Biological treatment of high strength wastewater in a rotating perforated tubes biofilm reactor

m ABSTRACT A novel biofilm reactor named as 'rotating perforated tubes biofilm reactor (RPT)' was used for treatment of synthetic wastewater with and without liquid phase aeration. Also a rotating bio-disc (BSD) system was operated under the same conditions as that of the RPT, in order to compare the performances of both reactors under the same operating conditions such as influent COD concentration and A/Q ratio (A=1.34 m2). The effects of major process variables such as feed wastewater flow rate, COD concentration and COD loading rate, liquid phase aeration, rotational speed of tubes and number of tubes on COD removal performances of both reactors were evaluated. Rotating perforated tubes biofilm reactor consists of two stages each containing 25 perforated tubes mounted on vertical discs. The discs containing the battery of tubes were rotated by using a motor and a shaft passing through the central hole on the discs. Organisms grow in form of biofilm on inner and outer surfaces of the tubes during rotation of tubes. The holes on surfaces of the tubes help the biofilm organisms on inner surface of the tubes to be exposed to air more effectively. The outer surfaces of the tubes were rough to facilitate biofilm formation. Due to immersion of all tubes in wastewater and better mixing in liquid phase, RPT is more advantageous as compared to classical rotating biodiscs. Liquid phase aeration was proven to be advantageous especially for high strength wastewaters at high COD loading rates. COD removal efficiency increased with increasing A/Q ratio and rotational speed of the tubes, but decreases with increasing feed COD and COD loading rate. Rotating perforated tubes biofilm reactor was found to be more advantageous as compared to rotating biodisc system resulting inIV higher COD removal efficiencies especially at low A/Q ratio and high COD loading rates. Kinetics of COD removal were investigated and kinetic constants were determined for both reactors. Empirical design equations were developed lo describe the systems' performance as a function of major process variables such as A/Q ratio and feed COD content.