Evaluation of the effect of irrigation with purified wastewater on the physical and chemical properties of soil

Introduction:
Due to the development of cities and increasing water consumption per day, a large amount of wastewater is being daily produced. The use of refined sewage in irrigating the green space prevents environmental pollution. This research was carried out to investigate the effects of refined sewage treatment on plant growth and its effects on physical and chemical properties of soil.
Material and methods:
After studying the research carried out inside and outside the country, a certain geographic area, facilities and equipment were evaluated. Then, with coordination with the related organizations, this study was carried out in Shahid Bagheri highway in Tehran. Irrigation of the plants as treatments were done as a completely randomized block design (CRD) under through two treatments (100% wastewater and 0% wastewater (well water which is current irrigation system)). Considering the irrigations as treatments for green space plants, characteristics of the applied sewage which was provided from wastewater Ekbatan treatment plant the effects of midterm period use of effluent (in one-year) physical and chemical properties of soil was carried out.the effect of irrigation with treated wastewater on the vegetative characteristics of selected species of green space (donut) by clay meter was recorded every three days regarding to the curved parts of the plant. Due to the limited amount of wastewater parameters and in order to verify and evaluate the results, the quality of the waste water was measured monthly in Ekbatan's WWTP laboratory and was compared to the standard of the Iranian Environment Organization.
Results and discussion:
By studying the role of wastewater on the growth and maintenance of urban green spaces in the form of a pilot study, the possibility of reuse of the wastewater from the sewage treatment plant of Ekbatan town was assessed. The aim of this study was to identify sustainable water sources in order to maximize of the wastewater recycling for the implementation of human ecology goals for sustainable development. The results showed that the effluent was in the permitted range for irrigation of green space. On the other hand, to investigate the effect of treated wastewater on the soil before and after the experiment, 18 soil samples were randomly selected, nine of which were sampled from 0 to 30 cm depth and nine others from the depths of 30 to 60 cm. All samples were mixed and transferred to the laboratory. The physico-chemical properties of the soil were measured at both depth ranges. The concentration of each element was within the standard limits, which is a proof of the non-contamination of the soil. In other words, the use of wastewater for irrigation does not lead to soil contamination and irrigation with wastewater causes an increase in the nutrition and fertility of the soil. Also, the growth rate of the organs as a function of the treatment conditions during the experiment had a significant difference.
Conclusion:
In general, the results of this study showed that the amount of physiological parameters of plants irrigated with wastewater was greater than that of well water. Therefore, it can be concluded that the use of wastewater for irrigation of green space is possible and has no negative effect on soil.