A Research On Experimental And Applied Of The Wastewater Treatment From V₂O₅ Production By Reduction-Sedimentation-Air Stripping-MAP Process

In this paper, we used the "Reduction sedimentation-Air stripping-MAP" process to remove the high concentration of heavy metal vanadium (V), chromium (Cr) and ammonia-nitrogen(NH3-N) from vanadium sesquioxide(V2O5) wastewater.High concentration of the heavy metals V, Cr and NH3-N was drained off the wastewater from vanadium sesquioxide(V2O5) production in Xichang Dixin vanadium titanium Industrial Ltd. According to local investigation and technology analyzed, we selected the two-step method to purification of wastewater treatment to deal with the wastewater after considered feasibility of technology and economy. The first step is to remove the V and Cr from the V2O5 production wastewater by Reduction sedimentation, and the next, Air Stripping-MAP was used to remove NH3-N from the pre-treatment wastewater by V2O5 production, to the high concentration of pollutants from V2O5 wastewater met the discharge and reuse standard.The experiment results showed that there were many factors could effect the efficiency of removing Cr6+ by Reduction-sedimentation, such as the pH value,reaction time,reaction temperature,precipitation pH values,reducers, and so on. With the 1.2 times of the theoretical amount of NaHSO3 as reductionship agent, When the wastewater temperature≥40℃, pH value of reduction reaction≤2.0, and maked sure that the pH value of reduced wastewater≤3.0, and the reaction time≥10 min, wastewater temperature of sedimentation≤40℃, the average concentration of Cr6+, Total chromium, total vanadium in outlet water which meet the grade-1 of Integrated Emission Standard of Wastewater (GB8978-1996). pH value,reaction temperature,Gas-liquid ratio and stripping time effected the efficiency of stripping removing NH3-N. Under the conditions of the wastewater temperature of 30～40℃, the pH of 10.5-11.0, the Gas-liquid ratio of 3000:1, the stripping time of 30 min pre-removal of NH3-N Wastewater. MAP used to remove NH3-N after stripping NH3-N; pH value,reaction temperature,sedimentation dosage molar ratio and reaction time were the main factors that could effect the efficiency of MAP removing NH3-N. When the wastewater temperature between 35～40℃, the pH between 8.5-9.0, the sedimentation dosage molar ratio between 1.0:(1.0～1.025):1.0, and with 30min of sedimentation time, the average concentration of NH3-N in outlet water which meet the Grade-1 of Integrated Emission Standard of Wastewater (GB8978-1996). The value is below the 15 mg/L.The experiment results reveal that removal rate of Cr6+, total chromium, total vanadium and NH3-N of the wastewater from V2O5 production were 99.93%,99.87%,99.30%,98.72 %, relative to the relevant parameters from the laboratory study. SS had also been removed in this process, the average concentration of SS in outlet water was 14.5 mg/L. Through the Biochemical biochemical pond, CODcr and phosphorus of wastewater had also been removed in this process, the average concentration of CODcr in outlet water was 37.5 mg/L, and the phosphorus was 0.16 mg/L, which can be used as water reuse, and meet the discharge standards.Removal of V and Cr of the wastewater from V2O5 production by Reduction-sedimentation featured with simple equipment, low capital, occupies small area, facilitate the operation and management, easy to deal with mixed wastewater, favorbale effect, on the water quality characteristics of adaptability. Removal of NH3-N of the wastewater from V2O5 production by Air-stripping featured with low capital, low operating cost, simple process, ease retrofit. Removal of NH3-N of the wastewater from V2O5 production by MAP featured with simple process, low investment in equipment, low power consumption, easy to run operation, high removal of NH3-N, reaction products are widely used MAP. Therefore, "Reduction-sedimentation Air-stripping MAP" process suitable for industrial applications, if the removing system was set up, it could save 0.923 million Yuan for the company. Undoubtedly.this study provided the theoretical guidelines and quantitative basis for the engineering design of removing the high concentration of the heavy metals V, Cr and NH3-N of the wastewater from V2O5 productionby "Reduction-sedimentation Air-stripping MAP" process.