Degussa adds Siemens wastewater plant

Erlangen, Germany -- With Chinese regulators becoming increasingly focused on environmental protection, Degussa Rexim (Nanning) Pharmaceutical Co. Ltd, part of Degussa (China) Co. Ltd, has installed Siemens water purification plant for the removal of nitrogen from wastewater.

Degussa decided to transfer production of L-methionine -- an amino acid used in preparations for treating infections -- to a 300-tonne/yr plant at Wuming, near Nanjing, in 2004. The existing wastewater treatment plant had to be adapted for the new manufacturing process, which produces different types of wastewater containing carbon and nitrogen compounds.

According to Siemens, its revised process engineering approach had to allow for the reaction conditions in a subtropical climate, ease of operation and the cost effectiveness of the process, which treats around 300,00 cubic metres of wastewater a year.

The treatment plant is based on a flexible two-lane, cascaded bioreactor that can be connected in parallel or series and run with variable gassing zones. Vertical flow round separators provide a secondary clarification unit to separate the biomass from the purified wastewater, while there is also a special facility for aerating the wastewater with fine bubbles.

Excess sludge produced by the biological purification is homogenized, concentrated and conditioned to enhance the dewatering characteristics of the sludge suspension. This is mechanically dewatered in a chamber filter press, with the sludge then alkalinised with caustic lime to prevent further biological activity and made ready in the storage area to be taken away for disposal.