Background
During heavy rain enormous masses of rain water fills up rivers and water courses and moving a lot of BOD (Biological Oxygen Demand) and COD (Chemical Oxygen Demand) from the acres to the rivers. The result is that the oxygen levels in the rivers decreases endangering the aquatic life and releasing chemical substances, a very bad smell is related to this as well. Later on, untreated waste water over floods waste water plant releasing untreated water into the sea.
What was needed was a new kind of aerator, that instantly can be set to operate and that can introduce sufficient amount of oxygen in a short time, is needed. This new aerator must have a rugged design making it possible to survive the hard conditions in our rivers but yet agile so it can be used in other applications as aquaculture and waste water treatment. The actual design was made in the form of a vandal proof “protective box”, with 10, Watreco FlowMixer 10 units connected in parallel.
The European Union conducted competitive selection to provide aeration for the “De Dommel” river system in the Eindhoven region of The Netherlands based on both O2 ppm and energy use performance.
FlowMixer was selected, installed and currently expanding to include over 100 more installations to improve the river water quality adversely impacted by the city waste treatment effluent.
Results
- The average amount of oxygen that was introduced into the river varied between 9,5 kg/O2/h (dry weather conditions) to 17 kg/O2/h wet weather conditions.
- The expected values were between 3 to 5 kg/O2/h.
- Because the VPT is a vacuum technology, the efficiency is depending on the outer pressure, i.e. the depth of the water.
- This means that if there is a higher water level the back pressure from the outside equalizes the sub-pressure inside. This was compensated with the aid of an auxiliary fan, and after introducing this fan, the process was very robust.
- The pilot plant had no observable effects on the aquatic fauna and flora.
- The pilot plant was not affected but the very high water flow and levels. Sometimes there was a difference of 3 m compared to normal levels.
- The design of the pilot plant was very sturdy and was not affected by contaminations such as bicycles, tree branches plastic debris, and similar.
