Purification Effect Of Daphnia Magna And Aquatic Plants On Eutrophic Water

Water eutrophication is an ecological issue of global concern.There are various measures for water governance,and bioremediation is one of the environmentally friendly repair methods that use natural materials for purification treatment.This thesis will observe the water purification effect of Daphnia magna and Scenedesmus quadricauda in artificial eutrophic water by constructing the combination of Daphnia-Algae.In addition,construct the Daphnia-Grass combination and the Daphnia-Algae-Grass combination,It can analyze the purification ability of different combinations of aquatic plants and animals in natural eutrophic water.The research results are as follows:(1)The combination of Daphnia-Algae has a significant effect on the removal of Total nitrogen(TN),Ammonia nitrogen(NH₄⁺-N),Total phosphorus(TP)and Chemical oxygen demand(COD)in water,and the removal rate is 63.97%,22.38%,56.18%and 47.24%.12.13%lower Biochemical oxygen demand(BOD)con-centration than initial value,and the p H was always within 7.00?7.70.The initial algae density of Scenedesmus quadricauda was 5.10�10⁶cells/ml.At the end of the experiment,the algae density of Daphnia-Algae combination increased by6.27%.Daphnia magna feeding algae slowed the growth rate of Scenedesmus quadricauda,and the Daphnia-Algae combination achieved better water purification and algae suppression effects.The Daphnia-Grass combination can significantly reduce nutrient content in water.The removal of TN,NH₄⁺-N,TP by this combination were 36.96%,81.76%,31.49%.At the end of the test,the Daphnia-Grass combination increased Dissolved oxygen(DO)content in water by22.83%.The plants grow well,The longest root length of plants in the Daphnia-Grass combination and Myriophyllum verticillatum L.combination increased by 294.67%and 281.03%,and the average fresh weight increased by31.09%and 23.34%.Daphnia magna has a certain effect on plant growth.(3)The comprehensive water purification effect of Daphnia-Algae-Grass combination was significant.The combination of Daphnia-Algae+Ruellia brittonian-Myriophyllum verticillatum L.,Daphnia-Algae+Ruellia brittonian-Salvinia natans(Linn.)All.-Myriophyllum verticillatum L.,and Ruellia brittonian-Salvinia natans(Linn.)All.-Myriophyllum verticillatum L.were set as treatment 1,2and 3.The TN removal rates of three treatment groups were 69.59%,72.43%,and68.47%,the NH₄⁺-N removal rates were 94.55%,95.82%,and 93.67%,and the TP removal rates were 19.85%,38.22%,and 37.49%.The comprehensive decontamination capacity were ranked from high to low as treatment 2>treatment3>treatment 1.The experiment showed that the combination of aquatic plants composed of"Daphnia magna-Scenedesmus quadricauda+Ruellia brittonian-Salvinia natans(linn.)All.-Myriophyllum verticillatum L."had the best effect of removing TN,NH₄⁺-N,TP,and can effectively increased the DO content reduces the BOD concentration and keeps the p H within the normal range.The three plants grew well in water.The maximum growth rate of the average plant height of Ruellia brittonian was 23.86%,The maximum growth rate of Salvinia natans(Linn.)All.and Myriophyllum verticillatum L.average fresh weight were 103.02%,49.35%,The maximum growth rate of the longest root length of Myriophyllum verticillatum L.was 563.55%.The Daphnia-Algae-Grass combination showed an remarkable effect of purifying eutrophic water in the experiment.