Wastewater treatment design parameter analysis using the Nan-Men contact bed treatment facility in Northern Taiwan

Contact bed treatment is one of the methods used for constructed wetlands. Taiwan introduced contact bed treatment to treat sewage in 2004. The reference design parameters are based on data obtained from developed countries. These foreign designs ignore the unique hydrological environment and climate of Taiwan. This study tried to analyze the water quality of the contact bed treatment system and to assess the efficiency of design parameter, based on that to propose design parameters to similar facilities on Taiwan. This study shows that the out-site contact bed treatment design should be changed to increase the aeration and disinfection parameters with the DO greater than 5 mg/L, BOD₅ optimal concentration of 10–25 mg/L, COD of 32–60 mg/L, SS of 15–25 mg/L, NH₃-N concentration can be greater than 16 mg/L, hydraulic retention time of two hours, gravel size of 10–15 cm, porosity of 30–50%, with the water flow rate less than 10 cm/s and sludge accumulation of 10 to 15 days. These studies conducted long term observation in accordance with local conditions. The above data are available to provide local design parameters for future follow-up designs.