In order to improve the distribution diversity of antibodies, a novel immune selection operator combining the antibody concentration and the sufficiency vector distance is proposed, and a scale-variable hybrid mutation operator, which introduces the mutative scale method in the hybrid mutation, is designed to improve the search efficiency. The convergence, stability and complexity of the algorithm are then analyzed, and an optimal control of operation cost is performed with the algorithm for wastewater treatment. Experimental results indicate that the proposed method is of high effectiveness, global convergence reliability and velocity.