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Water for the process is pumped out of the Urola River. The water system is almost totally closed, so water consumption hardly reaches 3 m3/ton. Our present waste water treatment plant includes a pre-treatment in a slurry pool where, on the one hand, fibres are recovered and reprocessed, and, on the other hand, the resulting effluent is transferred to an homogenising pond intended to equalise any generated waste.
    Thereafter, waste products undergo a primary, physicochemical treatment consisting in dissolved air flotation followed by decantation. Downstream, the waste temperature is reduced to 30¼C in a cooling tower before waste proceeds to the activated sludge process (biological treatment) that takes place in two parallel biological reactors, each 450 m3 in capacity, a secondary decanter and a sludge recirculating tank. The output effluent is conveyed to a tertiary treatment plant prior to being dumped into the river. Sludge proceeding from the three treatment processes are directed to a sludge basin that feeds a centrifugal sludge dewatering line.