Advanced Treatment Research Of Biological Aerated Filter On Dyestuff Wasterwater

Biological Advanced Filter (BAF) is a recently developed process to treat organic wastewater at home and abroad. Compared with traditional activated sludge system, the main advantages of BAF are stronger treating capacity, better treating effect, less relationship with water temperature, higher capacity for absorbing shock load, no requirement for secondary settlement tank, simpler technology flow and more reasonable bacterium structure. Both research and application of prevailing advanced treatment of sewage are summarized in the article. The principles, advantages and shortcoming of all kinds of technique are reviewed. Furthermore, the process principles, organic pollutant removal, oxygen requirement, solids production and backwashing of typical BAF are analyzed. The key technique of BAF such as the principle influence factors and the removal of nitrogen when operating are also introduced.After secondary biochemical treatment, dyestuff wastewater is in bad degradation. The Upflow Biological Areated Filter (UBAF) was designed for the advanced dyestuff wastewater treatment during the experiment. The effect of gas to liquid ratio and hydraulic loadings on effluent were studied and the main pollutants removal orders were analyzed. The experimental results show that gas to liquid ratio has much greater effect on removal rate of NH4+-N than on SS, turbidity and CODo With the increasing of gas to liquid ratio, the removal rate of NH4+-N can be enhanced but not to do for SS, turbidity, chroma and CODo Besides, the removal rate of NH4+-N and CODcr decrease with the increasing of hydraulic loadings. But it has not evident effect on them when the hydraulic loadings is less than 0.59m3/(m2 h). The experimenal results show at the optimum operating condition when the gas to liquid ratio is 2:1, hydraulic loadings is 0.39m3/(m2*h), SS, turbidity, CODcr and ammonia nitrogen reduction avarage 71.12%, 77.2%, 48.53% and 86.81% respectively. And the corresponding effluent concentration are 22.88mg/L, 5.89NTU, 43.52mg/L and 2mg/L respectively. The average removal rate of chroma even reaches 94.25% under the operating condition.The influence of stuffing height on BAF is particularly discussed in the article. The relationship between removal efficiency of SS, turbidity, chroma, CODcr, NH4+-N and height are investgated for operating BAF. The results show: (1) Maximum loading of CODcr, main capture of SS appear in range of 0-20cm of BAF and maximum loading of ammonia nitrogen appears in range of 40-60cm of BAF. The active layer of nitrifiers is deeper than heterotrophs in BAF. (2) Although biodegradation of pollutant only exists in part area of filter, a given height of stuffing provides a possibility that BAF normally operates in high loading and resists overloading. (3) As a UBAF with granular and active carbon media, the optimum media height for the removal of SS and CODcr is 60cm and 60-80cm respectively. The height for NH4+-N, chroma and turbidity are all 80cm.Study was made on the possibility of shortcut nitrification-denitrification in BAF. The test shows that no high ability of organic and nitrogen removal can be achieved at filteration rate of Im/h, gas to liquid ratio of 0.3:1, water temperature of 20.2-23, influent CODCr loading of 70.53mg/L, NH4+-N loading of 9.75 mg/L, TN loading of 18.34 mg/L. Furthermore, the obvious NO2-N accumulation and nitrification-denitrification were not found in the biofilter. The experiment also shows the backwashing of simultaneous water and gas meets the process requirement for BAF. It has been proved we can achieve good effect of backwashing under the intensity of gas 14L/ (m2'h) and the intensity of water 5.8 L/ (m2h). All these conclusions will bring much reference to the further research of BAF and the improvement of process.Candidate: Chen Yibiao (Enviromental Engineering) Supervised by: Chen Jihua (Professor)...