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Primary treatment
What is it about?
The first stage of a WWTP removes a large fraction of particulate matter from the influent wastewater after mechanical pre-treatment for sand and grid removal. This primary treatment removes fine particles by physico-chemical treatment, typically by simple sedimentation in a primary clarifier. More advanced primary treatment uses chemical dosing to improve particle separation with sedimentation, filtration or flotation.
What technologies are used?
- Chemically enhanced primary treatment
- Dissolved air flotation
- Microscreen (Drum+Discfilter)
- Two-stage activated sludge
Secondary treatment
What is it about?
The secondary treatment step in a WWTP consists of a biological process to remove dissolved organics and nutrients. Typically, microbial biomass feeds on the dissolved substances in an activated sludge system, converting them to gases (CO2, N2) or fixing them in sewage sludge.
What technologies are used?
- Activated sludge
- Advanced control
- Clarifier
- Deammonification
- Mainstream Anammox (1-stage)
- Mainstream Anammox (2-stage)
- Membrane aerated biofilm reactor
- Moving Bed Bioreactor (MBBR)
- Nitrification/Denitrification
- Two-stage activated sludge
Tertiary treatment
What is it about?
Tertiary treatment is applied to polish WWTP effluent quality before discharging it into receiving waters and have a targeted removal of specific groups of substances. Multiple treatment principles are available to remove residual solids, dissolved organic and inorganic substances, or reduce microbial contamination.
What technologies are used?
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Nitrogen removal or recovery in the sidestream
What is it about?
Effluent water from sludge dewatering after digestion contains high amounts of dissolved nitrogen in the form of ammonia, increasing the nitrogen load to the mainstream WWTP with recycling of the sludge water. This nitrogen can be removed or even recovered into a nitrogen product in a separate treatment of this sidestream, reducing the nitrogen return load to the WWTP.
What technologies are used?
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Grid gas production
What is it about?
Biogas produced at a WWTP can be converted into biomethane (> 95% CH4) by separating CO2 and impurities or converting CO2 into methane using a biological or catalytic methanation process. Biomethane can then be directly injected into the public gas grid, providing stable revenues for the operator due to high storage capacity of the grid and stable gas prices.
What technologies are used?
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Valorisation of biogas on-site
What is it about?
Anaerobic digestion of sewage sludge generates biogas, which can be valorised on-site at the WWTP. Biogas can be utilised in combined heat and power plants to produce electricity and heat for self-supply or for sale to external customers. Other forms of valorisation include gas boilers or microgas turbines.
What technologies are used?
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Smart Grid
What is it about?
A WWTP requires electricity for water treatment, but it can also generate electricity from biogas produced in digestion of sewage sludge. This dynamic profile of electricity supply and demand can be coupled with the highly dynamic market of electricity in the public grid, enabling an integrated operation of this “smart grid” to minimise energy costs and optimise revenues for the WWTP operator.
What technologies are used?
- Biological methanation
- Catalytical methanation
- Combined heat and power (CHP) plant
- Gas boiler
- Gas scrubbing
- Load balancing market
- Load shifting
- Microgas turbine
- Optimise electricity use
