13 km east of Zurich, Switzerland, there is a small town called Uster. This small town with a population of less than 40,000 is estimated that many people have not heard of it. But if you come from the textile industry, or have ever paid attention to the Xinjiang cotton incident, you may know that there is a company in this small town called Users.
What exactly is this business that dares to name it after a city?
In this small editor quoted a Weibo netizen named geo-textile: "The world's cotton testing and cotton yarn testing are controlled by the Swiss USER company, you do not use its standards to be returned, China in the 80s was very poor in order to export cotton yarn and cotton cloth, was forced to buy Switzerland's expensive cotton yarn dryer, these companies are sitting on the tip of the pyramid to grab excess profits of the giants." Xinjiang has a lot of Users cotton detectors, 6 million a piece. ”
However, today Xiaobian is not to introduce textile wastewater treatment, nor to brag about the level of machining in Switzerland, but to share the history of the development of sewage plants in this small city. Because I came across their water plant introduction book on the Internet, I was immediately attracted to a sewage plant with a daily treatment capacity of less than 20,000, and I was stunned to sort out the 90-year development history for myself. More interestingly, its history may help us better understand the drivers of wastewater treatment technology in the West, so I'd like to share this in this column.
Changes under the Great Depression
From 1929 to 1933, history books called a global economic crisis on Earth, known as the Great Depression. But the economic crisis has not alleviated environmental pollution, on the contrary, many of Europe's water environments are deteriorating. Switzerland is no exception: scholars at the University of Geneva in Switzerland have counted the history of heavy metal content in two Lakes in Switzerland, as shown in the figure below, where heavy metal pollution in these deep mountain lakes peaked around the middle of the 20th century. It is not difficult to understand why Switzerland's first Water Protection Act also came into being during that period (1955).
Sedimentary trace elements (in micrograms/g) recorded near Lake Geneva (304 m) and near lake Lucerne harbour (110 m) | Image source: Springer
But as the saying goes, freezing three feet is not a day's cold.
In 1933, when fish died in Lake Greifensee, west of the Swiss city of Uster, the city of Uster realized the importance of sewage treatment and began to draft a municipal sewage treatment plan in the same year. However, due to the Great Depression and the second world war that followed, plans for a sewage plant in Uster were shelved. It was not until after 1956 that his first sewage treatment plant was ushered in. This is already a year after the Swiss Federal Water Protection Act. Either way, Uster finally had its own sewage plant, which underwent constant change over the next 60 years.
In their official wastewater works profile released in 2021, they have sorted out the timeline of wastewater treatment in The City of Users, and let's take a look:
1931
Uster drafts the first wastewater treatment plan
1932-1933
Lake Grifensee saw fish poisoned by contaminated water bodies
1933
The city's Ministry of Construction has raised the general sewerage project (GKP) requirements and built a centralized sewage plant in Users.
1938
Government committees approved the wastewater plant project, but post-World War II economic difficulties put the plan on hold.
1955
As the economy moves forward, Uster's sewer network continues to expand.
In the same year, the Swiss Confederation amended the Water Protection Act.
1956
The Jungholz wastewater plant is operational and consists of mechanical and biological treatment processes.
1958
Jungholz wastewater plant adds chemical phosphorus removal (80% phosphorus removal rate)
1968
In December of this year, Uster held a referendum on the construction of a second sewage plant in Nänikon.
1971
The Nänikon wastewater plant is put into operation.
Switzerland introduces a new version of the Water Protection Act.
1973 – 1977
The Jungholz wastewater plant was expanded with the addition of two parallel treatment lines.
1981
The Jungholz wastewater plant adds a coagulation filtration process.
1985
The Jungholz wastewater plant adds a cogeneration unit.
1987
The Jungholz sewage plant began to have a system for the harmless disposal of sludge.
The sewage pipe network is 80 kilometers long, and most of it is a mixed rain and sewage pipe network.
1991
The first PC computer was added to the Jungholz wastewater plant
1993
In November of this year, the city of Uster held a referendum on the abolition of the Nänikon sewage plant, which was shut down in 1994.
1999
In September of this year, the City Council approved a proposal for wastewater waste heat utilization at the Jungholz wastewater plant and signed a contract with EKZ Zurich Electric Engineering.
2000
In January of this year, the wastewater plant received iso 14001 certification from the Swiss Association for Quality and Management Systems (SQS) and the waste heat from the wastewater plant will be used for heating 57 apartments.
2001
In May of this year, the office building of the sewage plant was approved for expansion.
In November of the same year, the heating source of the plant was converted to biogas combustion. In December of the same year, the sewage plant was replaced with a new cogeneration gas turbine.
2003
On May 1, Switzerland announced that sludge from sewage plants is banned from being used as fertilizer for agriculture. In the same year, the wastewater plant heated 72 new apartments.
In November of the same year, the Jungholz wastewater plant received two awards, Médaille d'eau and the Swiss Energy Innovation Award.
2004
Inauguration of the new office building.
2007
Install the new grille equipment
2008
In March, the groundbreaking ceremony for biological cleaner production was held: the old gas meter was dismantled;
From April to June, a new sludge return pump will be installed;
In August, the first treatment line of the sewage plant was shut down and emptied.
