PRODUCTION DEPENDENT SPECIFIC DATA OF PAPER MILL WASTEWATERS: INFORMATION FOR TREATMENT AND REUSE

Abstract

Specific data on paper mill wastewaters, especially ratios of BOD, COD and TOC as weU as specific loads of these parameters in mechanically treated production wastewater of paper mills, depend strongly on the type of paper produced in the mill. These data and the respective correlations are known from previous research of the authors. The selection of suitable wastewater treatment processes, which are state of the art or best available technology (BAT) in the paper industry, depends on the type of wastewater characterized by these specific data. Minor or major parts of the wastewater - depending on the type of paper produced - can be reused in the production prior to external treatment. When the proportion of water reused prior to external treatment tends to be high, due to anoxic degradation in the internal circuits the type of dissolved organics may change. This can be easily detected by calculation of the BOD/COD ratio. For a certain system, the specific amount of water needed depends on the intensity of use for production, compared with other, not production dependent, uses. This may be detected by a calculation given here. When no discharge to the sewer is suitable, the excess amount has to be treated biologically for discharge to surface water or for further reuse. Treatment processes discussed are: activated sludge treatment, anaerobic treatment followed by activated sludge treatment, high capacity trickling filter followed by activated sludge treatment, aerobic submerged biofilters, low capacity trickling filters. Advanced treatment processes are combined with these processes, when BAT is required. For reuse of the biologically treated water, for all types of treatment except biofilters, a sand filter or similar equipment has to be added.