Chamam B, Heran M, Amar RB
The aim of our work is to compare the performances and the quality of treated water of a Tunisian textile industry through a conventional activated sludge (CAS) and a membrane bioreactor (MBR). During the first period, CAS and MBR1 worked under similar biological conditions (MLSS of 4-6 g.L-1). MBR showed a better global efficiency. Permeate of MBR was always free from TSS and turbidity whereas CAS treated water contained TSS and turbidity varying respectively between 0 and 0.13 g.L-1 and 10 and 20 NTU. If colour and soluble COD removal efficiency was closed (95% and 97%), it appeared necessary to add coagulant in the CAS to insure an adequate sludge settling and complete the colour removal. During the second period, the sludge retention time was increased in the MBR2 in order to reach 8-10 g.L-1 of suspended solids. The COD effluent value was further reduced (MBR2: 50 mg.L-1, MBR1 150 mg.L-1 and CAS 180 mg.L-1). The SRT allows a reduction of 20% of the sludge production but this effect was counterbalance by rheological sludge properties. Furthermore, the MBR has shown great aptitude to withstand high loading rate variations and to product a constant quality effluent.