The article aims to develop a method for purifying the waste gas containing formaldehyde in low concentration by using biological Trickling Filter. Our experimental research is done to purify the waste gas with formaldehyde in low concentration, in which microorganism fungus were developed and packed into the biological tricking filter with biofilm packing-material. In doing so, we have studied the effect of the concentration of formaldehyde in influent gas, the gas flow and the influent flow in purificatio...