Description:
Solar drying technology is based on the heating of the sludge until the temperature reached in the greenhouse and drying through the evaporation of water from its surface. As a result we have a product with solids content above 70%.
Due to the development of temperatures above 50oC for a long period of time, the sludge is hygienized and can be used as fertilizer. Furthermore, the dried sludge produced from solar drying has high calorific value and thus can be used as fuel in a waste-to energy plant, either on-site installation or in larger co-ombustion plants (electricity, cement, waste incineration plants)
Greenhouses:
- are lightweight constructions made of galvanized steel support structure in a watertight concrete surface with walls on three sides 1m height and 0,25m width
- covered either with polymer or glass cover
- are equipped with sensors that record the monitoring parameters inside and outside of the greenhouse and regulate the process
- have robots moving vehicle or mechanism mounted on the walls of the greenhouse to mix the sludge
- Drying of the sludge to a solids content of at least 70%
- Low investment costs, operating and maintenance
- Closed system that minimizes odor and other environmental nuisances
- Fully automated operation and monitoring
- Modular system, easily expanded
Advantages:
Case Study:
MESOGEOS constructed in Hersonisos landfill a solar drying plant, with a surface of 950m2 to treat 2000 tons of sludge produced per year from the Hersonisos WWTP. The following table shows the operational parameters of the system.
| Parameter | Unit | Value |
| Total quantity of incoming sludge | tn/year | 2.000 |
| Solids content of incoming sludge (%) | % | 18,00 |
| Solids content of dried sludge (%) | % | 60,00 |
| Sludge height in greenhouse | cm | 10 |
| Total quantity of dried sludge | tn/ year | 600 |
| Water evaporated | tn/year | 1.400 |
| Treatment cycles annually | Number/year | 26 |
| Drying duration | Days/cycle | 14 |