Water Re-use
Water Re-use
In recent years, it has become clear that the way towards high efficiency soaking, liming, pickling and chromium tanning processes would be based on recovering and re-using floats from the same processes. Reuse of process liquors offers a good method for reducing waste volume. It is reported that used lime liquors can be reused 10-12 times.
Depending on raw materials, the liquors from the main soak can be recycled to the dirt soak.
Part of the second lime wash may be recycled to start a new lime liquor. Lime washes together with some washes (deliming and non-enzymes bating) can be recycled back to the soak.
With the application of these techniques, water consumption can be reduced considerably. However, chemicals and other contents of the rinsing water may cause difficulties in the process step to which water is recycled. Inappropriate processing of the recycled water may damage the hides. Of course, technical equipment for collecting, cleaning, and monitoring water exists, but the extra effort and investments are required, which means tanners have to be really committed to the reuse of water.
Parameter | Without water recirculation | With water recirculation |
Wastewater | ~ 12 m3 per tonne of raw hide | ~ 9.5 m3 per tonne of raw hide |
Energy | 6.3 GJ per tonne of raw hide | 6.3 GJ per tonne of raw hide |
Chemicals | ~ 450 kg per tonne of raw hide | ~ 450 kg per tonne of raw hide |