Domestic wastewater management in Greece: Greenhouse gas emissions estimation at country scale

Abstract Information regarding the domestic wastewater management in Greece was collected and the greenhouse gas emissions from wastewater treatment plants were estimated at country scale using a steady state comprehensive model. In 2016, 220 domestic wastewater treatment plants operated in Greece, serving 91% of the total population and treating almost 1.74 × 10 6 m 3 wastewater per day. All systems provided secondary biological treatment, while 83%, 57% and 93% of them provided also biological nitrogen removal, biological phosphorus removal and wastewater disinfection, respectively. Wastewater reuse was applied in 13% of the existed plants, while 38% and 31% of the produced sludge was incinerated and disposed to the landfills, respectively. The average daily production of wastewater was 210 L per capita, while the average sludge production was 15.3 Kg dry solids per capita and year. The total amount of greenhouse gas emitted from Greek treatment plants was 892,454 t CO 2 e per year. The on-site emissions contributed to 68.8% of the total emissions and the off-site emissions to the rest 31.2%. Biogenic emissions were calculated to 72.7% of the total emissions. Biogas use and net power consumption were the major mechanisms contributing to the on-site and off-site emissions, respectively. The major source of CH 4 was sludge disposal to the landfills, while N 2 O was mainly emitted through nitrification/denitrification during wastewater treatment. The contribution of on-site and off-site greenhouse gas emissions was affected by treatment plants' capacity; on-site emissions were much more important in plants with more than 100,000 population equivalent. Calculation of the specific CO 2 equivalent (CO 2e ), CH 4 and N 2 O emissions showed that the average per capita daily production was 0.21 Kg CO 2e d −1 , 4 g CH 4 d −1 and 60 mg N 2 O d −1 . Future actions should be taken to assure efficient operation of smaller treatment plants, promote wastewater reuse and integrate reduced greenhouse gas emissions strategies on plants’ design and operation. It is the first time that the greenhouse gas emissions from wastewater treatment plants are estimated at a country scale in Europe.