AC24’s School of Solids Offers a Unique Look at a Biosolids Operation 

AC24 PREVIEW: School of Solids, Tuesday, April 9
Roni Gehlke, Clean Water Magazine editor, Resource Recovery


During AC24’s School of Solids, CWEA members will be given a unique opportunity to spend the day at an operating wastewater treatment and resource recovery facility. The day will focus on understanding how biosolids are managed, the technologies used to treat the biosolids, and how to operate and maintain those technologies and supporting equipment. The pre-conference workshop will be held at the Fairfield-Suisun Sewer District (FSSD), the first in the country to partner with the private sector to produce a biosolids-derived liquid fertilizer.

A series of education stations will be set up along the solids treatment train, where small hands-on classes will be held. Each education station will be led by an experienced certified wastewater treatment plant operator, with other operations and maintenance folks bringing their experience into the mix.

“We’ll be able to show the equipment working to treat and move the biosolids,” said Mary Martis, the current chair of CWEA’s Biosolids Committee and one of the co-founders of the School of Solids. “Additionally, there will be another unit offline and/or partially broken down in the vicinity of each of the operating equipment stations to give everyone a look under the solids.”

Martis said this will give those touring the facility the opportunity to look inside and see how the equipment works.

“Usually, when you take a tour like this, it relies on someone conducting the tour and telling you how the unit works,” said Mark Harris, another co-founder of the program and the O&M manager at West County Wastewater. “With the unit broken down next to the working unit, it gives you a big added value to see what’s going on inside.”

In 2021, a group of seasoned professionals were discussing organizing a tour of the Roseville Dry Creek Wastewater Treatment Plant as part of the upcoming CWEA annual conference. During the discussion, they came up with the idea of creating a School of Solids during the tour. The School of Solids tour was designed to include a host of stations/outdoor classrooms that covered different aspects of Dry Creek’s biosolids operation, with opportunities for hands-on experiences. Each station had an educational session led by volunteer operations and maintenance professionals who came from treatment plants around California to provide a comprehensive learning experience.

A similar program will occur at Fairfield-Suisun, except this facility has a slightly different process. This wastewater treatment plant is also unique because, since May 2015, FSSD has had a Public-Private Partnership agreement with Lystek International Limited. The Lystek operation converts biosolids into fertilizer, which is an innovative way of beneficially using the material.

The partnership provides physical space at the District’s wastewater treatment plant for Lystek to operate a biosolids processing facility, also called the Organic Material Recovery Center, or OMRC.

“Lystek’s OMRC accepts dewatered biosolids from the District, as well as biosolids from other wastewater treatment plants around the San Francisco Bay Area and other areas in California. These biosolids are further conditioned in the OMRC process using thermal, chemical, and physical treatments until they meet EPA’s Class A standards,” explained Ben Carver, operations manager at FSSD. “Afterward, it is sold to local farmers as a liquid fertilizer for sub-surface injection.”

Lystek’s services provide FSSD with a solution to CA Senate Bill 1383, which requires diverting biosolids away from landfills.

FSSD is responsible for maintaining and operating a 70-mile-long sewer system that includes 13 pump stations. They are also in charge of wastewater collection, treatment, water recycling, and stormwater management services. The wastewater treatment plant has a design capacity of 23.7 MGD average dry weather flow and can handle a wet weather operational capacity of 45 MGD. The District caters to over 135,000 customers comprising of residential, commercial, and industrial sectors in a 48-square-mile area.

Carver said that the biosolids treatment train consists of two Alfa Laval Aquabelt two-meter gravity belt thickeners for secondary sludge thickening, as well as two single-stage mesophilic anaerobic digesters with mechanical mixing. Added to the system are one FKC screw press and 40 asphalt-lined drying beds for solids dewatering. Biogas is captured and utilized to produce heat and electricity.

The AC24 School of Solids will include an expanded version of the SOS Notebook with focused content on FSSD’s biosolids program. The tour will include 50-minute sessions at six stations showcasing FSSD’s operation and offering Q&A opportunities. The six stations include:

  • thickening stations with an emphasis on gravity belt thickener technology, polymer basics, and when it’s time to change
  • high-strength liquid waste receiving plus anaerobic co-digestion, waste management agreements, enhanced biogas production, sidestreams, and nutrient management
  • dewatering with an emphasis on belt filter press technology and co-digestion impacts to dewatering
  • biogas conditioning, plus biogas utilization, cogeneration, and renewable natural gas
  • Lystek ORMC, Public-Private-Partnerships, and farming as a beneficial use
  • A look at the future of biosolids management, PFAS, microplastics, and other unregulated organic compounds, as well as emerging technology solutions

“Lystek’s process is not used at any other wastewater plant in the U.S.,” Johnson Ho, a co-founder of the School of Solids and the O&M manager at Vallejo Flood and Wastewater District, said. “This plant is showing the present with the future at this School of Solids.”

Join this pre-conference workshop at the Annual Conference in Sacramento on Tuesday, April 9 at 7:00 a.m.