Efficiency Of Nitrogen And Phosphorus Removal From Aquaculture Wastewater By Marine Algae

Seawater aquaculture in our country has developed rapidly in recent years. However, a large quantity of untreated aquaculture wastewater rich in N/P nutrients was discharged into the sea, leding to eutrophication in coastal environment. Therefore, N/P nutrients removal in aquaculture wastewater is important to marine environment protection. Nutrients removal with algae is one of most potential wastewater treatment methods. Algae can not only absorb the nutrients in wastewater, but also produce some valuable products, such as oil, protein, pigments and polysaccharides. In this research, several marine algae species isolated from Hainan seawater were used to determine the efficiency of wastewater nutrients (N and P) removal from aquaculture wastewater.Chlorella sp.HNC11and Amphora sp. HNY were isolated from Hainan coastal seawater. Efficiency of nitrogen and phosphorus removal from shrimp breeding wastewater by the two microalgae strains was studied. Results showed that both strains grew well in shrimp breeding wastewater. The relative growth rate of A.sp. HNY cultured with shrimp breeding wastewater was3.73times higher than that of the alga cultured with Ningbo3media. After4days cultivation in a3L flask, the percent reduction rates of phosphorus by C.sp. HNC11and A.sp. HNY were95.1%and90.8%, respectively. And the ammonia removal rates by C.sp. HNC11and A.sp. HNY were87.1%and37.4%, respectively. However, reductions of nitrate and nitrite by the two microalgae strains were not significantly.12tropical marine algae species inciuding Chlorella sp. CM, Chlorella sp. JW2, Chlorella sp. HNC11, Skeletonema costatum, Platymonas Subcordiformis, Chaetoceros muelleri, Isochrysis galbana, Amphora sp. BQW, Gracilaria tenuistipitata, Gracilaria lichenoides, Bryopsis plumose (Huds.) C.Ag and Amphora sp. HNY were used to determined the N/P removal efficiency in juvenile shrimp aquaculture wastewater. Results showed that the absorption rates of the total nitrogen, the active phosphorus and the total phosphorus in the sewage of the C. sp. JW2is45.1%,100%,88.3%.The absorption rates of the ammonia nitrogen of C. sp. CM, P. Subcordiformis, C. muelleri and B. C.Ag are as high as88.7%,88.9%,91.1%and98.5%, respectively. The absorption rate of ammonia nitrogen of G.tenuistipitata and G.lichenoides come next. The absorption rates of the nitrite nitrogen of P.Subcordiformis, A.sp. HNY and I.galbana are43.2%、24.0%、19.5%, respectively. The absorption rates of the nitrate nitrogen A.sp. BQW and G. tenuistipitata are54.3%and31.5%, respectively.8tropical marine algae species were used to measure the N/P removal efficiency in the artificial wastewater with orthogonal experiment method. Results showed that the main factor influencing the ammonia nitrogen absorption efficiency of the algae was thet initial ammonia nitrogen concentration in the artificial wastewater. The initial phosphorus concentration in the wastewater is the main factor influencing the phosphorus absorption rate of the algae. Growth rate of G.tenuistipitata is significantly higher than that of G.lichenoides. Growth rates of C.sp.HN.C11and C.sp. JW2under the low nitrogen levels are significantly higher than that under the high nitrogen levels. Growth rate of the G.tenuistipitata is significantly (P<0.05) higher than that of G.lichenoides. With fluorescence microscope examination, the two strains of Amphora sp. Accumulated more oil than the two strains of C. sp.,A.sp. BQW produces oil well.Finally Artem ia salina is cultured with C. sp. JW2in artificial wastewater. It is found that the decontamination ability of C.sp. JW2with Artem ia salina is stronger, so putting the Artem ia salina into the microalgae does not affect the decontamination ability of the microalgae and the nitrogen and phosphorus content is lower than no Artem ia salina microalgae.