[Variation of pollutants along the height of two media BAF during advanced treatment of dyeing wastewater].

A pilot-scale process with the capacity of 15 t x d(-1) was applied for treatment of the secondary biological effluent from a dyeing industrial park wastewater treatment plant. We studied the variation of pollutants along the height of two media biological aerated filter (BAF), investigated the feasibility of the cheaper and lighter suspended media to substitute activated carbon. The results showed that while the influent average COD and color were 50.2 mg x L(-1) and 58 times, the effluent average COD and color of activated carbon and suspended media BAF were 35.0 mg x L(-1), 18 times and 44.3 mg x L(-1), 26 times, and both of the effluent met the first level A criteria specified in the Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant (GB 18918-2002), while it met the first level A criteria at the height of 2 400 mm in suspended media BAF, higher than the height of 1 800 mm in activated carbon BAF. The removal variation of color, TN and ammonia along the height of suspended media BAF is similar to the activated carbon BAF, but with a low removal efficiency of COD, mainly related to its less biomass. Therefore, suspended media to substitute activated carbon is feasible to the wastewater treatment plant, but the size and material of the media still need to be optimized, and to enhance the biomass, the hybrid process of suspended media with activated carbon BAF may be used to reduce the cost if it is necessary.