Biosolids SPOTLIGHT

Biosolids SPOTLIGHT: A focus on the people of biosolids who work in our region

August 2024 - MABA Biosolids Spotlight 

Provided to MABA members by Bill Toffey, Effluential Synergies, LLC 

SPOTLIGHT on Two New Members and Two Great Programs

Capital Region Water in Harrisburg, PA

The 60 foot by 160 foot covered biosolids storage pad, with a capacity of about 50 truck loads of biosolids cake, has been a family project. The Longnecker family, with patriarch 76-year-old Glenn and wife Sharon, son Jamie and his wife Gail, and son Danny built this framed and fabric covered shed in Elizabethtown, situated within the cluster of homes, barns, garages and roosts that comprise their farm. The shed is complete, the ribbon has been cut and the first deliveries of digested cake have been received from the Capital Region Water (CRW) plant 25 miles upriver on the Susquehanna River. The Longneckers grow field corn, soybean and barley on 300 acres for a herd of 200 steers and flocks of 30,000 chickens and guinea hens. In erecting this storage facility, the Longneckers ensure their ongoing supply of CRW biosolids, and avoid the “mess” that field unloading of cake had been for their nearly 20 years of biosolids use. 

spotlight 1

Three generations of Longneckers all joined in on the construction of the 60’ by 160’ biosolids storage facility on their 300-acre farm outside Elizabethtown, PA, a 25-minute truck ride from CRW’s plant in Harrisburg

 spotlight 2

The covered storage facility can hold upwards of 1,200 tons of biosolids cake for fertilizing field corn, soybeans and barley in support of their herd of steer and their flock of poultry

One big winner in this story is CRW, one of MABA’s newest public utility members, operating a 21 MGD facility in the city of Harrisburg, Pennsylvania. CRW is now rebuilding its land application program after years of landfill co-disposal.  This rebuild is part of a long-range program for reinvestment in its biosolids treatment facilities, the implementation of a biosolids master plan completed in 2018 for this plant. CRW produces approximately 2,500 dry tons of solids annually, a number expected to grow as the agency implements a project to truck-in sources of additional gas-producing organic matter for its digesters. 

Jess Rosentel, Chief Operations Officer, can readily enumerate the series of improvements that have been completed over the past several years.  A capstone of these just broke ground in June 2024, the Energy Recovery Improvements Project. Improvements to solids handling systems include such features as: installation of 1/4 inch screens at its headworks; complete rebuild of its mesophilic anaerobic digesters, including interior surface liners, replacement of gas mixers with linear motion mixers and installation of fixed covers with gas holding capacity; and separate digestion of primary and secondary solids, both sources thickened ahead of digestion by gravity belt thickeners.

spotlight 3

CRW, undertaking a series of solids handling improvements set forth in a 2018 master plan upgraded the anaerobic digesters, including adding a fixed cover in support of linear motion mixers

A key component of the digester project is the hydrolysis pretreatment of thickened waste activated solids. This process decision was supported by a comprehensive solids and energy planning model developed by engineering consultant Arcadis, managed for CWR by Arcadis’s Eric Auerbach, which showed that improved volatile solids destruction would benefit both biogas production and reduced biosolids utilization costs. 

CRW chose for WAS hydrolysis the Pondus alkaline thermal hydrolysis system manufactured by Centrisys in Kenosha, WI, and represented locally by Kappe Associates, both MABA members.  In contrast to the better-known Cambi thermal hydrolysis process that treats combined solids under high temperature and pressure to a Class A level of pathogen reduction, the Pondus system will pretreat the waste activated secondary solids at low temperature and pressure using an alkaline addition. The process will be ahead of thickening and mesophilic digestion, producing instead a Class B biosolids.  CRW did not target Class A treatment, as it is comfortable with its Class B options for utilization. Instead, CRW prioritized improved volatile solids destruction for reduced hauling volumes and increased biogas yield in support of its outlets for Renewable Natural Gas.

