Effect of a dehumidifier on the solar drying of sewage sludge-based biomixtures

Abstrakt

One of the methods for treating sewage sludge is drying. In the Polish climate, the period from autumn to spring presents a challenge, rendering the natural sludge drying process inefficient. As an auxiliary measure, a dehumidifier can be employed, which, when combined with the use of biocomponents added to the sludge intended for drying, significantly improves the outcome of the process. The drying of sludge mixtures with additives was conducted during the autumn-winter period in a 10 m² polytunnel, divided into two sections: one unassisted and the other assisted by a dehumidifier. Sludge mixtures supplemented with walnut shells, wood chips, and sawdust, as well as sludge without additives serving as a control sample, were dried. It was found that the application of a dehumidifier, even solely during the initial phase of drying, facilitated a final reduction in the moisture content of the mixtures to 30–20% after just 40–60 days, which is sufficient for their storage, transport, or further utilization. The amount of water evaporated from the mixtures with additives in the assisted section, along with the drying rate, was several times greater. For the sludge without additives, the difference in the amount of evaporated water was as much as 30-fold. The final result achieved for the mixtures with biocomponents, owing to the initial moisture content and the structure of the material being dried, was considerably superior to that of the sludge without additives, a finding previously confirmed in earlier studies conducted under natural conditions during the spring-summer period.