In general, first-order rate laws are assumed. Chemical oxygen demand, total phosphorus, and total nitrogen are modeled as individual first-order decays. The user can specify all rate parameters or use default values. Point sources as well as non-point pollution can be modeled.
Point sources are generally water supplies with associated treatment plants.
The user can specify treatment types and methods or choose from a list of pre-defined common ones. Non-point pollution includes total nitrogen and phosphorus loads, which the user can specify, including their seasonal variation.