DESASS: A software tool for designing, simulating and optimising WWTPs

This paper presents a very useful software tool to design, simulate and optimise wastewater treatment plants. The program is called DESASS (DEsign and Simulation of Activated Sludge Systems) and has been developed by CALAGUA research group. The mathematical model implemented is the Biological Nutrient Removal Model No.1 (BNRM1) which allows simulating the most important physical, chemical and biological processes taking place in treatment plants. DESASS calculates the performance under steady or transient state of whole treatment schemes including primary settlers, volatile fatty acid generation systems by primary sludge fermentation, activated sludge systems for biological organic matter and nutrient removal, chemical phosphorus precipitation, secondary settlers, gravity thickeners and sludge digesters (aerobic and anaerobic). Biological conversions occurring in settlers and thickeners (primary sludge fermentation, denitrification) are also taken into account, i.e. they are considered as reactive elements. DESASS also includes pH calculation coupled to biological processes in all the elements, so pH effect on biological processes can be directly simulated. Furthermore, the effect of sidestreams on nutrient removal efficiency can be estimated because the performance of the whole plant can be simulated.