STOAT - Dynamic modelling of wastewater treatment plants

STOAT is a PC based computer modelling tool designed to dynamically simulate the performance of a wastewater treatment works. The software can be used to simulate individual treatment processes or the whole treatment works, including sludge treatment processes, septic tank imports and recycles. The model enables the user to optimise the response of the works to changes in the influent loads, works capacity or process operating conditions.

Using STOAT can help you to:


STOAT contains a wide range of features which makes it stand out from its competitors, including:

Users of STOAT are located all over the world. The software is used by the majority of the UK waster utilities, a range of international consultancies and municipalities in the USA and Europe.

STOAT is part of the WRc family of process models, which also includes OTTER and Plan-It STOAT. Users benefit from a dedicated team of developers and support engineers.

STOAT has been developed over the past 10 years to simulate treatment processes within wastewater treatment plants. During its development, each process model was validated against performance data from sewage treatment plants. Extensive modelling work has subsequently been undertaken to confirm the validity of individual process models. The software contains models for the following processes:

The Windows interface allows users to quickly build a plant model and enter the data using simple dialogue boxes. Results can be shown while a simulation is taking place and are stored as data files for subsequent analysis.

A number of typical case studies are summarised below:

Process Modelling as an Aid to Process Selection

STOAT was used to compare the performance of high rate activated sludge and sequencing batch reactors for the extension of a works which serves 1 million population equivalent, where space is limited. Comparisons were made on the basis of effluent quality, sludge production, effect of increased loads and overall capital and operating costs.

Optimisation of Works Operation

An operator of a large (1 million pe) treatment works wanted to establish whether an oxygenated activated sludge plant could use air rather than oxygen. STOAT modelling indicated that this was possible, which led to substantial operating cost savings.

Determination of the Amount of Spare Capacity of a Works

The operation of two linked plants was modelled, and the processes optimised to allow an increase in the amount of tankered waste accepted. As a result, effluent quality has improved, and the client has been able to increase profits by accepting more tankered wastes.

Supported Operating Systems

STOAT Version 4.1 is currently available, running under IBM-PC compatible computers and Microsoft Windows and NT operating systems. STOAT is the only whole-works model that runs under this range of windows systems. A datasheet specifying the full hardware requirements is available.

Future Development

Further processes and options are being added to STOAT for release. Currently under development are: