Abstract:
When seeking the use of sewage sludge generated in treatment plants, it is
necessary for this material to undergo processes that reduce the content of
biodegradable organic matter, the concentration of pathogenic microorganisms,
and the moisture content, in order to obtain a product that does not pose a risk to
human health and is primarily dry, facilitating transportation and handling. The
objective of this study was to evaluate the treatment of sludge from UASB reactors
in Planted Drying Beds (PDB) systems, characterizing the physicochemical and
microbiological parameters of this sludge after treatment. Three vertical flow PDB
planted with Cyperus papyrus were constructed and subsequently monitored for 6
months. The loadings applied were approximately 6, 7, and 8 kgTS/m²week,
corresponding to 255, 304, and 363 kgTS/m²year for Leach Bed 01, Leach Bed
02, and Leach Bed 03, respectively. The results demonstrated the effectiveness
of CWs in reducing the sludge volume, showing a 79% reduction in the loaded
sludge, with total solids content ≥ 65% and volatile solids/total solids ratios below
0.39 (VS/TS ≤ 0.39) for all three leach beds at the end of the resting period. After
three months of resting, the biosolid also presented low pathogen concentration
(E. coli < 4.00E-1 MPN/gST). Leach Bed 01, Leach Bed 02, and Leach Bed 03
presented nitrogen dry mass contents of 11.8%, 13%, and 12.7%; phosphorus
contents of 0.05%, 0.03%, and 0.13%; and potassium contents of 0.5%, 0.63%,
and 0.36%, respectively. The metals analyzed showed values well below the limit
established by CONAMA Resolution No. 498/20, where for Cd, for example, the
obtained value was 96% below the established limit. According to CONAMA
Resolution No. 498 of 2020, the parameters obtained from the generated biosolids
allow their classification as Class A.