Pretreatment of WAS with hydrolysis was a key objective.  CRW had earlier installed Enhanced Nutrient Removal and had witnessed the troubling performance of its Belt Filter Presses (BFPs) to achieve the goal of 20 percent solids.  This is because ENR produces phosphorus accumulating bacteria that under anaerobic conditions release Extracellular Polymeric Substances (EPS) that interfere with release of bound water during press operations.  Hydrolysis promises to disintegrate the EPS to promote a far more dewaterable feedstock to the BFPs and hence significant reduction in total cake production.

Arcadis also guided CRW toward an innovative energy program for its solids treatment, providing two special components. First, a high strength liquid waste receiving station has been built which will allow CRW to accept trucked-in liquid High Strength Organic Waste (HSOW).  This organic loading will supplement the blended primary and hydrolyzed WAS by up to 20 percent of total organic loading. Some of the biogas from anaerobic digestion will still go to boilers for internal energy use, but CRW will not need to replace its 40-year-old ICE generators. Instead, it will process the biogas to standards for Renewable Natural Gas set by UGI Energy Services (UGIES) for injection into a pipeline conveniently situated along its property boundary. CRW will operate the gas clean up equipment, but UGIES will operate the equipment for continuous monitoring of gas quality, a step required for pipeline injection. The revenue from the sale of the RNG to UGIES is nearly double the basic commodity price because of the value of the RINs (Renewable Identification Numbers) assigned to biogas.  CRW will also receive tipping fee revenue for acceptance of HSOW. Nearby Derry Township Municipal Authority (DTMA), featured in the July SPOTLIGHT on Thermal Processes, has many years of experience with HSOW, and substantial additional sources of HSOW have been identified nearby by consultant Material Matters, as this region has a deep agricultural economy and many food processors.

spotlight 4

Recent ground-breaking for the Pondus thermal hydrolysis system will add to the complex of equipment that includes the gas clean up system and the receiving station for the High Strength Organic Waste liquids that provide supplemental biogas production

This comprehensive biosolids system overhaul has taken teamwork. Rosentel gives credit to colleagues throughout the chain of command. Roy Hoke, Operations Supervisor, has championed the efforts to bring the new equipment online and ensure good performance. David Stewart, the Chief Technical Officer, was instrumental in vetting the choice of processes and equipment. CEO Charlotte Katzenmoyer and the board were engaged all along the way in understanding the choices and supporting the investments.  Centrisys had to patiently await the conclusion of the yearlong negotiation between CRW and UGIES over terms of its contract before it could break ground on its Pondus system.  Arcadis remains tied to CRW in its review of equipment installation.  Material Matters is helping CRW set up its agency’s system for monitoring land applications by Longneckers and other farmers that may be attracted to CRW’s improved biosolids quality.

Upper Occoquan Service Authority in Centerville, Virginia

Biosolids dryers are the key feature of the Class A Exceptional Quality management program at Upper Occoquan Service Authority (UOSA). Its two dryers enable UOSA to dependably produce 7,000 dry tons annually of dried biosolids pellets for a wide variety of agricultural and horticultural uses in the northern Virginia region around Manassas.   UOSA operates the Millard H. Robbins Water Reclamation Plant, serving four jurisdictions: Prince William and Fairfax Counties and the cities of Manassas and Manassas Park.  It discharges an average of 42 MGD of effluent to a reservoir watershed, and hence it is tasked with very stringent standards for treatment. UOSA’s culture of innovation and high performance is captured in its solids treatment as well as its liquid treatment components. 

