"Annually Tehran municipality draws 300 mcm from underground water tables, which will be replaced with treated wastewater as soon as the complex is ready," Morteza Ezodin was quoted as saying by ILNA.
Moreover, farmers in the Varamin Plains, 40 kilometers south of the capital, and the Tehran Oil Refinery (Tondgouyan Refinery) will get 15 mcm and 16 mcm of wastewater per annum.
Water is presently supplied by Mamlou Dam, 30 km southeast of Tehran that has a capacity of 250 mcm and currently holds 220 mcm of water, according to Financial Tribune.
It provides south Tehran with potable water and helps meet the needs of large farmlands in Varamin and Pakdasht – two main leafy vegetable growing regions.
The plan, which has registered a work-in-progress rate of 75%, will add 250 mcm of recycled water to Tehran's water reserves per year.
"Currently close to 3.3 million residents have access to the Tehran wastewater network," he said, adding that the figure is expected to reach 11 million when the infrastructure is up and running by 2023.
The volume of Tehran water reserves has been put at 1.06 billion cubic meters, 70% of which comes from surface water and 30% is groundwater.
Expansion of wastewater network has been a priority in the sprawling capital in the recent decades, but lack of funds in addition to rapid expansion of urban areas has slowed, and at times hampered, the process.
Religious Constraints
Unlike some countries, recycled wastewater is not used for drinking purposes in Iran as it does not comply with Islamic tenets.
“It is used only in the industrial and agricultural sectors in Iran due to religious concerns,” Behnam Vakili, the head of the department in charge of wastewater networks at the National Water and Wastewater Engineering Company, said
Stressing that Iran’s wastewater output is estimated to at 1.2 billion cubic meters per year, Vakili said 70% of water used by households can be reused in wastewater treatment plants.
He said while 48% of the country’s treated wastewater is used in the agricultural sector, about 45% of that enters surface waters, less than 0.5% is utilized in industrial units and 5% goes for watering urban green space.
If wastewater is not properly treated it can have dire consequences on the environment and human health.
Other than contaminating drinking water, it can cause harm to marine and wildlife habitats, oxygen depletion and restrictions on recreational water use as well as on fish harvesting.