Gem-APS (Aerated Precipitation System)

Phosphate and Ammonia reduction

Introducing the latest innovation in our extensive portfolio of domestic wastewater treatment products: the Marsh Gem-APS (Aerated Precipitation System)

The Gem-APS is designed to further reduce phosphates, ammonia and BOD from wastewater that has been previously treated in a domestic sewage treatment plant.

Note: Remote alert monitoring available for dosing. This can alert either Marsh Industries or the occupier when additional chemicals are required (including SMS/Telemetry options).

Positioned at the outlet end of any existing sewage treatment plant, the Gem-APS treats the discharged wastewater in a controlled process, involving small volumes of chemical dosing and aeration, in compliance with British Water and local environmental regulations, allowing the remaining effluent to be safely discharged to a river, ditch or drainage field.

Chemical dosing amounts are pre-configured based upon the expected flows and loads of the sewage treatment plant (Full scaleable detail available). The Gem-APS can also be regulated to reduce phosphate levels further.

Marsh offers commissioning and servicing of the Gem-APS, it is strongly advised to use this service when setting up the unit.

Phosphate: 0.9mg/L
Ammonia: 0.4mg/L
BOD: 2mg/L

The Gem-APS is a unique innovation for use on sites where phosphate discharge is a problem or where ammonia and BOD requirements are strict for planning consent.


  • Tested in accordance with BS EN 12566-7 Annex A at PIA GmbH test facility in Aachen, Germany
  • Small footprint and shallow dig for easy installation provides enhanced health and safety benefits
  • Heavy duty shell as standard enables installation in all ground conditions. Unique ‘keying-in’ lip assists anchoring into granular or concrete surrounds
  • Near silent, energy efficient compressor (located externally) with integral alarm
  • Unique Polylok tertiary filter reduces suspended solids helping to extend drainage field life
  • Lockable lid for safety and security
  • Low level chemical alarm/indicator to ensure continuous phospahte reduction. Remote alert monitoring also available.


Gem-APS brochure
Marsh Civils product portfolio and specifications
Marsh Civils product portfolio and specifications