Class A biosolids products have been a commitment of UOSA for several decades, but the dryers were not UOSA’s first venture into production of Class A biosolids.  Windrow composting of its pressed biosolids cake was the original technology UOSA worked with, using to its advantage a remote location.  As the plant was expanded in 2001 from 32 MGD to 54 MGD and its digester capacity was expanded, UOSA moved also to a Swiss Combi closed loop rotary dryer.  The capacity of this innovative dryer, assembled for UOSA in 2004 by Berlie Technologies in Canada (now Groupe Berlie-Falco), was supplemented with the RDP Advanced Alkaline treatment system which had been installed in place of composting. RDP subsequently was kept in place to cover as a backup processing system for UOSA’s dryers if Part 503 requirements for drying were not met by the dryers or if they were down for servicing.  The Swiss Combi dryer, which is a single pass dryer with a 3.5 ton/hour evaporative capacity, could not always meet the solids volumes or meet the drying standard.  UOSA’s drying capacity was then amplified with the installation of an Andritz Rotary Drum Dryer, a triple pass dryer with a 4.4 ton/hour evaporative capacity, which became the primary equipment for Class A treatment. The Swiss Combi is pulled into operation in the Spring season, when the Robbins plant works to draw down its winter accumulation of microbial solids, “culling the herd,” as Solids Supervisor Kevin Gately calls it.

spotlight 5

Kevin Gately, UOSA Solids Supervisor, with a sample of biosolids pellets produced by the Andritz rotary drum dryer

 spotlight 6

UOSA’s rotary dryers produce rounded pellets of uniform size and strength, with a strong market value

Class A heat drying is a necessary biosolids treatment step for UOSA. Brenda Arce, Process Operations Engineer, explains that the biosolids feedstock to the dryer is a blend of digested primary sludge and undigested thickened waste activated sludge (TWAS). Without drying, a blend of TWAS and digested primary solids would not meet Class B standards, so land application of a blended cake is not an option during downtime of the dryers.  UOSA’s three digesters are set up for primary sludge digestion. The primary feed and digested solids drawdown are carefully balanced to keep the anaerobic system stable and free from foaming. Biogas is deployed in multiple ways: for gas mixing of the digester, for boilers to heat the process and to make steam for carbon regeneration, and for fuel for electricity generation in internal combustion engines. The off gas of the engines and boilers is directed back to the liquid treatment process to re-carbonate the flows after high lime chemical treatment for phosphorus capture.  Digestate and thickened WAS are blended and held in a short-term storage tank until called upon for centrifuge dewatering in Westfalia and Alfa Laval (Sharples) centrifuges, which both produce 20 percent cake feed to the dryers. Centrifuges and dryers are operated Monday through Friday.

spotlight 7

UOSA's three primary solids digesters with biogas collection system on their fixed covers

spotlight 8

The control panel for the polymer activation skid for UOSA’s automated polymer feed system

The polymer feed rate is automated, an example of UOSA’s culture of high performance.  Dosage is controlled by real time measurement of total suspended solids with a sensor in the centrate trough.   Operators clean the probes daily. and an instrument technician is on call when operators notice bad readings. A skid mounted polymer mixing system provided by ProMinent Fluid Controls replaced an earlier in-line mixer. Together, these improvements have helped control this costly aspect of solids treatment.

Thermal drying is followed by pellet cooling and screening. Oversized pellets can be crushed and undersized material can be returned for blending back in with fresh cake. The screened pellets are temporarily stored in silos, of which there are four, each with a 200-ton capacity. One of the silos is reserved for pellets that are determined to be not within specification as Class A product by temperature monitoring.  All silos are protected from hot spot development with a nitrogen purge system.  The entire drying operation is kept nearly dust free with the use of sonic air fans mounted in the ceiling and with regular hosing down of all surfaces. According to Gately: “We have had no explosions, knock on wood,” a sentiment to which Lead Operator Jimmy Ojeda quickly agrees. 

A constant in UOSA’s solids program is Synagro, the service company handling biosolids pellets as a soil amendment product for land application. Steve McMahon, Mid-Atlantic Product Sales Manager, arranges pellet distribution to landowners, golf courses, landscapers and soil blenders under the trade name Granulite in Virginia, North Carolina, Pennsylvania, Alabama and South Carolina.  UOSA understands that its pellets, with good uniformity and strength and with low odor, are among the best pellets that Synagro can offer to customers.  Should the pellets be off spec in any way for the fussier customers, McMahon can readily distribute them to farmers eager for the nutrients. Synagro also covers for UOSA the Virginia DEQ regulatory requirements for reporting and site permit compliance.

spotlight 9

Synagro markets UOSA pellets under its Granulite trade name to farmers and landscaping customers

With close attention to excellence in design, operations and maintenance of all steps in the solids treatment process, UOSA has a biosolids recycling program that stands with the best in the Mid-Atlantic region.

