Package Sewage Treatment Plants

Why sample a Package Sewage Treatment Plant?

Regular emptying of a package sewage treatment plant does not determine whether it is operating as designed and within consent limits. Sampling the final effluent from the plant can identify if the plant is within consent or has exceeded the discharge limits. There are many reasons why a plant may not be working as expected, see our article Potential reasons for my package Sewage Treatment Plant not meeting consent

Sampling and testing the final effluent can help to pinpoint the reason behind a failure.


Maintenance of Package Sewage Treatment Plants

As a normal part of the operation of a package Sewage Treatment Plant (STP), solids (also referred to as sludge) are produced. The sludge will build up over time and the depth will exceed the manufacturer’s guidelines. At this point, the tank will need to be de-sludged.

If the tank is not de-sludged, the treatment plant will work less efficiently, and the quality of the treated effluent will decrease beyond the allowable limits (the consent to discharge permit).

If the effluent quality is worse than permitted, the environment could potentially be polluted. In addition, damage could be caused to the soakaway system.
Non-compliance of the permitted consent to discharge issued by the Environment Authority, the environmental regulatory governing body, will place the owner of the installation at a potential risk of prosecution.

Frequency of Maintenance

It is generally recommended that desludging of STPs follows the following schedule:

  • Commercial Sewage or Wastewater Treatment plants: 3 monthly
  • Domestic Sewage or Wastewater Treatment plants: 6 monthly

All Sewage Treatment Plants must have been sized in accordance with the British Water Code of Practice. Depending upon the current loading into each system, the final discharge properties and quality, the frequency of desludging may need to be adjusted.

Advantages of Sampling

Regular sampling and testing of the treated effluent (sample taken from the sampling point of the installation) will help to determine the following:

  • If the plant is more heavily loaded than designed, the condition of the effluent may indicate a more frequent emptying schedule is required, conversely a lighter loading may enable a less frequent emptying schedule
  • The compilation of an historical sample analysis record can show evidence of compliance
  • Highlight issues with the plant – Obtaining samples can determine whether the use of excessive quantities of surfactants (detergents, bleaches, and other chemicals) is affecting the quality of the final effluent

Our Sampling and testing service for Treatment Plants

We have worked with owners of individual properties with an STP, multiple properties that share a plant, schools, nursing homes, pubs, restaurants and many other types of property that need to ensure that their package treatment plant is operating within the specified limits. We also are employed by property owners who have issues with their plants, we can provide independent testing and analysis to determine if there is a problem.

See our case studies page for examples..