Experimental Study Of Biological Slow Filtration Removing Heavy Metal In Micro-polluted Water

Biological slow filtration technology is quite mature. It is a very suitable water treatment device with simple manufacture, convenient management, low price and good treatment effect. In this paper, through comparing the biological slow filtration system, find the best treatment of filter material. Through the experiment along the layer, find the best filter material height. Through the treatment of micro polluted water containing heavy metals, find the effect of treatment and the interaction between different pollutants.Hanging film experiment shows the hanging film time of different slow filter columns is different. Activated carbon slow filter column with the shortest uses 16 days, zeolite and quartz sand filter columns with a long time use 24 days and 27 days respectively. Changes in temperature have a great influence on the ability of microorganisms to remove pollutants. On the whole, the water quality of activated carbon biological slow filter is best. Effluent turbidity of three biological slow filters is similar. Three biological slow filter effluent quality can reach the standard of drinking water. Single factor experiment of ammonia nitrogen shows that with the increase of the concentration of ammonia nitrogen, the removal efficiency of COD_Mn decreases, the removal efficiency of ammonia nitrogen increases. It shows that the increase of the concentration of ammonia nitrogen can inhibit the activity of heterotrophic microorganisms and improve the activity of the nitrification bacteria. Single factor experiment of COD_Mn shows that with the increase of the concentration of COD_Mn, the removal efficiency of COD_Mn increases, the removal efficiency of ammonia nitrogen decreases. It shows that the increase of the concentration of COD_Mn can improve the activity of heterotrophic microorganisms and inhibit the activity of the nitrification bacteria. Microorganisms are mainly distributed in the surface of the filter layer 20 cm. Most are in the upper 5cm. The distribution height of different kinds of microorganisms is different. The most suitable filter material height is about 50 cm.When the water only contains hexavalent chromium,its effect on the removal of pollutants is different, hexavalent chromiumis toxic to microorganisms. Different kinds of microbes are affected differently, the adaptability of nitrification bacteria is the most. So do different biological slow filtration systems, active carbon biological slow filtration system has the strongest adaptability, and the water quality is best. After a certain period of time, the three biological slow filtration system can be restable. But the activity of the microorganisms are lower than before, the removal rate of the pollutants reduces. With the increase of hexavalent chromiumconcentration, the phenomenon will be more obvious. When hexavalent chromium concentration is 0.15mg/L. Only effluent water quality of activated carbon biological slow filter can reach the standard of drinking water. Microorganisms have a certain adaptability to hexavalent chromium, but only to a certain extent. The experiment of the active carbon biological slow filtration system shows when the hexavalent chromium concentration is 0.2mg/L, the microorganisms begin to die. With the increase of COD_Mn concentration, the removal efficiency of the three biological slow filtration system to the six valence chromium increases. When the concentration of ammonia nitrogen increases, the concentration of the six chromium in the effluent of the three biological slow filter columns is almost unchanged. It shows the microorganism which can remove the six chromium depends on the organic matters in water, and the dependence on the ammonia nitrogen is very small.When the water only contains nickel, its the removal rate of each pollutant is similar to that of the six chromium. When the concentration of nickel is 0.16mg/L, the effluent quality of the three biological slow filtration systems can not reach the standard of drinking water. The experiment of the active carbon biological slow filtration system shows that when the concentration of nickel is 0.16mg/L, the microorganisms start to die. COD_Mn and ammonia nitrogen concentration increases, the removal efficiency of three biological slow filtration systems is almost unchanged. It shows microorganisms of removing nickel do not depend on organic matter and ammonia nitrogen in water.Water contains hexavalent chromium and nickel. With the increase of nickel concentration, the removal efficiency of three biological slow filter columns on hexavalent chromium reduces, COD_Mn and ammonia nitrogen are also the case. With the increase in the same concentration of nickel, the degree increases. In the presence of hexavalent chromium, the removal rate of nickel is lower than before.