Ensign sewage treatment plants

Marsh Ensign sewage treatment plants are widely regarded as one of the most efficient, reliable and economical systems on the market.

The Ensign:Standard is a robust unit with no internal moving parts meaning simple installation and commissioning and minimal long-term maintenance and cleaning.

Class leading performance

CE ApprovedTested and approved to BSEN12566-3/A1:2009 all Ensign units provide treatment well within national consent requirements. Published test results of 11.5:19.2:8.4mg/ltr (BOD:suspended solids:ammonia), with influent concentrations on test higher than those chosen by most competitor plants, effectively equates to 97% pollutant removal.

Unrivalled choice

Ranging in size from 4 to 50 PE in Ultra, Standard and Shallow versions of each, and with a wide range of ancillaries, almost all site, consent and budget requirements can be met by units from the range.

Why choose the Marsh Ensign?

End users, merchants and installers alike recommend the Ensign range due to its ease of installation, reliability, and cost-effective operation and maintenance. All backed by technical support from local contacts.

ensign sewage treatment plants

In addition to anaerobic digestion taking place in the primary settlement chamber [2] the Ensign unit allows the clarified water to pass into a second ‘aeration’ chamber [3] where it is treated to remove the dissolved constituents. Here aerobic bacteria, supported by diffused air and mobile media, ensures full treatment is achieved before the treated effluent and ‘sloughed off’ bacteria flows to a final settlement chamber [10]. The final effluent is then discharged to the drainage field or watercourse via a Polylok filter.


  1. Inlet
  2. Primary settlement chamber
  3. Aeration chamber
  4. Compressor with alarm
  5. Compressor housing (External or internal options)
  6. RCD / Electrical connection
  7. PVC pressure pipe for diffuser(s)
  8. Bio-media
  9. Stainless steel mesh
  10. Final settlement chamber
  11. Sludge return
  12. Unique Polylok tertiary filter (Only on Ensign:Ultra units)
  13. Outlet
  14. Access lid
  15. Integral lifting eyes
  16. Stabilising feet
  17. Unique ‘keying-in’ lip

Ensign:Ultra operating principal

1. Inlet with ‘Forsheda seal’
Forsheda seal provides flexibility in the joint for easier installation.
Optional risers to increase invert depth are available.

4. Compressor with alarm
Low-energy compressor provides minimal running, maintenance and servicing costs. Integral alarm detects low pressure in air line.

5. Compressor housing (External or internal options)
The compressor can be housed internally or externally with no difference in cost. External recommended to increase compressor life, and supplied as standard on 4PE, shallow and pumped outlet versions.

6. Plug / socket connection
Standard electrical connection

7. PVC pressure pipe for diffuser(s)
Provides a protective conduit for the air diffuser line. Can be easily removed for maintenance and cleaning.

8. Bio-media
High specification bio-media (310m3 per m2) and membrane diffusers ensure even circulation to eliminate ‘dead spots’. The bio-media is contained by a stainless steel securing mesh to ensure no migration during handling or potential flooding.

9. Stainless steel mesh
Retains media in aeration chamber during transportation and handling, and in the event of flooding.

11. 32mm sludge return
Larger diameter sludge return prevents the possibility of blockages and improves system circulation. Provides higher effluent quality whilst balancing flow over a 24 hour period or periods of intermittent use.

12. Polylok tertiary filter is NOT supplied on Ensign:Standard range

13. Outlet with ‘Forsheda seal’
Forsheda seal provides flexibility in the joint for easier installation.
Optional pumped outlets are available.

14. Standard lid
Marsh lid protects inner components whilst blending into the surrounding environment.

Ensign:Ultra operating principal

Model (pop) Length Width +/-100mm Height Inlet invert Inlet dia Outlet invert Outlet dia
4 1600 1332 1575 540 110 600 110
6 2602 1650 1935 550 110 625 110
8 2602 1650 1935 550 110 625 110
10 2602 1650 1935 550 110 625 110
12 2860 1912 2139 550 110 625 110
16 2860 1912 2284 720 110 800 110
20 3650 1912 2284 720 160 800 160
25 3650 1912 2284 770 160 850 160
30 4200 1912 2284 770 160 850 160
35 4200 1912 2284 770 160 850 160
40 5200 1912 2284 770 160 850 160
45 5200 1912 2284 770 160 850 160
50 5200 1912 2284 770 160 850 160

Larger population sewage treatment plants may be supplied as multiple tank configurations.
For precise tank sizes and configurations, please contact Marsh Industries.
All dimensions in mm.

Marsh Ensign range

Marsh domestic brochure

Installation/technical manual

CE Certificate

Carbon vents/covers
Carbon vents and covers
Elevated compressor housings
Distribution boxes
Distribution boxes
Anti-flood valves
GRP kiosks