Beamhouse and tanning operations: Process chemistry revisited

Leather processing technologies are under critical review in recent times. Traditional methods in leather processing have involved the use of large am ounts of water and chemical inputs. The general practice in tanneries has i nvolved the use of nearly 35-40 litres of water per kilogram of leather pro cessed. Processes have not been audited for utilisation of chemical inputs. In some cases, the utilisation levels of chemicals employed fall in the ra nges of 40-75%. Such non-optimum use of chemical and water inputs has led t o problems in both cost effectiveness due to material loss and pollution fr om unused chemicals. It has become essential that the beamhouse and tanning processes are audited for their environmental loads. Whereas there is sufficient awareness in leather processing industries rega rding the costs of compliance with national environmental regulatory norms, the potential benefits of cleaner production technologies with respect to cost saving are not fully understood. Further, with increasing inventory co sts, audit of beamhouse and tanning processes is becoming crucial. Process time in leather making operations is influenced by several physico-chemical parameters. One of the major factors influencing the process time of beamh ouse and tanning operations in leather processing is the duration needed fo r diffusion of materials. A re-visit to the chemistry of beamhouse and tann ing operations at this critical juncture is worthwhile. An attempt has been made in this work to critically review the process chem istry and discuss possible improvement options. Some case studies are prese nted in this work where reduction of BOD and COD levels by 30-40%, Total Di ssolved Solids by 25-35%, sulphide by 50-60% and chromium by 98-99%has been achieved under real field conditions through improved beamhouse and tannin g operations.