Construction of phases 7 and 8 of the South Wastewater Treatment in Tehran is underway to expand the coverage of the sewage network in Rey County, south of Tehran.
The treatment plant includes eight units and is intended to cover a population of 4.2 million people, the Energy Ministry news portal Paven reported.
Currently, six units with an input capacity of 675,000 cubic meters per day are in operation, covering a population of 3.35 million people.
The output of the treatment plant is used mainly for agriculture and irrigation. The resulting sludge (as compost) is used as fertilizer.
The treated wastewater is transferred to the irrigation network of the Varamin Plain, 40km southeast of the capital, and is used to irrigate about 90,000 hectares of land.
Moreover, the biogas power station of South Tehran Wastewater Treatment Plant is operating with a nominal annual production capacity of 44 gigawatts of electrical energy and 140 terajoules of thermal energy.
This amount is enough to meet the electricity needs of a residential town of 60,000 people, and saves consumption of about 100,000 barrels of crude oil (400,000 cubic meters of gas) per year.
The biogas power station, operational since 2013, curbs the emission of 200,000 tons of greenhouse gases, especially methane, annually by converting them to electricity.
The generated electricity helps the wastewater treatment plant meet 70% of its requirement.
A biogas plant is a decentralized energy system that can lead to self-sufficiency in heat and power needs, as well as reduce environmental pollution.
Biogas is produced during an anaerobic digestion process. A biogas plant can convert animal manure, green plants, waste from agro industry and slaughterhouses into combustible gas.
It can be used in similar ways as natural gas in gas stoves, lamps or as fuel for engines. It consists of 50-75% methane, 25-45% carbon dioxide, 2-8% water vapor and traces of O2, N2, NH3, H2 and H2S.
Tehran’s South Wastewater Treatment Plant is the biggest of its kind in the country. The two new units are needed due to the population density of southern areas.
As long as the new units are not operational, about 30% of tap water in the region should be supplied from underground resources that have lower quality compared to dam water.
Six wastewater treatment plants are up and running in Tehran Province, producing 450,000 cubic meters of processed sewage a day, of which 30% are supplied to industries and the rest goes to waste as there are no buyers for the valuable commodity.
The output, which complies with environmental standards, is piped largely to southern Tehran for farming and industrial use, and is also suitable for watering green spaces.
The annual processing capacity of wastewater treatment plants in Iran has surpassed 2 billion cubic meters.
There are about 258 effluent processing facilities across the country, which treat 6 million cubic meters of wastewater per day.
Close to 53% or 9 million water subscribers nationwide are linked to the sewage network, of whom 5.7 million are in the capital city of Tehran.
Industries’ total annual demand for water is estimated to be about 1.3 bcm that can be met through treated wastewater.
The current processing capacity has helped reduce extraction from underground resources by as much as 1.5% or 1 bcm per year.
