Compact and efficient Biological Nutrient Removal system optimised for removal of Nitrogen to very low levels








A recent PWS installation where only the kiosk is visible above ground, the tanks having been buried.

The Problem

Eutrophication and excessive algal growth can be harmful to the environment in rivers, lakes and other water bodies. Particularly in partially enclosed marine areas, such as estuaries and harbours, Nitrogen is usually the main hazardous nutrient needing to be controlled.

The Solent Area, between the Isle of Wight and the Mainland of England, is a particular area of concern and Natural England has produced a policy paper requiring the calculation of a Nitrogen Balance for all new residential developments in this area. This will inevitably lead to lower discharge permit limits and the need to remove Total Nitrogen at more sewage treatment works.


The Solution

TN-REM is a compact, efficient, Biological Nutrient Removal process optimised to achieve very low levels of Total Nitrogen in treated water. The process offers a reliable and robust solution to nutrient removal, using purely biological treatment without the use of chemicals. It also has a much smaller footprint and consumes less energy than more traditional BNR systems for Nitrogen removal.

The key advantages of the TN-REM process are:

  • Total Nitrogen (TN) of less than 5mg/l
  • Removal of Phosphorus can be achieved at the same time if required
  • Effective in all seasons
  • Lower capital expenditure
  • Lower operating costs
  • Smaller footprint, saving space and cost
  • Modular and scalable allowing cost to be spread
  • High quality effluent capable of re-use without tertiary treatment
  • Virtually odour-free process

TN-REM is suitable for works serving from ten to tens of thousands of people.

TN-REM is particularly suitable for dedicated treatment for new residential developments that are required to demonstrate Nitrogen Neutrality; and also where connection to mains would unacceptably delay the development or involve prohibitve cost.