دانلود رایگان مقاله انگلیسی استفاده مجدد از فاضلاب صنعتی و کشاورزی برای آبیاری سبزیجات در شرایط مدیترانه ای - الزویر 2018

abstract

In many countries of the Mediterranean region, characterized by frequent drought periods, agricultural production often occurs under water deficiency or conditions that cause the depletion of the existing water resources. In these areas, the reuse of reclaimed wastewater for crop irrigation could contribute to mitigate/decrease water shortage, support the agriculture sector and protect groundwater resources. In 1.5-year field experiments in Southern Italy (Apulia Region), the effects of irrigation with treated agro-industrial wastewater on soil properties, crops yield and qualitative traits of crop products, including their microbiological safety, were assessed. Groundwater (GW), secondary treated wastewater (SW) and tertiary treated wastewater (TW) from an innovative “on-demand” UV disinfection system were used to irrigate tomato and broccoli, cultivated in succession. The three irrigation water sources and the corresponding irrigated soils, plants and crop products were analyzed for the main physico-chemical characteristics, quali-quantitative parameters and fecal indicators. SW and TW showed higher values of the main physico-chemical parameters than GW. SW irrigated soil resulted in a significant increase of NH4-N, Na+, SAR, EC (below the threshold value beyond which a soil is defined as saline) during the first tomato crop cycle, and of pH during the broccoli growing season. Irrigation with treated wastewater did not significantly affect the marketable yield nor the qualitative traits of tomato and broccoli crops, except for the Na+ and NO3 − content (below the threshold levels defined by the European guidelines for vegetables). High levels of E. coli (above the Italian limit for reuse), Fecal coliforms and Fecal enterococci (up to 104 CFU 100 ml−1) were observed in the SW and, when chlorination was not done, in the TW. Nevertheless, E. coli was not isolated from any sample of soil, plant and crop product, probably due to its rapid die-off. Moreover, low concentrations of Fecal coliforms and Total heterotrophic count were found in plant and crop product. The drip irrigation system used, which avoided the close contact between water and plant, may have contributed to this. Under the conditions applied in this study, the reuse of treated agro-industrial wastewater for irrigation can be considered an effective way to cope with agricultural water shortage in the Mediterranean area.

4. Conclusions

This paper presents a 1.5-year field study of reuse of treated agro-industrial wastewater. Secondary treated wastewater (after activated sludge process and sedimentation) and tertiary treated wastewater (after ultrafiltration and UV radiation) were used to irrigate two vegetable species in succession (processing tomato and broccoli)in a closed system where an agri-food company cultivated and processed vegetables and had wastewater as by-product.

The findings of the present study indicate that agro-industrial effluents have the potential to be recycled for irrigation after a ter-tiary treatment composed of ultrafiltration and “on demand” UV disinfection processes. The yield of tomato and broccoli crops as well as the most important qualitative parameters of tomato fruits (i.e dry matter content, soluble solid content, titratable acidity, pH) and broccoli heads (i.e dry matter content, diameter) were not influenced by the irrigation with treated wastewater.

The microbiological characteristics of the two treated wastewaters were considerably different from the conventional water source (groundwater) and also between each other. Nevertheless, the microbiological quality of the tomato fruits and broccoli heads was not affected by the type of irrigation water used. The dieoff of fecal indicators in the soil and the drip irrigation method, by reducing the direct contact between the water and the plant, limited the possible contamination of the crops products. Moreover, this type of irrigation system reduces the amount of irrigation water that needs to be supplied, so avoiding deep water percolation and surface water run-off processes, so it can be recommended for wastewater reuse in irrigation.