Counter-current Washing

[2] [6] [10] [25] [28] [30] This measure is employed frequently on continuous preparation and dye ranges for water and energy savings. Clean water enters at the final wash box and flows counter to the movement of the fabric through the wash boxes. Thus, the cleanest water contacts the cleanest fabric, and the more contaminated washwater contacts the fabric immediately as it enters the actual process. This method of water reuse is opposed to the traditional washing method of supplying clean water at every stage of the washing. Water and energy savings are related to the number of boxes provided with counterflow. Counter-current washing can be applied at desize washers, scour washers, mercerizing washers, bleach washers, dye ranges and printhouse soaper ranges.

It is also easy to implement in existing mills where there is a synchronous processing operation. In a non-synchronized processing system, the use of a counter-current flow principle for washing from the following washing machine to the preceding one may become more difficult. In such a case, the reusable water could be collected in a common sump and then the water from the sump could be pumped to appropriate washing machines used on earlier cycles. It has been found that apart from savings in fresh water consumption, there are additional benefits of effluent blending to yield neutralization and equalization effects [10].

References from reviewed literature:

In [2] Brent Smith, A Workbook for Pollution Prevention by Source Reduction in Textile Wet Processing, available from the Pollution Prevention Pays Program, North Carolina Department of Environment, Health, and Natural Resources, Raleigh, N.C., 1988