Valorização agronómica/energética de lamas de ETAR

Mestrado em Engenharia do Ambiente - Instituto Superior de AgronomiaThis work aims to evaluate the use of 4 different sewage sludges as a fertilizer: mixed sewage sludge (primary+secondary sludge), dehydrated mixed sewage sludge; anaerobically digested sewage sludge and anaerobically digested sewage sludge treated with quicklime (CaO). Two aerobic incubations were performed with mixtures of sludge and the top layer of a Haplic Pdzol, at a rate equivalent to 10 ton dry matter ha- 1. During 140 days, the CO2-C emissions and the mineral N in soil were periodically measured. At the end of the incubation period, several soil properties were evaluated. The higher CO2-C emission was found in the mixed sludges while the anaerobic sludge presented the lower value. The treatment of anaerobic sludge with lime led to an increase of CO2-C emission and nitrogen mineralization from the sludge, indicating that lime treatment promoted more favorable conditions to sludge mineralization. At the end of the incubation period, sludge-amended soil had higher pH, more evident on the lime-treated sludge, and higher amounts of available nutrients, namely, nitrogen, phosphorus, potassium and calcium. The balance between applied carbon and C-CO2 emission, proved that sewage sludge increases carbon accumulation in soil