Search

Minimizing the biological sewage sludge (BSS) produced by wastewater treatment plants (WWTPs) represents an increasingly difficult challenge. With this goal, tests on a semi-full scale Thermophilic Alternate Membrane Biological Reactor (ThAlMBR) were carried out for 12 months. ThAlMBR was applied both on thickened (TBSS) and digested biological sewage sludge (DBSS) with alternating aeration conditions, and emerged: (i) high COD removal yields (up to 90%), (ii) a low specific sludge production (0.02–0.05 kgVS produced/kgCODremoved), (iii) the possibility of recovery the aqueous carbon residue (permeate) in denitrification processes, replacing purchased external carbon sources. Based on the respirometric tests, an excellent biological treatability of the permeate by the mesophilic biomass was observed and the denitrification kinetics reached with the diluted permeate ((4.0 mgN-NO3−/(gVSS h)) were found comparable to those of methanol (4.4 mgN-NO3−/(gVSS h)). Moreover, thanks to the similar results obtained on TBSS and DBSS, ThAlMBR proved to be compatible with diverse sludge line points, ensuring in both cases an important sludge minimization. [ABSTRACT FROM AUTHOR]

Thermophilic biological fluidized bed reactors operating in aerobic/anoxic alternate conditions proved to be a feasible solution for sewage sludge minimization. However, to date, no data about energy released by thermophilic biota (ThBio) are available in literature. This work aims to estimate specific thermal energy released by ThBio highlighting the influence of daily anoxic conditions. A pilot-scale reactor (1 m3) was fed continuously with mesophilic sewage sludge and monitored for more than four months and a thermophysical model was applied to estimate thermal energy released by ThBio (k T,biota and k T,COD). Results suggested that the increase of daily anoxic time stimulated COD removal (92.7 ± 1.3 % vs. 81.3 ± 4.9 %, with 6 h and 0 h of daily anoxic time, respectively). The thermal energy released by ThBio was strictly dependent on anoxic conditions. In fact, increasing anoxic conditions from 0 h d−1 to 6 h d−1, k T,biota and k T,COD reduced from 1.8 ± 1.3 Mcal kg−1 VS kg−1 COD and 26.6 ± 13.7 Mcal kg−1 COD to 0.5 ± 0.1 Mcal kg−1 VS kg−1 COD and 15.6 ± 4.2 Mcal kg−1 COD , respectively. Although, biological mechanism responsible of this behaviour is not completely clear, this work can serve as reference for future studies about the optimization of conditions to maximize thermal energy release from ThBio during organic substance degradation alternate aerobic/anoxic, in view of subsequent energy recovery. [Display omitted] [ABSTRACT FROM AUTHOR]