Iwater pollutionnteresting chemical reaction in Water pollution
                                                                  —-—-  Eutrophication
The water eutrophication is water contains too much solubility nutrient salts （mainly NH3 - N， NO3 —- N， NO2 — N and PO4 — P）， make water algae phytoplankton growth such as a large number of breeding, and cause heterotrophic microorganisms strong metabolic activity of dissolved in water， make water metamorphism, and destroy the ecological balance of water phenomenon
1。The cause of eutrophication
The water eutrophication can be divided into natural eutrophication and cultural eutrophication. Natural lakes have a from oligotrophic to eutrophic development process， from oligotrophic transition to rich nutrition， and to develop into the swamp, until death， lake natural law of development， this is a long historical process， but human activity will greatly accelerate the process。
2. The harm of water eutrophication
The water eutrophication of the main following features：
（1) Funded by reduction, water in the blue green algae and green algae multiply， plankton individual number huge increase;
(2) Due to the plankton， a big increase in the number of bacteria in the water to a large increase of suspended solids， transparency reduced；
(3） Produce a peculiar smell of organic substance;
(4) Death algae residues decomposition release make water to maintain higher TN， TP， Water pH value rise
（5) The water of oxygen balance is destroyed
3.The water eutrophication status
In the 1980 s of lake (reservoir eutrophication survey results show that: in eastern China， the survey lakes most has entered the eutrophication status (such as chao lake, tai lake， the hongze lake, NaSiHu, etc.）, a few in the reservoir eutrophication edge， many urban lakes has reached a serious eutrophication （such as nanjing xuanwu， hangzhou west lake， jiujiang Kennedy TangHu， guangzhou dongshan lake, wuhan ink lake， etc。), forming a wide strip distribution of dongting lake and poyang lake eutrophication has happened nutrient conditions； Yunnan plateau lakes general retention time is long, the water exchange capacity is weak， once into the lake nutrient load overweight， the eutrophication development speed, is China’s eutrophication of dianchi lake areas and sensitive area, such as， different longhu, qi the luhu nutritional status is quite high, especially in dianchi lake eutrophication problem is more serious， The northeast, and find new, Tibetan areas of the lake eutrophication level is relatively low， the general is in the state of nutrition
Nearly twenty years， our country eutrophication development speed is fast. Over the years the survey results show that the number of lake eutrophication of lakes survey prop
ortion from the 1970 s to 80 s to 80 s 41％ 61%， to the late 1990 s and up to 77％, our country the development of lake eutrophication trend is very serious。
In the investigation of the reservoir, in eutrophic state of reservoir number and capacity of the survey accounted for 30.8％ and 11.2% of the reservoir， the reservoir of nutritional status in number and capacity of the survey accounted for 43.6％ and 83。1％ of the reservoir。 In general， the reservoir water quality is good, but on the verge of city and water reservoir as there are many appeared to eutrophication evolution trend， especially near the town of eutrophication degree is higher， such as Beijing’s the guanting reservoir， tianjin in bridge reservoir， shihezi city mushrooms reservoir near to eutrophication degree.
in addition, in recent years our country such as part of the river water river， pearl river， gezhouba reservoir HuangBaiHe also appeared water bloom and eutrophication reports。 Visible eutrophication has become China's water environment protection is the most important environmental problems
4。The prevention and control of eutrophication
A: control， such as nitrogen and phosphorus nutrients inflows
Through the technology reform, product improvement, reduce the phosphorus content of wastewater。 In the detergent branched alkyl benzene sulfonic instead of sodium phosphate substitute, agricultural production， reasonable control fertilizer wastewater shunt, bait casting breeding, cultivation planning， to take account of economic benefit and ecological benefit， ecological benefit in the first place
B： physical methods to strengthen management
Ponds， reservoir water exchange， when there is appropriate when water can be introduced to a dilution effect, out of nitrogen and phosphorus and algae material； Deep lakes or reservoirs, try to draw a deep， to reduce the eutrophication degree； In the lake by mechanical method aeration and promote the flow of water, has sediment phosphorus release, improve oxygen condition， strengthen the mineralization， reduce phytoplankto
n photosynthesis effect; Usually algae density is small， so the flocs is not easy to precipitation. By gas floating can achieve good effect to remove algae. After the eutrophication blue algae "water bloom” nitrogen content is very high， can collect used in fertilizer， feedstuff, reduce water nitrogen and phosphorus load
C： the prevention and control of chemical methods