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 mEnCd^ (referring to modelling enhanced coagulation) that enables WTP operators to rapidly determine coagulation chemicals. Implementation was carried out in a fourstage process comprising model evaluation by (1) jar tests and pilot-scale studies, (2) comparison of mEnccf-' predictions with historical water quality and coagulant dose trends at Adelaide metropolitan WTPs, (3) parallel studies where mEnCcF predictions were compared with the usual methods applied by operators for chemical dose determination and (4) application of tvEnCcP for dose determination and review. United Water international (UWI) began using mEnCö' in July 2003 for prediction of chemical doses for coagulation control and have used the model from July 2004 to adjust coagulant doses.
Cylindrospermopsin (CYN) is an emerging cyanobacterial toxin whose detection frequency is increasing in water bodies worldwide. Because it has a high propensity to exist in extracellular form, effective water treatment practices are required to ensure removal. In this study, powdered activated carbon (PAC) and chlorination were evaluated for CYN removal under practical water treatment plant conditions. The homogenous surface diffusion model (HSDM) was used to predict CYN adsorption using two different PACs. The HSDM also aided in the derivation of a PAC dose table that could be used to optimize PAC application for CYN removal. Chlorine was shown to be an effective oxidant for CYN; the chlorine concentration times contact time value of 3 mg × min/L was shown to be sufficient for complete CYN oxidation in two drinking waters. This study provides pertinent information for the application of PAC and chlorination practices for optimal CYN removal.
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