The Edwards (1997) model is a Langmuir-based semiempirical model designed to predict OC removal during alum coagulation. The model is on a non-linear function derived from physical relationships, primarily the process of Langmuir sorptive removal (Tipping 1981, Jekyl 1986).
coagulate(data, coefs)
coagulate_base(DOC, dose, pH, UV254, K1, K2, x1, x2, x3, b, root = -1)Arguments
- data
A data frame containing columns
DOC,dose,pH, andUV254.- coefs
The output of
edwards_coefs()or a similar named vector containing elementsK1,K2,x1,x2,x3,bandroot.- DOC
The initial DOC concentration (mg/L).
- dose
The coagulant metal concentration (Al3+ or Fe3+) in mmol/L.
- pH
The pH of coagulation.
- UV254
The absorbance of UV254 (1/cm). With
DOC, used to calculate SUVA.- K1, K2
Empirical fitting coefficients relating to SUVA.
- x1, x2, x3
Empirical fitting coefficients relating to pH.
- b
The Langmuir term.
- root
The solution to the equation presented in Edwards (1997) is a quadratic with two roots.
rootcan be 1 or -1 to account for these roots, however we see no evidence that anything except -1 here results in realistic predictions.
Value
A vector of predicted organic carbon concentrations (in mg/L) following coagulation.
References
Edwards, M. 1997. Predicting DOC removal during enhanced coagulation. Journal - American Water Works Association, 89: 78–89. https://doi.org/10.1002/j.1551-8833.1997.tb08229.x
Jekel, M.R. 1986. Interactions of humic acids and aluminum salts in the flocculation process. Water Research, 20: 1535-1542. https://doi.org/10.1016/0043-1354(86)90118-1
Tipping, E. 1981. The adsorption of aquatic humic substances by iron oxides. Geochimica et Cosmochimica Acta, 45: 191-199. https://doi.org/10.1016/0016-7037(81)90162-9
Examples
alum_jar_tests <- edwards_data("Al")
alum_jar_tests$DOC_final_model <- coagulate(alum_jar_tests, edwards_coefs("Al"))
plot(DOC_final_model ~ DOC_final, data = alum_jar_tests)
