| Currently more and more aquaculture wastewater directly emission without treatment, which is made the receiving water body eutrophication and biodiversity reduce. As far as inntensive farming water bodies, the ammonia pollution has become a major stress factor restricting the aquaculture environment, and organic matter and total nitrogen pollution is a key factor restricting the development of aquaculture. Biological contact oxidation plusing trickling filtration technique processing of aquaculture wastewater still has good pollutant removal efficiency under high hydraulic loading. While constructed wetland has good nitrogen and phosphorus removal efficiency. At present, it is relatively rare in researching aquaculture wastewater treatment with the above two types of biological purification technology. This paper researches them which will provide a theoretical reference for future engineering applications.The experimental study lasted nearly a year, and the main conclusions are as follows:(1) For biological contact oxidation plusing trickling filtration technique:At the same combined packing density, through the biological contact oxidation unit CODMn and TP removal rates decrease gradually while TN removal rate increases gradually with the reduction of HRT. Ammoniation reacts in the unit, and TN removal mechanism is the traditional nitrification-denitrification. through the trickling filtration unit CODMn、ammonia and TP removal rates decrease gradually while TN removal rate increases gradually with the hydraulic loading increasing. Overall, nitrogen and phosphorus removal is not very good with the device.(2) For constructed wetland technique:In the conditions of no aeration and hydraulic loading of0.31m3/m2·d, through the constructed wetland unit ammonia and TN removal rates decrease gradually with increasing influent concentration. In the conditions of no aeration, through the constructed wetland unit all pollutants removal rates decrease gradually with increasing hydraulic loading. It has a significant effect on the removal of pollutants because of different aeration system, and aeration is conducive to remove pollutants with the constructed wetland. When constructed wetland is not aeration, the way of denitrification is traditional nitrification-denitrification, while it will appeare simultaneous nitrification-denitrification with aeration.(3) Biological contact oxidation plusing trickling filtration dealing with aquaculture wastewater, the optimum operating parameters are as follows:combined packing and wastewater volume ratio is equal to9.24%; biological contact oxidation unit HRT is equal to0.85h; trickling filtration device hydraulic loading is equal to27.2m3/m2·d. Under best operating conditions, the average influent concentration of CODMnlOmg/L, ammonia2.4mg/L, TN6.2mg/L and TP1.7mg/L, CODMn and ammonia nitrogen removal rates are56.3%and40.81%. The average concentration of CODMn and ammonia nitrogen of effluent are4.5mg/L and0.83mg/L, which achieve the requirements of the III surface water quality standard. While TN and TP removal rates were56.3%and40.81%, and the average concentration of TN and TP of effluent are2.371mg/L and1.389mg/L, which do not achieve the requirements of the III surface water quality standard.(4) Taking the role of nitrogen and phosphorus removal into account, constructed wetland dealing with aquaculture wastewater, the optimum operating parameters are as follows:pre-aeration (air-water ratio=1:1); hydraulic loading is equal to0.15m3/m2-d. Under best operating conditions, the average influent concentration of CODMn10mg/L, ammonia2.4mg/L, TN6.2mg/L and TP1.7mg/L, CODMn、ammonia nitrogen and TN removal rates are82.75%,83.68%and88.85%. The average concentration of them in effluent are1.74mg/L、0.39mg/L and0.68mg/L, which achieve the requirements of the III surface water quality standard. At the same time, NO2-N removal rate is57%, and the average concentration of that in effluent is less than O.1mg/L, which achieves the basic conditions for the growth of aquaculture animals(NO2-N≤0.1mg/L) giving by Yangzhou fishery ecological environment monitoring station. TP removal rate is84.72%, and the average concentration of TP in effluent is0.26mg/L. Although it is not up to the standard, exceeding concentration is little.(5) During biological contact oxidation plusing trickling filtration operation, the biofilm needs to flush periodically. Combination packing biofilm washes once a week. At the summer high temperature, ceramsite filler washes once half a month. While ceramsite filler washes once a month at the low temperature. During constructed wetland operation, it needs to internal aeration periodically, which could solve the problem of obstruction internal the constructed wetland. |
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