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Breakthrough for EDR wastewater recycling in Czech power project

October 30

Collaboration between Evoqua and Pure Water Group has secured a landmark order for a ready-to-run electrodialysis recovery (EDR) system in the Czech Republic. Using Evoqua’s NEXED® EDR technology, Pure Water Group of The Netherlands will deliver a system to MICo Engineering s.r.o, to recycle wastewater at a biomass-fuelled heat and power plant.

The NEXED® system is being built by Pure Water Group, for the first EDR project of its type in Czech Republic. The equipment will recover water by concentrating the high-salinity waste stream from a reverse osmosis (RO) plant. Water is required for cooling and boiler top-up at the ‘Domaradice’ 9.1 MWe cogeneration power plant operated by Carthamus a.s., in Český Krumlov.

At the Domaradice location the municipal potable supply is the only water source available to the power plant. As the main contractor for design and realisation of the water treatment system, MICo Engineering s.r.o was challenged with minimising water costs and wastage by recovering and recycling as much water as possible, in an economically viable scheme.

In a typical RO system, about 25% of the water treated is discharged as wastewater. Many reduce this loss by feeding the reject water directly into a second RO system. However, there are restrictions with biofouling, silt fouling and scaling, which then limit the recovery possible.

Evoqua’s new EDR recovery technology allows users to reduce salinity levels with low energy consumption. An advanced, low-pressure electrodialysis membrane technology enables tuning of water output quality, using power adjustments, to minimize plant footprint and energy consumption.

The key components of the 2-stage EDR skid are two NEXED3-4A-1 modules with a production capacity of 1.8m3/hour at 0.5bar, together with a frequency controlled pump and power control unit. As the EDR modules are fully tuneable, they will accommodate anticipated operating conditions varying between 85% water recovery with 74% salt removal and 75% water recovery with 77.4% salt removal.

In addition to the EDR system, Pure Water Group will also supply a purification system based on Evoqua’s Ionpure continuous electro-deionisation (CEDI) modules. This system will fulfil the conventional role of post-RO purification, polishing the low salinity permeate to produce boiler make-up water.

The water treatment scheme will also make use of stored rainwater, as a diluent for the low-salt waste stream, which will then feed the turbine cooling system, following ultrafiltration. Wastewater with high salt concentration will be used to in spraying and cooling the fuel ash.

Pure Water Group’s managing director, Johan Ossenblok, singled-out the project as a significant breakthrough for the technology and the application, commenting: “I consider this to be a major achievement and am grateful for the efforts made by all Evoqua and Pure Water Group specialists involved in the marketing, sales, engineering and piloting process. MICo is making great progress as an OEM in this field and we are proud to display the EDR equipment at Aquatech Amsterdam 2017.