| 摘要 |
<p>1473665 Treatment of sewage IMPERIAL CHEMICAL INDUSTRIES Ltd 23 April 1974 [16 May 1973 21 Nov 1973] 23328/73 and 53921/73 Heading C1C A method for the treatment of sewage comprises a step wherein the sewage is circulated around a system comprising a downcomer and a riser communicating with each other at their upper and lower ends, an oxygen-containing gas being supplied to the sewage as it passes through the downcomer which is of such length that the oxygen transfer rate into the sewage is at least 0À1 kg. O 2 /hr./m.<SP>3</SP> of liquid. This circulation step may form the aeration and/or digestion stage in the secondary treatment of sewage. The sewage may be circulated from a storage basin situated at or below ground level. An apparatus for circulating sewage in the above way is shown in the figure. The riser (15) and downcomer (14) are in this case contained within a single vessel divided by partition (23) and extending into a shaft below the base of basin (13). Downcomer (14) extends below the lower end of partition (23), or alternatively the lower part of partition (23) is perforated, to allow the lower ends of the downcomer and riser to communicate with each other. The downcomer is of such length that the oxygen transfer rate into the sewage is at least 0À1 kg. O 2 /hr./m.<SP>3</SP> of liquid. To achieve a suitable flow pattern in basin (13), the upper end (24) of the downcomer extends above the base of the basin and flow directing means (25) is provided. Other suitable forms of apparatus are also described. Reference has been directed by the Comptroller to Specification 1,353,008.</p> |
