DEEPER BLUE – DEEP buffering for Effluent Reuse

In the DEEPER BLUE project, the reuse of WWTP effluent to potable water quality through reverse osmosis is coupled to subsurface buffering of the produced drinking water, a principle called ‘Aquifer Storage and Recovery (ASR)’. Waterunie, a joint subsidiary company of the drinking water utilities and WRE members Farys and De Watergroep, executes this project at the WWTP of Aalst in collaboration with WRE member Aquafin and with the support of research platform CAPTURE. This initiative fits within a program of the Flanders Environment Agency VMM, which is part of the Blue Deal of the Flemish Government.

Effluent reuse
Membrane technology is used to purify a part of the effluent of the WWTP to drinking water. The project as such realizes a new source for drinking water production and diversification of these sources, which further strengthens the drinking water supply. Safety comes first here. The treatment will be designed according to the ‘multi-barrier’ principle. Here, reverse osmosis (RO) ensures that no micro pollution, bacteria or viruses end up in the produced drinking water. Waterunie intends an optimal sustainability in this operation, with attention to the total ecological footprint, including energy demand and use of chemicals.

Picture 1. The WWTP of Aalst were the DEEPER BLUE project is currently being built by Waterunie (in the upper left corner of the picture). The water reuse and ASR project will be fully operational in 2026. (Copyright FARYS).

Deep buffering
The produced drinking water is buffered deep underground, according to the Aquifer Storage & Recovery (ASR) principle. In wet periods with a surplus in water, the produced drinking water will be injected into the deep aquifer, called the Sokkel (= Aquifer Storage). This way, the project accumulates a strategic supply of injected water, which can be extracted during extended dry periods and overall water scarcity (= Aquifer Recovery). As such, the ASR system provides an answer to the spread of water availability in time and acts as a winter-summer battery for drinking water. Currently, the ASR borehole is being drilled and the ambition is to go 240m below ground.

Picture 2. The drilling works for the ASR borehole in which Waterunie wants to create a winter-summer battery for drinking water (Copyright FARYS).

Climate robustness
The underground buffer is coupled to the nearby Farys high-pressure water mains pipe for drinking water. This way, the produced drinking water will be available not only in Aalst, but it can also be distributed in the rest of Flanders. DEEPER BLUE thus increases the water availability in Flanders and offers an enhanced geographical distribution of drinking water. Boths aspects of the project – the temporal and geographical spread – increase the climate robustness of our water supply. This innovative concept contributes to the Flemish goals for Circular water management and the Strategic Plan for Water Supply.

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Contact
Prof. Bart De Gusseme
Project manager DEEPER BLUE
Sr. Expert – Dept. Innovation Farys
bart.degusseme@farys.be