Marsh Sewage Treatment Plant Problem & Solution

Illegal discharge
Marsh Sewage Treatment Plant
Colchester, Essex, CO6
17 November, 2015
6 Person

If you live in a rural area of the UK, your home will most likely be connected to a private drainage system, with the most common system being a septic tank.  In recent years we’ve seen an increase in septic tank replacements due to more stringent regulations surrounding the use of septic tanks.

It is widely known that many septic tanks discharge directly into ditches and streams throughout the UK.  Such discharges have been an offence since 1991 when the Water Resources Act came into force, including discharges that predate the enforcement date. A discharge of this type from a septic tank renders the homeowner liable to prosecution by the Statutory Authorities.


With the Environmental Agency and Local Authorities becoming more stringent on the use of septic tanks, it has been necessary for us to carry-out septic tank replacements using modern sewage treatment plants. Sewage treatment plants are specifically designed to ‘treat’ the receiving sewage to the extent that the final treated effluent is acceptable for discharge to ditches and streams.

Septic Tank Replacement – Case Study

We were contacted by the owners of this property in Essex after they had been informed their septic tank was pumping into a nearby ditch and causing pollution.  The homeowners had been advised that they would need to investigate the options regarding a septic tank replacement and employ the services of an ‘off mains’ drainage specialist.

After conducting a site inspection, Mantair engineers recommended replacing the septic tank with a Marsh ENsign sewage treatment plant, which would produce a ‘treated’ effluent suitable for discharge to the nearby ditch.

Based on the property having four bedrooms and in accordance with the British Water Flows and Loads Code of Practice – 4, a six-person Marsh system was recommended for installation.


The Marsh ENsign sewage treatment plant is a ‘single tank’ system using a three stage treatment process. Central to the operation of the Marsh system is the aeration chamber.  Within the aeration chamber aerobic micro-organisms develop through the use of fine bubble aeration and floating plastic media.  This aeration process provides an extremely robust means of treating sewage, and provides an ideal solution for septic tank replacements.

As part of the project Mantair engineers liaised with the local Building Control Department to obtain the relevant approvals for the installation.

Prior to any ancillary works commencing, Mantair engineers scanned the proposed location for the Marsh system and areas where excavations were taking place to ensure that no underground services were present.


The scope of the installation works included:

  • Exposing the existing foul drainage pipe work and diverting to the location of the Marsh ENsign sewage treatment plant;
  • Installation of the Marsh system in a suitably sized excavation, including for a concrete base and back-fill;
  • Locating the air blower within a remote blower housing;
  • Provision of an RCD protected power supply to the blower housing;
  • Installation of the air main from the air blower to the Marsh system;
  • Connection of the outlet from the Marsh system onto the existing outlet drainage;
  • Emptying and filling-in of the existing septic tank.


On completion of the ancillary works, Mantair engineers commissioned the Marsh ENsign sewage treatment plant, including setting of air valves, checking all pipe work joints and viewing the final discharge.

All machinery was removed from site with the garden being left in a neat and tidy manner.

If you would like a Mantair engineer to visit you regarding a septic tank replacement, please contact us on 01255 853890. or complete the form below.