A Study On Ozone And Biological Activated Carbon Filtration Technology For Wastewater Reuse

Aimed at reclamation of sewage, a pilot-scale experiment was conducted to treat the effluent from the secondary sedimentation tank of Xi'an Beishiqiao Wastewater Purification Center by Ozone and Biological Activated Carbon (O3-BAC) process. The experiment studied the removal efficiency of pollutants, the oxidation characteristic of ozone, and the characteristic of biological activated carbon filtering bed.The results showed that the O3-BAC process could remove organic matters, turbidity, color and odor efficiently. The average removal efficiencies of color, turbidity, UV254and TOC were 92%, 82.8%, 57.9% and 25.8% respectively, and although TN was not reduced, the form of nitrogen was changed obviously, with most of organic nitrogen, NO2-N, NH3-N oxidized into NO3--N. The effluent quality was good enough to meet the standards of miscellaneous and landscaping water.The ozonation didn't decrease the total amount of organic matters, but changed molecule structure and character of them. The organic matters with high molecule weight and unsaturated functions were oxidated into those with lower molecule weight and saturated functions. The biodegradability of organic matters was increased, with BDOC increasing from 0.725 mg/L to 1.917 mg/L as the result. Most of the organic matters in raw water were those with aromatic, carboxyl groups and hydrocarbon chains, and after ozonation, the amount of biodegradable matters such as lipid, carboxyl and aliphatic substances was increased.It was also revealed that biomass in the biological activated carbon bed decreased correspondingly with the depth of carbon bed, and the biomass mainly centralized at the upper and middle of filtering bed. Similarly, the removal efficacy of organic mattersdecreased when the depth of carbon layer increased. The removal amount of TOC and BDOC by BAC was 1.142 mg/L and l.206mg/L, respectively, and the two values was so close, which demonstrated that biodegradable organic matters were mainly removed by metabolism, and undegradable organic matters still remained in the form of TOC. The above result was in accordance with the analysis results of GC-MS.