Rethinking Wastewater
What is happening?
96 million cubic metres of drinking water - the combined volume of Lake Zurich and Lake Greifensee - is the amount used in Switzerland each year for toilet flushing alone. The conventional system of alluvial sewerage had its justification when it was implemented more than 100 years ago: It improved comfort, for example, but also hygiene standards and therefore disease control in cities. The way wastewater is managed today, on the other hand, shifts the problem and even creates new problems: Discharges of various wastewater and problematic substances occur on the long journey to the wastewater treatment plant (WWTP). Nutrients and pathogens from human faeces, microplastics from road runoff and heavy metals from industrial wastewater are mixed together and heavily diluted in the sewage system. Once they reach the sewage treatment plant, all the substances have to be separated out again.
Due to long residence times in sewer pipes, uncontrolled biological processes take place before the wastewater even reaches the WWTP, leading to the production of climate-damaging emissions such as methane and nitrous oxide. According to the Federal Office for the Environment (FOEN), these greenhouse gases are 28 and 265 times more harmful to the climate than CO2 respectively.
Emergency reserves opened
As far as the operation of centralised and large-scale wastewater treatment is concerned, the system of alluvial sewers and WWTPs in urban areas is relatively efficient, although the plants are only geared towards the elimination of a few substances. However, recovering valuable nutrients such as nitrogen, phosphorus and potassium from the previously produced mixture of many substances is a very complex process, as the FOEN stated in a report in 2006.
Incomplete wastewater treatment in WWTPs also results in nutrients being discharged into bodies of water. Large quantities of phosphorus in particular lead to eutrophication of rivers and lakes. In fact, the pollutants in our freshwaters are responsible for most of our progressive loss of biodiversity. 81% of the world's freshwater species have declined over the last 40 years.
While nutrients in water bodies are disruptive substances, they are urgently needed elsewhere: They are used in the soil to nourish plants and are essential for our food production and security. In 2021, Switzerland was dependent on 340 thousand tonnes of fertiliser imports to cover its fertiliser needs. When the war in Ukraine began and 7% of these imports were cut off due to the import ban from Russia, this led to a national fertiliser crisis. In the meantime, emergency reserves had to be built up.
Time to question the linear approach
We are facing an acute increase in water scarcity worldwide, a loss of biodiversity and a global imbalance in nutrient flows. At the same time, the demand for drinking water and nutrient resources continues unabated. With skilful resource management, it would be possible to recover these nutrients locally and thus promote the circular economy. It is therefore time to question the linear approach and enable alternative, circular ways of wastewater treatment.
Specific
Problems:
Increasing Public Toilet Demand –
but how handle Waste Management and Accumulation?
Public restrooms are rising in demand. Especially in sensitive locations like parks or remote areas, ecological solutions are requested. As the setting often does not allow a conventional sewer grid connection, the toilets rely on costly and labor-intensive manual emptying and discharge. More sustainable and autonomous sanitation solutions are advised.
Specific
Problems:
Waste of Water
The growing need for public toilets in the light of current water wasting practices in the public toilet sector scream for novel resource efficient sanitation solutions.
Specific
Problems:
Costly Installations and Infrastructure
The installation of conventional on-site treatment technologies for remote households or cabins involves significant costs for transportation, machine intensive excavation and other infrastructure works.
Specific
Problems:
Rescue biological systems
On-site wastewater handling based on biological treatment is challenged and often destroyed by high nitrogen loads. By separating and treating the nitrogen rich urine stream this issue can be solved.
Specific
Problems:
Unused Resource Potential
The state starts to push for nutrient recovery from wastewater. The recovery from wastewater treatment plans is however inefficient and costly. Novel approaches guide the way to zero discharge and 100% fertilizer production.
