How Sewage Treatment Plants Work

The compact, below-ground sewage treatment plant shown in this cutaway illustration is a watertight enclosure designed to allow solids in the sewage to settle and decompose via an aerobic (oxygen-assisted) biological action.
  • Coarse solids are screened out and retained for gradual breakdown.
  • The screened fluid is continuously distributed over plastic media by an airlift pump operated by an electric blower, which is sited a short distance away. This maximises the natural aerobic process.
  • Subject to relevant official consents, the resulting effluent can be dispersed into a watercourse or suitable ground soakaway.

Sewage treatment plants are typically of GRP (glass-reinforced plastic) construction.

sewage treatment plant diagram




The illustration to the left shows a typical sewage treatment plant installation. Key elements:

  1. Wastewater and sewage from the property is fed through to the treatment plant.
  2. The treatment plant allows the solids to settle out and actively treats the sewage via an aerobic (oxygen-dependent) process, breaking it down.
  3. The resulting effluent, which is typically 95% clean, can be discharged into a nearby ditch, stream, river, lake or land drain system, subject to appropriate permissions and approvals.




Like a septic tank, a sludge of settled-out solids will accumulate inside.  The sewage treatment plant will then need emptying, which Bates Environmental can arrange for you. The size of the sewage treatment plants needs to be matched to suit the level of usage it will encounter, which depends on the number of occupants in the property and levels of use.

Contact Us

Bates Environmental Ltd

58-64 Station Street
PE11 4UJ

Tel: 0800 043-37-11
Fax: 01775 822-983

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