For more information, contact Mary (Firestone) Baker at [email protected] or 845-901-7905.

 

July 2024 - MABA Biosolids Spotlight 

Provided to MABA members by Bill Toffey, Effluential Synergies, LLC 

SPOTLIGHT on Thermal Processes in the MABA Region 

We are close, really very close!  There is no risk of jinxing any of the four projects by predicting that, within 24 months of this SPOTLIGHT, the MABA region will have four operating thermal systems for depolymerizing biosolids.  These are the four: BioforcetechEarthcare BethelEcoremedy and CHAR Technologies. Not among these four are those “in the pipeline” projects introduced in other regions (374WaterGenifuelKORE Infrastructure, Heartland HelioStorm). Also not listed are other projects in the MABA region that are either not truly “off-the-ground” (Saratoga Biochar Solutions) or that are awaiting some big actions to revive them (Aries Clean Technologies and Biowaste Pyrolysis Solutions).  But having four on track is amazing, as they are near MABA members, and each holds the possibility of becoming reference facility operations. This is a breakthrough in biosolids technologies. 
 
A special aspect of the four projects in the Mid-Atlantic region is how they allow for useful comparisons. Two are municipal projects (Ephrata and DTMA); two are private ventures (CHAR Technologies and Earthcare Bethel).  Pyrolysis and gasification are both represented. The residuals range in quality from biochar to ash.  A common element is the processes are autogenous, meaning sustained without outside fuel sources. Expected feedstocks range from raw cake to digested cake to digested dried pellets. One technology (CHAR) proposes a mobile unit suited for use by multiple small treatment plants, a second technology (Bioforcetech) is suited for fixed installation at a small plant, a third (Ecoremedy) for installation at a medium size plant, and the largest of the bunch (EarthCare Bethel) is a standalone plant accepting sources of organic residuals from multiple classes of industrial and municipal plants.  Yes, should all of these prove successful, the Mid-Atlantic region will be blessed by an array of options that will be references for the entire U.S., and perhaps beyond. 
 
Earthcare Bethel
Earthcare’s gasification facility in Bethel, Pennsylvania, is the furthest along, as it is getting ready for its first deliveries of biosolids cake the last week of July 2024. Earthcare Bethel, LLC (a venture of Earthcare LLC, Earthcare Solutions LLC and BLDPC Ventures LLC) consists of two gasification units, both sized for 40 dry tons of feed daily, one primarily gasifying an agricultural residual and a second, newer unit committed to biosolids cake.  While connecting to the electric utility delayed start-up, the facility has been able to go through commissioning of both units. Leading the development effort is Sean Sweeney, an engineer and Senior Vice President at Barton Loguidice DPC and now Earthcare Solution’s Executive Vice President. But the vision for this facility is that of company founder Mike McGolden, who has delivered over the past 20+ years on ten thermal facilities in the U.S. and abroad. Earthcare gasifiers accept a variety of organic waste feedstocks, though the Bethel facility is the first with a unit devoted to biosolids.  The “secret sauce” for the Bethel facility is the availability nearby of high carbon poultry litter that, when gasified alone or in combination with biosolids, produces a biochar conforming to standards of the International Biochar Initiative for use as a soil amendment and for use in site remediation, both in collaboration with its allied enterprises, EcoChar LLC and EcoChar Environmental Solutions, LLC.

spotlight 1

Earthcare Bethel has completed installation of its drying and gasification facility in Bethel, PA, for producing biochars from biosolids and agricultural residuals, and shipments of biosolids will begin before the end of July 2024.

