Capacitive Deionization (CDI) is an electrochemical technology for removing charged species like ions of salt from water. Fundamentally it works on “capacitive ion storage”, a phenomenon where in response to energy applied as voltage or current across CDI electrodes, ions of salt are accumulated and stored capacitively as electrical double layers (EDL) at the surfaces of CDI electrodes (similar to a capacitor or battery). Since the accumulation of ions is dominated by physical phenomena (no chemical reaction), it is a reversible process with systems based on CDI technology being characterized by low energy requirements, reduced maintenance and a long service life.

Stockholm Water Technology AB (SWT) has patented a unique membrane-less CDI system architecture using three-electrodes to reduce system power consumption and improve operational flexibility. This enables SWT products to control the ion content of treated water at lower input power and with tunable water recovery  compared to other widely used water desalting technologies like reverse osmosis (RO). The low power requirements allow the CDI systems to be powered by commercial solar cells or batteries for remote and portable applications. SWT products are chemical free and can be custom-sized using their novel multi-modular architecture to provide flexibility in terms of quality and quantity of water to be treated at low CAPEX and OPEX.



  • Remote communities (mobile or stationary); solar powered
  • Individual supply to homes
  • Industrial water clean-up – Towards zero discharge
  • Reverse Osmosis (RO) Brine Treatment for Maximum Recovery – Reduced pollution
  • Mobile disaster and emergency back-up water supply – Life saver
  • Boiler or Cooling Tower Water Conditioning – Avoid scaling
  • Food & Beverage Production Applications – Provide conditioned input water quality
  • Municipal Water Treatment – Multiple uses
  • Hydroponic Irrigation Systems – Remove unwanted ions
  • Laundry Feed Water – No need for salt for softening water
Home drinking water solutions

Stockholm Water Technology has developed a cost-effective wall mounted system for home drinking water solution.The system powered by a single CDI module (110 mm x 200 mm) can generate 20-50 liters of desalinated water per day. The product capacity is expandable with the addition of external reservoirs and can be battery or solar cell powered in case of utilization for remote or off-grid locations without electricity (small scale rural applications). The product has a multi line LCD display which gives the user live information on water consumption and water quality. It is suitable for installation in homes and in remote locations for producing affordable and safe drinking water on demand.

Marine solutions

Stockholm Water Technology products can be adapted to suit marine requirements for both small boats and medium sized marine vessels. The high water recovery capacity of the products, light weight and small real estate requirements are beneficial for marine vessels. The systems can also be optionally solar or battery powered to ensure water availability in emergency situations. The unique multi-modular design enables us to meet customer demands at low cost and space requirements. The desalting systems are chemical free and have low maintenance costs.

Off-Grid solutions

Stockholm Water Technology has developed a fully automated “Scalable Modular design” for complete home water solutions for operation in temperature ranges from 5 – 60 °C. Suitable for homes located on remote locations without municipal water supply (archipelago etc.).

The input water source can be ground, surface or sea water. The product can also be designed for use with solar modules and batteries for operation in locations outside the power grid. Product features include:

  • Flexible output water salinity- for use as gardening water or home water, including for drinking
  • Maintains nutritional balance – Keep essential minerals in water; re-mineralization for human consumption not necessary
  • High Water Recovery- Waste very little water
  • Minimum Maintenance- Developed with robust carbon materials & low process pressure for longer life
  • Low Fouling Potential- No membranes involved
  • Environmentally Friendly- Optionally solar powered
Industrial Water

Stockholm Water Technology products are membrane free capacitive deionization (CDI) based systems, which makes them suitable for meeting the very specific requirements of industrial water treatment.

The products remove contaminants from water through electro-adsorption of the charged species, which makes the technology extremely viable for removing ionic contaminants which cause scaling issues in membrane based technologies. Mentioned below are examples of some of the commonly removed ions from water and relevant industries where this could be applied:

Rural communities

Rural communities in developing regions of the world are the most affected by lack of clean drinking water. The size of the communities can range from less than a hundred to several hundreds to thousands of people who often do not have access to electricity.

Stockholm Water Technology has developed a unique solution to address water issues in rural communities by using an innovative, chemical free, solar-battery operated water desalination systems which can be sized using a “lego-like” architecture to provide flexible water treatment solutions for a wide range of water quality, quantity and temperatures.

The systems comprise of individual desalting units (cells), which are incorporated into modules and the modules are combined in a series-parallel architecture to define the capacity of a system.

This generates multi-level modularity giving SWT the flexibility to tailor their products for the quality and capacity of the water to be treated, lowering application specific costs and real estate requirements due to the considerably smaller footprints of SWT systems.

The solar or battery operated systems have in-built water monitoring and correction systems to guarantee clean and safe drinking water for all.



Technology development for Capacitive Deionization currently promoted by SWT, started in the group of Prof. Joydeep Dutta in 2006 at the Asian Institute of Technology. The technology underwent continuous development until 2017, with in-depth scientific inputs from several scientists, students and researchers. The current product design for sustainable commercial applications was developed and optimized by SWT in Stockholm, Sweden in collaboration with KTH, Royal Institute of Technology.

Extensive laboratory tests have proved the product to be rugged and currently large volume prototypes are being validated in various application domains in and around Stockholm, Sweden. Developments over the last decade has made the current group as one of the Top 5 research groups in the world in capacitive deionization technology and top 30 in the world in Water Treatment.


  1. Swedish Patent SE 540976 C2: (issued on 12 Feb 2019): Device for capacitive deionization of aqueous media and method of manufacturing such a device, Karthik Laxman Kunjali and Joydeep Dutta
  2. PCT Application: 2018 (Application no. PCT/EP2018/066435; filing date: 20 June 2018): Desalination device and method of manufacturing such a device, Karthik Laxman Kunjali and Joydeep Dutta


Stockholm Water Technology is pleased to work with you on piloting this technology.  To ensure a custom built solution, Stockholm Water can provide you a cost benefit analysis to showcase advantages of this technology.  In order for us to complete a study, we need the following information from your utilities, maintenance or engineering team:

  • Feed water quality & source;
  • Treatment targets (conductivity, hardness, TDS, temperature, etc.);
  • System capacity (flow-rate requirements);
  • Chemical consumption of existing water treatment system;
  • Unit prices of chemicals used the water treatment process

Do you have a question? Let us know.