9 1.8%, lakes with poor nutrition account for 3.2% and lakes with rich nutrition account for 5.0%. In a short period of 10, most of the lakes in poor trophic state have transited to those in middle trophic state, and the proportion of lakes in poor trophic state has rapidly decreased from 3.2% to 0.53%, while lakes in middle trophic state have transited to eutrophic state, and the proportion of lakes in eutrophic state has sharply increased from 5.0% to 55.01%[/kloc-] In recent 10 years, the water quality in the lower reaches of Hanjiang River in Wuhan has deteriorated sharply, showing eutrophication. In the 1990s, there were two "water blooms" in which algae proliferated rapidly.
List some cases:
(1) East Lake in Wuhan, West Lake in Hangzhou, Xuanwu Lake in Nanjing, Daming Lake in Jinan and Dahuofang Reservoir in Fushun in China are all affected by eutrophication. In recent years, red tides have also occurred from time to time in the coastal areas of China. For example, from August to September of 1989, a large-scale red tide rarely seen in the world appeared in the coastal areas from Huanghua County, Hebei Province to Tanggu, Tianjin, which caused serious losses to the shrimp industry.
(2) In recent years, with the increase of sewage discharge in the surrounding areas of Taihu Lake, water eutrophication is becoming more and more serious, and water blooms occur frequently in summer. In severe cases, green algae cells cover the whole water body, water plants stop water supply, and residents in water villages drink sewage. At the same time, the contents of organic matter and ammonia nitrogen in the water seriously exceed the standard, especially the dissolved DOC organic matter accounts for 88% of the total organic matter COD. Because the conventional drinking water treatment process itself has the weaknesses of organic micro-pollutants, ammonia nitrogen and so on. It can not be completely and effectively removed. Chlorination process can not effectively eliminate pathogenic microorganisms such as oxygen-resistant pathogenic parasites in domestic water, and it also leads to the formation of organic chlorides that are more harmful to human health. It is difficult to guarantee the safety of treated drinking water. Ozone biological activated carbon technology uses ozone oxidation and biological activated carbon filter, combined with ozone chemical oxidation, physical and chemical adsorption of activated carbon, biological oxidation degradation and other technologies to remove trace organic substances, chlorine-containing disinfectant by-products and other organic indicators in raw water, and improve the safety of drinking water.
(3) 1998 In the spring, a raging red tide swept through the Hong Kong Sea and the waters near the Pearl River Estuary in Guangdong. When the red tide passed, the sea was red and smelly, and a large number of animals such as fish died in the water. The local farms suffered heavy losses. According to the report of Economic Daily on May 3rd 1998, fishermen in Hong Kong lost nearly HK$ 1 billion in this red tide incident. More than 300 tons of precious cultured fish died in the mainland, with a loss of more than 40 million yuan.