Patent GB-551645-A (GB)
Title: Improvements relating to the treatment of aqueous material capable of exhibiting an electric potential, such as sewage or impure water, to eliminate undesired characteristics thereof
IPC: C02F1/76
Filed: 1940-03-30
Abstract: 551,645. Automatic control systems. WALLACE & TIERNAN CO., Inc. March 30, 1940, No. 5750. Convention date, April 10, 1939. [Class 38 (iv)] [Also in Group XXXVI] Sewage, impure water &c. is treated to eliminate undesired characteristics by supplying halogen thereto, determining the electrode potential with respect to that of a standard' half-element and utilizing this potential for guiding or controlling the supply of halogen so as to maintain the electrode potential of the treated material below that which would be determined if free halogen were present and above that which would be determined if the undesired characteristics were present in objectionable amount. Sewage flowing through a pipe 10 has a small portion continuously withdrawn through a pipe 12 and passed into a container 14, the excess liquid being discharged through a pipe 15. A baffle 17 may be provided to cause the liquid to move outwardly as shown by the arrows. A calomel half-cell comprises a reservoir 25 connected by a tube 24 with a tube 21 passing down into. the container 14 and containing an electrolyte such as a solution of potassium chloride. The lower end of the tube 21 is bent as shown and may be plugged with a gelatinous substance 28 such as agar saturated with potassium chloride. A supply reservoir 29 containing an additional quantity of electrolyte may communicate with the tube 21 through a stop-cock 30. A lead-in wire 31 is sealed into the bottom of the reservoir 25 and is in contact with a mercury electrode 32. Above this is a quantity of calomel 33 or a mixture of mercury, calomel and potassium chloride. An electrode 35 of platinum or gold is sealed in a tube 36 and extends. into the liquid in the container 14. This electrode is connected to a battery 40 supplying a potentiometer 41 having an adjustable contact .43, which is connected to the grid 47 a of valve 45 and to the filament 48 of a valve 46. The grid 50 of the valve 46 and the filament 51 of the valve 45 are connected to the mercury electrode 32 through a switch 58 intermittently closed by a cam 57. Solenoids 59, 60 are included in the plate circuits of the valves' 45, 46 and are provided with cores 63, 64 carried by an arm 61 pivoted at 62. The arm 61 carries a contact 65 which engages with contacts 66, 67 to close the circuit of one or other of the field windings 79, 80 of a motor 76. These windings are wound so as to produce. rotation of the motor in opposite : directions. If the electrode potential of the sew- :age departs from its normal value the grid of one of the valves 45, 56 becomes positive with respect to the cathode and the plate current increases, while the filament of the other valve becomes positive with respect to the grid and the plate current decreases. The arm 61 is thereby rotated and causes the contact 65 to engage oneof the contacts 66, 67 so as to cause rotation of the motor 76 in a direction to restore the balance by moving the contact 43. The electrode potential is then indicated on a scale 90 and the supply of chlorine through a supply pipe 10a is adjusted in order to keep the pointer 91 within the predetermined optimum range of electrode potential, which is below the minimum potential which would be detected if free halogen were present above the maximum potential detectible in the material when an undesired characteristic such as hydrogen sulphide is present. The supply of chlorine may be automatically regulated by the motor 76.