A biogas power station for units 5 and 6 of South Wastewater Treatment Plant in Tehran was inaugurated on Tuesday.
It has two generators for the simultaneous production of electricity and heat with a total nominal capacity of 2.4 megawatts, the Energy Ministry’s news portal Paven reported.
In addition to collecting biogas from sewage treatment process and preventing its release, the plant produces electricity and heat from the waste, avoiding the consumption of fossil fuel to produce power. This helps prevent the release of greenhouse gas emissions (carbon dioxide) into the atmosphere.
The power plant can produce 15 million kilowatt hours of electricity per year and prevent the emission of 75,000 tons of CO2 annually.
Prior to the launch of this plant, another biogas station was operating in South Wastewater Treatment Plant with a nominal annual production capacity of 44 gigawatts of electrical energy and 140 terajoules of thermal energy.
This volume is sufficient to save about 100,000 barrels of crude oil (400,000 cubic meters of gas) per year.
Operational since 2013, the plant 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.
The wastewater treatment facility processes close to 500,000 cubic meters of sewage per day and delivers it to farmers in Varamin Plain 40 km southeast of the capital.
A biogas plant is a decentralized energy system that can lead to self-sufficiency in heat and power needs, apart from reducing 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.
Compare this with natural gas, which contains 80-90% methane. The energy content of the gas depends mainly on its methane content.
Tehran’s South Wastewater Treatment Plant is the largest of its kind in the Middle East. Currently, six units are operating and two more are under construction.
Sewage Network
The construction of units 7 and 8 of the treatment plant is underway to expand the coverage of sewage network in Rey County, south of Tehran.
The treatment plant is intended to cover a population of 4.2 million people. It has now an input capacity of 675,000 cubic meters per day, 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, 40 km southeast of the capital, and is used to irrigate about 90,000 hectares.
As long as the new units are not operational, about 30% of tapwater 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 260 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.