2009
In June, the first SBR reactor was completed.
In July, a new filter feed pump was installed
In November, the installation of the fresh fan system was completed.
In December, the SBR system in the East End began commissioning operations.
2010
In June, the SBR module in the West End was put into operation.
2016
In November, SBR's circulatory system was adjusted from static to dynamic.
2017
In September, telephone communication equipment was replaced and a personal alarm system was installed
2019
In May, the city council approved a new expansion plan for the sewage plant.
2020
Install a new grit pond to collect sand and grease.
Status of the sewage plant
After looking at the history of sewage development in Uster, let's take a look at the current situation of the only sewage plant in the city, the Jungholz sewage plant.
About a decade ago, the Jungholz sewage plant underwent an expansion (2008-2011) and today has a capacity of 48,000 population equivalents (PE), mainly treating domestic sewage generated by about 35,000 residents in the city of Uster and about 5,500 residents in the neighboring city of Griffin. On rainy days, the treatment capacity of the wastewater plant can reach 800 l/s. It is expected that in 2030, the treatment capacity of the wastewater plant will be increased to 60,000 population equivalents.
At present, the sewage plant uses the SBR process, a total of 6 SBR reactors, HRT about 8 hours, the effluent discharged into Griffin Lake.
The Jungholz wastewater plant is small but well-equipped, and they are moving towards carbon neutral wastewater plants in a variety of ways, such as:
1 Photovoltaic systems are installed on the roof of office buildings
2 The SBR reactor uses a microporous aeration system
3 Online control system: dissolved oxygen sensor, aeration on demand, reduce unnecessary energy consumption;
4 Medium temperature anaerobic digestion system (35–38 °C, total volume 1500 m³, SRT 20 days), electricity and heat recovery through cogeneration equipment.
The data shows that the electricity self-sufficiency rate of the sewage plant is 40%, and the self-sufficiency rate of thermal energy is 100%. In addition, they applied water source heat pump technology to recover waste heat from sewage. At present, these thermal energy provides heat energy for about 900 people in 400 households. That's why they call the Jungholz wastewater plant an ecological power station.
In addition, the plant has a reclaimed water reuse system, for water that does not need to use drinking water, the central control system will distribute the clean effluent to the special pipe to achieve water reuse.
The next decade
Switzerland is the first country in the world to implement point source control of emerging pollutants. As early as 2014, the Swiss Parliament approved the revision of the new Swiss Water Protection Act, which sets limits on micropollumines contained in the effluent of sewage plants, and requires some sewage plants to be retrofitted, adding advanced treatment processes, and taking the removal rate of 12 indicative pollutants as the criterion, and the removal rate is not less than 80%. The goal is to upgrade 100 of Switzerland's around 650 wastewater works by 2040, with the Jungholz wastewater plant among them.
In fact, as early as 2016, the sewage plant has submitted a new 15-year long-term plan to the city council, which is mainly divided into three stages:
Phase 1 (2017 – 2020): Renovation of the mechanical treatment section, mainly the replacement of grit tanks and the renovation of office buildings,
Phase 2 (2019 – 2025): Renovation of the sludge treatment line, construction of two new anaerobic digesters;
Phase 3 (2024 – 2030): Upgrading of biological treatment processes and deep treatments, adding process technologies for the removal of micropolluminants.
Phase I has been completed. As shown in the figure below, a small sewage plant already has a very modern style office building. In the view of the editor, this is also the embodiment of the increasing emphasis on architectural design in sewage plants around the world.
The second phase of work, affected by the epidemic, has been postponed from 2019 to February 2022. The reason for the construction of new anaerobic digesters is mainly that the two old digesters have been running for many years and need to be gradually retired. Therefore, the sewage plant will build two new anaerobic digesters without affecting the daily operation, and also spend time on the architectural design (see figure below).
Phase III work is expected to begin in 2 years. Switzerland seems to be paying considerable attention to the problem of micropollumines, and the renowned Swiss Federal Institute of Water Science and Technology (EAWAG) is also testing the effects of different removal technologies. It is estimated that the Jungholz wastewater plant is also waiting for the test results of the scientific institute in order to select a suitable treatment method.
Interestingly, despite the escalation of the wastewater plant's processes, the City Council has stated that the water bills of the citizens of Uster will not rise significantly as a result and will remain at the level of 150 francs per year.
In addition to its day-to-day operations, the sewage plant is also involved in a number of scientific research projects. For example, they collaborated with Eawag on N2O emissions and "poor nitrification" of the SBR process, and the results have been published in the 2021 International Water Association journal Water Research, and the name of the famous Professor Eberhard Morgenroth can even be seen in the list of authors.
brief summary
All the way from 1956, we can see that the changes in the Jungholz wastewater plant are closely related to the changes in people's lives. They believe that there are three main drivers of changes in sewage plants: population development, rising treatment standards and innovative treatment technologies. Xiaobian even believes that since they have an SBR process, this means that the sewage plant has the conditions to introduce the aerobic particle sludge process and alginate recovery technology to achieve the transformation of the sewage plant into a resource recovery plant. If there is such a day, the city of Uster can brag about this as a case of sustainable development.
Finally, a batch of photos of the Jungholz sewage plant are attached: