Most tidywater functions required a water object. Start
by creating a water with define_water. There are a lot of
optional arguments that correspond to different water quality
parameters. Start by specifying everything you know, or at least all the
parameters relevant to the modeling you want to do. Parameters are all
lowercase and use common abbreviations or chemical formulas. If you
aren’t sure what the correct argument name is, check the
define_water documentation. Concentrations are specified in
the most common units - usually mg/L or ug/L depending on the parameter.
Units are also in the documentation, so make sure to check carefully
until you are familiar with the system.
mywater <- define_water(
ph = 7, temp = 15, alk = 100, tot_hard = 100, na = 100, cl = 80,
cond = 100,
toc = 3, uv254 = .02, br = 50
)
#> Warning in define_water(ph = 7, temp = 15, alk = 100, tot_hard = 100, na = 100,
#> : Missing values for calcium and magnesium but total hardness supplied. Default
#> ratio of 65% Ca2+ and 35% Mg2+ will be used.
#> Warning in define_water(ph = 7, temp = 15, alk = 100, tot_hard = 100, na = 100,
#> : Missing value for DOC. Default value of 95% of TOC will be used.Now that we have a water, we can apply treatment models to it. The
main models require a water input and will usually output
another water or a number. Functions in tidywater follow
the naming convention treatmentapplied_parametersmodeled.
For example, when we want to dose chemical and see the impact on
pH/alkalinity, we use chemdose_ph. There are a lot of
available chemicals, which you can view with the documentation. Most
chemicals are specified using the chemical formula in all lowercase,
except hydrated coagulants, which are named. Units for the chemical are
also specified, and are usually mg/L as chemical.
dosed_water <- chemdose_ph(mywater, hcl = 5, alum = 20)
mywater@ph
#> [1] 7
dosed_water@ph
#> [1] 6.67Now dosed_water has updated pH chemistry based on the
hydrochloric acid and alum doses. However, other slots in the water,
such as TOC, have not been updated. If we also want to know how the
coagulant impacts TOC, we need to apply chemdose_toc as
well. This function defaults to published model coefficients, but
because it’s an empirical moodel, you could also select your own
coefficients.
coag_water <- chemdose_toc(dosed_water, alum = 20)
dosed_water@doc
#> [1] 2.85
coag_water@doc
#> [1] 2.424969We can also solve for chemical doses to change the pH with
solvedose_ph. This function outputs a number instead of a
water.
caustic_req <- solvedose_ph(coag_water, target_ph = 8.6, chemical = "naoh")
fin_water <- chemdose_ph(coag_water, naoh = caustic_req)We can apply similar principals for disinfection. Note that we have
to specify the chlorine dose in both chemdose_ph and
chemdose_dbp because they are calculating two different
things. In this example, the DBP function displays some warnings because
the water we are modeling is outside the bounds of the original model
fitting. This is common, and something you should always be aware of
(even if tidywater doesn’t warn you). We can use
summarize_wq to view different groups of parameters in the
water.
dist_water <- chemdose_ph(fin_water, naocl = 4) %>%
chemdose_dbp(cl2 = 4, time = 24, treatment = "coag")
#> Warning in chemdose_dbp(., cl2 = 4, time = 24, treatment = "coag"): UV254 is
#> outside the model bounds of 0.016 <= UV254 <= 0.215 cm-1 for coagulated water.
#> Warning in chemdose_dbp(., cl2 = 4, time = 24, treatment = "coag"): Temperature
#> is outside the model bounds of temp=20 Celsius for coagulated water.
#> Warning in chemdose_dbp(., cl2 = 4, time = 24, treatment = "coag"): pH is
#> outside the model bounds of pH = 7.5 for coagulated water
summarize_wq(dist_water, "dbps")
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Tidywater functions can also be applied to data frames using the
_chain (output a water column) or _once
(output numeric columns) suffixes. To learn more about those functions,
look at the documentation or read the helper function vignette.
If you want a more detailed introduction to tidywater, check out the intro vignette.