A carbon bed electrolyser unit for liquid effluent treatment comprising: a reactor made of reinforced cement concrete, fiber reinforced plastic, or polypropylene or combination thereof having inlet and outlet valves, the outlet valve carrying the treated effluent from the said reactor, a buffer chamber to hold liquid effluent that adopts single channel flow path through a inlet valve inside the said buffer chamber, a set of carbon anode plates being fixed to one side of the said reactor and a set of stainless steel cathode plates being fixed to the opposite side of the said reactor; wherein the said anode and cathode electrodes being made of shorter width than the width of the said reactor and being placed vertically in reactor and parallel to each other in a cathode-anode-cathode-anode type alternate arrangement, all anode plates fixed to one side of the reactor body at specified distances parallel to each other, with centre-to-centre distance in the range of 0.25 - 0.35 m and all the cathode plates are fixed to the opposite side of the reactor at a inter-cathode centre-to-centre distance of 0.25 - 0.35 m which allows single channel flow path for liquid effluent, all cathodes are fixed to the bottom of the reactor while anodes can be lifted by an offset distance in the range of 0.05 to 0.1 m (2 to 4 inch) or vice versa in an alternative electrode arrangement to allow for vertical mode of single channel flow of liquid effluent from one section to the next section till the treated effluent flows through outlet, the height of electrodes is so adjusted that it is in the range of 25-35% less than the height of the reactor thereby allowing for free board that allows for holding any scum or foam which may form during operation and thus avoids overflow and spillage of effluent, bus bars, made of aluminium or copper or combination thereof, are used to connect all the anodes or cathodes separately, and connected to positive (anode) and negative (cathode) poles of an electrical rectifier, a granular activated carbon with high surface area being provided in the space between each pair of said electrodes to form a packed carbon bed in each compartment for adsorption as well as particle electrodes, a long covered leak proof opening at the bottom along the length of the reactor to conveniently remove the spent carbon, a galvanized iron welded structure. a reactor made of reinforced cement concrete, fiber reinforced plastic, or polypropylene or combination thereof having inlet and outlet valves, the outlet valve carrying the treated effluent from the said reactor, a buffer chamber to hold liquid effluent that adopts single channel flow path through a inlet valve inside the said buffer chamber, a set of carbon anode plates being fixed to one side of the said reactor and a set of stainless steel cathode plates being fixed to the opposite side of the said reactor; wherein the said anode and cathode electrodes being made of shorter width than the width of the said reactor and being placed vertically in reactor and parallel to each other in a cathode-anode-cathode-anode type alternate arrangement, all anode plates fixed to one side of the reactor body at specified distances parallel to each other, with centre-to-centre distance in the range of 0.25 - 0.35 m and all the cathode plates are fixed to the opposite side of the reactor at a inter-cathode centre-to-centre distance of 0.25 - 0.35 m which allows single channel flow path for liquid effluent, all cathodes are fixed to the bottom of the reactor while anodes can be lifted by an offset distance in the range of 0.05 to 0.1 m (2 to 4 inch) or vice versa in an alternative electrode arrangement to allow for vertical mode of single channel flow of liquid effluent from one section to the next section till the treated effluent flows through outlet, the height of electrodes is so adjusted that it is in the range of 25-35% less than the height of the reactor thereby allowing for free board that allows for holding any scum or foam which may form during operation and thus avoids overflow and spillage of effluent, bus bars, made of aluminium or copper or combination thereof, are used to connect all the anodes or cathodes separately, and connected to positive (anode) and negative (cathode) poles of an electrical rectifier, a granular activated carbon with high surface area being provided in the space between each pair of said electrodes to form a packed carbon bed in each compartment for adsorption as well as particle electrodes, a long covered leak proof opening at the bottom along the length of the reactor to conveniently remove the spent carbon, a galvanized iron welded structure.