MidAtlantic Biosolids Association

SPOTLIGHT on National Technology Leaders

In the MABA organization, we can proudly count among our members individuals with national statures for their leadership in the biosolids profession. They have built a reputation from years of service, presentations to national and regional conferences, participation in our professional organizations at national and local levels, and being ready to lend advice and support to colleagues. They are also a firm commitment to advancing the state of the art in the equipment and practices that they recommend to public agencies who turn to them for advice. They are also, every one of them, just really fun people to have as colleagues. 

 Mohammad Abu-Orf

Dr. Mohammad “Mo” Abu-Orf, Residuals Group Practice Leader, Hazen and Sawyer ([email protected], 856-332-4030).  Mo has over 28 years’ experience in biosolids master planning, process optimization, evaluation of innovative technologies, and conceptual design in the areas of dewatering, stabilization, and energy recovery, and has 130 conferences and peer-review publications and 5 patents to his name. Recently, Mo has been focusing on evaluating and demonstrating technologies for PFAS removal from biosolids.  Prior to Hazen, Mo worked with AECOM, Siemens, Veolia, and academia. This diverse experience allows Mo to enjoy his role evaluating innovative technologies and providing highly technical services to reduce the cost of biosolids processing operations. From his home in south New Jersey, a property at which he is revealing master gardening and landscaping aptitudes (find Mo hiding in the picture of his garden), Mo has also launched three children, of whom he is exceedingly proud, into successful careers in law and nursing for his elder daughters and TBD for his son, a senior at Fordham University. 

Natalie Sierra     

Natalie Sierra, National Leader of Brown and Caldwell, Biosolids and Energy Service Line ([email protected], 650-533-3892). Natalie works with her fellow biosolids enthusiasts all day, every day.  Her project work focuses on biosolids master planning and helping utilities with developing market-based biosolids management strategies, including service procurement support. She has been involved in biosolids since her undergraduate days at Cornell Agricultural and Biological Engineering and her Masters from UNC Chapel Hill, where she supported a larger research project on metals uptake in different types of crops where biosolids had been applied.  Natalie says, “my passion for the field really got ignited thanks to Bonnie Jones at SFPUC, the utility where I later served as the biosolids manager, seeing the benefits of biosolids first-hand and understanding what a huge environmental impact they can have when used beneficially got me hooked for life.” Natalie has served in leadership positions in regional biosolids associations, WEF member associations, and WEF RBC, helping to spread the good word about biosolids and to work towards a sustainable future for our industry as a key solution to climate change. Natalie lives outside of Boston, MA, with her husband Neal and two daughters, Sylvia (10) and Tessa (7).  She proudly says, “They can all tell you where their poop and pee go after they flush. We love to travel in our spare time and hope to be able to visit my family in Spain this summer.  We also like hiking and biking as a family, even in the cold of New England!” 


Richard Tsang

K. Richard Tsang, Senior Vice President, CDM Smith Inc. (919-325-3577, [email protected]). Richard first learned about sludge during his graduate study in environmental engineering in Canada. As part of graduate research, he conducted lab analyses on wastewater and sludge. When he decided to further his study after completing the master program, he went to Duke University where he met one of his mentors Professor Aarne Vesilind. He completed his study under Aarne on sludge dewatering and characterization and has been working in the biosolids field ever since. In his 32 years with CDM Smith, Richard was fortunate to have worked on all aspects of biosolids as well as water residuals projects, for clients around the country as well as internationally. Richard is intrigued by how technologies evolved on solids treatment over the years and spends a considerable amount of time studying and investigating different technologies. Richard loves traveling with his wife Karen and tries to visit biosolids facilities at different destinations when he can. Richard has been very active with WEF and has served on various committees. He is the current chair of the IWA Sludge Management Specialists Group and looks forward to being out there meeting with biosolids people again. 


