient-rich cake left over from the digestion process (or the wastewater treatment sludge remaining after the water treatment process), and mixing it in a pug mill.

Additives and/or nutrients can be included here to customize the formulation. The pug mill thoroughly mixes the feed materials (along with process recycle) to form agglomerates. These granules are then dried in a rotary dryer, where the tumbling action further rounds them. A cooling step reduces the temperature of the product, yielding a product that will hold up to handling and storage, but still deliver nutrients in a timely manner upon application.

As each source material differs in how it will respond to granulation, pilot testing is required to work out process variables and scale up the process to full-scale production.

FEECO Vice President and General Manager, Lee Hoffmann, who is also a member of the Brown County Phosphorus Committee, had this to say on the matter: “The importance of utilizing our organic wastes to their fullest potential is becoming increasingly critical as the world hosts a growing population. Add to that that some of our resources are essentially being wasted as runoff, and it’s easy to see why this approach makes sense. As a fertilizer industry veteran and an expert in the transformation of wastes into value-added products, we are well positioned to provide solutions to this market.”

Conclusion

Phosphorus is an invaluable nutrient to life on Earth. Maximizing available resources, while taking the pressure off of finite phosphate reserves is essential for long-term, sustainable phosphorus management.

Considering that renewable phosphorus resources in the form of manure and biosolids are often going to waste and even contributing to environmental issues, the potential these organic wastes hold to meet sustainable phosphorus goals is an incredibly valuable opportunity.

 

Opinions expressed here do not necessarily reflect those of the Sustainable Phosphorus Alliance.

About FEECO

FEECO provides feasibility testing, process and product design, and custom processing equipment for organic waste materials, including biosolids and manure. From idea, to complete process solution and custom equipment, FEECO offers capabilities in transforming organic wastes into value-added, marketable products. FEECO is based out of Green Bay, WI. In addition to their custom process equipment and systems, they offer a unique testing facility where they can conduct both batch and continuous, pilot-scale tests to simulate commercial production conditions.

Reclaiming the Value of Urine for Agriculture

By Tatiana Schreiber of the Rich Earth Institute

Abe Noe-Hays is a co-founder of Rich Earth Institute. The institute promotes collecting and using human urine as a plant fertilizer. Here Abe applies pasteurized urine to a test bed of lettuce. Photo by Marcin Szczepanski/Senior Multimedia Producer, University of Michigan, College of Engineering
Photo by Marcin Szczepanski

What is the potential for reclaiming the phosphorus present in human urine for agricultural use? World-wide there are a number of projects exploring this question, but few in the United States.[1] A small-scale but exciting example is the Rich Earth Institute’s Urine Nutrient Reclamation Project (UNRP) in Brattleboro Vermont.  Since 2012, Rich Earth has been collecting urine from 150 – 200 households in the community, transporting and sanitizing it, and using it as fertilizer on test fields of hay and vegetables. Rich Earth currently invites participants to save urine at home and bring it to a central depot. The long-term goal, however, is to support the wide-spread use of simple toilets and storage systems that can divert urine from aging sewage, storm water and water treatment systems, many of which are underperforming in cases of extreme weather events and changes in water cycles due to climate change.  Urine accounts for roughly three-quarters of the nitrogen and roughly half of the phosphorus in municipal waste streams. Research Director Abe Noe-Hays estimates that one thousand gallons of urine contains the equivalent of 109 pounds of urea, 13 pounds of triple superphosphate, and 29 pounds of muriate of potash (KCl), as well as smaller amounts of calcium, magnesium, sulfur and micronutrients Therefore, substituting urine for chemical fertilizers can be an appealing prospect depending on the nutrient needs of specific crops and the nutrient status of soils.

