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. 

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. 

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.

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.

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.