A Case Study of a Full Scale Dyeing Wastewater Treatment Plant Using Biological Activated Carbon Fluidized Bed Process

The strict effluent quality standard in Taiwan has challenged the environmental engineers to search efficient and effective systems for industrial wastewater treatment. The wastewater research group of Center for Environmental, Safety and Health Technology Development (CESH) of ITRI (Taiwan) developed an advanced wastewater treatment process using activated carbon as the fixed film media for tertiary industrial wastewater treatment. Biological activated carbon (BAC) process combined both physical adsorption and biological degradation can extend the retention time of pollutant compounds in the system therefore enhance the biodegrade potential of the pollutants. This paper presents the experience of start-up and operation of a full-scale dyeing wastewater treatment plant using the biological activated carbon (BAC) process. A BAC fluidized bed reactor with a capacity of 2000 CMD was established to treat the effluent of the existing chemical flocculation process. The BAC process achieved stable effluent COD concentrations below 80 mg/L over one and a half years' operation with the hydraulic retention time (HRT) of 3.5 hours. The influent COD concentrations of the BAC fluidized bed reactor were under 250 mg/L. Stable performance was also resulted under shock loading conditions. The effluent COD concentrations can meet Taiwan's effluent quality standard (effluent COD below 100 mg/L for industrial wastewater effluent) consistently. The start-up and routine operational data showed the BAC process were effective in removing both organic compounds and color of the textile wastewater. The regeneration frequency of activated carbon adsorption process and BAC process was compared. The BAC process can extend the time of operation through biological regeneration to more than 10 times of the activated carbon adsorption process. The only need for activated carbon supplement is to compensate the abrasion lost in the fluidized bed reactor. Cost analysis was evaluated based on eighteen months operation data of the full-scale wastewater treatment plant. The capital cost of the BAC fluidized bed process was about 10,000 NT (300 U.S. dollars) per cubic meter treated wastewater per day (CMD) and the operation and maintenance cost were about 1∼2 NT (0.03∼0.06 U.S. dollar) per CMD. The low operational cost and stable system performance made BAC process highly competitive in industrial wastewater treatment market in Taiwan.