Optimal　control　is　commonly　utilized　in　the　wastewater　treatment　process　(WWTP).　In　WWTP　the　effluent　quality　and　operational　cost　should　be　optimized　by　solving　the　optimal　set　points　of　dissolved　oxygen　and　nitrate　nitrogen.　However,　due　to　the　unknown　disturbances　of　WWTP,　the　optimal　operation　objectives　have　strong　uncertainties.　Therefore,　it　is　crucial　to　solve　the　optimization　problem　of　the　operation　process,　which　has　become　the　major　obstacle　to　the　optimal　control　of　WWTP.　For　overcoming　this　obstacle,　a　double　closed-loop　robust　optimal　control　(DCL-ROC)　method　is　designed　in　this　paper.　First,　a　double-closed-loop　scheme,　contains　a　close　optimization　loop　and　a　close　control　loop,　is　formulated　to　realize　the　optimal　control　of　WWTP.　Second,　a　closed-loop　robust　optimization　(CL-RO)　algorithm　is　designed　to　solve　the　optimal　set　points　with　enhanced　robustness.　Third,　an　adaptive　controller　based　a　fuzzy　neural　network　is　proposed　to　control　the　process　variables　with　superior　accuracy　and　robustness.　The　experimental　results　by　using　benchmark　simulation　model　No.1　(BSM1)　demonstrate　the　effectiveness　of　DCL-ROC.　©　2023　IEEE.