Development and implementation of the software mEnCo^© to predict coagulant doses for DOC removal at full-scale WTPs in South Australia

Conventional surface water treatment plants (WTPs) rely on optimised coagulation for effective clarification, filtration and chlorination performance. WTPs operated at sub-optimal coagulation conditions are at risk from failing treated water microbial, disinfection by-product, chemical and aesthetic quality goals as well as incurring excessive sludge production and treatment cost. This is especially important when treating water that contains a high concentration of natural organic matter (NOM). Removal of NOM by coagulation can be enhanced by optimising the inorganic coagulant dose and coagulation pH. This paper describes the development and implementation of a software model mEnCo^© (referring to modelling enhanced coagulation) that enables WTP operators to rapidly determine coagulation chemicals. Implementation was carried out in a four-stage process comprising model evaluation by (1) jar tests and pilot-scale studies, (2) comparison of mEnCo^© predictions with historical water quality and coagulant dose trends at Adelaide metropolitan WTPs, (3) parallel studies where mEnCo^© predictions were compared with the usual methods applied by operators for chemical dose determination and (4) application of mEnCo^© for dose determination and review. United Water International (UWI) began using mEnCo^© in July 2003 for prediction of chemical doses for coagulation control and have used the model from July 2004 to adjust coagulant doses.