Development of a hybrid system: Moving Bed Bioreactor-Membrane Bioreactor (MBBR-MBR) for textile wastewater treatment

Textile industry is one among the major pollution causing industries worldwide. Traditional physico-chemical treatments of textile wastewater are relatively expensive and generate large quantities of waste. Biological methods are generally cheaper and have been applied to remove organic substances and colour. Among them, membrane bioreactor (MBR) is a mature technology used in textile wastewater treatment while moving bed biofilm reactor (MBBR) technology is a relatively new method. Due to the biofilm attached to suspended carriers, MBBR is able to treat a larger organic load comparing to conventional biological treatments but the worsening of the biomass decantation is the main problem of MBBR. In many cases, this requires the addition of coagulant products. However, with the combination of membrane, the hybrid system MBBR-MBR is able to treat very high organic load and to remain a well-clarified effluent. A MBBR-MBR pilot-plant was investigated to treat textile wastewater from a local textile industry. The pilot plant is composed of an aerobic reactor filled with 25 vol. % of the suspended biofilm carriers, connected to the submerged membrane tank. The flow rate was 110 L/d and the hydraulic retention time (HRT) was 1 day. The removal performance of COD, suspended solid and colour demonstrated that the MBBR-MBR system is able to treat textile wastewater with a great efficiency and with a short HRT. Furthermore, the treated wastewater reaches high quality levels in terms of organic matter content, suspended solids and colour, which allows the reuse of the effluent for new dyeing processes. This action implies an important saving of water and dyeing auxiliaries such as salt and alkali.