In the production of bulk drugs the main molecule is produced in the reactor/fermenter followed by multi-step separations and purifications involving various types of physical and/or chemical processes. At the penultimate stage often the drug is precipitated and separated by centrifugation or filtration. The centrifugate/filtrate, also known as Mother Liquor (ML), is normally sent to ETP for further treatment essentially to reduce BOD, COD, SS, TDS etc. to acceptable limits fixed by the respective pollution control boards.

Incorporation of suitable RO on the ML can recover the valuable drugs which otherwise causes pollution when drained to the ETP. Typically 0.2 to 3% of the valuable drugs, depending upon their solubility, are lost into the ML as the existing processes are incapable of further recovery. However, this small but significant quantity can be recovered if concentrated through RO. Therefore RO acts as a partial pollution control system besides being a source of additional revenue. Following Illustrations explain the general scheme recovery of specific drug/precursors.

The typical mother liquor from a chemical reaction contains 0.3 to 0.4% of dissolved 6 APA, 15% Methanol, 2% Methylene Chloride and 3 - 4% salts. The membrane process concentrates the 6 APA to 3 - 4% using the solvent stable SelRO membranes. These membranes being solvent stable are not affected by organic solvents. The concentrated 6 APA solution thus obtained, can be added upstream before solvent extraction for additional recovery, the permeate stream obtained from the membrane system goes to the effluent with reduced pollution load to the extent of 6 APA recovery. Typically 70% recovery is possible, which makes the membrane process extremely attractive with pay back period of less than 6 months.