Terry Goss     

Terry Goss, North American Biosolids Practice Leader, AECOM ([email protected], 215-987-8087). Terry has a B.S. in Chemical Engineering from North Carolina State University and an M.S in Environmental Engineering from Villanova University. During Terry’s 17-year career, his main technical focus has been biosolids process technology, energy, and resource recovery.  Terry has worked on the planning, design, and commissioning of numerous facilities.  He was a contributor to the 5th Edition of the Metcalf & Eddy/AECOM Wastewater Engineering Textbook. Terry is a licensed Professional Engineer in North Carolina.  He and his wife Jennifer, two daughters (Piper and Sidney), and two dogs (Loki and Hopper) live in Raleigh and enjoy traveling, spending time outdoors, taking walks, swimming, and visiting local parks.  With a recent new baby, sleep and free time are in short supply! 


 Todd Williams

Todd O. Williams, P.E., BCEE, Residuals Resource Recovery Practice Leader, Jacobs ([email protected], 804-833-9122).  Todd has had a 41-year career in environmental engineering. As a young graduate from Virginia Tech, he began his career managing the 20 MGD James River wastewater treatment plant in Newport News, Virginia, where he started up one of the first aerated static pile sludge composting facilities in the country, a facility making high-quality compost even to today, now by a third-party contractor.  His passion was stimulated by the enthusiasm of Maryland horticulturist Dr. Francis Gouin on the wonderful garden results of biosolids compost, and this compelled Todd to join Eliot Epstein’s E&A Environmental composting consultancy, providing the firm with engineering expertise. He moved on to CH2MHill (now Jacobs) in 2005, assisting communities throughout North America with new and emerging biosolids technologies, including advanced digestion, drying, pyrolysis, gasification, and composting.  From 2010 to 2013, Todd chaired WEF’s Residuals and Biosolids Committee. With the support of his wife of 41 years, Amy, Todd has had the privilege of traveling extensively, working with his many U.S. clients, and traveling with Amy as a volunteer on medical missions, like the one to Niger, Africa, shown in the photograph with giraffes behind him.  With three children and, believe it or not, 10 grandchildren, Todd has the long game in mind, approaching solids management with a view to the benefit of future generations.  If you want to test just how much his grandkids know about his career, Todd invites you to meet him and his oldest grandson (age 9) on the golf course, so the boy can tell you exactly what Todd does,…and then he will whip the both of you.


Biosolids News You Can Use

If You're Using One of These Popular Fertilizers, Stop Now, New Study Says
National (5/26/21) - A recent study by the Sierra Club and Ecology Center of Michigan that tested PFAS and PFOS levels in popular fertilizers sold in stores found that some fertilizers contained levels of the chemicals above what is set by state guidelines. A separate study by UCLA scientists suggests that there may be more microplastics in biosolids than previously suspected.
Study: Potentially Harmful 'Forever Chemicals' Found in Popular Garden Fertilizers

Why Scientists Don’t Want Our Poop To Go To Waste
Discover Magazine (5/16/21) - This article reviews the beneficial use of biosolids outside of land application. It touches on using biosolids in construction materials and energy production.
Biosolids From Sewage Water Could Solve Global Carbon Emissions and Power Shortages

What to Expect for PFAS
WWD Magazine (5/13/21) - This article explains what we might see for the future of PFAS monitoring and regulation and some of the challenges related to regulation and monitoring. 

WSSC Water Advances Innovative Piscataway Bioenergy Project
Laurel, MD (5/20/21) - WSSC Water Commissioners have approved an 18-year contract with Washington Gas (WGL) for the construction and installation of approximately 900 feet of natural gas pipeline and related infrastructure to supply natural gas to, and convey renewable natural gas from WSSC Water’s Piscataway Bioenergy facility in Accokeek, Maryland in Prince George’s County. This project is part of a larger innovative initiative to produce Renewable Natural Gas using biosolids from the five WSSC resource recovery facilities. The gas will be sold on the open market with the Renewable Fuel Credits generated also available to sell to the petroleum industry. 

Newark Officials to Hear Challenge to Planning Board Role in Aries Energy Facility Proposal
Newark, NJ (5/19/21) - Aries Clean Technologies applied to construct a biochar production facility in Newark that has been met with opposition from environmental activists. The application is expected to come before the zoning board to review before June 10th and they will determine whether Aries made the proper decision when it referred the matter to the planning board.

