TREATMENT OF PAPER COATING COLOR EFFLUENTS BY MEMBRANE FILTRATION

Dilute coating colour effluents are created during the coating of pape r and board. After treating the colour effluents with ultrafiltration, the retentate can be reused as coating colour and the permeate can re place fresh water. At the same time, the load on the external treatmen t plant is reduced. In this investigation, pilot-plant experiments wer e performed at a paper mill. A high and steady flux, 120 l/m(2) h, was achieved at a colour concentration of 10-15%. The flux at 40% was low er but steady, 50 l/m(2) h. The membrane performance when treating fiv e coating colours with varying composition was studied in laboratory e xperiments. The composition of the colour had a significant influence on the membrane performance. A colour containing starch exhibited the lowest flux and the lowest COD retention of the colours included in th e study, while a colour in which the clay had been replaced by CaCO3 e xhibited the highest final concentration of 60%.