UASB-A/O Process For Corn Starch Wastewater Treatment

The corn starch-production wastewater is a kind of high concentrated organicwastewater, which contains a great variety of pollutants and complicated components. Inthis thesis, corn starch wastewater was treated by “Up-flow Anaerobic Sludge BlanketReactor （UASB）-A/O process. The rapid start-up and sludge granulation in the UASB wasinvestigated and the performance of organic contaminants and ammonia removal in A/Oprocess was evaluated. The technical and economic analysis of the whole treatmentprocess was also carried out.The start-up of the UASB was conducted at low COD concentration and highhydraulic loading when feeding intermittently. The start-up of the UASB was completedafter running for25d when the influent COD concentration and organic loading rate werecontrolled as3000～3500mg·L^-1and1.0kgCOD·（m³·d）^-1, respectively. After that, theinfluent organic loading rate was increased to7.0kgCOD·（m³·d）^-1, and the effluent CODconcentration decreased to581～695mg·L^-1with a average removal rate of84.5%afterstable running for20d.The sludge floc formed in the UASB when the influent organic loading rate reachedto3.5kgCOD·（m³·d）^-1, and the sludge granulation appeared when the influent organicloading rate reached to7.0kgCOD·（m³·d）^-1. When he influent organic loading rate reachedto8.5kgCOD·（m³·d）^-1, a large amount of granular sludge was observed, indicating therealization of sludge granulation.The fiber media was filled in both anoxic and aerobic reactors of A/O process, andintermittent feeding and aeration was applied in the start-up period. During the start-upperiod, the influent COD and ammonia concentration were638～682mg·L^-1and149～174mg·L^-1, respectively. The DO concentration in the aerobic reactor was3～4mg·L^-1and there was no aeration in anoxic reactor. The recycle ration was1.5. The start-up wascompleted when the removal rates of COD and ammonia reached up to80%stably. Afterthat, the influent organic loading rate was increased and the removal rates of COD andammonia were86.8%and84.5%, respectively, after a stable running of60d. Theoptimal performance was obtained when the recycle ration was1.5and the DOconcentration was4mg·L^-1. The denitrification and nitrification were realized in theanoxic and aerobic reactors, respectively.The treatment capacity of this project was4000m³·d^-1and the total investment was12million yuan. The treatment cost was1.83yuan·（m³）^-1. The average effluent COD concentration was84mg·L^-1when the influent COD concentration was6700～7200mg·L^-1, which meets the requirement of discharged standard. The reduced amounts ofCOD and ammonia were8299t·a^-1and126t·a^-1, respectively, indicating the significantenvironmental benefit.