Messer is supplying CO2 and hardware to Gezhouba Environment & Engineering to neutralise alkaline wastewater. The company cleans sludge pumped from Lake Dian. The largest inland lake in the Yunnan Province is polluted as a result of over-fertilisation. Water is extracted from the sludge using an alkaline calcareous medium. This process wastewater is strongly alkaline afterwards, containing around 500 milligrams of lime per litre. Carbon dioxide fed in via tube reactors constructed by Messer lowers the pH and reduces the hardness of the water. In contrast to the previously used hydrochloric acid process, no chloride ions are liberated as a result. The treated wastewater can then be returned directly to the lake. As an added benefit, process costs have been reduced by over 30 percent too.