State Tightens Rules for Sewage Sludge Used as Fertilizer but Leaves a Loophole in Place
Florida (6/2/21) - Florida’s new regulations for biosolids will expand limits on where and when biosolids can be applied and increase monitoring. The rules will apply to Class A and B biosolids, but not to Class AA. It is expected that facilities will work to bring the quality of their biosolids to Class AA to avoid the additional regulation and reduce other costs in the management of the biosolids. 

Technology Promises Big Savings
Marinette, WI (5/2/21) - Marinette Water and Wastewater Operations Manager Warren Howard plans to implement operations of an advanced drying technology system designed by China-based Guangzhou Shincci Energy Equipment at the city’s wastewater treatment plant (WWTP). Tyco Fire Products LP reimbursed the city to help pay for the new system. Tyco is a defendant in a recent lawsuit settlement in U.S. District Court, stemming from PFAS contamination of many private drinking water wells in the Town of Peshtigo, resulting from Tyco operations.

Worcester Polytechnic Institute Researchers Working to Turn Toxic Sewage Sludge into Renewable Energy
Worcester, MA (5/3/21) - A team of researchers at Worcester Polytechnic Institute (WPI) received a nearly $2 million grant from the U.S. Department of Energy (DOE) to create renewable fuel from sewage sludge.

Fort Worth’s Use of ‘Sewage Sludge’ on Farmland is Still Causing a Stink in Rural Areas
Fort Worth, TX (5/10/21) - Biosolids were applied to farmland in Bosque County, south of Fort Worth, and community members noticed unpleasant odors. They started a campaign claiming that biosolids are a nuisance to families and a potential health hazard. In Fort Worth, all sewage sludge is treated at the Village Creek Water Reclamation Facility. The city announced plans last year to build a thermal dryer facility to produce pellets and significantly reduce the amount of biosolids applied each day by more than 70%, according to Bala Vairavan, a senior project engineer for Synagro.

City Will Make Improvements to Wastewater Biosolids Facility; Funding Estimated to Save Ratepayers $25 Million
Jefferson City, MO (5/11/21) - The Missouri Department of Natural Resources has awarded $100 million in financial assistance to the City of Kansas City for upgrades to its Blue River Biosolids Wastewater Facility. The improvement project includes replacing the aging incinerators with a thermal hydrolysis process, as well as rehabilitating the existing facility.

Yelm Water Reclamation Facility to Undergo Transformation by End of the Year
Yelm, WA (5/11/21) - Yelm’s water reclamation facility will be incorporating biosolids drying (The BioDryer) into their facility so sludge can be processed into biosolids fertilizer on site. Yelm’s current water reclamation facility, which uses sequence batch reactors (SBR) was built in the late 90s and was the first of its kind in the state.

Starkville Utilities Plans to Turn Wastewater into Fertilizer
Starkville, MS (5/13/2) - Starkville Utilities Department is adding screw presses and drying components to their wastewater treatment system in order to produce Class A biosolids. Most of the biosolids will be taken to Mississippi State University for use on pasture land, bidding materials, and as a topsoil.

Public Review for Draft Statewide Biosolids General Permit
Olympia, WA (5/18/21) - The Washington Department of Ecology has issued a draft statewide general permit for biosolids management and is asking the public to provide comments. The draft permit is expected to help streamline some requirements, reducing the regulatory burden for about half of the 375 or so facilities in the state without compromising environmental protections. The permit was also reorganized to improve efficiency and implements online reporting so that information collected by Ecology – like facility reports – is available immediately.

Sludge Facility Upgrades Delayed
Sarina, ON, Canada (5/21/21) - Labor shortages and delays in materials delivery may push back the expected completion date of upgrades at a treatment facility that is part of the St. Andrew Street wastewater treatment plant. The facility is expected to close for two months while the work is being done. A contract for hauling the sludge while the facility is closed has yet to be awarded. 

