| With the improvement of people's living standard,the demand for mariculture products also increases.The scale and density of mariculture are constantly increasing,and the environmental problems caused by mariculture wastewater discharged in the process of mariculture are increasingly serious.The constructed wetland of soil white bone has a good prospect for the treatment of mariculture wastewater.At present,there are many researches on the treatment of mariculture wastewater at home and abroad,but there are few reports on the mechanism of using constructed wetland to treat mariculture wastewater.In this paper,a constructed wetland was constructed with Avicennia marina.By measuring the total nitrogen,ammonia nitrogen,total phosphorus,chemical oxygen demand and total organic carbon removal rate in shrimp culture wastewater,the microbial community structure Avicennia marina constructed wetland was analyzed,and the treatment law of shrimp culture wastewater Avicennia marina constructed wetland was explored.At the same time,the treatment of shrimp culture wastewater by hydraulic loading Avicennia marina constructed wetland was also studied.Effect.The main results are as follows:1.Effect of Avicennia marina Constructed Wetland on Removal of Nitrogen,Carbon and Phosphorus in Shrimp Aquaculture WastewaterThe removal rates of total nitrogen and ammonia nitrogen were 77.19%-84.66%,91.63%-97.98%in the constructed wetland with stone as the substrate,41.40%-61.69%,47.08%-79.79%in the constructed wetland without vegetation with stone as the substrate,respectively.The removal rates of total nitrogen and ammonia nitrogen in the constructed wetland with stone as the substrate were significantly higher than those with stone as the substrate.No vegetation constructed wetland was used as substrate(P<0.05),but there was no significant difference in total phosphorus,chemical oxygen demand and total organic carbon removal rate between the constructed wetland with Avicennia marina and the constructed wetland without vegetation based on stone(P<0.05).The removal rates of total nitrogen,ammonia nitrogen,total phosphorus,chemical oxygen demand and total organic carbon were 77.19%,98.49%,82.88%,82.99%and 68.42%respectively after 18 days of treatment of shrimp aquaculture wastewater with Avicennia marina constructed wetland,and the effluent concentration was lower than the discharge standard of seawater aquaculture wastewater(GB3097-1997).The removal rates of total nitrogen and total organic carbon were 59.88%~70.01%,73.86%~81.67%in Avicennia marina constructed wetlands based on oyster shell.respectively.The removal rates of total nitrogen and total organic carbon were37.38%~50.20%,5.68%~22.31%in vegetation-free constructed wetlands based on oyster shell.respectively.The removal rate of organic carbon was significantly higher than that of vegetation-free constructed wetland using oyster shell as substrate(P<0.05),but the removal rate of ammonia nitrogen,total phosphorus and chemical oxygen demand of Avicennia marina constructed wetland using oyster shell as substrate was not significantly different from that of vegetation-free constructed wetland using oyster shell as substrate.The removal rates of total nitrogen,ammonia nitrogen,total phosphorus,chemical oxygen demand(COD)and total organic carbon(TOC)were 68.54%,74.82%,42.31%,84.73%and 81.67%respectively after 18 days of treatment of shrimp aquaculture wastewater with oyster shell constructed wetland.Total nitrogen,chemical oxygen demand(COD)and total organic carbon(TOC)effluent concentration were lower than those of seawater aquaculture wastewater discharge standard(GB3097-1997),while the concentration of ammonia nitrogen and total phosphorus effluent was higher than that of seawater aquaculture.Emission Standard for Reproductive Wastewater(GB3097-1997).2.Analysis of Microbial Community Structure Avicennia marina Constructed WetlandProteobacteria,Actinobacteria,Firmicutes,Nitrospinae were 58.07%,6.80%,3.31%and 0.74%respectively,which were significantly higher than those of vegetation-free constructed wetlands based on stones(P<0.05).Cyanobacteria accounted for 5.36%of the total bacteria in the constructed wetland with no vegetation and stone as the substrate.Avicennia marina constructed wetlands based on oyster shell and vegetation-free constructed wetlands based on oyster shell were dominated by Chlorophyta and proteobacteria,accounting for 69.86%and 8.80%,65.94%and 16.95%respectively,followed by unclassified microorganisms,accounting for 3.50%and 5.37%respectively.The proportion of Omnitrophica,Verrucous Microflora and Viscose Spherical Microflora in biofilm of oyster shell-based constructed wetland was 7.56%,2.55%and 1.17%respectively,which was significantly higher than that of oyster shell-based vegetation-free constructed wetland(P<0.05),while Proteus was significantly lower than that of oyster shell-based vegetation-free constructed wetland(P<0.05).3.Effect of Hydraulic Load on the Treatment of Shrimp Aquaculture Wastewater by Avicennia marina Constructed WetlandHydraulic load is one of the factors affecting the treatment of shrimp aquaculture wastewater Avicennia marina constructed wetland.The contact area between shrimp aquaculture wastewater and Avicennia marina constructed wetland is different under different hydraulic load conditions.The effect of Avicennia marina constructed wetland on shrimp aquaculture wastewater is the best under the optimal hydraulic load.When the hydraulic load was 0.06 m~3/(m~2.d),the removal rates of total nitrogen,ammonia nitrogen and total phosphorus Avicennia marina constructed wetland reached the maximum,which were 66.6%,75.0%and 41.81%respectively.Chemical oxygen demand and total organic carbon removal rate did not change significantly under different hydraulic loads(P>0.05).Avicennia marina constructed wetland for ecological restoration of eutrophic water body has the advantages of high efficiency,economy and environmental protection,which provides a good solution to the increasingly serious aquaculture environmental problems in China.However,it still needs to be strengthened in screening aquatic plants or microbial community structure with strong purification ability. |
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