Rich Earth’s field tests on hay over several years have shown equivalent yields between urine-fertilized and chemically-fertilized test plots, both significantly higher than unfertilized plots. Forage quality remained high, and one farmer has been able to achieve a solid second cutting of hay where previously yields were not sufficient to warrant a second cutting.  Farmers participating in the project have had good results applying the sanitized urine to hayfields without dilution; one of Rich Earth’s goals is to develop a concentrated product that can be applied directly to reduce labor requirements. While it is likely the nitrogen rather than the phosphorus from urine is what has been the most significant nutrient in these Vermont test fields (because the soils were not deficient in phosphorus at the start), these experiments are an important model for the potential of recycling human waste for fertilizer world-wide.

Among hay and vegetable farmers in New England that Rich Earth has surveyed, interest in the potential of a urine-derived fertilizer is high, although farmers are cautious.  Respondents wrote, for example, “I think it is a great way to start closing the nutrient cycle – counting humans as part of the whole environmental web,” and “Could be a silver bullet; cost effective, renewable, recycling,” and “It’s about time we started using this valuable nutrient in the field instead of allowing it to contaminate drinking water by flushing it down the toilet.” Research suggests that farmers who currently practice organic or ecological methods may be more open to using urine than conventional farmers, but they may also have more concerns about potential contaminants in the urine including their impact on the health of soil biota. Not surprisingly, many also express concerns about how their customers may respond to the use of urine-derived fertilizers on their crops.

Rich Earth’s research aims to respond to some of these concerns. The organization will assess farmer interest and technical needs with regard to using these fertilizers on animal feed and fiber crops, perennial crops (such as fruit trees), ornamentals and other non-edible and edible crops. Testing indicates that heavy metal levels are extremely low – on average a thousand times below accepted risk levels. And although fiber, biomass, and animal feed crops could utilize all urine-derived fertilizer for the foreseeable future, Rich Earth has conducted field studies with lettuce and carrots to examine the fate of pharmaceuticals as well as biological components (viruses and bacteria) when urine-derived fertilizers are used for growing edible crops. Final results from this research have not yet been published, but the data so far indicate that while trace levels of pharmaceuticals could be detected in both lettuce and carrot tissue, the levels were very low. As Noe-Hays puts it, “a person would have to eat a salad from the study plot every day for two thousand years to get a single dose of acetaminophen (Tylenol).” With regard to bacteria and viruses, this research is ongoing, but current standards specify that urine can be effectively sanitized by pasteurization or by storing it from one to six months before using. Rich Earth’s ongoing research will help to better understand what happens under different storage and treatment practices.

With regard to public perceptions, Rich Earth’s social research seeks to learn more about what people know and think about what happens to their waste currently, and discover the most useful communication strategies to help attitudes evolve. In surveys and interviews with people who have contributed urine to the UNRP over the last four years, one important message stands out: people can and do change their attitudes over time. Although sometimes reluctant and uncomfortable at first, participants have become more and more enthusiastic about saving their urine and seeing it reused for agriculture. Learning about the value of urine as a fertilizer has inspired much of this evolution. For example, one person said, “I am so impressed by this simple process that turns a waste product into something so useful, saves water and avoids chemical fertilizers in our soil. Amazing! I love the environmental education that happens when curious visitors ask about that weird jug in our bathroom. It has started some good conversations!”

Of course there are no “weird jugs” when simple urine-diverting toilets are employed. Rich Earth is working towards more wide-spread use of these systems for source-separation and nutrient reclamation from urine, including addressing regulatory issues. Until now, human waste has been seen by regulatory agencies as something to be “disposed of” so as to protect public health.  But Rich Earth sees urine is a resource. Rather than needing to be “disposed of,” it should be collected and made use of as a “value-added” product. The organization currently has a permit for a mobile-pasteurizing unit through the Vermont Agency of Natural Resources’ Watershed Management Division. This has allowed local regulators to become comfortable with the concept of recycling urine for fertilizer. Using this permit, Rich Earth has developed the tools and equipment needed for larger scale processing of urine.

