Sewage sludge contains lots of valuable elements which are prized as fertiliser for use in agriculture. Phosphorus in particular is an important nutrient for plants. Researchers at Landshut University of Applied Sciences are therefore looking at ways in which wastewater treatment facilities can use sewage sludge effectively, particularly in rural areas. They are doing this in conjunction with partners based in the Czech Republic.
The sludge that settles in sedimentation tanks is full of valuable substances like phosphorus, nitrogen or potassium. For this reason, it is often used in agriculture as fertiliser on fields. However, the sewage sludge also often contains contaminants which are harmful to the environment and health such as microplastics, heavy metals like copper or zinc, hormone disrupters such as plasticisers, or pharmaceutical residues.
According to the coalition agreement between the parties of the German federal government, spreading sewage sludge as fertiliser is to be discontinued and instead the compounds containing phosphorus are to be recovered for subsequent use in fertilisers.
Recovering phosphates from sewage sludge
"Phosphorus is a finite resource and easily accessible reserves are expected to be depleted in the next 80 to 120 years. German wastewater potentially contains around 70,000 tonnes of phosphorus which could be recovered each year, whereas Germany alone consumes some 120,000 tonnes per year," explains Prof. Diana Hehenberger-Risse from the Technology Centre for Energy at Landshut University of Applied Sciences.
It is now mandatory for large wastewater treatment plants to recycle phosphorus. This could also make ecological sense for smaller facilities. However, according to Hehenberger-Risse, "The modifications required to recover phosphates are technically complex and require massive investment on the part of smaller sewage plants. To make it worthwhile and ensure that sewage charges don't skyrocket, municipal authorities need to cooperate and find a joint solution."
To find out what that could be, the environmental scientist is working on a research project known as greenIKK. Partners on the project include her colleague at Landshut, the chemist Prof. Josef Hofmann, IKOM Stiftland (a special purpose association) and the Czech Forestry and Game Management Research Institute. The Landshut faculties for Mechanical Engineering and Interdisciplinary Studies also participate substantially in the project. Together their objective is to use sewage sludge effectively. "This reduces the emission of greenhouse gases and increases resource efficiency," says Hehenberger-Risse. The project is scheduled to run until the end of 2019 and is being financed by the European Regional Development Fund.
The objective: to use sewage sludge effectively
The researchers are focusing on the district of Tirschenreuth in Bavaria and the neighbouring region of Tachov/Cheb in Czechia. "Among other things, we are looking at how to recover phosphorus, nitrogen and trace elements from wastewater and sewage sludge in a commercially and ecologically viable way," explains Hofmann. "Our Czech partners are assisting us with chemical analysis. As well as measuring the phosphorus content, they will be determining its quality as a fertiliser, i.e. how easily plants can utilise it."
Often some of the sewage sludge from facilities is dried and incinerated. Phosphorus can also be extracted from the ash. A complex process of drying is necessary to ensure that the sludge burns readily. "That requires a lot of energy," says Hehenberger-Risse. With the project partners she therefore wishes to test whether wastewater treatment plants can use solar power for drying purposes and if so which ones. They are also exploring whether it makes sense for plant operators to join forces and dry sludge from various local authorities at central facilities.
Small wastewater treatment plants need to be both ecologically and economically sound
"To date, there have only been studies about disposing of sewage sludge and which deal with some aspects of specific wastewater treatment sites, towns, cities or administrative districts. This project is designed to consider methods of disposal and related options by taking an integrated, holistic approach," says Hehenberger-Risse in summary. At the end of the project, she and her colleagues will draw up recommendations for action enabling participating authorities in Germany and the Czech Republic to make good, common use of sewage sludge across borders from both an ecological and economic perspective. According to Hehenberger-Risse, "This can then likewise benefit other communities in neighbouring regions."
Ulrike Schnyder | idw - Informationsdienst Wissenschaft
Gran Chaco: Biodiversity at High Risk
17.01.2018 | Humboldt-Universität zu Berlin
Dead trees are alive with fungi
10.01.2018 | Helmholtz Centre for Environmental Research (UFZ)
What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...
For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.
Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...
At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.
No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...
Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.
Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...
The oceans are the largest global heat reservoir. As a result of man-made global warming, the temperature in the global climate system increases; around 90% of...
08.01.2018 | Event News
11.12.2017 | Event News
08.12.2017 | Event News
17.01.2018 | Ecology, The Environment and Conservation
17.01.2018 | Physics and Astronomy
17.01.2018 | Awards Funding