In the framework of a voluntary programme of risk reduction and environmental protection, EXPANSIA has opted to neutralise its alkaline effluents with CO2. 

 

EXPANSIA is a chemical/pharmaceutical company. At its Aramon (Gard) site, it has set up an installation to neutralise, using CO2, the basic effluents coming from organic synthesis and presenting variable pH values (maximum pH around 14). This process is introduced upstream of biological treatment on immobilised supports.

 

A large number of industrial processes, in the chemical industry, but also in the food, textile and leather industries among others, generate alkaline effluents that must be neutralised before being subjected to further treatment. The control of the pH and the calco-carbonic re-balancing also plays a key role in producing drinking water.

 

More often than not, alkaline effluents are neutralised using strong acids (sulphuric, hydrochloric, nitric, etc.). However, this technique has several disadvantages - additional saline pollution, difficulties in precisely regulating the pH, corrosion, manipulation of hazardous reagents.

 

An alternative technology, neutralisation with the weak acid H2CO3 generated by a solution of CO2 in water, seems particularly interesting. Its benefits include: no corrosion, no special implementation precautions, no feeder pumps (transport by natural pressure), no extraneous ions, no risk of over- acidification, stability of the pH obtained, alimentary nature of the acidifier.

 

One of the major advantages is that the slow neutralisation curve of the carbonic acid is quite different from the curves of the powerful acids. This avoids errors of dosage. And finally, from an environmental point of view, the use of CO2 contributes to the reduction of greenhouse gas emissions.