Wastewater　treatment　processes　(WWTPs)　are　complex　industrial　processes　with　disturbance　and　strong　nonlinearity,　and　it　is　difficult　to　accurately　track　the　pre-designed　dissolved　oxygen　concentration　(DOC)　in　a　finite　time.　To　solve　these　problems,　a　robust　dynamic　surface　control　strategy　with　fixed　time　observer　(DSRC-FTO)　is　proposed　to　achieve　a　stable　control　performance　for　DOC　in　this　paper.　The　contributions　of　DSRC-FTO　are　three　folds.　First,　an　adaptive　interval　type-2　fuzzy　neural　network　based　on　predictor　(P-AIT2FNN)　is　applied　to　adaptively　imitate　the　strong　nonlinearity　of　WWTPs.　Subsequently,　a　weight　adaptive　law　is　formulated　using　the　predictor　error　to　minimize　modeling　errors.　Second,　a　fixed　time　observer　(FTO),　based　on　dynamic　surface　technique,　is　developed　to　actively　suppress　the　unknown　disturbances.　Third,　it　is　proved　that　the　designed　FTO　can　converge　in　fixed　time.　Then,　the　finite　time　stability　of　DSRC-FTO　can　be　proved.　Finally,　DSRC-FTO　is　tested　on　the　benchmark　simulation　model　no.　1　(BSM1).　Compared　other　existing　methods,　DSRC-FTO　can　realize　accurate　control　for　DOC　in　a　finite　time.　©　2024　Technical　Committee　on　Control　Theory,　Chinese　Association　of　Automation.