Earthcare Bethel will be operated as a merchant facility, accepting deliveries from multiple haulers bringing in dewatered biosolids of varying treatment levels, including raw sludges. Sweeney is looking for biosolids cake that is between 18% to 25% in solids content. Cake will be delivered to a receiving building where it is loaded into a hopper for blending with dried agricultural litter to achieve an optimum moisture and energy content for feed to a triple pass drum dryer.  The discharge goes through a cyclone separator, with the solids directed to the gasifier. The syngas coming off the gasifier is fuel for both the gasifier itself and for the dryer, and the system is operated to allow significant carbon to be fixed in the char rather than completely oxidized.  The gasifiers will eventually run 24 hours a day, seven days a week.  The system includes blending with additives and activating the char so that it is tailored to meet customer requirements. The state Solid Waste facility permit will be tied to production for commercial biochar outlets. During start up, Earthcare will be collecting samples of the feedstock and the final product to demonstrate product conformance to state biosolid standards and IDI biochar standards.  While the system is not designed with PFAS or microplastics in mind, Earthcare believes its system will be shown to mitigate both.
 
Ephrata Borough Authority and Bioforcetech
Ephrata Borough Authority’s installation of the Bioforcetech facility is close behind EarthCare.  Its two Centrisys centrifuges and four proprietary dryer units, called BioDryers (slowly rotating drums that are aerated and heated), are already in operation, and the pyrolysis unit is installed and is in the commissioning stage. The origin of this project was a response to an RFP by Ephrata to design a Class A biosolids stabilization facility at its Treatment Plant #1, a plant with a current flow of 2 MGD and designed for 3.8 MGD, to replace a system that had no stabilization process.  The Borough’s original concept was a temperature-phased anaerobic digester system with centrifuge dewatering, producing a Class A cake that could be used by local farmers. The engineering firm of GHD assembled an alternative proposal, subsequently accepted by the Authority, which followed the success of the Bioforcetech pyrolysis process at Silicon Valley Clean Water in Redwood City, California, which boasted useful biochar products.  The biosolids is first dried in a “BioDryer,” a proprietary system resembling an enclosed composting chamber and then processed through a pyrolysis unit to produce biochar. 

spotlight 2

Ephrata Borough Authority, with centrifuges and the Bioforcetech BIoDryers (pictured here) installed and operating, is now starting up the newly installed pyrolysis unit, with assistance of consultant GHD.

GHD has led the efforts to bring this technology to Ephrata. Charles Winslow is the project manager overseeing the purchase of the system and guiding the installation. The components in place today include centrifuges and BioDryer, which together take solids up to 75%. Start-up is now imminent for the third element, the pyrolysis unit, which will receive a continuous flow of cake for final drying to 95% followed by thermal depolymerization in the absence of oxygen to produce a biochar.  A key aspect is the oxidation of the syngas produced by the pyrolysis unit, using 30% of the heat for operating the pyrolysis and the other 70% for drying the biosolids in the BioDryer and in the storage unit after dewatering. Carbon filters and wet scrubbers are the air control system off the pyrolysis unit. Supplemental fuel is only used for start-up.  The pyrolysis units, now in their second generation of design, are expecting two months of operation before cleaning.  The biochar will be marketed by Bioforcetech, the revenue from which will be shared with the Authority.  PFAS concerns were a secondary, but deciding factor, in Ephrata’s selection of the system; the primary driver was the cost effectiveness of the total operation compared to other advanced stabilization technologies. 
 
Synagro’s CHAR Technologies
CHAR Technologies, out of Ontario, Canada,is manufacturing a demonstration unit of its high-temperature pyrolysis process. This demonstration unit was purchased by Synagro, which saw its role in solids processing at small plants and a potential to scale up to large facilities. The system Synagro purchased from CHAR is skid mounted and mobile, and, without a dryer component, is set up to process dried biosolids pellets. The expected initial trial in the Mid-Atlantic region is Baltimore’s Back River Treatment plant.

spotlight 3

Synagro purchased the mobile pyrolysis unit shown here, designed and built by Canada-based CHAR Technologies, with an eye toward demonstrating it at Baltimore’s Back River plant, where Synagro operates a biosolids dryer.