Compost, Renewable Gas Facility Proposed for Former Brenda Mines Site
BC, Canada (5/21/21) - Glencore and Brenda Renewables have partnered to reopen the Brenda Mines site to turn it into a facility that can process local municipal organic waste, yard waste, as well as biosolids, and turn it into renewable natural gas and high-nutrient compost. If all goes according to plan, the facility will start construction in 2022. Construction of the initial facility is expected to take six months, then they will operate it for a year to get reliable results of the effects of the compost products in the plots in the area.
Bacteria Mulled for Sewage-Eating Duties in Kelowna, Peachland

EU Green Week - Production of Bioplastics from Sewage Sludge
EU (5/13/21) - A pilot plant for Polyhydroxyalkanoates (PHA) bioplastics production is in operation at the STP Wuppertal-Buchenhofen. The organic carbon from primary sludge is converted within a two-step biological process to PHA which can be used for further bioplastics production. There is an online visit introducing attendees to the project WOW. 

Hefty Price Tag for Cornwall Co-Digestion Project
Cornwall, ON, Canada (5/12/21) - The city of Cornwall is planning to ban sending organic waste to landfills starting in 2025. They are now exploring the best way to expand their capacity to accept additional organic waste at their wastewater treatment plant which will use it to produce biogas and biosolids. The financing of the project could be offset by public or private investments, but there is a history of such partnerships going awry in Ottawa which has made some decision makers weary.

Kinava Launches the Green-Waste-to-Biofuel Business with Hybrid Hydrothermal Carbonization Technology
Dangjin, Chungcheongnamdo, South Korea (5/20/21) - Kinava Co. and Korea East-West Power Co. are collaborating on constructing the Hybrid Hydrothermal Carbonization Green Pellet Pilot Project, which is a demonstration project for converting sewage sludge and wood wastes to biosolids fuel at Dangjin Power Plant. High interest in renewable energy by the utility company has accelerated waste to energy business and investment from various investors including venture capitals.


Phosphorus Is Taxing

Phosphorus has been in the news lately, perhaps because I watch for all things “P.” I learned from one news report that yet another hypothesis has been explored to explain the high concentration of phosphorus on the Earth’s crust, one that points to the solubilization of P during a period of intense electrical storm activity at Earth’s creation (Lightning Might Have Sparked Early Life on Earth). The Atlantic story from February, “Humanity is Flushing Away One of Life’s Essential Elements: we broke phosphorus,” reminds us that the explosive rise of humanity on Earth over the past 200 years arose not exclusively with the discovery of how fossil carbon could be deployed for mechanical energy, but also from the discovery of fossil sources of phosphorus that could boost agricultural production and, hence, sustain the era of industrialization.  I have also keyed in on the role of phosphorus in fresh and brackish waters in promoting excess growth of cyanobacteria, the source of HABs, or harmful algae blooms, which can kill fish, birds, pets, and, not incidentally, people (Time for bold action to protect Lake Erie from toxic algal blooms: George A. Elmaraghy). It is this last news commentary that holds the most importance to us biosolids professionals.  The article points to the growing consensus that excess total soil phosphorus from organic amendments is responsible for dangerous HABs. This issue with phosphorus, with no clear solution, is just plain taxing to read. 

Compared to carbon in the political and social marketplace of environmental ideas, phosphorus management is woefully undervalued.  Yet, it shares some interesting parallels.  The unrestrained release of carbon dioxide from fossil fuel use is akin to the unrestrained release of phosphorus from our agricultural and wastewater management systems. Both releases pose major environmental consequences. 

Scientists and economists have spent decades delving deeply into ways of reducing the unrestrained release of carbon.  They look to internalize the external costs of carbon emissions and to compel conversion to a non-fossil fuel global economy using incentives consistent with our global economic system. Broad agreement has formed around the idea that the most promising control measure is a carbon tax. Even with this agreement, carbon taxation can barely get out of the starting gate (see Carbon Tax, Its Purpose, and How It Works). Its simpler cousin, carbon emission trading, is a voluntary marketplace for carbon emission trading. In that system, a ton of carbon equivalent is valued at about $20 (Value of Carbon Market Update 2020), but this is hardly a value that would sustain major innovation in the energy sector, hence the need for a tax.  A recent economic study suggested a tax of $50 per ton of carbon dioxide equivalent (Harnessing the Power of Markets to Solve Climate Problems).  NOAA estimates that the global emission of carbon in 2019 was 10 gigatons, which corresponds to a HUGE potential tax needed for economic leverage to solve a HUGE environmental challenge. 

