F. Cecchi

Anaerobic co-digestion of sewage sludge: application to the macroalgae from the Venice lagoon

Abstract Possibilities of co-digestion of sewage sludge (SS) with other organic wastes are examined in this paper. Anaerobic co-digestion of macroalgae of the Venice lagoon (A) with SS, in wastewater treatment plants is studied in detail. This approach can contribute to the solution of the final disposal of the 50 000 m 3 of macrophytes harvested each season. These are mainly Ulva rigida and Gracilaria confervoides . In the experiments A and SS were mixed at different ratios (20–40% algae, TS basis) and fed to mesophilic (37°C) and thermophilic (55°C) digesters which operated at 11- to 15-day hydraulic retention times and 1.7–4.4 kgTVS/m 3 /day organic loading rates. It was concluded that the mesophilic co-digestion process is applicable with potentialities of around 30% of the present SS flow-rate. Thermophilic digestion is not possible, because of the inhibition of methanogens probably due to the activity of sulphate-reducers.

A combined anaerobic-aerobic system to treat domestic sewage in coastal areas

Abstract This article presents the results for the treatment of raw sewage in an anaerobic-aerobic system at pilot plant level. Experiments were carried out in summer and winter, with different loads and temperatures (19°C and 12°C) to evaluate the potential of this system to be used in touristic-coastal areas. Results show that removal efficiencies are similar in both seasons because temperature balances the excess of the summer load. However, the overall yield coefficient for sludge production is reduced around, compared with reported values for conventional activated sludge processes. Nitrification takes place in Rotating Biological Contactors with good yields at hydraulic loads below 0.13 m 3 /m 2 ·d.

The use of organic fraction of municipal solid waste hydrolysis products for biological nutrient removal in wastewater treatment plants

Experiments in a continuous UCT-bench scale plant using synthetic wastewater, have been carried out to demonstrate the feasibility of using the biodegradable organic fraction of municipal solid waste (BOF-MSW) as an easily biodegradable C source for nitrogen and phosphorous removal. Yields obtained are quite good and the additional load introduced by the use of the fermentation products of the BOF-MSW can be considered negligible. In addition, the basic mass balances carried out, show that the amount of easily biodegradable C-source needed to treat the wastewater produced by a given unit of persons can be obtained from the amount of BOF-MSW generated by this unit.