Waste-water treatment plants (WWTPs) are an integral component of sustainable urban environments. They employ special controllers to optimise the various physical, chemical and biological treatments. However, considerable time and funding are expended during the design of these controllers. The idea behind the EU-funded ′Advanced control solutions for waste water treatment′ (Add Control) project is to use a simulation model to facilitate and accelerate WWTP controller development. A team of experts in software development and environmental engineering is working side by side with WWTP operators to find the best solution. The novel simulation software is comprised of three different layers addressing mass, instrumentation and actuation and, finally, automation and control. The goal is to enable testing of WWTP controllers over the full range of possible operating conditions. The software is to be validated at both industrial and municipal WWTPs participating in Add Control. In addition to aiding the design of better WWTP controllers, this software may also help companies involved in process automation reduce production time and costs.