Phosphorus is also a huge environmental challenge.  Phosphorus flows from its source in mines to farms to soil, to food, and then to its ultimate release to sinks in river sediment and oceans, where it is lost to any possibility of beneficial recovery, even though phosphorus reserves essential for agricultural production may ultimately prove finite.  The flow of P is almost entirely uni-directional, in the same manner as the carbon in fossil fuels goes from mines eventually to the atmosphere where it is irrecoverable.  What is the voluntary marketplace for phosphorus emissions? What does the research on a phosphorus tax say about pricing? There is no market and there is no economic research. Agronomists, farmers, and environmental regulators have been struggling to understand and to manage the flow of phosphorus onto and off of farmlands without the benefit of such marketplace or research. 

Persons smart in the study of sustainability have called attention to this gap in the phosphorus issue.  The authors of Reconsideration of the Planetary Boundary for Phosphorus write of  “the contrast between large amounts of P needed for food production and the high sensitivity of freshwaters to pollution by P runoff. At the same time, some regions of the world are P-deficient, and there are some indications that a global P shortage is possible in the coming decades. More efficient recycling and retention of P within agricultural ecosystems could maintain or increase food production while reducing P pollution and improving water quality.” This observation would clearly include recycling the phosphorus that is captured in biosolids. Similarly, in the article Phosphorus use-efficiency of agriculture and food system in the US, the researchers observe “Improving yields of livestock and crop cultivation without additional phosphorus input and reducing household food waste are shown to be effective measures to improve life-cycle phosphorus use-efficiency.” They call for “a concerted effort by all entities along the life-cycle for efficient use of phosphorus.”  That effort would naturally include us biosolids practitioners. 

If a program in the wastewater profession exists for a “life-cycle for efficient use of phosphorus” I am having problems finding it.  The “big-thinkers” in the study of P know this, too.  In Our Losing Phosphate Wager, the writer concludes: “most of that phosphate-containing organic sludge is treated and sterilized …  But it is not recycled for use in chemical fertilizers… Let’s invest in methods of recycling this massive amount of phosphate waste.” 

Why is it the case that so much phosphorus is wasted?  Current regulatory requirements and economic equations would have such “concerted efforts” and investments seem nonsense. The paper Cost-effectiveness of phosphorus removal processes in municipal wastewater treatment pegs the cost of phosphorus removal from wastewater at $42 to $61` per pound of phosphorus, in comparison to the commodity value of phosphorus at about 12 cents per pound. P removal is evaluated at treatment plants for value other than fertilizer value. The 2019 WEFTEC paper “A Review for Practitioners of 10 years Industry Experience with P Recovery Technologies” frames the primary drivers as operational and maintenance savings, such as reduced polymer usage, improved cake solids, dependable permit compliance, and reduced struvite deposits in tanks and pumps. The imperative for phosphorus extraction technology has a noble aspect as resource recovery, but not a monetary or regulatory imperative.  A Wikipedia article on “peak phosphorus” duly notes “research on phosphorus recovery methods from sewage sludge has been carried out in Sweden and Germany since around 2003, but the technologies currently under development are not yet cost-effective, given the current price of phosphorus on the world market.” 

Yet in the Mid Atlantic region, high phosphorus concentrations in biosolids may well pose a threat to the goal of biosolids recycling. Environmental consequences of phosphorus releases have grown in this region, particularly in the harm to the Chesapeake Bay and Great Lakes “sinks.”  The Great Lakes Restoration Initiative (GLRI) confers “a priority to reduce phosphorus runoff” for reducing HABs, harmful algae blooms (Preventing HABs  Approaches for reducing phosphorus releases to the Chesapeake Bay are extraordinarily rife with economic, technical, and political complexity, as implicit in the Chesapeake Bay Foundation’s Phosphorus Management description of Maryland’s Phosphorus Management Tool, and by the Pennsylvania DEP’s proposal to introduce within its biosolids general permit aspects of phosphorus control

