**5. Conclusions**

Insights about the effects on the infiltration process produced by continuous use of TWW for irrigation have been provided. Infiltration measurements earlier realized by the Hood infiltrometer in three adjacent field plots characterized by the same soil type and different durations of TWW irrigation (0, 2, and 5 years, named 0YR, 2YR, and 5YR) have been exploited to estimate the associated Philip

model parameters, saturated hydraulic conductivity Ks, and sorptivity S. From infiltration simulations performed by the model under the hypothesis of ponded conditions, applicable during irrigation, a quantitative estimate of TWW usage e ffects has been carried out.

Specifically:


The results of this research would indicate that the use of treated wastewater leads to the reduction of the required water used to irrigate soil limiting runo ff. This is an important outcome of this work that indicates the use of treated wastewater in irrigation practice as one of the possible strategies to be adopted in arid zones to increase irrigation e fficiency. However, further investigations are required to establish the link between irrigation e fficiency defined here and crop production. Furthermore, complete knowledge of TWW long-term e ffects on quality characteristics of water and agricultural soils is still lacking.

**Author Contributions:** Conceptualization, investigation, methodology, writing—original draft preparation and writing—review and editing, A.A.A., M.A.G., M.Z.A., R.M., C.S., T.A.G., and A.F. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was financed by the Deanship of Research at the Jordan University of Science and Technology for financial support.

**Acknowledgments:** The authors are thankful to C.Corradini for proofreading the paper.

**Conflicts of Interest:** The authors declare no conflict of interest.
