水体富营养化英文PPT

1、Eutrophication of water,Definition,Eutrophication is one of the water pollution .It is mainly caused by human activities. When a large amount of nutrients , such as nitrogen and phosphorus ,are discharged into large lakes, estuaries, bays and other water bodies which flow slowly, it will cause a phe

2、nomenon that algae and other plankton in water multiply rapidly, dissolved oxygen decreases , water quality deteriorates and a large number of fish and other organisms die.,Mechanism,Excess nutrients(N、P),Autotrophic organisms (especially blue-green algae and red algae) grow quickly,Other algae spec

3、ies gradually reduce Plankton and other small organisms die,Be decomposed by aerobic microorganism consume dissolved oxygen in water,Fish and other aquatic life die,Or be decomposed by anaerobic microorganism Produce hydrogen sulfide and other gases,Identification index,Nitrogen content 0.20.3 ppm B

4、iochemical oxygen demand(BOD) 10 ppm Phosphorus content 0.010.02 ppm The number of bacteria is more than 100000 in per ml of water(pH=910) The content of chlorophylla in characterized algae 10mg/L,Source,Excess nitrogen and phosphorus in the water body mainly come from industrial waste water and dom

5、estic sewage, organic waste, livestock and poultry manure and agricultural chemical fertilizer.,Control method,Engineering methods,Digging up the lake sediments It is the main ways of reducing the self-concentration of nitrogen and phosphorus in eutrophic lake. Deep aeration Taking artificial lake d

6、eep aeration and supplementing oxygen from time to time is conducive to inhibit the release of phosphorus from sediment. Inject water Injecting water containing low concentrations of nitrogen and phosphorus into lakes can dilute nutrient concentration.,Control method,Chemical methods,Coagulation and

7、 sedimentation Many kinds of cations can cause the phosphorus to precipitate from the aqueous solution effectively , such as iron, aluminum and calcium For example, the long lake in western Washington state is a eutrophic water body. In October 1980,people add aluminum salt into the lake to precipit

8、ate the lakes phosphate. In the summer of fourth years after the addition of aluminum salt, phosphorus concentration in the lake water became from the original 65 g/L to 30 g/L, the water quality of the lake has been significantly improved.,Control method,In the chemical method, another way is to ki

9、ll algae with algaecide. This method is suitable for the water body of the lake water bloom. After algaecide kills the algae, the decomposition of algae will still release phosphorus. Therefore , algae killed by algaecide should be promptly removed, or some appropriate chemicals should be added into the water body to make phosphate precipitate.,Control method,Biological methods,Use aquatic life to absorb nitrogen and phosphorus in order to remove nitrogen and phosphorus in water. For example, som