Ongoing research, now funded with a four-year grant through the National Science Foundation, will allow the organization to learn more about what regulators need to know and how best to communicate with them so that regulations can be written that will protect human health and the environment by keeping urine out of the waste stream and returning it to the soil.  Step by step, community by community, it will then become possible to close the loop and recycle the abundant nutrients, such as phosphorus, that we so generously expel in liquid form every single day.

Opinions expressed here do not necessarily reflect those of the Sustainable Phosphorus Alliance.

Tatiana Schreiber is an independent scholar with a doctorate in Environmental Anthropology. She teaches in the areas of agroecology, environmental studies and writing at Keene State College in New Hampshire and is a research associate at Rich Earth Institute. She also operates Sowing Peace Farm in Vermont, selling organic seedlings of heirloom and unusual varieties of vegetables and medicinal plants. Contact her at tatiana@richearthinstitute.org 

[1] http://www.ecosanres.org/pdf_files/ESR2010-1-PracticalGuidanceOnTheUseOfUrineInCropProduction.pdf

Inaugural Post

Greetings,

After a summer of media filled with stories of algal blooms wreaking havoc on our waterways, the challenge of phosphorus pollution can seem overwhelming. But there is good news. I’ve had the privilege over the past several months to speak with many people at the forefront of addressing the phosphorus challenge. I’ve spoken with our international network of scientists whose analyses point the way towards better phosphorus management practices; with entrepreneurs who have developed technologies for phosphorus recovery and recycling; with NGOs who are raising public awareness and putting pressure on regulators to act; with farm groups who want to be good stewards and reduce their footprints; and with regulators who want to craft enlightened policy.

The good news is that there is no shortage of goodwill and brain power available, and you’ll be hearing from some of those altruistic intelligentsia right here on this blog. We’ll promote their contributions in our quarterly newsletter, our twitter feed, and our LinkedIn page, so please keep an eye out.

A couple of common themes have emerged from my discussions:

  1. There’s strong appetite for cross-sector knowledge sharing and the development holistic approaches to dealing with phosphorus pollution. People tend to work in silos, but recognize that problems are common. Some of the same issues and uncertainties are being faced at municipal wastewater facilities that are being faced at manure lagoons. How do we make phosphorus recovery economically viable? What are the regulatory constraints on safe secondary phosphorus use? There’s also an expressed need for networking opportunities to connect organizations across the value chain and build trust. That’s why we are developing a technical webinar series and hosting our Phosphorus Forum 2017 event on May 19 in D.C.
  2. Animal waste management is the low-hanging fruit, diffuse phosphorus is the high-hanging fruit. Agriculture is the biggest user of phosphorus and the biggest generator of phosphorus pollution. Practices such as 4R nutrient stewardship can help mitigate phosphorus misapplication issues, but how do we manage phosphorus after use? Technologies for extracting or otherwise utilizing phosphorus from animal wastes are commercialized, but those for handling diffuse phosphorus from run-off—not so much. If we want to tackle phosphorus pollution expediently, we probably need to concentrate now on enabling practices and technologies for phosphorus recovery from animal wastes and wait for diffuse phosphorus management technologies/practices to catch up. In the long term, though, comprehensive approaches are needed.
  3. There’s real value in having the strong academic network we’ve inherited from the Alliance’s five-year-old progenitor, the NSF’s Phosphorus Sustainability Research Coordination Network (P-RCN). Industry likes to incubate and vet ideas in the academy, where risk is low, and there is great expertise and passion among academics, some of whom have been working on these issues for decades. We’re going to fan these flames as much as possible, including making the Phosphorus Forum 2017 event a joint meeting of the P-RCN and the Alliance.
  4. The Europeans are way ahead of us. Luckily, we have friends in Europe who’ve cleared a path forward for us, particularly at the European Sustainable Phosphorus Platform. While our own focus will be on North America, the phosphorus challenge is global, and we will need to coordinate with efforts such as theirs. We get to peer into our own future by looking at their present.

We’re looking forward to working with you on these critical issues and hope your organization will help us build this network by becoming a member.

Happy Holidays,
Matt Scholz