Biosolids management challenges clean-water plants in a variety of areas — cost, energy efficiency, resource recovery, product quality, odor control and more.

A process developed by Sedron Technologies is designed as a complete, holistic solids handling system that delivers a dried Class A product with a variety of potential end uses. Sedron was introduced to the wastewater industry through involvement with the Reinvent the Toilet Challenge created by the Bill & Melinda Gates Foundation. That experience led the company to explore solutions for other waste streams.

The Varcor system is based on a proven thermodynamic process called mechanical vapor recompression. In addition to the dry solids, it yields distilled water and ammonia solution. The process is not susceptible to biological or chemical upsets and can process septage and biosolids (as well as agricultural manure).

A variety of options are available for implementing the system, from installation and operation by Sedron to outright purchase of the technology by the clean-water plant. Lucas Reid, program manager and business development representative, talked about the process in an interview with Treatment Plant Operator.

What was the genesis of this technology?

Reid: In 2011, the Bill & Melinda Gates Foundation contracted us to develop a technology called the Janicki Omni Processor as a way to help solve sanitation problem in developing countries. That process could take an incoming waste stream at about 20% solids and dry it in an evaporative dryer to 90% solids. That dry material was combusted in a boiler to produce steam to turn a turbine and generate electricity; the evaporated water was condensed and could be treated to any desired standard.

How did news about this technology spread?

Reid: We built a pilot unit in 2013. In 2014, a video of Bill Gates drinking treated water from the unit went viral. We started getting phone calls from around the world; people saw the Omni Processor as a silver bullet for their problems. Dairy farmers called and asked if we could process manure. We said no because dairy manure had only about 4% solids. But the calls kept coming, and we found a way to process that low-solids material economically, without any biological or chemical systems — an all-thermal process.

What do you see as the advantages of a completely thermal process?

Reid: First, with a thermal process, you kill all the pathogens. Second, it doesn’t matter what the input material is. As long as the waste stream is pumpable and flowable and contains water and solids, our system will process it.

What thermal process is used in the Varcor system?

Reid: The Varcor system uses a mechanical vapor recompression, in which we run steam through a compressor and increase its pressure and temperature using a very small amount of energy. We can then use that hotter steam as an energy source for evaporating the incoming water. It’s about 30 times more efficient than evaporation by direct boiling. We use a natural gas steam generator to kick-start the system. That takes four to six hours, and then the system runs continuously.

How is the evaporator designed to use that heat to dry material efficiently?

Reid: After looking at many types of dryers and evaporators, we settled on thin-film drying. It’s like cooking crepes on a griddle: We apply a very thin amount of material, heat it until the water is gone and then mechanically scrape the dried material off.

What happens to the liquid evaporated from the waste stream?

Reid: The water and everything that has a lower boiling point evaporates. In the wastewater industry, there’s a lot of ammonia in those streams. We developed a patented process to remove this ammonia and concentrate it into its own stream. So we’re left with clean water, a 20% aqueous ammonia solution and the dry solids.

How would you describe the value of your process to a wastewater treatment plant?

Reid: Originally we targeted biosolids management and the ability to take the material to a 90% dry Class A product. When we investigated further, we found an additional benefit in sidestream nutrient removal. The filtrate or centrate from biosolids dewatering is very high in ammonia; it goes back to the headworks and accounts for a high percentage of the plant’s nitrogen loading. Our process removes that high-ammonia return stream and recovers the nutrients.

What is done with the aqueous ammonia solution?

Reid: We take that product away and work with farmers and fertilizer companies to use it as a fertilizer. The volume of aqueous ammonia depends on the size of the unit and the concentration of ammonia in the waste stream. Our current commercial system is designed to process 90 gpm of waste. For septage, the ammonia content can range from 20 to 200 ppm, which results in 30,000 to 40,000 gallons per year. For a wastewater treatment plant with anaerobic digestion, the ammonia content can be 900 to 1,700 ppm. Regardless, we will work to find a beneficial use for the product.

How much maintenance does this system require?

Reid: We designed the process for ease of operation and maintenance. All the pumps, piping and other components, except for the evaporator, are standard industry items. The wear surfaces on the rotating discs use a very hard material call Hardox (SSAB). The scraper blades are easy to replace without tools. The control system is fully automated. Our O&M cost is competitive with other technologies. The system is designed to run because we know the material doesn’t stop coming. 

What is being done to prove out this technology?

Reid: We have our first large-scale pilot processor running on a dairy farm in Texas, and our first commercial unit is on a dairy farm in Indiana. We’re working with a number of wastewater treatment plants to run their products through our test unit in Sedro-Woolley, Washington. We have a septage processing facility south of Seattle that will be operational in the first quarter of next year. We’re going to own and operate that facility, taking septage from local haulers and biosolids from wastewater treatment plants. We’re doing this because we want to prove that the technology works.