Strategy & Techniques for Restoration of Healthy Aquaecosystem from Toxic Super Eutrophic Water Body

Abstract

There are complex river-lake systems in the Taihu Lake catchment with total water surface area of 6174.7 km 2 , and population density of 1079/km 2 , including Taihu Lake water surface area of 2338 km 2. The water systems in this catchment have healthy aquaecosystems during long history. However, in some riverlets in this catchment the water quality was estimated as "acute toxicity for higher organisms" and over standards for many heavy metal elements content; there were no any living plants and macro organisms in the water body, because there were developed a series of industry with abundant release of heavy metals and difficult decomposition organic chemical components along the riverlets during last decades. The even more serious situation was observed in sediments of the riverlets. How to restore such riverlet into a healthy aquaeosystem with abound plants and higher organisms? The main strategy and techniques are described in this paper as summarizing a report of engineering in a riverlet in Wuxi New District during last years, which leads to restore the aquaecosystem into a healthy one with abundant surface plant cultured on floating islands and observed living fish, lobster, frog, toad, mollusk and others in the riverlet. The main techniques are: 1) softwall buffer technic; 2) floating eco-island technic by using which can culture any plant which can be cultured in solution; 3) immobilized nitrogen cycle bacteria (INCB) technic; 4) tattering esters and other big-molecule organic chemicals by using electronic pulse technic and photosensitization technic; 5) mist spray facility technic for improving dissolved oxygen in deep water layers; 6) technic for buffering and suppressing H2S release from water; 7) the appropriate portion of surface with cultured plant to the total water surface area is about 1/3; 8) Cress [Oenanthe Ljavanica (Bl.) DC.] and Myriophyllum verticilatum L. may be cultured in Taihu Lake catchment during the whole year as main plants with mosaic combination of other supplement plants in different seasons.