Improving sludge drying processes with a solar greenhouse

Sludge handling in a wastewater treatment plant (WWTP) is associated with significant operational costs, which vary based on the plant’s site and the treatment method used in both the wastewater and sludge handling units. Recent studies have pushed for the development of creative and cost-effective methods aimed at lowering surplus sludge distribution costs.

Sun greenhouse drying systems are a beneficial alternative for medium-small-scale WWTPs located in climate zones defined by strong solar radiation, with the goal of adopting environmentally friendly operations and utilizing renewable energy sources. Traditional solar greenhouses use both solar-generated hot water and energy provided by the greenhouse effect.

A dynamic greenhouse for sludge drying is made out of an impermeable floor warmed by hot water pipes where the wet sludge is placed and a transparent ceiling (polycarbonate or glass) that creates the greenhouse effect.

Static solar greenhouses for sludge drying founded on the assumption of heat convection have not yet been presented to the best of the researchers’ knowledge. In light of this, the current research presents the first findings obtained with a unique closed-static solar greenhouse setup for sludge drying. The use of a forced ventilation system rather than hot water below the wet sludge for sludge drying was the solar greenhouse’s key innovation, as was the use of 100% green energy for the whole system’s functioning.

Sorrenti, A.; Corsino, S.F.; Traina, F.; Viviani, G.; Torregrossa, M. Enhanced Sewage Sludge Drying with a Modified Solar Greenhouse. Clean Technol. 2022, 4, 407-419. 

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