March 9, 2011
Kurita Develops Electro-Osmosis Dehydrator "Hydopress™ E" to Contribute to the Reduction of Waste and CO2 Emissions
Kurita Water Industries Ltd. (Head Office: Shinjuku-ku, Tokyo; President: Hiroshi Saito) has started a sales of its newly developed electro-osmosis dehydrator named "Hydopress™ E" to help customers reduce waste and CO2 emissions at their factories and other facilities.
Kurita developed this system by applying its unique sludge dewatering technology. The system first charges sludge with electricity to generate an electro-osmotic flow. It then uses the flow and pressure generated to move solids to the positive electrode and water to the negative electrode, thereby effectively dewatering the sludge. By using this technology, sludge volume can be reduced by up to about 50% compared with a conventional dehydrator. In addition, the amount of energy needed to dry and incinerate the dewatered sludge can also be reduced, which in turn reduces the emissions of CO2 to about one-third of the previous amount.
Kurita will promote the application of this system as a technology that is highly effective in reducing environmental impact, targeting both domestic and overseas customers engaged in a range of industries.
In recent years, an increasing number of customers have focused their efforts on minimizing the volume of sludge generated to reduce the total amount of waste produced. Sludge generated from wastewater from a range of industrial processes has a high water content. Most of the sludge is disposed of as waste, before which it needs to be dewatered. At present, belt-press dehydrators and centrifugal dehydrators are the mainstream products used to dewater sludge, but these machines can reduce the water content of the sludge to only around 80%. Demand for dehydrators that can further lower the water content has been increasing among customers who want to minimize the generation of sludge.
Customers who dry and incinerate dewatered sludge within the premises of their factories use fossil fuel for the process, and they need to reduce the associated fuel costs and CO2 emissions from the use of the fuel.
2. Kurita's Initiatives
(1) Kurita's idea
Kurita had been developing and delivering mechanical dehydrators to a range of customers, but in order to meet the customers' need to reduce their environmental impact through further reduction of waste and CO2 emissions, Kurita decided to develop an electro-osmosis dehydrator that would substantially reduce the water content of even organic sludge, which is difficult to dewater. Such a dehydrator would help the customers reduce the volume of sludge generated.
(2) New electro-osmosis dehydrator "Hydopress™ E"
Conventional mechanical dehydrators pressurize sludge to dewater it, while the new electro-osmosis dehydrator has built-in positive and negative electrodes to charge sludge with electricity and generate an electro-osmotic flow. The sludge is then dewatered through the generated flow and pressure. This unique technology efficiently and stably dehydrates sludge to a very low water content regardless of the density or properties of the sludge.
1) Dehydration mechanism
By the application of direct voltage to the sludge placed in between the electrodes, sludge particles that carry a negative electric charge gather to the positive electrode and water molecules that carry a positive electric charge move to the negative electrode, passing through the filter.
- Application of direct voltage to the sludge
- Movement of sludge particles to the positive electrode and of water to the negative electrode due to the electro-osmotic flow
- Dehydration at the negative electrode side
- *The surface of the filter located at the negative electrode side is not clogged with sludge particles because the particles are repelled by the negative electrode, which enables the smooth flow of filtrate.
2) Technological features
- While the water content of sludge dewatered by a conventional dehydrator is around 80%, the water content of sludge dewatered by the new technology can be as low as 50%. Even organic sludge, which is difficult to dewater using a conventional system, can be dehydrated to a very low water content.
- The voltage and electric current conditions are independently adjustable for each electrode, which enables optimization of the dehydration rate.
- The sludge is dehydrated to a very low water content and becomes self-combustible, which in turn eliminates the need to use supplementary fuel for the incineration of the sludge.
- Due to the heat generated by electro-osmosis, the decay of the dewatered sludge is prevented and pathogenic bacteria can be sterilized in a highly effective manner.
- The system has a simple structure for easy maintenance, including the cleaning and replacement of the electrodes.
- The built-in electrodes are highly durable and can be used for up to three to four years, which contributes to the substantial reduction of the running cost.
3. Effect of Introduction (Benefits to Customers)
The technology can be used for various applications. Compared with the use of a conventional dehydrator, the following benefits will be gained by introducing the new system or by using it in combination with existing dehydrators.
- The volume of sludge generated can be reduced by up to 50%, leading to a substantial reduction in waste disposal costs.
- The dehydrated sludge has a very low water content. It is therefore not necessary to use supplementary fuel to incinerate it. This contributes to a substantial reduction in the consumption of energy such as petroleum and heavy oil, which in turn reduces CO2 emissions to about one-third of the previous amount.
- Generated sludge can be widely used as compost or biomass fuel material.
4. Future Deployment
For the reduction of waste and CO2 emissions, Kurita will promote the sales of Hydopress™ E to a range of customers who need to reduce the generation of sludge. In particular, customers engaged in the food, chemical, automobile and electronics (LCD) industries generate a large amount of sludge (mainly organic sludge), and the use of this new technology will bring about many benefits to the customers. Kurita will promote the sales of the system especially to these customers.
Kurita will introduce the application examples of this technology at the 45th Annual Conference of the Japan Society on Water Environment in March 2011.