A wastewater treatment plant’s main task is to receive and treat wastewater. The treatment must also enable recycling and reuse of the wastewater content, be carried out in a resource-efficient manner and not contribute to global heating or other environmental impacts.
Resource efficient and environmental friendly wastewater treatment
Wastewater treatment challenges
Many existing wastewater treatment plants are facing increasingly stringent emission requirements, lack of capacity due to increasing load, and surrounding buildings that are creeping closer. Therefore, renovations and expansions may be required, at the same time as costs for investments and operation must be reasonable.
Wastewater treatment requires resources, primarily in the form of electricity, chemicals, basins, mechanical equipment and personnel. Tougher treatment requirements to increase the quality of the treated wastewater can lead to a greater need for resources. Digitilisation and automation are important tools for reducing the need for resources, but there is still great potential in the development of new biological, physical and chemical treatment methods.
Resource-efficiency and climate impact
Resource-efficient treatment often means a lower environmental impact, but not always. Climate impact from wastewater treatment can be significant in direct emissions of nitrous oxide, methane and fossil carbon dioxide. Both measurements of emissions and system analyzes are important in order to be able to assess the environmental impact of a wastewater treatment plant.
The purpose of this focus area
The purpose of this focus area is to develop new wastewater treatment processes, but also to further develop existing processes and process combinations. The goal is resource-efficient, environmentally friendly, compact and robust wastewater treatment plants with a good working environment.
What is SWR working with within the area?
Increase the amount of organic material that can be utilized
The organic material in the wastewater can be extracted in various ways and used as an energy source and as mulch and carbon sink in agricultural land. If organic substances in the wastewater pass the pretreatment at the treatment plant, and go on to the aerated part of the biological treatment, about half of the carbon disappears as carbon dioxide. In addition, energy is required to aerate the water and maintain the microbial activity. Organic carbon source from the wastewater is at the same time a necessary asset in the unaerated zones, for today’s conventional biological nitrogen and phosphorus separation via denitrification and aerobic luxury absorption of phosphorus.
In order to increase the amount of organic material for the sludge treatment, we work to
- improve physical-chemical separation of organic substances,
- produce internal carbon source for biological nitrogen and phosphorus removal, and
- implement anaerobic ammonium oxidation (anammox).
Reduce energy use when aerating
The aeration in the biological treatment normally accounts for 30-50% of the electricity use at Swedish sewage treatment plants. We work to try to reduce the need for aeration, but also try to make the aeration more efficient.
We do this by
- reducing the load on the aerated biological processes (better pretreatment, introduce anammox), and
- improving the design, control, operation and maintenance of existing and new aeration facilities.
Compact waste water treatment
When rebuilding and expanding a waste water treatment plant, the treatment at the plant needs to continue in the meantime. In addition, site availability has often decreased due to previous developments and the fact that the buildings around are creeping closer. Compact waste water treatment is therefore often preferred when renovating and expanding.
However, compact solutions have long been associated with higher energy consumption, for example when introducing membrane bioreactors (MBR). Aerobic granular sludge (AGS) is a technology that is both compact and energy-efficient. Pre- and post-filtration are more compact solutions than, for example, sedimentation, and increase carbon separation and improve the quality of the purified water respectively. Innovative solutions with moving beds (Moving Bed Biofilm Reactors = MBBR) that include anammox can also generate compact and energy-efficient solutions.
At the moment we are working on studying
- start-up and operation of the Nordics’ first AGS facility,
- the separation efficiency in pre-filtration,
- direct membrane filtration, and
- compact and energy-efficient MBBR solutions.
Reducing greenhouse gas emissions
Municipal waste water treatment leads to direct emissions of the powerful greenhouse gases nitrous oxide and methane. Biological nitrogen removal at municipal waste water treatment plants can cause emissions of the powerful greenhouse gas nitrous oxide, and can often account for a very large proportion of the waste water treatment’s climate footprint. Emissions of methane occur during digestion gas and digestion sludge handling. Methane emissions also occur at the treatment plant’s inlet due to methane formation in the pipeline network. Sludge storage also generates nitrous oxide and methane emissions.
We are working to
- study nitrous oxide emissions and develop strategies to reduce these when studying new biological process solutions,
- develop methodology for nitrous oxide and methane emission measurements from pools,
- study process solutions to avoid post-denitrification with fossil carbon source, and
- carry out environmental system analyzes for studies of new technical solutions.
Process modeling and model predictive control
By using mathematical models, it is possible to gain an increased understanding of how processes work without carrying out, or at least prioritizing among, time- and resource-consuming experiments.
Digitization enables more advanced automation as well as the generation and easier handling of larger amounts of data at the treatment plants. Model predictive control, where process models are used to simulate a range of outcomes depending on the value of the control signal, can lead to cost and energy savings as well as better quality of treated wastewater.
We are working to
- set up data models when studying process solutions to, for example, understand boundary conditions and develop control strategies, and
- implement model predictive control at a treatment plant.
Objectives of the focus area
By 2025, we must know how we:
- utilize incoming carbon in the best way
- can expand with a very small surface requirement,
- can reduce our nitrous oxide emissions
- can streamline our operations through model predictive control
Focus area leader
David Gustavsson
david.gustavsson@vasyd.se
+46 738 530 150