CHAR Technologies’ Pyrolysis Demonstration Unit (PDU) depolymerizes dried biosolids through pyrolysis, a high temperature thermal process operating in the absence of oxygen in a rotary kiln chamber with an external burner.  Except during start-up, the PDU is autogenous, as it is fueled with the syngas generated during the breakdown of biosolids, a major beneficial feature of the system.  The syngas contains dust, steam, hydrogen, carbon monoxide, carbon dioxide and methane, so the PDU is equipped with scrubbers that convert the syngas for internal use in the pyrolysis unit, with excess syngas combusted, along with exhaust gases from the pyrolysis unit, in a thermal oxidizer unit before being discharged through the stack. The excess syngas will be evaluated for suitability to use as supplemental energy for drying facilities at future installations. At full deployment, the PDU will produce approximately 143 standard cubic feet per minute of high heating value syngas and roughly 4 tons per day of inert carbon-rich biochar that can be used as a soil amendment or used as fill.  Approximately 26 gallons per hour of high Chemical Oxygen Demand ("COD") wastewater will be discharged back to the WRRF for treatment.
 
Derry Township Municipal Authority and Ecoremedy
Derry Township Municipal Authority (DTMA), Hershey, PA, is ready to pull the trigger on constructing the Ecoremedy gasification system, having navigated several complex processing, finance and permitting challenges that would rightfully cause any reasonable wastewater manager to pause.  The story of how Ecoremedy came to be is part of the larger story of DTMA’s biosolids program.  DTMA has “seen it all” with biosolids treatment and use. At one time, Derry had incinerators; these were followed by liquid injection to farmlands of lime stabilized biosolids; in  turn, this program was followed by anaerobic digestion with biogas fueled indirect paddle dryers. But “stuff” happened, such as a flood that damaged cogeneration equipment, irreparable wear and tear to its dryers, and problems with farmer complaints about dusty dried biosolids. While DTMA is back using Class B cake on farms, a master planning effort led by Brown and Caldwell was guided by DTMA’s goal of returning to Class A product and on staying ahead of the regulatory curve, which seemed to be pointing to PFAS regulation and restrictions on Class B use. DTMA also sought to preserve its “net energy positive” reputation with hauled-in organic waste feeding its iconic egg-shaped digester.

spotlight 4

The operator visually checks centrate return from the centrifuges to verify capture rate and polymer dosage, both factors in ensuring performance goals are being met.

Yes, DTMA’s 5 MGD plant has a complex set of moving parts, but Bill Rehkop, Executive Director for DTMA (PA), thrives on complexity.  When Ecoremedy, a local firm that had been experimenting with gasification of manure, turned its focus to biosolids with a demonstration project in southeastern Pennsylvania’s Morrisville STP, Rehkop took note.  He enlisted Brown and Caldwell, a firm with deep biosolids experience, to accompany DTMA in doing the detailed work of ensuring Ecoremedy’s success in delivering a facility that left no aspect to chance, including details of conveyance, storage, ventilation, odor and dust control, and fire/explosion protection. On top of this, Rehkop has consistently held as a core goal that of ensuring reliable flow and use of DTMA’s biosolids should an interruption of the gasification system occur, as he could move on a dime back to the use of Class B biosolids to farmlands.  Rehkop has also been persistent: confronting the intention of state regulators to reclassify its biosolids as industrial residuals; seeking to maximize state financial incentives (Penn Vest revolving fund) and procurement mechanisms (COSTARs); and, designing its gasifier to operate as a regional biosolids facility.  At the end of the process, DTMA will be producing a mineral rich ash, low in carbon because of nearly complete use of carbon for energy production. It will be a system that drives energy efficient drying and depolymerization process to yield a residual with soil building and plant nutrient attributes.

For more information, contact Mary (Firestone) Baker at [email protected] or 845-901-7905.

 

June 2024 - MABA Biosolids Spotlight 

Provided to MABA members by Bill Toffey, Effluential Synergies, LLC 

SPOTLIGHT on Henrico Water Reclamation Facility 

Henrico County Virginia’s biosolids program is in a sweet spot. Division Director James Grandstaff, Henrico Department of Public Utilities Water Reclamation Facility (WRF), can confidently stand by his biosolids program for meeting today’s goals while looking well into the future.

