What to do if standing waters run out of oxygen? This is a question that is posed a lot in the warm summer months. The use of mobile skimmers and submersible aerators is a proven way of biologically reactivating water reservoirs. Pump manufacturers like Tsurumi even hire out these devices.
Lots of ponds and water bodies become stagnant in the summer: If a green layer of small duckweed (Lemna minor L.) closes the surface of the water, it is often no longer possible to use the water. This swimming plant flourishes in waters that are relatively still and rich in organic nutrients. If the oxygen content drops below a certain level, the water can become biologically stagnant and turn into a hostile environment.
Therefore specialists recommend using a surface skimmer. The pump manufacturer Tsurumi, whose European headquarters are based in Düsseldorf, has the model 8-FSP in its program. “This is a kind of floating pump that removes the coating from the upper water layer”, explains Andreas Rössig who works for the manufacturer. After three hours of skimming, the 500 m? water body was transformed beyond all recognition: Seven cubic metres of duckweed were suctioned off into the waiting tank, and the surface of the water was clear again. The suction unit, which only weighs 38 kg, and its three red floats, achieves an intake rate of around 250 l/min. The submersion depth of the suction opening can be adjusted; 50 mm is usually adequate. This method is comparatively inexpensive, especially as the pump only requires a motor output of 750 Watt.
However, to restore the biological balance again and to avoid repeat eutrophication, oxygen needs to be added to the water. This can be achieved with submersible aerators with efficient pumps. Instead of one large one, several smaller units can be used at the same time. For instance, Tsurumi’s starter model of the TRN series with a 0.75 kW motor output. The aerators, which only weigh 55 kg, blow the ambient air into the water to enrich it with oxygen. One special advantage of units working in parallel is that the water is mixed more evenly. These aerators could easily work continuously in the summer months and be activated as required during the other months. The devices are mobile and are therefore not attached permanently in the tank. Compared to other aeration methods, the TRN models stand out thanks to the low overall costs and almost maintenance-free operation.