| In recent years,the aquaculture industry has developed rapidly.While meeting people’s increasing nutritional needs for aquatic products,the aquaculture wastewater is directly discharged into the environment without treatment,which has a certain impact on coastal water quality.Hainan Province is a tropical ocean island with the smallest land area and the largest ocean area in China.It is of great significance to strengthen the protection of Hainan’s marine ecology and form a good situation of socio-economic development and good ecological environment.In this study,we focused on establishing a harmless ecological treatment technology for industrial aquaculture and pond aquaculture wastewater in Hainan Province.On the basis of the investigation of aquaculture wastewater in Hainan main mariculture areas,large seaweeds and filter-feeding animals were selected as effective purification biological objects,and the purification effect of large seaweeds was compared and the dominant species were selected.A series of experiments on the effect of filter-feeding bivalves on the filter-feeding of single-cell algae and the purified effect of aquaculture wastewater,established a Hainan mariculture wastewater ecological treatment technology model,and launched applications and demonstration.The main research results include the following four parts:1.Investigation and analysis of source water quality in Hainan’s main mariculture areas and wastewater from different mariculture models.The research results show that:（1）Refered to"Maritime Aquaculture Water Discharge Requirements（SC/T9103-2007）",four main mariculture areas（Qionghai,Dongfang,Wenchang,Lingshui）had different levels of pollution from the source of the water quality of aquaculture water,29%of the source water quality of inorganic nitrogen exceeded the requirements of the secondary standard,and 21%of the source water quality of inorganic phosphorus exceeded the requirements of the secondary standard.（2）With reference to"Maritime Aquaculture Water Discharge Requirements（SC/T9103-2007）",under different mariculture models in the four typical aquaculture areas in Hainan Province,69%of the aquaculture wastewater exceeded the level secondary standard for inorganic nitrogen,and 67%of the aquaculture wastewater exceeded the level secondary standard for inorganic phosphorus.（3）There was a significant negative correlation between p H,DIP and TP in aquaculture wastewater,a significant positive correlation between cadmium and lead,a very significant positive correlation between COD and TP,a significant positive correlation between lead and DIP,and a very significant positive correlation between DIN and TN,DIP and TP were extremely significantly positively correlated.Therefore,during the mariculture process,not only the mariculture models must be optimized,but also the program management for the discharge of aquaculture wastewater must be carried out.2.Comparison of purification effects on large seaweeds and selection of dominant species.The research results show that:（1）Eight large seaweeds had significant differences in the removal efficiency of nutrients in aquaculture wastewater,C.linum and G.bailiniae exhibited a high ammonium removal efficiency of 98.2%and 85%,respectively.The highest removal efficiency of phosphate by G.salicornia and G.bailiniae were 36.5%and 30.4%,respectively.C.linum and G.bailiniae had better removal effects on nitrogen and phosphorus nutrients than the other six seaweeds.（2）Eight large seaweeds had significant differences in their ability to remove ammonium,nitrate,nitrite,and phosphate in aquaculture wastewater.During the whole experiment,the concentration of ammonium in the treatment group of C.linum was the lowest,and had the best ammonium purification effect.G.salicornia and G.bailiniae had the best phosphate purification effect.（3）At different densities,G.bailiniae and C.linum had significant differences in the removal efficiency of nutrients in aquaculture wastewater.G.bailiniae with density of 10g·L-1 and 12 g·L-1 had the highest removal efficiency of inorganic nitrogen and phosphate in aquaculture wastewater,and there was no significant difference between 10 g·L-1 and 12g·L-1 G.bailiniae.C.linum at 12 g·L-1 exhibited the highest inorganic nitrogen and phosphate removal efficiency,a 98.90%inorganic nitrogen removal and 47.50%phosphate removal,respectively.Therefore,choosing 10 g·L-1 G.bailiniae and 12 g·L-1C.linum have the best purification effect on aquaculture wastewater.3.Study on the effect of filter-feeding bivalves on the filter-feeding of single-cell algae and the purification effect of aquaculture wastewater.The research results show that:（1）In the comparison of the feeding effects of Oyster,Mytilus edulis and Pteria Penguin on single-cell algae,it was found that Oyster and Mytilus edulis had better intake efficiency for five single-cell algae than Pteria Penguin,indicating the filter feeding of Oyster and Mytilus edulis best effect.（2）Mytilus edulis preferred filter-feeding Chlorella vulgaris,while Oyster and Pteria Penguin prefered filter-feeding Platymonas subcordiformis.（3）Oyster,Mytilus edulis and Pteria Penguin had obvious removal effects on nitrate,phosphate,total nitrogen and total phosphorus in aquaculture wastewater.Among them,the high nitrate removal efficiency of oyster and Mytilus edulis could reach 49.7%.The ammonium content in the oyster treatment group did not decrease,but increased,and the ammonium excretion efficiency reached 22.3%.（4）Oyster and Mytilus edulis had the best removal efficiency of suspended particles matter in aquaculture wastewater than Pteria Penguin.Oyster,Mytilus edulis and Pteria Penguin exhibited the removal capability of chlorophyll a（Chla）,COD and BOD in aquaculture wastewater.Therefore,it is feasible to select filter-feeding bivalve with good filter feeding effect for ecological restoration of eutrophication.4.The establishment of a technical model for ecological treatment of marine aquaculture wastewater in Hainan.The results show that:（1）After the fourth-level treatment,suspended solids,total residual chlorine,copper,zinc,and inorganic substances in pond aquaculture wastewater in the breeding farm of Xincun,Lingshui County Nitrogen,inorganic phosphorus,COD and BOD indicators had all been significantly reduced,which met the requirements of the first level discharge standard of"Marine Aquaculture Water Discharge Requirements（SC/T9103-2007）".（2）The aquaculture wastewater treatment system was stable.After three tests,it was found that the suspended solids,total residual chlorine,copper,zinc,inorganic nitrogen,inorganic phosphorus,COD and BOD in aquaculture wastewater comply with the"Maritime Aquaculture Water Emission requirements（SC/T9103-2007）"the first level emission standard requirements.Therefore,the establishment of a"physical and chemical treatments+filter-feeding bivalves+functional microorganisms+macroalgae purification effects"marine aquaculture wastewater ecological chain hierarchical treatment technology model,which has a significant purification effect in aquaculture wastewater,low construction cost,stability and scalability. |
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