Henrico County’s WRF serves a geographically large wastewater system that wraps around Richmond, Virginia. It serves 330,000 people, treating about 40 million gallons daily and producing 110 wet tons daily of anaerobically digested cake, or about 40,000 wet tons annually. The WRF is located at a far southeastern corner of the county, out of sight of populated areas, and with space to spare for its processes and products.

One important attribute of Henrico’s sweet spot is that its solids processing systems have been thoughtfully shaped to support the WRF’s tough environmental standards. Its three centrifuges are operated in afternoon and evening shifts to conform to the pattern of high influent flows to the plant, helping the plant ensure compliance with its strict effluent standards for nitrogen (5 mg/l) and phosphorus (0.4 mg/l). The plant has an enviable 60 days of covered storage and another 60 days of uncovered storage for biosolids. For Grandstaff, the principal benefit of this storage is not so much in enabling distribution of biosolids that meets seasonal demand by his farmer customers, which is one goal, but in meeting a high standard of quality control, by enabling complete regulatory compliance with biosolids standards. No biosolids leaves the WRF until all data on compliance with pathogen and vector reduction standards and on pollutant and nutrient concentrations have been received and compiled for the NANI – the notice and necessary information -- the form released to the land application contractor Synagro prior to biosolids shipments. 

spotlight 1

This is a ground level view of the holding area for biosolids cake, with both the covered storage and the open storage, each able to carry up to 60 days of storage. This capacity enables Henrico to hold product ahead of all process and quality data being received to document compliance for the monthly Notice and Necessary Information form.

Phosphorus in effluent and in biosolids has been a challenge for many treatment facilities in the mid-Atlantic region, and again Henrico is in a sweet spot for phosphorus management. The utility receives the residuals from drinking water filtration plants that the county also runs. This is an alum residual that has the effect of binding with phosphorus. The benefit to Henrico’s WRF is that struvite formation within the plant is not a problem. Also, return flows of P in the centrate to the head of the plant are controlled when the centrifuges are operated for the 10 to 14 hours during periods of high plant flows, helping keep P concentrations diluted. Even so, as another sweet spot, Grandstaff looks forward to studies that examine technologies for phosphorus capture in the side stream centrate flow.

Another sweet spot is the good quality of the Class B cake. The four anaerobic digesters are operated with a solids retention time of over 20 days at a temperature of 98 to 99 degrees F. This is a combination of time and temperature that readily meets standards for a Process to Significantly Reduce Pathogens, which Grandstaff confirms with an “above and beyond” testing for fecal coliform in the cake. The standard of 38 percent volatile solids reduction for the Vector Attraction Reduction standard is also confidently met, but again confirmed with testing “above and beyond” of liquid sludge samples for stability using the 40-day test. This extra stabilization testing is a hedge against an occasionally large flow of alum residuals into the digesters that can confound monthly calculations of VS destruction. 

spotlight 2

Weekly biosolids cake samples are collected from the discharge conveyor for pollutant characterization, nutrients, and VS and PR compliance. Note the consistent, cloddy texture of the cake which verifies the solids content at or above 22 percent.

Henrico’s anaerobic digesters are a part of the biosolids sweet spot story. Solids flow to a set of three primary and one secondary digester. The digester capacity is such that the solids can be handled by three of the four digesters. This capacity allows Grandstaff to put digesters on a cleaning cycle every four years, ensuring not only full hydraulic capacity but also allowing timely repairs, such as clogged nozzles. While biogas is currently used as fuel for boilers that heat the digesters and 5 plant buildings, Grandstaff sees biogas as a resource with a higher value. He looks forward to a future Public-Private-Partnership contract that would cover biogas cleaning and offsite delivery as renewable natural gas. The current electricity price of $06.8 per kWh enjoyed by Henrico has made installation of its own co-generator system non-economic, and the low rates also have interfered with responses to a PPP for production of RNG. 

