Data description

Data description

Emissions to water

Water that is taken in must be treated before it is used in the process, and it is again treated after the process before it is released as effluent to a recipient. The substances in the effluent after wastewater treatment are reported. All mills have some sort of effluent water treatment, either mechanical treatment by sedimentation or in addition biological anaerobic and aerobic or chemical treatment of the effluent. A few mills send their effluent water to an external communal treatment plant. The volume of effluent water is reported separately for treated process water and thermally polluted effluent (e.g. cooling water). All mills have reported the figures for outgoing effluent water to the recipient i.e. effluent water after final treatment. The amount 
of substances (COD, BOD, suspended solids) per m3 of effluent from the different mills show very little variation when the efficiency of the waste water treatment station is the same. The amount of substances per tonne paper production may however vary according to the amount of effluent, depending on specific circumstances in the paper production process in the different mills. In the questionnaire for data collection, a number of other emissions were asked for such as oils, nitrates, acids, AOX, chlorate, chlorides, borates, phenol, Hg, Pb etc. Few mills were able to report figures, probably because there are no or few measurements. Only COD, BOD5, suspended solids, total nitrogen and total phosphorus are based on data from most mills in addition to the total volume of effluent waters. Due to the water treatment it is possible that the content of certain substances per m3 is higher if the water is taken from a river than in the effluent released into the river. In an LCA this would mean that the production of paper could be credited for the reduction in substances, although in practice this rarely happens. This principle is illustrated in Figure 13.

Figure 13 Potential credit for reduction of substances in the effluent water

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