“Why are we still outsourcing our sludge dewatering?”, water-link was wondering in early 2012. Together with GEA, the Antwerp water company has built a container with a polymer make-up unit and a decanter centrifuge to optimise sludge dewatering. “Our sludge dewatering/transport operations are now automated and we’re saving half of our operating costs,” says Sven Kempeneers, Process Engineer at water-link. He sums up the 6 wins the installation of the decanter yielded for water-link.

water-link on the Belgian market

water-link logo

As the largest water producer in Flanders, water-link serves three market segments: the residential market, industrial users and other water companies. Specifically, water-link supplies drinking water to more than a million people every day. Sven Kempeneers: “In our main water stream, we purify the surface water by removing suspended solids, micro-organisms, algae, etc. Sludge dewatering therefore only takes place on the residual stream, but it does have an impact on our main stream.”

WIN #1 – more efficient process

“We used to store the sludge in a basin, where it was treated and removed by an external partner once or twice a year. With such a long storage period, the sludge would get more degraded (e.g. ammonia formation) – particularly in the summer. Now that our new plant is up and running, sludge dewatering takes place continuously: the waste solids are removed and taken away immediately. This means we can work more efficiently: we’re recovering more water of a higher purity from the sludge, and it’s then easier to recycle it back into our main stream.”

WIN #2 – better results

“As a rule of thumb, 1% more dry solids should cut operating costs by 5%. Thanks to this plant, we’re getting dry solids that are more concentrated. We’ve been able to increase the percentage of dry solids from 0.1% to 16-22%. GEA also gave us a guarantee that we would be able to obtain at least 600 kg of dry solids per hour, and they’ve delivered on that. Since the plant was commissioned, we’ve carried out three performance tests, with consistently good results.”

WIN #3 – reduced environmental impact

“The sludge is more concentrated, which cuts down on the quantities we have to remove. The sludge is also reused as a fuel in the cement industry and before long it will also start being used as a building material for elevating dykes and roads.”

WIN #4 – keep it simple

“I have to admit that water-link didn’t know much about sludge dewatering techniques; nor did we have the people or resources to look into the subject in any detail. Apart from a few civil engineering aspects, GEA managed this project from start to finish: the design (taking into account stringent requirements in terms of soundproofing, insulation and ventilation), contracting, the various components of the plant, delivery, commissioning and even training of our staff and monitoring team. Thanks to comprehensive automation, intervention by our operating people is kept to a minimum.”

WIN #5 – no worries, even after commissioning

“As a result of this all-in approach, GEA has been able to guarantee not only a better result, but also a good post-commissioning service. GEA is a local player with a team of ten technicians. There’s someone available 24/7 so we never have to worry about a thing. The five-year maintenance costs were also very reasonable.”

WIN #6 – investment recouped in half the time

“Our investments in construction projects of this kind normally pay for themselves over ten years. Based on the current ROI calculations, we should recoup this investment in just five years.”

Top-class product

The results are impressive and water-link is delighted. Their enthusiasm is in no small measure due to the way GEA tackled the obstacles that arose during the project. “This aluminium sludge is not easy to deal with,” explains Sven. “You can’t compare it to the biologically active sludge at Aquafin, for instance. There’s more algae in the summer than in the winter and from time to time a stream of activated carbon comes through. But GEA took responsibility for the project all the way through and dealt with problems effectively as they cropped up – and they could always rely on support from their German parent company too. There were stressful moments for both of us at times, but in the end GEA has come up with a top-class product and we’re very happy with it.”

6 wins for waterlink infographic
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