System Uses the Sun for Biosolids Drying

THERMO-SYSTEM from Parkson Corp.

The THERMO-SYSTEM active solar biosolids dryer from Parkson Corp. uses 95 percent solar energy and ambient air to remove water from biosolids, producing a dry Class A material that can fuel waste-to-energy plants, coal power plants, or cement kilns.

The odorless, biologically stable and nearly pathogen-free end product also can be used as fertilizer or soil conditioner. The drying plant, which resembles a large greenhouse, has a louver-controlled fresh air inlet, sensors that monitor the climate inside and outside, a PLC that controls and monitors the drying process, speed-controlled ceiling fans for optimal airflow, and exhaust fans to maximize drying.

Biosolids containing 15 percent solids can be dried to 75 percent dried solids or more. Liquid material can be pumped into the drying chamber, or cake can be trucked in. Dried product is removed with a front-end loader or screw conveyor.

The system’s main advantage is in energy savings. “You have to burn about 100 liters of oil for every ton of evaporated water or use about 100 to 140 kilowatt hours of electrical energy,” says Dr. Markus Bux, inventor and THERMO-SYSTEM CEO. “With the solar drying system, you use 20 to 40 kilowatt hours of electrical energy per ton of evaporated water. And you reduce your CO2 footprint by 90 percent.”

Underfloor heating and heat exchangers are available for colder climates. Inside each drying chamber is a four-wheeled, fully automated Electric Mole. Resembling a Volkswagen Beetle, it makes one to 30 trips lasting 20 to 60 minutes around the drying plant each day. Its stainless steel paddles help mix and aerate the biosolids. Each Mole measures 7 feet long, 4.5 feet wide and 3.5 feet high and weighs 1,300 pounds. The number of units per plant varies with facility size.

Engineered with few moving parts, the drying system can be used in wastewater treatment plants from 0.2 to 40 mgd. The largest such plant, in Spain, covers 215,000 square feet and uses 24 Mole vehicles. 888/727-5766;


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