European Commission logo
Joint Research Center (JRC)
SimpleTreat

Sewage Treatment Plant Model

HealthEnvironmentwastewaterchemicalsdegradationphase partitioningeffluentssludge

overview

HealthEnvironmentwastewaterchemicalsdegradationphase partitioningeffluentssludge

main purpose

SimpleTreat 4.1 is an exposure and emission model developed to estimate chemical emission from sewage treatment plants and exposure in surface water within the framework of risk assessment of chemicals. The current version is a revision of SimpleTreat 4.0.9, please see the release note for details. SimpleTreat 4.0 and 4.1 are both updates of SimpleTreat 3.1, which supported the chemical act 30 years ago in the Netherlands and later in the European Union (EU). The revision from v4.0 to v3.1 was necessary to account for more recent scientific insights with respect to behavior of chemicals in domestic sewage and activated sludge.

summary

SimpleTreat was developed to enable calculation of the fate of organic chemicals in a biological wastewater treatment plant (WWTP) ecosystem.

The model is a steady state, multiple box model solving the mass balance of a contaminant taking into account phase partitioning, degradation and volatilization. The model estimates concentrations of contaminants in effluents and sludge, and the corresponding discharges through air (volatilization), solid and liquid discharges from the plant.

The model is designed to appraise the environmental fate of a chemical undergoing treatment in a WWTP. It can be used in regulatory applications as well as in the assessment of policy scenarios of wastewater treatment.

model type

  • Other: null

ownership

Third-party ownership (commercial companies, Member States, other organisations, …)
Dutch National Institute for Public Health and the Environment (RIVM)

licence

Licence type
Non-Free Software licence

homepage

https://www.rivm.nl/en/soil-and-water/simpletreat

details on model structure and approach

The model assumes steady state and complete mixing of the contaminant in the compartments of a WWTP. It assumes partitioning to follow linear isotherms. The description has limitations on validity for ionic and polar compounds. The mass balance of a contaminant in the various phases and compartments within the WWTP is solved as a system of linear equations.

model inputs

  • Physicochemical properties of the contaminant:
    • Air-water partition coefficient
    • Degradation rate
    • Solids/water partition coefficient
  • Operating conditions of the WWTP (particularly the hydraulic loading rate and sludge retention time).

model outputs

  • Concentration of the contaminant in the different compartments and phases of the WWTP, including sludge and effluents.
  • Percentage of the contaminant mass in the effluents that ends up in the sludge and effluents, and degradation/volatilization removal efficiency (%).

model spatial-temporal resolution and extent

ParameterDescription
Spatial Extent/Country Coverage
The model is generic and can be applied to a WWTP in any location. The model is not spatially explicit (the WWTP is represented as a set of interconnected boxes).
Spatial Resolution
Other
Not spatially explicit
Temporal Extent
Other
Steady state
Temporal Resolution
Other
Steady state models can be applied independent of time. They refer to the time for which inputs are valid.