Land application of biosolids is a key sustainability feature for Henrico treatment program. Grandstaff has been moving Henrico to as nearly complete beneficial use of biosolids as can be economically and programmatically accomplished. Though co-disposal in municipal solid waste landfill is available as an emergency backup at any time, the goal for Henrico and its current contractor Synagro (a Mid-Atlantic Biosolids Association member) is full land application of biosolids. Henrico’s Class B anaerobically digested cake is great quality for the region’s farmers, according to Allen Guilliams, Synagro’s Director of Operations in Virginia, who points to its consistent quality and low odor as positive attributes for farmers. Guilliams is a 40-year veteran of biosolids application in this part of Virginia and is thereby a survivor of many historic challenges with land application. Guilliams and the land application operators with Synagro Virginia gratefully acknowledge today’s strong support from the Virginia Department of Environmental Quality and the efforts of the Virginia Biosolids Council for the improved climate for biosolids in Virginia over the years.

spotlight 3

A view from within the cab of the front-end loader preparing to lift Henrico WRF biosolids cake into an awaiting manure spreader (not pictured). Note the tri-axle dump truck equipped with wheels for safe unloading on farmlands.

The sweet spot for Henrico biosolids is the skill of Guilliams and the Synagro team at carefully matching his many nearby farmer customers with the Henrico product. They match the farmers’ planned sequences of row crops (mostly corn and soybean) and cover crops (e.g., oats, rye and fescue) with availability of biosolids. Biosolids are mostly applied in soil surface applications to meet the no-till farming practices used in this region. Synagro’s large land base is adequate to meet the increasingly important goal for phosphorus management by rotating fields for biosolids on a three-year cycle. Because Synagro manages biosolids from several utilities that employ lime stabilization, they are able for some farmers to balance the acidifying effects of anaerobic cake with biosolids-borne lime. Another unique feature for Henrico is that gaps in the seasonality of agricultural demand for biosolids can be filled by Synagro with silviculture applications to Loblolly Pine tree farms. 

The sweetest spot arises from the strong team that works to make the biosolids program happen. This starts with Grandstaff himself, an effective manager with private-sector plant management experience, who has that special “touch” that empowers his staff to “own” their processes, create work arounds when needed, find economies and prepare for unexpected situations. One example has been with the effective control of dosage in polymer use, keeping rates well below industry standards, with clear budget benefits.

spotlight 4

The operator visually checks centrate return from the centrifuges to verify capture rate and polymer dosage, both factors in ensuring performance goals are being met.

The strong team includes the engineers at Hazen and Sawyer, a MABA member. Hazen staff at the Richmond office have partnered with Henrico through a generation of equipment upgrades and expansion. Hazen has been working at Henrico since 1998 and oversaw its expansion from 45 MGD to 75 MGD, completed in 2012. Major projects underway today include upgrades to 11 clarifiers, to primary and secondary BNR systems, and to deep beds for tertiary filtration. Hazen is also doing a conceptual design for metal salts additions to fine-tune phosphorus loading conditions, and looking at options for P removal through side stream treatment of centrate.

Grandstaff sees up ahead the need for a master planning effort. A key concern, as with many other MABA members across the region, is the effects of PFAS study and regulation-writing that are currently in full swing at EPA and in state government. While an early examination of wastewater and biosolids at Henrico points to no significant industrial sources of PFAS to its WRF, Grandstaff believes that a prudent course ahead is the study of technologies that could reduce PFAS and other currently unregulated organic contaminants, such as microplastics. The consultant tapped in the future to help guide Henrico’s master plant will find in Henrico’s adaptability and flexibility the kind of "sweet spot” that will ensure a solid biosolids future. 

Henrico WRF is the featured tour of the Mid Atlantic Biosolids Association 2024 Summer Symposium. The symposium begins with a Tuesday night reception on July 9 and completes on Thursday, July 11th, at the Omni Richmond in downtown Richmond. The WRF tour, which will be held on Thursday morning, 8:00 to 9:30 AM, is detailed in the program brochure.

For more information, contact Mary (Firestone) Baker at [email protected] or 845-901-7905.

 
<< first < Prev 1 2 3 4 5 6 7 8 9 10 Next > last >>

Page 4 of 13