NOVELTY - The laboratory scale biphasic anaerobic packed bed reactor such as acidogenic and methanogenic reactors for treatment of high biochemical oxygen demand (BOD) containing waste water, is claimed. The reactors: are glass reactors connected in series with Teflon(RTM: Polytetrafluoroethylene) bushings and connectors to accommodate continuous flow; have a total volume of 4-16 liters and a void volume after packing with bedding material is adjusted to 2-8 liters; are made to generate a total of 5 days of retention in which the acidogenic reactor includes 1 day retention.    USE - The laboratory scale biphasic anaerobic packed bed reactor such as acidogenic and methanogenic reactors is useful for the treatment of high biochemical oxygen demand containing waste water (claimed).    ADVANTAGE - The laboratory scale biphasic anaerobic packed bed reactor has greater biological stability and reliability and higher reaction rate thus rapidly degrading biological wastes, and enables simple and economic treatment of high biochemical oxygen demand containing waste water with improved biohydrolysis and gasification.    DETAILED DESCRIPTION - The laboratory scale biphasic anaerobic packed bed reactor such as acidogenic and methanogenic reactors for treatment of high biochemical oxygen demand (BOD) containing waste water, is claimed. The reactors: are glass reactors connected in series with Teflon(RTM: Polytetrafluoroethylene) bushings and connectors to accommodate continuous flow; have a total volume of 4-16 liters and a void volume after packing with bedding material is adjusted to 2-8 liters; are made to generate a total of 5 days of retention in which the acidogenic reactor includes 1 day retention and the methanogenic reactor includes 4 days retention; and are separately subjected to startup in decoupled conditions. The flow is discontinued by locking the connectors when needed. The methanogenic reactor achieves 2-2.5 generations of slow growing methanogens, and is started with diluted cow dung slurry and enriched methanogenic inoculum. The acidogenic reactor is first acclimatized for 2 days with high BOD containing effluent. A biogas slurry containing methanogens is added to the acidogenic reactor to allow small growth of methanogens to scavenge excessive hydrogen produced due to rapid fermentative activity of non-methanogens due to which the load of methanogens is reduced and the number of non-methanogens producing acids is increased. The reactors are initially operated in a batch mode for biofilm development, and then acetate, propionate and butyrate mixture is added in 5:2:1 ratio at a rate of 1 Kg/M3/d for 30 days, where the biofilm development is visible after 30 days. After 45 days of separate startup and biofilm formation, the reactors are coupled for keeping a retention time of 5 days. The reactors are: started with system retention of 6 days in which acidogenic reactor includes 1.5 days of retention and the methanogenic reactor includes 4.5 days of retention; and operated with industrial waste water for keeping the retention time of 5 days and altering an organic loading rate. The feeding of reactors is done continuously with peristaltic pumps.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of a biphasic reactor.    Column adapter (1)    Column section (2)    Metal flange with rubber ring (5)    Gas port hose (8)    Effluent drain valve. (9)