Effluent Monitoring

Most sewage treatment plants have a 'discharge consent' issued by the Environment Agency. This is a quality of effluent which the system must achieve in order to discharge to the environment. The Environment Agency carry out a random sampling of sewage treatment plants to ensure they are producing a quality of effluent within the consented limit. If a system is shown not to achieve the required consent, the Environment Agency can pursue criminal action against the system's owner (which in a property group would go to board level) or issue a fine.

A typical consent would comprise of the following elements:

  • BOD - Biochemical Oxygen Demand or BOD is a chemical procedure for determining the uptake rate of dissolved oxygen by the biological organisms in a body of water. BOD measures the rate of oxygen uptake by microorganisms in a sample of water at a temperature of 20°C over an elapsed period of five days in the dark.
  • SS - Suspended solids, this is the number of solid particles still present in the effluent. The amount of total suspended solids indicates the insoluble content of the sewage. The average strength of domestic raw sewage in the UK is 300 to 400 mg/l.
  • NH4 - The nitrogen in sewage is assessed as ammoniacal nitrogen. This indicates the amount of nitrogenous organic matter which has been converted to ammonia. The average strength of crude domestic sewage will have a combined nitrogen content of 40 mg/l to 60 mg/l. pH values. A typical consent limit is 20mg/litre. The pH of a liquid is a measurement of its acidity (low figures of 3 to 5) or alkalinity (high figures of 9 to 12) with a neutral of 7.0. The average strength of crude domestic sewage is slightly alkaline at 7.2.


Filta carry out final effluent sampling and analysis as part of a sewage treatment plant maintenance contract or as a stand-alone service. After each analysis, we provide a written report which is issued to the client certifying performance.

Our service is carried out in 3 Stages:

Site Survey

Site Survey

Filta will survey your establishment, to correctly identify your requirements.



Our trained engineers will install a grease management system to suit your needs.



On a regular basis, we will ensure the equipment is working effectively & efficiently.

For more information about our water pumping solutions or to discuss the requirements of your commercial establishment, contact our team on 01788 550100.