Reuse of treated municipal wastewater for globe artichoke irrigation: Assessment of effects on morpho-quantitative parameters andmicrobial safety of yield

This study was performed over two growing seasons to evaluate the effects of three irrigation sources on the morpho-productive and microbiological parameters of globe artichoke yields: secondary wastewater (SWW), tertiary wastewater (TWW), and fresh water (FW, control). Escherichia coli, faecal enterococci and Salmonella spp. were monitored in the irrigation waters, the artichoke plants and heads, and the root-zone soil. Bacteriological analysis for total heterotrophic counts were determined for plants, fruit and soil. The irrigation waters were sampled, throughout the irrigation period of the crop, to characterise their physico-chemical properties. The chemical parameters of the SWW (i.e., TSS, BOD5 and COD) were significantly higher compared with those of the FW and TWW. The SWW and TWW significantly affected total marketable heads as number and weight per hectare, with higher yields than for the FW. Total marketable heads (as main, secondary, processing heads) were significantly higher in terms of weight per hectare for the SWW and TWW than for the FW (25%, 16% increases, respectively), as was the main head production for marketable weight (57%, 33% increases, respectively). The microbial qualities of the SWW and TWW were significantly different, with the SWW characterised by higher levels of E. coli and faecal coliforms, while frequently positive for Salmonella spp. Nevertheless, the microbial safety of the artichoke yield was not affected. The reduction in all of the faecal indicators from water to soil and from soil to plant can be explained by the irrigation system, which avoids direct contact of water with plant and aerosol dispersion; by the relatively rapid die-off of faecal bacteria in the soil; and a possible barrier effect of the rhizosphere environment. These data show that if municipal wastewaters are adequately treated, they can be used for irrigation. Thus, they represent a valid alternative to conventional water resources for irrigation of artichoke crops.