Ensign Package Sewage Treatment Plant (4 Person and above)



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Marsh Industries ENsign range of sewage treatment plants treat final effluent to British and European Standards to allow it to be discharged back into the watercourse whilst reaching national consent standards. Our tanks can be manufactured with either a gravity or pumped outlet to meet your site requirements.

Marsh Industries only use 100% virgin resin (no chalk fillers) in all our products. Lead times for Domestic Sewage Treatment Plants are normally only 5-7 working days.

 Advantages of using Marsh Tanks:

  • No moving parts
  • Low running and maintenance costs (Approx. £52.00 per a 6PE)
  • Easy installation with ‘keying-in’ lip and lifting eyes
  • Tested and certified to BSEN12566-3
  • 50 year design life
  • 25 year structural guarantee

A shallow option is available for areas in high water table or hard rock conditions please call for more information and pricing

Prices from £1,434.00 including delivery to mainland UK for a 4 person system


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Ecomerchant Ensign Installation

Package Sewage Treatment Plant's (or PSTP's) are often a suitable option where groundwater in the surrounding environment is vulnerable, drainage field percolation values are restrictive or direct discharge to watercourse or surface water sewer is the preferred discharge method.

In addition to the anaerobic digestion taking place in the primary settlement tank (as septic tanks) the Ensign unit allows the clarified water to pass into a second 'aeration' chamber where it is treated to remove the dissolved constituents. Here aerobic bacteria, supported by diffused air and mobile media, ensure full treatment is achieved before the treated effluent (and 'sloughed off' bacteria) flow to a final settlement chamber prior to discharge.

PSTP's should be sized using the latest version of British Water Flows & Loads (a pdf version of the latest edition is available to download from the ‘Technical Info’ tab) which provides detailed information on sewage production figures and sizing calculations

Regulatory authorities for the control of pollution in the UK normally require treatment plants conforming to BSEN12566:3 to be demonstrated as capable of producing a minimum effluent discharge quality of 20:30:20 (Biochemical Oxygen Demand;Suspended Solids: Ammoniacal Nitrogen in mg/ltr), although in certain areas more stringent site-specific qualities may be required

No surface water should enter the system as this can reduce the system's capacity and cause solids to be flushed out which may prematurely block drainage field or cause pollution

As with septic tanks sludge should be removed annually or in line with manufacturer’s instructions

Ensign Features

  • Tested to BSEN12566:3 and CE-marked to ensure compliance with latest environmental and Building Regulations requirements
  • Class-leading effluent quality of 11.5:19.2:8.4 (BOD:SS:NH4 ) ensures discharges well within national consent standards
  • Three chamber system correctly sized for separation and retention of solids improves final effluent quality
  • Standard or shallow options enable suitability for all site conditions (including driveways - subject to plinth/surround to prevent superimposed loadings)
  • Shallow option ideal for groundworks involving bedrock or high water table as the low profile allows for safe, cost effective installation
  • Low energy compressors ensure minimal running, maintenance and servicing costs > High specification bio-media (310m3 per m2 ) and membrane diffusers ensure even circulation to eliminate 'dead spots'
  • Internal recirculation (from final to primary chamber) continues treatment process to provide higher effluent quality whilst balancing flow over 24 hour period or periods of intermittent use
  • Integral lifting eyes for improved on-site handling
  • Unique ‘keying-in’ lip to assist anchoring into granular or concrete surround
  • Optional extras include patented Polylok filter to further reduce suspended solids and extend life of drainage field; extensions for deep installations; pumped outlets for sites with adverse levels; and many more

    Ecomerchant Ensign Graphic

      Frequently asked question about Sewage Treatment Plants

      Question: Does a sewage plant have to meet a UK Standard?
      Answer: The ENsign plant has been tested to EN12566:3-2005 this is highest testing standard for European testing. The high test results mean the ENsign can discharge direct to a ditch, watercourse or percolation bed.

      Question: Why should I buy the Marsh Ensign sewage treatment plant? and does it smell and is it noisy?
      Answer: The ENsign Sewage plant is manufactured in the United Kingdom. The plant is odourless and operates almost silently and is backed with a 25 year structural guarantee. The ENsign Sewage plant is extremely energy efficient and normally only requires 30 minutes of annual maintenance. The six person ENsign Sewage plant is extremely strong and is only 1.95m in depth with an inlet invert of 500mm, this design reduces both the time and cost of installation, in normal ground conditions the unit only requires a pea-shingle surround.

      Question: What is a pumped outlet?
      Answer: A pump is fitted into the Marsh ENsign plant where there is no natural fall of gravity from the outlet pipe. The pump allows the effluent to be pumped to a higher level. We recommend the compressor is sited externally when a pump is fitted, together with a high level alarm. The Marsh ENsign design means that the pump is easy to fit and accessible and means a separate pump chamber does not need to be installed saving both money and time.

      Question: I have been told you cannot fit a sewage plant into my driveway.
      Answer: You can fit a Marsh ENsign plant, the plant can be adapted, so if required it can be installed in a vehicle driveway, please contact by phone or email for more details.

      Question: I need a treatment plant for my holiday home, it will not be used all the time, and will it smell?
      Answer: No, The ENsign is designed with an internal recycling-system, this means the ENsign plant is ideal for intermittent use. The recycling system stops the primary chamber becoming septic.

      Question: My drain is deep can I still connect up to the ENsign Treatment plant?
      Answer: Yes we can supply invert risers which cater for deeper inlet connection up to a further 1metre.

      Question: Are sewage plants expensive to run? Should I look at a non electric Bio-system?
      Answer: No, the power of a Marsh ENsign Six Person plant is 50w this means the running cost is approx. £52.00 per annum. Bio-systems are normally designed with a very deep outlet that can mean a pump needs to be fitted, which has a higher running cost than that of a compressor. Some need full concrete surrounds, and the layers of media in a Bio-system will need cleaning and also it requires a large separate primary chamber.

      Question: Is there a sewage plant suitable for multiple dwellings or industrial sites?
      Answer: The Marsh ENsign Sewage treatment plants are designed for both domestic and commercial buildings with no access to the main sewer network. We sell sewage plants up to 300 persons. Please contact us so we can prepare a quotation and Loads and Flows table that can be used to gain planning and EA/SEPA approvals.

      Question: Will an unsightly lump or cover be showing in my garden, where my sewage plant would be?
      Answer: No for gravity outlets the compressor is housed in the unit keeping the visual impact and any noise to an absolute minimum. For pumped outlets we recommend housing the compressor externally in a discreet “bird house design” housing that can be up to 10m from the sewage plant.

      Question: How do I install the Marsh ENsign treatment unit?
      Answer: The ENsign plant comes with lifting eyes to make unloading installation faster and safer.We designed the Ensign plant to self-level on the base and with our unique pipe connections ensure the installation is undertaken efficiently and correctly. The six person ENsign Sewage plant is extremely strong and is only 1.95m in depth with an inlet invert of 500mm, this design reduces both the time and cost of installation, in normal ground conditions the unit only requires a pea-shingle surround. For guidance ideally the Ensign plant should be 7m from a dwelling or10m from a stream.

      1. Good Product Review by kuldeep

        great thanks (Posted on 21/06/2018)

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