Monday, April 09, 2007

Planned Indirect Potable Reuse in Belgium

Belgium has a relatively new planned indirect potable recycling scheme which is not well known in Australia. For this reason, I thought it might be interesting to take a quick look at it.

The northern region of Belgium is known as Flanders and like most of Belgium, Flanders relies heavily on groundwater extraction for potable water supplies. Flanders is among the most densely populated areas of Europe. It is highly industrialised and is also home to much intensive agriculture. These factors have led to severe over-extraction of many important aquifers.

In 1990, the Flemish government established the water utility company ‘Aquafin’ to establish and operate advanced sewage treatment infrastructure in Flanders. Aquafin now operates more than 200 sewage treatment plants (STPs) and the effluents from several of these are reused for industrial applications, -most commonly as industrial cooling waters.

The Intermunicipal Water Company of the Veurne Region (IWVA) is responsible for the production and distribution of drinking-water in the western part of the Flemish coastal plain. In the early 1990s, it became apparent that the IWVA could no-longer continue to increase the groundwater extraction from its dune aquifer catchments of St. Andre and the Westhoek to fulfil the growing potable water demand. Groundwater recharge of the unconfined aquifer of the St. Andre catchment was identified as the optimum solution. Treated effluent from Aquafin’s nearby Wulpen STP was selected as the source for the production of water to recharge the aquifer.

IWVA constructed the Torreele advanced water treatment plant adjacent to the Wulpen STP, with a production capacity of 2,500 megalitres (2.5 billion litres) per year, -equivalent to around 40% of the local potable water demand. The Torreele treatment scheme is shown below (click to enlarge).

Secondary effluent from the Wulpen STP is pre-screened with mechanical screens before chlorination and retention in an equalisation basin. It is then treated by ultrafiltration (UF) membranes before further chlorine treatment and then reverse osmosis (RO) membrane treatment. Finally, the water is subjected to ultraviolet (UV) radiation. The advanced-treated reclaimed water is discharged to a 70 cm deep, 1.8 hectare pond for infiltration to the groundwater aquifer.

After a residence time of at least 40 days, the water is extracted from the aquifer from 112 wells located at various distances (around 40 to 100 m) from the infiltration pond.

The UF and RO membrane concentrate streams are discharged into a nearby brackish water canal that flows 7 kilometres to the sea. Since 2003, tests have been performed on the concentrate using a constructed wetland to successfully reduce nitrogen, suspended solids and, to a lesser extent, organics in the concentrate.

Since the groundwater recharge began in 2002, there has been a gradual increase in the groundwater levels in the aquifer, providing a valuable protection against saline water intrusion from the North Sea.

The Torreele/Wulpen project was recently profiled in the weekly international newsletter ‘Water Desalination Report’ (2 April 2007, Vol 43, No 13). The editor of the Report included the comment:

“As this newspaper recently noted: just because it isn’t called reuse, doesn’t mean it isn’t reuse. Virtually every potable water supply in Europe is, to some extent, an example of ‘unplanned’ indirect potable reuse. But the Torreele/Wulpen project is the most honest example where the local community has been well informed that the water supply has been reclaimed”.

I don’t have any actual information regarding just how informed the community is or what the community response was. However, I would be very keen to find out. So if you can find any information –perhaps on the internet or any local contacts-, I would be most interested to hear of it.

Thanks to Davide Bixio at Aquafin for supplying most of the information (and the image) presented here.


Anonymous said...

I like how the treatment scheme looks kind-of like a strange robotic Kanagroo. Do you think they designed it like that on purpose?

Stuart Khan said...

G’day Anonymous,

This is an interesting observation. However, no, I tend to think that it is unlikely that ‘looking like a robotic kangaroo’ was a significant design consideration.

Liara Covert said...

I was unaware of Potable Reuse in Belgium, though I lived in France for 6yrs and gained insight into recycled H2O there. A Canadian living in Melbourne, one of my friends heads a committee aiming to save the future of $100 million Victoria pool industry. Drilling a boar and tapping into aquifers was unsuccessful. They need new sources of water since rainfall isn't dependable. I brought up a desalination plant proposal, comparing the new plant in Western Australia with rejected proposals in Sydney. I was told it was too expensive for government and industry and they do not seem to desire to cooperate seriously. The greater Australian public and leaders appear to be disconnected from reality of H20 availability. People here often use water as if its unlimited. Cost/liter in homes is relatively low so people have no sense of its real value. Fines are not enforced for disregarding water restrictions. Government permts key industry to use water as if unlimited. What will it take to persuade government & industry to work together? Industry could convert to use salinated water for cooling while also using excess energy to fuel the desalination process and create fresh water. Let's hope we won't all have to distill fresh water before long.

Stuart Khan said...

Thanks for this comment, Liara.

I agree that we need to closely examine the signals that we send out regarding the value of water. By the way, the desalination plant in Sydney is ‘full steam ahead’ and the Victorian Government has also been seriously considering one for Melbourne. However, Melbourne does present some significant challenges in terms of sustainable brine discharge. The brine would either have to be discharged into Port Phillip Bay (unlikely to be acceptable), or transported at significant cost to the open ocean.

Melbournian said...

But if Melbourne builds a recycled water plant, where would the RO waste stream go? Out to sea. Similar issue.

Stuart Khan said...

Yes, indeed it is essentially the same issue (assuming such a recycling scheme also uses reverse osmosis). One difference is that the volume would be less for a recycling scheme (because the recovery is higher). Furthermore, the chemical load of the coastal STPs is already discharged into the same waters, hence the only change would be to a lower volume, more concentrated discharge. But I agree that this is not ideal and is a major limitation of reverse osmosis technology.

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