The paper reports results of treated wastewater reuse field experiments carried out in Apulia (Southern Italy). Fennel and lettuce were irrigated with four different water sources: three reclaimed wastewater streams, obtained by applying different treatment schemes to the same municipal wastewater, and a conventional source (well water). Differences between the three effluents were significant in terms of suspended solids and faecal indicators. Both lettuce and fennel yields were enhanced by the high content of nutrients in the effluent of one of the treatment plants, which had been operated for partial nitrogen removal. In particular, fennel productivity was enhanced by replacing chemical fertirrigation with the supply of nutrients contained in the irrigation water.

Escherichia coli (E. coli) is one of the most commonly adopted indicators for the determination of the microbiological quality in water and treated wastewater. Two main types of methods are used for the enumeration of this faecal indicator: membrane filtration (MF) and enzyme substrate tests. For both types, several substrates based on the β-D-glucuronidase activity have been commercialized. The specificity of this enzyme for E. coli bacteria has generated considerable use of methods that identify the β-D-glucuronidase activity as a definite indication of the presence of E. coli, without any further confirmation. This approach has been recently questioned for the application to wastewater. The present study compares two methods belonging to the above-mentioned types for the enumeration of E. coli in wastewater: MF with Tryptone Bile X-glucuronide agar and the Colilert®-18 test. Confirmation tests showed low average percentages of false positives and false negatives for both enumeration methods (between 4 and 11%). Moreover, the counting capabilities of these two methods were compared for a set of 70 samples of wastewater having different origins and degrees of treatment. Statistical analysis showed that the Colilert®-18 test allowed on average for a significantly higher recovery of E. coli.

Two identical bench-scale Self-Forming Dynamic Membrane BioReactors (SFD MBR) were set-up and operated for the treatment of real urban wastewater. The two bioreactors were equipped with meshes of different mesh pore size. Meshes having pore size values of 20 and 50 µm were tested under solid retention time (SRT) of 15 d, whereas meshes with 50 and 100 µm pore sizes were compared under SRT of 50 d. The results of long-term experiments showed very good overall performances by all systems at the steady state. High flux (in the range 61–71 L m⁻² h⁻¹) and very good effluent quality were obtained, with average suspended solids and chemical oxygen demanding values below 10 mg L⁻¹ and 35 mg L⁻¹, respectively. The mesh pore size did not have a major influence on the average cleaning frequency. However, the pore size affected the effluent quality in correspondence of two particular conditions: (i) immediately after mesh cleaning; and (ii) during operation under high suction pressures (mesh clogging not promptly removed through cleaning). Moreover, the mesh cleaning frequency was observed to be dependent on the SRT. In tests with 50 d SRT, the cleaning requirements were very low (one every five days), and this limited the influence of the mesh pore size on the effluent quality. In conclusion, in SFD MBR, the role of the mesh pore size on the effluent quality may be more or less relevant depending on the operating conditions that directly influence the Dynamic Membrane formation.