These regulatory initiatives stem from work by soil and nutrient scientists that connect the dots between total soil phosphorus and phosphorus loadings in streams. Recent journal articles discuss these complex connections. Many agricultural regions have soils with excess phosphorus. In the report A statewide assessment of the impacts of phosphorus-index implementation in Pennsylvania we learn that “The soils data indicated that statewide about 50% of samples had P levels in excess of those required for optimal crop production.” These soils pose a risk for watersheds: The report The Challenges of Managing Legacy Phosphorus Losses from Manure-Impacted Agricultural Soils explains that “soil test phosphorus (STP) concentrations that far exceed agronomic optimum… from long-term manure applications often serve as a source of P via a gradual release of dissolved P in runoff or leaching events. These losses of “legacy P” from manure-impacted soils are difficult to control and are linked to water-quality degradation in sensitive water bodies, like the Chesapeake Bay.” Scientists have studied the option of stopping additional P additions, as might occur from ceasing the use of manure and biosolids. The report  Agronomic and environmental phosphorus decline in coastal plain soils after cessation of manure application found that “over the 15 years, the M3-P across manure treatments declined steadily at 7.7–15.3 mg kg-1 yr-1.  ….sufficient P will persist for decades as indicated by the abundance of agronomic and environmental P pools.” 

If organic residual sources of carbon, nitrogen, and micronutrients from manures and biosolids are to be used in agricultural systems, the sources will by necessity also contain phosphorus. Are there ways to reduce the potential for phosphorus impacts? One major to reduce potential P release from biosolids is to precipitate the biosolids-borne phosphorus as an iron or aluminum mineral, as can be verified by the Water Extractable Phosphorus test (see  Assessment of plant availability and environmental risk of biosolids-phosphorus in a U.S. Midwest Corn-Belt Soil).  But for other organic residuals control technologies, deployment and demonstrated cost-effectiveness at the farm have not yet been shown. Nutrient management planners surveyed in Pennsylvania recommended “PA-PI [Pennsylvania Phosphorus Index] should more strongly discourage manure application to fields with insufficient ground cover, near subsurface drainage and surface inlets, and during winter. In addition, the PA planners said the PA-PI should more strongly encourage soil conservation practices such as no-till, use of cover crops, and vegetated buffers”(Nutrient management planners' feedback on New York and Pennsylvania phosphorus indices). Since much manure and biosolids are surface applied as part of a no-till conservation plan, one study (Best management practices to minimize agricultural phosphorus impacts on water quality) suggested: “ … the one-time plowing of P-stratified soils may reduce the long term loss of P in surface runoff as long as plowing induced erosion is minimized, providing landowners an additional option in keeping these soils in production under P-based nutrient management strategies.” Yet, the cost-effectiveness of many soils and farm management techniques for phosphorus are not fully researched and validated. The report One size does not fit all: towards regional conservation practice guidance to reduce phosphorus loss risk in the Lake Erie watershed  concludes “however, the application of specific conservation practices in certain environments (e.g. no‐till with surface application, cover crops) may not be effective and can even lead to unintended consequences.” 

We biosolids managers have a conundrum in our approach to phosphorus. In the mid-Atlantic region, many of the farmlands to which biosolids might beneficially and economically be delivered have soils with phosphorus levels already adequate for crop growth.  We also have technologies available that can capture a significant proportion of the phosphorus, removals of 40 percent or better of total loads of phosphorus received in the effluent, and in a form that can be delivered to farms and soils in need of phosphorus.  But we do not have a driver in place that can match the cost of phosphorus extraction at our treatment facilities to the benefits of reducing phosphorus release to the environment or of returning phosphorus to agricultural regions that need it.  Purely hypothetically now, and for the sake of argument, what if a phosphorus tax were applied to the discharge of phosphorus to our publicly owned sewers, the proceeds of which would be directed to farmers or to wastewater operations or to both? Phosphorus is an issue that, like climate change, resists a compartmentalized, “one-size-fits-all” solution. We need innovative approaches and we need financial resources.  Indeed, the situation with biosolids phosphorus is taxing.


