Water is a valuable resource. There are now systems that can treat drinking water on site – and are also economical. A pioneering project in Berlin is already in operation.
Engineer Erwin Nolde leads into the basement of a student dormitory in Berlin. Here he is in his element: large gray tanks stand in a row, pipes run through the entire room. His pride and joy: a “gray water recycling plant”. Nolde’s mission: save water.
A laptop sits on a makeshift desk. Nolde calls up a few curves and explains what his system can do: “The house uses almost 30 cubic meters of water per day, and we recycle around 20 cubic meters of it.”
Small apartments, high Water consumption
The system has been in operation for almost a year and is the largest of its kind in Berlin. There are around 400 residential units in the house, each 16 square meters small – but with a shower. A very high water consumption, concentrated in a small space. Ideal conditions for efficient recycling.
Nolde has always been bothered by the fact that drinking water is consumed too carelessly. For him it’s a complete waste. Although his system cannot convert the waste water from showers and sinks back into drinking water, it can at least convert it into so-called “process water”. This can then be used to flush the toilets.
The engineer Erwin Nolde with two water glasses: The difference between the drinking water and the process water cannot be seen.
Standards also for process water
Nevertheless, the water must meet standards and therefore be filtered. “Everything is organic,” says Nolde, pointing to tanks around two meters in size in which small plastic cubes float. There are microorganisms on their surface that clean the water. “All they need is a little air, which we supply,” says Nolde. In addition, the water is passed through a sand filter and irradiated with UV light to kill germs.
Nolde fills two glasses with water. One with drinking water from the tap, the other with its process water. Visually there is no difference to see. “Theoretically, you could even drink it,” he says with a smile about his process water.
Heat from shower water
The engineer hates inefficiency. This becomes clear, for example, when he talks about how much water is wasted in Berlin – and how much energy. He has also come up with something for this: “Used shower water arrives here in the basement at around 30 degrees Celsius,” says Nolde. “With a heat exchanger we get five degrees out of it. We later use this heat to heat the drinking water.”
Nolde has worked on his solutions for decades; first at university, then in a company he founded himself. “The technology has been around for 15 years,” he says. But it took a while before he got his first big order.
Investment of 300,000 euros
The Berlinovo company had the student residence with the gray water system built. André Haßmann, head of the construction department, calculated carefully in advance whether the project would be worthwhile. “We said we’d give it a try and then we just jumped on it. Because the numbers were definitely impressive.”
Berlinovo invested around 300,000 euros in the facility. In addition to the technology in the basement, a good part of the sum goes to additional pipes that are necessary for recycling.
It pays off – after a few years
Haßmann had calculated that the project would pay off after almost twelve years. But after a year of real operation, it seems clear that things could happen even faster. Because water and energy prices are rising faster than expected. The result: the company should recoup its costs much more quickly. “It will level off after eight to nine years,” says Haßmann.
There are also ecological aspects. “We save water and energy and ultimately also CO2,” says Haßmann. The concept is almost a rarity: it makes ecological sense and pays off relatively quickly. So why aren’t such systems installed more often?
More projects planned
“We’re a bit irritated too,” says Haßmann and shrugs his shoulders. His industry, the construction industry, is also quite conservative. “In any case, we now look at every project with regard to ‘grey water: yes – no?’, and we know: it can pay off relatively quickly.”
The company is currently building two more dormitories with gray water recycling systems. This time, 800 – twice as many – residential units are to be connected.