Clean ship handles urine and fecal flows smartly

For the 46 households in project Schoonschip in Amsterdam-Noord, QUA-VAC BV has supplied silent and water-saving vacuum toilets. These toilets are connected to a vacuum piping system that collects the streams of urine and feces (also known as black water) in a vacuum station. From here the wastewater is pumped further, until it finally exits into a  digestion unit where it is fermented and converted into biogas, heat and electricity. In addition, phosphate is extracted from the wastewater, from which fertilizer pellets are made for the plants, vegetables and trees in the floating housing estate.

"A vacuum toilet is a toilet in which the flushing water and the flows of urine and feces to be discharged are not drained by gravity, but by means of negative pressure," says Arjan Krebs, Project Engineer at QUA-VAC BV. "When flushing, a small amount of water (about 1.2 liters) flows into the toilet bowl. At that same moment, an exhaust valve in the toilet is activated and opened, after which the toilet is flushed based on negative pressure. With a pressure differential of -0.6 bar, the streams of urine and feces to be discharged are sucked out of the toilet and through the vacuum line, into the vacuum pumping station. This process takes only a few seconds, after which the suction valve is closed again." To ensure proper transport, QUA-VAC drew up a design for the entire vacuum network and vacuum station. "We have extensive experience in this and can provide maximum relief to customers."

Substantial water savings, minimal environmental impact (footprint)
Whereas (standard) free-flow toilets use 6 to 8 liters of water per flush, for flushing the vacuum toilets only 1.2 liters is enough, says Patrick Vos, Outside Sales at QUA-VAC BV. "A considerable drinking water saving is the result, which can become very interesting in the near future. Moreover - thanks to the efficient treatment of the limited amount of wastewater - the environment is significantly less burdened. Less wastewater goes to the treatment plant, which also means that less energy is needed to treat the wastewater. As a result, CO₂-emissions reduced significantly." Krebs: "The green, new sanitation saves up to 10,950 liters of drinking water per person per year. Also, more raw materials are extracted from the wastewater than with standard treatment. Thus the vacuum system fits perfectly with the ambition of Schoonschip, which is to become Europe's most sustainable floating district."

Quietest vacuum toilets on the market
Project Schoonschip is part of the Buiksloterham area development project, which includes the development and construction of several hundred homes. These homes are being built across the Johan van Hasselt Canal. "For these homes, QUA-VAC is supplying a total of 640 vacuum toilets," Krebs says. "Chosen were the Evac Optima 5 toilets, which are among the quietest vacuum toilets on the market. A control unit with flush memory ensures that the toilet always waits for sufficient vacuum before performing the flushing process. Without the user having to wait for it. The advanced suction valve ensures that - should the vacuum unexpectedly fail - flooding is prevented."

Continuous buffer vacuum
Project Schoonschip's Evac 10 HQE 140 vacuum pumping system includes a large 1,100-liter receiving tank with two vacuum and two discharge pumps. "In the tank, a vacuum buffer is created. So that when a toilet suction valve is opened, all vacuum is not immediately lost. In addition, the tank serves to temporarily store black water. When the tank for 30-40% is filled with wastewater, this water is forced under the Johan van Hasselt Canal, towards the vacuum station of project Buiksloterham and the fermentation unit. Because the new sanitation for Buiksloterham is not ready at this time, the black water from the Schoonschip households is still temporarily squeezed to the existing sewer." 

The pilot in Buiksloterham offers Waternet the unique opportunity to discover whether decentralized sanitation produces better results than centralized treatment. Following this project, Waternet wants to introduce the new sanitation in other places in Amsterdam.