Coupling Ozonation-Ceramic Membrane Filtration System For Recirculating Aquaculture Wastewater Treatment

Coupling catalytic ozonation-ceramic membrane filtration technology is a novel, efficient and advanced wastewater treatment technology. It can not only concentrate the poisonous and harmful substances in the waste water by using membrane intercepting process, but also can decompose the pollutants intercepted by membrane filtration by catalytic ozonation. However, preparation of efficient and stable ozonation catalytic membranes in the coupling catalytic ozonation-ceramic membrane technology is one of the key steps. In this study, an efficient ozone catalyst was screened and loaded on the catalytic membrane. Then, the membranes were applied to the coupling catalytic ozonation-ceramic membrane filtration system for recirculating aquaculture wastewater treatment. A new coupling catalytic oxidation-ceramic membrane filtration system was established for practical recirculating aquaculture water treatment. The present study provides an efficient pratical wastewater treatment technology for the water pollution control and resource utilization. The main contents of this work are as follows:(1) Preparation of all kinds of ozone catalyst with different method. The catalytic oxidation properties of different catalysts were compared. The results showed that the morphology of iron oxide had little impact on the catalytic decomposition of ozone and its ability of catalytic degradation of nitrobenzene was poor; The catalytic ozone decomposition ability of manganese oxide nanorods was strong, but no efficient for the printing and dyeing wastewater treatment; The oxalic acid removal rate of titanium oxide doped with manganese was 63.8% and its kinetic constant was 0.03436 K/min, which was 1.5,3.4,5.7,10.2,20 times that of TiCoxOy, TiCexOy, TiFexOy, TiO2 and without catalyst, respectively.(2) Catalytic ceramic membranes were prepared successfully by coating Ti-Mn sol using a layer-by-layer technique and their performance were investigated, including membrane flux, the morphologies of membranes, and so on. SEM and EDX images showed that Ti-Mn oxide was not only coated on the surface of ceramic membrane, but also penetrated into the ceramic membrane. XRD spectrum showed that the preparation of ozone catalytic ceramic membrane consists of three parts:the substrate (Al2O3), interlayer (rutile TiO2) and catalytic layer (rutile TiO2, no characteristic peaks of manganese oxide were found). Membrane flux test showed that the flux of Ti-Mn/TiO2/Al2O3 and TiO2/Al2O3 membrane was 269.6 L/m2·h·bar and 340.5 L/m2·h·bar, respectively.(3) In the study, the performance of three kinds of technologies were compared, including membrane separation technology, coupling ozonation-membrane filtration system and coupling catalytic ozonation-membrane filtration system. It was found that the membrane filtration alone were not feasible in the aquaculture wastewater treatment because the removals of ammonia nitrogen and nitrite were relatively low. The coupling catalytic ozonation-membrane filtration system showed the most superior performance in the aquaculture wastewater treatment, with the good permeate quality meeting the requirement of aquaculture water reuse (Turbidity≈0 NTU, CODMn≤3 mg/L, NH4+-N≤0.1 mg/L and NO2--N≤0.005 mg/L), enhanced membrane antifouling, and higher removal efficiency of organic matters.(4) A pilot-scale coupling catalytic ozonation-membrane filtration system was designed for the recirculating aquaculture wastewater treatment at a fish farm. Long-term operating results showed that the system kept a stable membrane flux and the output water quality kept good which satisfied the second sea water quality standard. This study established a coupling catalytic ozonation-ceramic membrane filtration system for practial recirculating aquaculture wastewater treatment and the coupling system is expected to be a promising strategy for recirculating aquaculture wastewater treatment.