RE-Salt initiative: Recycling of industrial salty process water

Tanks of the pilot plant - Re-Salt
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German Federal Ministry of Environment (BMUB)

In many industrial processes, large amounts of waste water, containing highly diluted common table salt (5-10%) are released into rivers, being a burden to the ecosystem, especially in terms of drinking water production. Salt is also a crucial raw material for the production of chlorine, key raw material for the manufacture of polycarbonate and other high performance plastics. After several years of research, now a pilot plant has been constructed and gone into operation within Covestro’s project Cycles (funded by German Federal Ministry of Environment BMUB), to demonstrate the reuse of low-concentrated salt- containing wastewater streams. The plant is operating with a throughput of 30m³/h of wastewater. After cleaning the brine, new salt is added to reach the needed concentration for chlorine production thus closing the loop from waste water to a valuable resource. Within another, currently ongoing, project RE-Salt (funded by the German Ministry for Education and Research BMBF), research is being conducted for the purification of saline waste water streams by adapted adsorptive and electrochemical processes.

Main results
  • The current reduction of 30m³/ waste water per hour allows already reducing the amount of salt used in chlor-alkali electrolysis by 20 000 tons per year;
  • The amount of fully desalinated water used will be cut by approximately 220 000 tons per year;
  • This saves 1000 tons per year of CO2 emissions thanks to increased resource efficiency; it is aimed to increase the flow rate up to 50m³/h;
  • The plant is still in test mode to ensure no negative long time effects occur;
  • After successful evaluation, the implementation will be extended to other Covestro sites: the implementation in the production of polycarbonate has an exemplary character. It is known that nowadays 60-70% of all chemically manufactured products come into contact with NaCl.