Research Of Sedimentation And Biological Aerated Filter Being Connected To Treat The Phosphorite Flotation Wastewater

It is necessary that the development and utilization of mineral resources to society economy. An investigation showed that the total production value of mining industries in 2001 was 529.543 billion, which took up 5.31 percentage of the industries'. At the same time, the wastewater came from mining industries took up 6.69 percentage of the total industries'. Mining industry made great contribution to country' economy on the one hand and brought very serious environmental problem on the other hand.Phosphorite resources are abundant in our country and hold the third place in the world, the reserve is enough to supply for 2000 years' demand. In recent years, the agriculture policy is regulated and the price of phosphorous ores is rising quickly, which lead to more and more phosphorite resources being exploited, as far as P₂O₅ is concerned, the production has reached 9Mt.Because of the low grade and complicated structure of collophane, the process of floatation needs not only fine degree particles but also quantity of reagent, so the wastewater includes high concentration of SS and chemical reagents, which makes the whole water body a steady collide system. For these reasons, the concentration of COD, TP and SS etc is much higher than the nation discharge standard. Many enterprises has to discharge the wastewater before it was well treated for less of technological resort, which causes serious pollution to the water in the vicinity, therefore, a series of trouble concerning health and economy happens.To solve these problems and recycle the wastewater, feasibility of chemical sedimentation connected biofilm to treat the phosphorite flotation wastewater in the paper is discussed. First we found the optimum coagulant and make sure the optimal dosage in small experiment. And then, A large amount of wastewater is precipitated with chemical coagulant before they are secondarily treated by biological aerated filter, before this, the condition of development of biofilm, the influencing factors to the treatment efficiency and the dynamic model of biological aerated filter have been studied. In these experimental processes, the concentration of contaminants are inspected in time.From the research of this experiment, some conclusions are drew: FeSO₄ is a high efficient coagulant to the alkaline phosphorite flotation wastewater, the effect can compare with the Al₂ (SO₄) 3 and Ca (OH) 2 in removing the COD_cr, TP and SS et though it needs less quantity of dosage, what's more, the effluent is neutral in pH and can bedirectly treated by biological aerated filter. When the enzymatic carrier is used as the filter bed, the backsludge from the secondary sedimentation tank of coke-oven plant is used as the inoculating sludge together with the way of upflow and closed aeration are used, the biofilm can be developed in 13 days. The experimental results showed that the wastewater quality, temperature, pH, HRT and the ratio of air to water and etc are the very important factors to the efficiency of BAF, the optimum parameters are these: the pH is 7.8, the ratio of air to water is 10 and the HRT is 12h, Besides, a given water temperature and filter height are necessary. When the HRT is less than 15h, the biodegradable velocity of COD is linear relationship to the residual COD concentration, and then, the dynamic model is established. At the last of the experiment, the feasibility of sedimentation and BAF connected to treat the real phosphorite flotation wastewater is testified, the concentration of C0D_cr, BOD₅, TP and SS is reduced from 375.6mg/L, 69.0mg/L, 986.4mg/L, 11247.8mg/L to 10.8mg/L, 3.0mg/L, 0.11mg/L and 10.2mg/L respectively, the effluent quality is superior to the nation discharge standard, so the good economic and social performance are created.