storm water purification with the 'wetpark' method

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This plant was completed in1999 to purify and even up the flow of rainwater collected at the built area of Kalmar main hospital. The purification principle is the same as the greywater purification plant at Teknikhuset, Kalmar Technical High School, a flow of water disrupted by the percolation through planted soild dividers (shore zones), where the plants can take up nutrients from the hyporheic water.

The water, around 66,000 m3 a year collects from the hospital area and the surrounding built area (to the right on the picture) and is led into Pond 2 and Pond 1 (Damm 2 and Damm 1 at the picture). These ponds are fitted with oil traps and works as sedimentation basins. Pond 1 is sealed on the underside with an HDPE plastic sheet. Its normal water level is about one meter above pond 2.

After the detention in Pond 1, the water passes through the soil bank to Pond 2 (Damm 2). This bank is built of limestone gravel, in order to adjust the pH level of the water. During the passage, the water is filtered through the material. The same procedure takes place between Pond 2 and 3 (Damm 2 and Damm 3 on the picture), but this bank is constructed of native soil only. On this, plants are planted and are taking up nutrients through their roots. This embankment is also provided with a small shed that works as an overflow passage for high water levels.

A stone rim (made from recycled granite stones from houses at the hospital area) with a small watershed separates Pond 3 and Pond 4 (under the bridge). The watershed also works as an oxygenator.

The sides of the ponds are undulating. By this, the shore-line will be as long as possible, thereby maximising their purification capacity. Between Pond 4 and Pond 5, the water passes through a pipe that makes the two dams communicate in order to give them the same water level. 

From Pond 5, there is two possible ways for the water. Either it flows out to the Målareviken into the Baltic, or it its pumped up to an artificial stream that goes to Pond 1 again. The pumping is continuous.
By this, an entity of water will pass the ponds on average 1,5 times, thereby increasing the purification capacity of the ponds.

From the beginning, it was thought that the pumping would be done by a wind pump, but this idea was later rejected due to its complications and it was considered too expensive.

So far, no data collection of effluent water from the system has been done, but the water is calculated to be sufficiently clean to be used as a source of non-potable water (for rough washing, toilet flush and the like) if such is needed. The main aim of the system, however, is to diminish the nutrient load on Målareviken, and by that, the Baltic. In order to accomplish this, the plants in the area must regularly be harvested. The nutrients collected will be recycled to agricultural land.

The area, with open waters, shores, intermediate forest areas, paths and rest places, is easily accessible for neighbours, hospital staff and patients. The name Wetpark is chosen for these qualities.

The principles of a wetpark
The wetpark at Teknikhuset
Household wetpark
Pond 1 with rivlet
Pond 2
Pond 3 with watershed
Pond 4 and bridge
Pond 5

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