■Main Methods of Biological Film Process There are the following methods in the biological film process: 1. Contact oxidation method 2. Trickling filter method 3. Immobilized microorganism method 4. Rotating biological contactor method 5. Aerobic filter method All of these share the common point of retaining microorganisms on the surface of a solid. ■What is a contact oxidation device? A biological contact oxidation device is one that submerges packing materials such as strings, rings, or honeycomb and corrugated plates in an aeration tank to cultivate a biological film on their surfaces. ■Method without returning sludge In the suspended carrier method, the sludge collected in settling tanks is not returned to the aeration tank. This is a significant difference from the activated sludge method. The carrier is retained in the tank by a screen, but fine suspended solids (SS) flow out, so they are separated by coagulation and sedimentation or pressurized flotation. ■With biological film, the nitrification rate can be about three times higher! Nitrifying bacteria that oxidize ammonia tend to form flocs poorly, so methods to increase concentration using carriers may be employed. The nitrification rate of the biological film method is about three times that of the suspended method. It can be configured without a settling tank, making sludge management easier, and if a settling tank is provided, SS and phosphorus can also be removed simultaneously through coagulation and sedimentation.

■There is also a method to introduce carriers into the activated sludge tank! To stabilize the retention of microorganisms, there is a biological film method that involves placing fixed contact materials or floating carriers in the aeration tank of activated sludge. ■Do floating carriers also help with oxygen dissolution?! Floating carriers made of resin are slightly lighter than water and flow within the tank due to air bubbles. By dispersing the bubbles and extending the time they remain in the water, they also enhance the rate at which oxygen dissolves. ■Can be used for high concentration wastewater! Biological film treatment using floating carriers can directly treat high concentration wastewater with BOD levels of 5,000 mg/L. When used for pretreatment, it allows for subsequent activated sludge treatment without dilution. In an example with a carrier filling rate of 67%, the guideline for BOD volumetric loading when aiming for a BOD removal rate of over 90% is 2.0 to 4.0 kg per cubic meter per day. This value is under the condition that the soluble BOD of the treated water is below 20 mg/L. ■Don't forget the subsequent processes Biological contact oxidation systems typically do not filter turbidity (SS), so they are often combined with coagulation sedimentation or sand filtration in the subsequent processes. Please feel free to consult with us first.