Abstract: With the proposal of national strategies such as the construction of national ecological civilization and the great protection of the Yangtze River, the importance of river water environment treatment is increasing day by day. The water environment treatment portfolio of large rivers is an important means to achieve ecological benefits, national strategic objectives and enterprise strategic objectives. Different from the general water environment treatment, the influencing factors of the water environment treatment portfolio of large rivers are more and more complex, the influence range is wider, its ecological utility and social benefits are more significant, and the degree of uncertainty and interference faced by the implementation of the portfolio is also greater. Therefore, how to improve the robustness of the economic benefits of the treatment enterprises on the premise of ensuring the ecological benefits and realizing the national strategy is an urgent problem to be solved. On the basis of defining the robust optimization problem of big rivers water environment treatment portfolio, according to the characteristics of big rivers water environment treatment portfolio, this paper analyzes the characteristics of big rivers r water environment treatment portfolio, as well as the connotation and characteristics of robustness. Secondly, in order to improve the robustness of the economic benefits of the portfolio under the uncertain environment, the robust optimization model of the portfolio of river water environment treatment is studied and constructed. Finally, combined with the Jiujiang phase I of the great protection of the Yangtze River, this paper carries out a case analysis, gives countermeasures and suggestions, and puts forward management enlightenment. The results show that the robust optimization model can not only ensure the ecological utility, but also improve the robustness of enterprise economic benefits, and make up for the deficiency of the traditional portfolio robust optimization model that pays more attention to economic benefits and less considers ecological utility. At the same time, managers can realize the trade-off between model robustness and reconciliation robustness according to their own decision preferences. The research results of this paper provide a basis for government departments and governance enterprises to identify, control and evaluate the factors affecting the portfolio objectives of river water environment governance projects.

Key words: Water environment treatment, Portfolio, Robust optimization model, big rivers, Great protection of the Yangtze River, Economic benefits of enterprises