PFAS Exposure

It has been exactly 2 years since I last did a library focused on PFAS.  I have been privately, fervently, hoping that the whole ‘crisis’ would have quietly gone away.  No such luck.  Maybe concerns have quieted down a bit, but depending on where you live, this contaminant is still driving policy decisions.  In fact, in our initial Biofest session planning meeting (YES THERE WILL BE AN ONLINE BIOFEST IN SEPTEMBER) we saw the need to have a session on PFAS.  We are hoping that the session will include how to put PFAS in biosolids into perspective.  This library is a step on that path. 

The first article (Per- and Polyfluoroalkyl substances (PFAS) in breast milk: Concerning trends for current-use PFAS) looks at concentrations in women’s breast milk.  Note that there is no direct link to biosolids here.  Smearing biosolids on one’s breasts prior to nursing is a good way to wean a baby, not to encourage weight gain.  The scientists sampled milk from 50 women and found PFAS in most.  They tested for 39 different versions, including 9 short-chain and 30 long-chain compounds.  Adding all versions together, they found a range of concentrations from 52 to 1850 pg/mL, with a median concentration of 121 pg/mL.  “pg/mL” means picogram per milliliter.  A picogram is 1 trillionth of a gram and a gram is one-thousandth of a kilogram.   A milliliter is a thousandth of a liter with one liter of water weighing one kilogram.  A trillion is a million millions or 10 12.  Expressing this as a solid concentration to get some perspective, 121 pg/mL is the same as 121 ng kg or 121 ppb.  The authors put this into perspective in terms of changes over time; as PFOS and PFOA have been phased out worldwide, their concentrations in milk have decreased.  Concentrations of PFOS have decreased by 50% in 8 years and PFOA in 17 years.  In the meantime, as we phase out these longer chain compounds but allow for the proliferation of shorter chain versions, the concentrations of short-chain PFAS in breast milk have been doubling every 4 years. 

In the June 2019 library, a PowerPoint presentation from Rooney Kim Lazcano reported the concentrations of 16 versions of PFAS in 13 different types of Class A biosolids as under 100 ppb, with one material containing just less than 200 ppb.  In other words, most of these biosolids products had concentrations that were less than concentrations in breast milk. 

Considering that the majority of biosolids are applied to agronomic crops and that enough are produced to cover about 0.1% of the arable land in the US every year, coupled with the fact that there are no reported direct applications (that I am aware of) to body parts, this strongly suggests that biosolids are not a primary pathway of human exposure.  So, let’s spend some time looking at potential pathways. 

The next paper (Environmental source tracking of Per- and Polyfluoroalkyl substances within a forensic context: Current and future techniques) talks about source tracking, figuring out where the PFAS is coming from using forensic techniques.  Think about this like our own version of the old TV series ‘Bones.’

Bones Picture

Here, the authors have a different graphic to describe their work, likely because of copyright issues.  

Note here that one of the authors of this paper is Chris Higgins, a researcher from the Colorado School of Mines, who has written extensively about these compounds in biosolids and concerns about plant uptake (more on that in article #4).   We rate the infographic in the WWTP category, though again, based on article #1; is he talking about effluent?  Anyway, this article talks about using signature isotopes to track the source of PFAS once it is found in an environmental sample.  This is a developing tool for these compounds and is complicated by their presence in such a wide range of products.  As is evidenced by article #3. 

Article #3 (Per- and Polyfluoroalkyl substances in dust collected from residential homes and fire stations in North America) focuses on concentrations of PFAS in dust from households and fire stations.  They sampled dust from 184 homes in North Carolina and 49 fire stations across the U.S. and Canada.  Here the authors also broke down compounds into long- and short-chain.  They also divided them as ‘legacy’ compounds and PFAA precursors.  Legacy compounds were higher in the fire stations, and the PFAA precursors were more common in homes.  The detection frequency of the up-and-coming compounds was 100% in both, with detection close to 100% for the legacy compounds.  If you add up the median concentrations of both classes of compounds in household dust, you get 2,100 ppb.  I found a paper on the importance of carpets for home exposure, but I opted to leave it out of the library.  Just ask if you want a copy.  

