Novel Combined Process For Ship Sewage Treatment

In view of the quality and quantity of ship sewage and the limit of cabin temperature, geographic and spatial location of the ship, we proposed three novel treatment processes to meet the continuously increasing emission standards of ship sewage which was established by IMO. These three processes for wastewater treatment were three-dimensional electrolysis-Fenton technology, Electro-Fenton followed by catalytic ozonation and the Electro-Fenton/O₃ system. Then the optimal process and device was chosen through comparison of COD removal efficiency, the instantaneous current efficiency and energy consumption during the treating process. We hope to obtain the process which is easy to manage and operate and can dispose wastewater quickly and efficiently with good resistance to shock loading and smaller floor space.The three-dimensional electrolysis-Fenton process was first studied. The results showed that Fenton reaction was significantly strengthened by the addition of 0.03 M H₂O₂, the COD removal can be up to 78% in acidic condition when activated carbon loaded by Fe and Mn?1: 1? was used as the particle electrode with the dosage of 150 g, the current density was 20mA/cm2, aeration rate was 5L/min and electrolytic time was 90 min.Secondly, the two main typical advanced oxidation technologies?Electro-Fenton and catalytic ozonation process? were studied respectively. Their optimum operating parameters during the sewage treatment were determined as follows:?a? Electro-Fenton process: Ti/IrO₂-RuO₂-SnO₂ and graphite arranged in parallel were used as anode and cathode respectively, Fenton reagent ratio was set as 1:4 with 0.01 M Fe²⁺, the aeration rate was 4L/min, the current density was 20mA/cm2, the distance between electrodes was 2cm and the salinity was 6g/L. The reaction rate decreased after 30 min. Considering the subsequent combination of catalytic ozonation, Electro-Fenton reaction time was selected as 45min;?b? Catalytic ozonation process: 200 g Ti-MC was served as heterogeneous catalysts for catalytic ozonation process with the TiO₂ content 5/27, ozone dosage was 6g/L, the oxygen flow rate was 2L/min and the rotating speed of peristaltic pump was 130 rmp.Then Electro-Fenton and catalytic ozonation process were combined for sewage treatment. Time distribution in the process was optimized in order to enhance the synergistic effect of the combinatorial device. Finally, COD removal of 82.8% was obtained with the total reaction time of 90min?45min Electro-Fenton and 45 min catalytic ozonation?.Furthermore, Electro-Fenton and ozone were introduced for ship sewage treatment by integrated method. The results showed that under optimal reaction conditions that included the current density of 20 mA/cm2, Fenton reagent(H₂O₂ and Fe²⁺) ratio of 3:1 with Fe²⁺ dosage of 0.01 M, the O₂ flow rate of 2L/min and the ozone dosage of 6 g/L, the integrated process by E-Fenton/O₃ system could effectively degrade sewage and achieve the removal of COD as high as 86.4% in 120 min.Finally, COD removal, instantaneous current efficiency and energy consumption were compared among three novel sewage treatment processes. Experimental results showed that: the combination of Electro-Fenton with catalytic ozonation showed higher COD removal with superior current efficiency and the lowest energy consumption during the sewage treatment process.