The effects of phytoremediation of treated urban wastewater on the discharge of surface and subsurface drippers (Case study: Gorgan wastewater treatment plant in northern Iran)

Clogging of drippers in drip irrigation systems is one of the main problems in exploiting unconventional water resources such as saline water and wastewater. Therefore, developing a method for avoiding the pores' clogging is an essential step in exploiting these water resources to compensate for the shortage of freshwater in droughts. Various methods, including chemical, physical, and biological techniques, have been introduced in this regard, each with its own advantages and disadvantages. This study was conducted to investigate the effects of phytoremediation on preventing clogging of surface and subsurface drippers when using well water and treated wastewater. The experiments were conducted at Gorgan University of Agricultural Sciences and Natural Resources, northern Iran. Experiments were performed in the form of split plots with six treatments and three replications to investigate the phytoremediation effects of Vetiver (Chrysopogonzizanioides), Pampas (Cortaderiaselloana), and control (no phytoremediation) for well water and treated wastewater on preventing drippers clogging in surface and subsurface irrigation systems for 105 days. The results showed that during the 3-day retention time, Pampas grass performed better compared to Vetiver and control in reducing the dripper clogging evaluation indexes, including Langelier saturation index (LSI), sodium absorption ratio (SAR), total hardness (TH), and total dissolved solids (TDS). Compared to control, this decrease in Pampas grass was 85.93%, 38.23%, 20.75%, and 16.85% for the above indexes, respectively. On the other hand, during the 105 days of the experiment, the maximum discharge of surface and subsurface drippers was 4.27 and 2.17 L/h, respectively, when using Pampas grass for well water. Similar results were obtained when using this plant for refining wastewater. The findings of this study revealed that the dripper discharges when using Pampas grass for both surface and subsurface drippers and for both water types are significantly higher (P < 0.05) than those for control or when using Vetiver for phytoremediation. Therefore, when using wastewater, Pampas grass can be practically used in complementary treatment units of drip irrigation systems to reduce operating costs.