The egg-shaped digesters at the Köhlbrandhöft plant, located by the Elbe with its port and cranes, have become a well-known landmark. Photo: Galya Simeonova/IVL
In Hamburg, wastewater treatment is a landmark and an inspiration
How do we best make use of the nutrients in wastewater? This was the focus of a trip to Hamburg, Germany, organized by IVL. Some 20 participants from Sweden studied advanced technologies for wastewater treatment, phosphorus recovery and biochar production.
We got to see full-scale technologies that are not common in Sweden, and learn about practical, technical and commercial experiences. It gave us several ideas for projects that we are continuing to work on
, says Mayumi Narongin-Fujikawa, water expert and project manager at IVL Swedish Environmental Research Institute.
Wastewater is the waste stream that contains the most plant nutrients, but only a small part of these nutrients are returned to agricultural land. The project Från jord till bord och åter till jord (literally From soil to table and back to soil), headed by IVL and funded by Formas, aims to increase the water and food industry's knowledge of circular nutrient management. To this end, IVL and the Swedish Nutrition Platform
External link, opens in new window. (led jointly by IVL and RISE) organized a study tour to Hamburg at the end of August 2024.
Hamburg is home to Germany's largest wastewater treatment plant, Köhlbrandhöft, operated by Hamburg Wasser and located on the Elbe River. The plant's comprehensive process combines mechanical and biological treatment, with the biological part on a separate island 2.5 kilometres from the main plant. It normally handles an inflow of 3.5 to 4 cubic metres of wastewater per second, but during heavy rainfall this can increase to as much as 9 cubic metres.
The sludge from the treatment process is digested in the iconic egg-shaped digesters that have become a well-known landmark in Hamburg. It then goes to the incinerator, which generates 89 000 MWh of electricity annually.
The tour started with a visit to Köhlbrandhöft, the large wastewater treatment plant owned by Hamburg Wasser. Photo: Jenny Franck
Phosphorus is recovered in an advanced process
The participants were given a presentation on Remondis TetraPhos®, an advanced process used to recover phosphorus from incineration ash. By way of ion separation and the addition of sulphuric acid, the phosphorus is converted into pure phosphoric acid. The pilot plant for this was built in 2015; a full-scale plant was started in 2019 and full operation is expected in 2025.
There is only one plant in Germany with the capacity to recycle 40,000 tonnes of ash per year, which is less than ten per cent of what will be required in 2031. Phasing in a new recycling plant takes time; one cannot expect to go from pilot to full-scale without problems. Therefore, it is important that nutrient recovery through sludge spreading on agricultural land is allowed until new phosphorus recovery technologies are fully tested and their resource consumption and climate footprint are evaluated
, says Andriy Malovanyy, development engineer at Stockholm Vatten och Avfall.
The Hamburg Water Cycle is a system to take care of wastewater in one part of the city. Grey water is treated and can be used for irrigation, toilet flushing or to maintain a constant water level in a pond. Photo: Mayumi Narongin-Fujikawa
Just one litre of water per flush
In 2019, residents began moving into the Jenfelder Au residential district, where the Hamburg Water Cycle source-separating system divides wastewater into black water (from toilets) and grey water (from bathing, dishwashing and laundry).
The system uses vacuum toilets that consume only one litre of water per flush. This significantly reduces water consumption and produces a concentrated black water that is used for energy production
, says Lisa Gren, IVL's coordinator for the Swedish Nutrient Platform.
Every day, 25 cubic metres of greywater are treated in an MBBR (moving bed biofilm reactor) combined with an ultrafilter. Two potential reuse areas are being investigated: the grey water can be used either for irrigation and toilet flushing in a nearby industrial park or to maintain a constant water level in a pond in the residential area.
Novocarbo burns wood chips using pyrolysis to produce biochar that can be used to improve the quality of agricultural land. Photo: Mayumi Narongin-Fujikawa
Biochar improves farmland
NovoCarbo Carbon Removal Park uses pyrolysis, i.e. combustion without oxygen, to produce biochar, which is used to improve the structure of agricultural land and increase its water retention capacity. The raw material is mainly wood chips, but the company is experimenting with other materials such as cherry pits. German legislation prevents the use of sewage sludge, but this is possible in other countries.
The plant has two lines where the pyrolysis produces biochar at temperatures between 600 and 700 degrees. The gas formed during the process is filtered and used for energy production.
Workshop and future collaboration
The visit ended with a workshop on phosphorus and nutrient recovery from wastewater, with David Montag from Urban Water Management at RWTH Aachen University and people from Hamburg Wasser and NovoCarbo. This laid the foundation for future collaboration.
The visit provided very valuable insights and inspiration for how sustainable solutions for circular nutrient management and innovative wastewater treatment can be implemented in Sweden
, says Lisa Gren.
Read more about the project Från jord till bord och åter till jord
Opens in new window. (in Swedish).
For more information, contact:
Mayumi Narongin-Fujikawa, mayumi.narongin@ivl.se, tel. +46 ()10-788 65 96