Recycling water is produced when washing out green concrete in ready mixed plants and prefabrication plants. Due to ist contents of cement the water is strongly basic (pH ~12). In case the recycling water can not be reused completely in production, it has to be clarified (separation of solids from the water). The clarified water can be reused for cleaning purposes or for example for the washing out of prefabricated elements. According to the regulations of the labour safety or due to specific on site conditions in the factory (for example: avoiding of colour shadows on washed out elements) it might become necessary to neutralize the clarified water. This can be achieved by using Carbondioxide (CO2 ). Because of the special buffer system CO2 developes with water a false dosing is nearly impossible. When using Carbondioxide no destructive substances are introduced into the clarified water.

The procedure

Continous neutralization in a pipe

The CO2 is injected into the recycling-waterpipe with a special dosing nozzle. A static mixer is responsible for optimal mixing and solving of the Carbondioxide in the recycling water.  A PLC controlled valve mounted in the feeding pipe is responsible for the dosing of the CO2 . The dissolved Carbondioxide reacts with water to carbonic acid, which neutralizes the basic components of the recycling water and this results in a decrease of the pH. In this way a reliable neutralization is achieved.

Discharging of neutralized water into sewer system

In case the clarified water should be discharged into a sewer system, it will be collected in a basin. In this basin an additional pH probe checkes the pH of the clarified water. The results are printed. The clarified water only is discharged into the sewer system when the reported ph corresponds with the reglementations of the local authorities. A bypass is installed to be able to return clarified water to the neutralization.