Operation and management of small sewage works.

  • Great Britain. Ministry of Housing and Local Government.
Date:
1965
Catalogue details

Licence: Public Domain Mark

Credit: Operation and management of small sewage works. Source: Wellcome Collection.

    15/86 (page 3)
    Sewage works 8. No two sewage works are exactly alike. They differ greatly in design according to their age and the local circumstances, in the strength of sewage received and in the times at which the highest and lowest flows arrive. Consequently no precise instructions can be given here to tell you when and how often different jobs should be done. The following chapters tell you the things which experience has shown are important in keeping small sewage works in good working order and can help in drawing up a programme of regular operation and maintenance suited to your particular works. CHAPTER 2 PRELIMINARY TREATMENT Screening 9. The sewage arriving at the works carries with it paper, rags, sticks, coarse grit and other objects. Some of these will float and others will tend to be held in suspension by the flow of the sewage, depending on their weight or the extent to which they have become waterlogged. If left in the sewage they could cause a good deal of trouble by blocking pumps, choking pipes or interfering with the operation of valves. The first step in sewage treatment therefore is usually the removal of these objects by passing the sewage through a screen where they are trapped and held, although on some works it has been found possible to work without screens. The cleaning of screens and the disposal of screenings is perhaps one of the more objectionable jobs on sewage works, but it need not be particularly unpleasant if the work is done regularly and the screenings are disposed of promptly. 10. You should clean the screen once a day, if possible. Large quantities of rags etc. may block it and cause a backing up of sewage in the sewer. This in turn may result in the settlement of solids in the sewer, and these, if the flow is not strong enough to move them on when the screen has been cleared, will collect more solids and