♻ Wastewater Treatment Plants and Climate Change

In a world where water gets more and more scarce, we must protect whats still available at all cost.

Untreated wastewater discharge threatens river ecology and the water supply of downstream communities. While riverwater is not directly used for drinking, the water is often treated through river bank infiltration. With more pharmaceuticals in the water and a warmer climate hosting better conditions for pathogens like coli bacteria and legionella, efficient wastewater treatment is a must. Wastewater treatment plants do a great job at retaining most contaminants, however conventional treatment mostly covers nutrients and suspended solids. Some microplastics (whose concentration I analyzed during my bachelor thesis in 4 treatment plants at WVER) and soluble molecules like most pharmaceuticals can discharge even through the (only in some plants present) final filtration.

Therefore, some upgrades to our conventional treatment plants are necessary.

The fourth treatment stage

The fourth treatment stage aims to eliminate everything harmful that is still in the treated waste water before discharged into rivers. There are 2 (+1) techniques currently implemented, stopping pathogens (☣) and chemicals (🧪):

☣🧪 Ozone: This one does both! Here, the molecule splitting power of ozone is harnessed to dismantle everything unwanted in the water. While relatively cost intensive, it is really effective at destroying contaminants below detection limit.

☣🧪 Activated Charcoal: Also a multi-talent. Activated charcoal consists of a multitude of small carbon tubes, entrapping any solutes flowing through. This also effectively filters out anything harmful. After some time in use, the coal starts clogging up and loosing its power. Then, it only needs to be exchanged and the used can get reactivated by combustion, burning all contaminants away.

(Ultra Violet light): While not able to destroy chemicals, UV is really effective for pathogens. Its sanitation powers are used in many fields like medicine and cleaning already. In wastewater treatment plants, water flows between powerfull UV-lights, which kill all pathogens.


💸 Its not cheap: All 3 methods are relatively cost-heavy. Ozone treatment needs pressurized liquid ozone shipped to the treatment facilities regularly. Charcoal needs to be reactivated after some time in use. And UV draws a lot of energy.

However, the fourth treatment stage can also be seen as an investment into drinkable water for oneself and future generations.


FU Berlin (2016) Fourth treatment stage, Fourth treatment stage • Integrated Water Resource Management – from traditional knowledge to modern techniques •. Available at: https://www.geo.fu-berlin.de/en/v/iwrm/Implementation/technical_measures/Wastewater-treatment/Off-site-treatment/Sewage-Treatment-Plants/Fourth-treatment-stage/index.html (Accessed: 31 May 2023).

wegewerk GmbH (2018) WVER: Größte Ozonungsanlage Deutschlands NIMMT Betrieb auf, WVER: Größte Ozonungsanlage Deutschlands nimmt Betrieb auf : Zeitung für kommunale Wirtschaft. Available at: https://www.zfk.de/wasser-abwasser/abwasser/wver-groesste-ozonungsanlage-deutschlands-nimmt-betrieb-auf (Accessed: 31 May 2023).

Meunier, C. (2015) Can a fourth waste water treatment stage be financed by the Waste Water Charge?, Umweltbundesamt. Available at: https://www.umweltbundesamt.de/en/press/pressinformation/can-a-fourth-waste-water-treatment-stage-be (Accessed: 31 May 2023).


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