Mega-WATS the model

Mega-WATS simulates biological and chemical processes in sewer networks in great detail. It predicts how wastewater constituents are transformed and degraded as the wastewater flows from its source to final treatment.

Mega-WATS simulates all relevant processes in all parts of the network. It simulates what happens in both wastewater and sewer air, predicts the amount and quality of sewer air vented to the urban atmosphere, calculates concrete corrosion, and simulates injection of chemicals to manage H2S and odor. The MegaWATS model is the by far most advanced tool for modelling processes in sewers, and has proven itself on large and complex catchments.

The WATS of Mega-WATS stands for Wastewater Aerobic/Anaerobic Transformations in Sewers and is the original concept developed for sewer process simulation. It has been developed at Aalborg University, Denmark, over the past three decades and is continuously extended and improved as knowledge of in-sewer processes increases. It constitutes the conceptual backbone of other sewer process models on the market and has as such set the paradigm for sewer process modelling.

In brief, modelling with Mega-WATS typically aims at analyzing and solving in-sewer problems such as

Key results obtained by modelling with Mega-WATS includes but is not limited to

The largest sewer system hitherto simulated is the City of San Francisco. Its network consist of more than 31.000 pipes with a total length of 1000 miles. The simulation time for this large network is 2-3 minutes.

Of the three models available on the market which can do some catchment scale sewer process modelling (Mega-WATS, SEWEX, Mike Urban coupled with Ecolab), Mega-WATS is by far the fastest for large drainage systems. It is the most proven and documented of the models, and also the original model upon which other models are based. Mega-WATS is constantly updated by the researchers who produce novel insights on sulfide and corrosion in sewers, and hence always reflects the state of the art. Unlike other sewer process models, Mega-WATS can, after a short training, be run in-house by sewer asset owners.


Additional literature

The theory and science behind the Mega-WATS model are published in the public domain and may be found Sewer Process and related journal publichations.  Such as those listed below.

Textbook by the creators of the Mega-WATS Model:

  • Hvitved-Jacobsen T, Vollertsen J, Nielsen AH (2013). Sewer Processes: Microbial and Chemical Process Engineering of Sewer Networks. Second Edition, pp 408, CRC Press, ISBN 978-1-43-988177-4

Scientific publications on the applications of the model can for example be found in:

  • Matias N, Matos R, Ferreira F, Vollertsen J, Matos JS (2018). Release of hydrogen sulfide under intermittent flow conditions – the potential of simulation models. Water Science & Technology, 77(3): 777-787, 

  • Vollertsen J, Revilla N, Hvitved-Jacobsen T, Nielsen AH (2015). Modeling Sulfides, pH and Hydrogen Sulfide Gas in the Sewers of San Francisco. Water Environment Research, 87(11): 1980-1989 (open source article at
  • Vollertsen J, Nielsen L, Blicher TD, Hvitved-Jacobsen T, Nielsen AH (2011). A sewer process model as planning and management tool – hydrogen sulfide simulation at catchment scale. Water Science and Technology. 64(2): 348-354,

An example of modeling a whole city. The network covers some 1500 km of pipes