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The paper reports the results of an investigation aimed at evaluating the performances of a periodic biofilter (SBBR) for treating municipal wastewater. The investigation was carried out at laboratory scale on real primary effluent coming from a municipal wastewater treatment plant located in Southern Italy. The SBBR was designed for carbon and nitrogen removal through one single stage. The results have shown that even at maximum organic load (i.e., 7 kg COD/m3.d), the COD in the effluent was lower than 60 mg/L. TKN removal efficiencies resulted high (i.e. 90-95%) up to an organic load of 5.7 kg COD/m3.d corresponding to a nitrogen load of 0.8 kg TKN/m3.d. NO3-N concentration in the treated effluent was lesser than 6 mg/L although in the SBBR treatment cycle no anoxic phase was scheduled. This indicated that denitrification extensively took place in the biofilter. The process was characterized by high suspended solids removal (about 90%) and by a negligible sludge production (lower than 0.01 kgVSS/kgCODremoved). In the SBBR, biomass grew as granules and was characterised by different measurements (biomass concentration, cellular protein and biomass density). Biomass density resulted very high, i.e. 200 gTSS/Lbiomass, and this permitted to achieve a biomass concentration such high as 40 gTSS/Lbed. Such biomass concentration did not cause any decrease of biomass metabolic activity as proved by its total protein content (29% of organic matter) and maximum oxygen uptake rate value (i.e. 50 mgO2/gVSS h).

The paper reports the results of an investigation aimed to evaluate the influence of hydrodynamic conditions on physical and biochemical characteristics of granular sludge obtained in a SBBR system. Biomass density resulted very high, i.e. 70-125 gTSS/L(biomass), and this permitted to achieve a biomass concentration such high as 17-45 gTSS/L(bed). An appropriate equation proved that the pressure loss, an easily measurable parameter, can be used for biomass porosity measurement and indirect assessment of biomass concentration in the biofilter. As for biomass biochemical characterisation, the EPS (Extracellular Polymeric Substances) content was rather low (5-7% of the total organic matter) and mostly made up of proteins whereas the cellular protein content, a parameter frequently used as an indicator of microorganisms activity, was high (30-60% of total organic matter).

This is the second of two papers each dealing with a specific technological option for replacing the Fenton's reagent with simpler processes for treating industrial wastewater. In particular, the paper reports the results of an investigation aimed to check, at lab scale, the effectiveness of an alternative wastewater treatment combining biological degradation and chemical oxidation with ozone. The treatment was carried out in a lab scale hybrid reactor fed with the biological stage effluent of a plant treating the wastewater of a large tanning district in Central Italy whose residual COD result still higher than the Italian COD Maximum Allowable Concentration (MAC) value (i.e., 160 mgO2/L) The results are very promising, considering that a removal efficiency of 41% (as COD) has been achieved by treating an influent characterized by a COD content fully biorefractory. In addition, the proposed treatment presents the significant advantage of no additional sludge production, as happens with commonly utilized tertiary processes (i.e. Fenton), that is characterized by high chemical sludge production.