May I remind the reader that one breathes in one’s home?  Granted, dust is thicker in some homes than others (please don’t drop by unexpectedly in my house for example), nevertheless concentrations in dust are 10x higher than in any biosolids products.  

Paper #4 (Assessing human health risks from Per- and Polyfluoroalkyl substance (PFAS)-Impacted vegetable consumption: A tiered modeling approach) takes us back to Higgins, who we know is no fan of biosolids.  He was an expert witness about PFAS exposure in the Kern County case if you want proof of that.  He is a good scientist, albeit one with a mission (one could say the same about me).  Here the authors model exposure through vegetable intake with plants grown in a home garden.  Plants are exposed to the compounds through irrigation water or through a presence in soil.  The authors have a table with reported toxicity values of the different PFAS compounds in different places, including different states, as well as international values.  These numbers go all over the map, suggesting that no one really knows what a dangerous level is.  Here it is important to report the range:

PFOA 0.8- 160 ng/Kgbw-day (nanograms per Kilograms of body weight per day)

PFOS 1.8-60 ng/Kgbw-day

Within the U.S., the range for PFOA goes from 0.45 in California to 20 for Vermont and for EPA.  For PFOS, the range goes from 1.8 in California to 20 in Vermont and for EPA. 

Higgins and team used the low range of the limits for their model and also considered a wide range of conservative assumptions and came up with the conclusion that the EPA limits for PFAS may or may not be sufficiently protective.  For the commercial grower using water that is contaminated, the water to crop to person pathway is likely significant.  Remember here that in an earlier paper Higgins, so no uptake of PFAS to wheat grain when grown on very high rates of biosolids (part of the Chicago long-term plots).  In another study, he saw an uptake of the short-chain versions into garden vegetables, the ones that are still being produced.  

I hope that all of this has convinced you that biosolids are not the problem here.  Not saying that PFAS isn’t a concern, just that if you really want to rid the world of PFAS, biosolids are not where you start.  If, however, you are feeling really backed into a corner, you can take a look at paper #5, Removal of PFASs from biosolids using a semi-pilot scale pyrolysis reactor and the application of biosolids derived biochar for the removal of PFASs from contaminated water.  Here the authors looked at pyrolysis as a way to stabilize biosolids that may also reduce the PFAS concentrations in the finished material.   You can tell the author’s perspective right off when they refer to biosolids not as a national treasure but as an ‘unavoidable by-product’.  A primary focus of the paper was to see if the resulting char could be used to scrub effluent of PFAS compounds, but they also looked at the impact of pyrolysis on PFAS in the biosolids.  Here is what they found:

So, significant reductions in PFOS and PFOA and no reductions or significant increases in the shorter chain or “now growing in prevalence” compounds.  The April library looked at the value of char as a soil amendment and found that it does not quite ‘Cut the Cake,’ old song reference there for those of a certain age.  

So, what do we know?

  • Concentrations of PFAS in biosolids are in the same range as in human breast milk. 
  • Concentrations of PFAS in biosolids are an order of magnitude lower than in household dust
  • Regulations are unclear about what is safe- also varying by an order of magnitude
  • New shorter chain versions are gaining prevalence while the longer chain, older compounds are slowly becoming history

To me, this means better communication and messaging.  To others, it may mean giving pyrolysis a once-over.  Silver bullet it isn’t, but it gives you different versions of these compounds.  

[Editors Note: This overview of PFAS was prepared before the release of the Sierra Club report “Sludge in the Garden: Toxic PFAS in-home fertilizers made from sewage sludge”]


MABA Event Presentations

2021 Webinar - March 2021 on Enhanced Digestion

2021 Webinar - May 18 2021 on Solids Treatment

2020 November Phosphorus 101 Webinar

2020 Summer Webinar Series

2019 Summer Symposium

2018 Annual Meeting & Symposium

2018 Summer Symposium

2017 Annual Meeting & Symposium

2017 Summer Symposium

2017 NJWEA Workshop

2016 Annual Meeting & Symposium

2016 Summer Symposium

2016 NJWEA Workshop