Research On Disposing Of Soybean Wastewater With Anaerobic-oxidation Ditch System

Soybean processing wastewater possesses great proportion in the food industrial wastewater, with the features of complex ingredient, higher concentration of organic pollutant and NH₃-N. Taking the UASB and oxidation ditch wastewater treatment projects as the research object, the dissertation studies the COD and NH₃-N removal on the start-up and under the operation conditions of UASB and oxidation ditch.The research about the treatment of UASB is divided into three stages: the sludge taming period, the load ascending period and the stable operation period. The oxidation ditch study is divided into the sludge taming period and the stable operation period. Many factors, such as the COD,NH₃-N concentration of influent and effluent water, pH, the volumetric loading and VFA etc are analyzed as time changes during different periods. Moreover, the affects on the removal rate of COD and NH₃-N is discussed.Using the sludge from old anaerobic system for the wastewater treatment shortens the taming period. When the COD concentration of influent water reaches to 1200mg/L, the COD removal rate can be up to 90% in 20 days. Under steady run of the UASB reactor, when the COD concentration of influent water is within 3700 mg/L～4000mg/L, the volumetric loading rate can reach to 3.7kg COD/(m³·d) and the COD removal rate can be up to 85%, while at the same time, the VFA concentration of effluent water drops to1.5～2.5 mmol/L. The COD treatment result is good and stable. When the NH₃-N concentration of influent water reaches to 25mg/L, because of the ammonization react, the NH₃-N concentrations of effluent water reaches to above 50mg/L, meaning the NH₃-N increases by 120%.Under steady run of the oxidation ditch, when keeping the sludge load of oxidation ditch in the scope of 0.03～0.06kgBOD/(kgMLSS·d) and the COD concentration of influent water at 350 450mg/L, the COD concentration of effluent water can be less than 100 mg/L and the COD removal rate rises to higher than 85%. The NH₃-N removal rate can reach to 88% and the NH₃-N concentration of effluent water drops to less than 10mg/L. The TN concentration of influent water can reach to 55mg/L and the TN removal rate reaches to 50%.The ingredients of TN in the effluent water include NH₃-N and N03--N, and N03--N possesses a great proportion in wastewater, which can be up to 75%～80%.The practice proves that the method of disposing Soybean wastewater with USAB-oxidation system has stable treatment effect. The quality of leaving water has met the Discharge Standard(GB8978-96) 1^st grade requirements, and thus creates great economic and environmental benefits.