Enter your raw water quality below. The tool calculates derived parameters (DO saturation, speciation fractions, ORP estimate, ionic strength), then flags which contaminants exceed DWSNZ MAVs and aesthetic values.
Use the quick preset chips at the top of the input panel to load a typical NZ source water profile as a starting point, then adjust to match your site.
All other tabs read their inputs from here — flow, pH and temperature in particular drive the kinetics and contactor sizing throughout the tool.
Side-by-side comparison of five oxidants — aeration, free chlorine, chlorine dioxide, ozone and permanganate — for your current source water.
Stoichiometric doses are calculated from electron-balance equations for Fe(II), Mn(II), H₂S and (where applicable) NH₃ breakpoint chlorination, with a configurable safety factor. They do not include organic oxidant demand from NOM — for chlorine, feed the stoichiometric dose plus the NOM demand from your separate Cl₂ demand / DBP tool.
Feasibility flags show whether each oxidant can practically handle each species at the current pH and temperature, accounting for catalytic media if you've selected it on the Contactor Sizing tab.
The design insights section below the table calls out the most important context-specific design considerations for your source water.
Detailed kinetics, stoichiometric demand, reaction equations and a removal-vs-contact-time chart for the selected oxidant. Switch oxidants using the segmented picker at the top.
The chart shows fraction of the target species remaining vs. contact time in an ideal batch / plug-flow reactor at the current pH and temperature. Actual contactor sizing (accounting for short-circuiting in real tanks) is on the next tab.
For permanganate, this tab also discusses ORP-based dose control — the practical method for managing KMnO₄ dose to avoid pink-water breakthrough.
This tab sizes the contactor (tank or pipe) needed to achieve a target removal in a real vessel, where some water short-circuits and other parcels stay longer than the average.
Terminology used here:
t₉₀, t₉₉, t₉₉.₉ — the reaction time needed for 90 / 99 / 99.9 % removal in an ideal batch (plug-flow) system. Calculated from first-order kinetics: [C]/[C₀] = exp(-k·t).T₁₀ — the hydraulic contact time of the slowest-moving 90 % of the flow, measured by tracer test. This is what disinfection regulations use and what we need to compare to t_required.BF (baffling factor) — BF = T₁₀ / τ, where τ = V/Q is the theoretical hydraulic detention. Typical values: 0.3 (unbaffled), 0.5 (moderately baffled), 0.7 (well baffled), 1.0 (plug-flow pipe).Sizing rule: we need T₁₀ ≥ t_required, so required theoretical detention τ_required = t_required / BF, and required vessel volume V = τ_required × Q.
Flow is read from the Source Water tab (design flow and turndown).
Time the water needs to be in contact with the oxidant to achieve the listed removal, in an ideal plug-flow / batch system. These are reaction times, not hydraulic detention times.
Translates the required reaction time into a real vessel, accounting for baffling. τ_required = t_required / BF.
Estimates the regulated by-products formed by each oxidant at the current stoichiometric dose, compared to DWSNZ MAVs.
THM and HAA formation from free chlorine reacting with NOM is not modelled here — feed the chlorine stoichiometric dose plus the NOM demand into your separate Cl₂ DBP tool.
~70 % of ClO₂ reduces to chlorite (ClO₂⁻). Up to ~30 % converts to chlorate (ClO₃⁻); UV light, residual chlorine and high pH increase chlorate.
DWSNZ MAV: Σ(ClO₂ + ClO₂⁻ + ClO₃⁻) = 0.8 mg/L (as ClO₂).
Bromate forms when bromide is present. Risk rises with O₃ dose, contact time, pH, NH₃ depletion, and lower DOC.
DWSNZ MAV: 0.01 mg/L (10 µg/L).
Excess KMnO₄ leaves residual MnO₄⁻ that gives pink colour. ORP-based dose control keeps the residual below the pink-water threshold (see the Design tab → KMnO₄).
Export this design as a PDF report or CSV data dump, or save the full input / output state as JSON for restoring later.
Select which tabs to include in the PDF. The PDF prints all selected tabs to a printable layout — when the browser print dialog opens, make sure to turn off "Headers and footers" in the More settings panel (the report itself does not include headers or footers).
The CSV is a flat dump of inputs, derived parameters, doses, kinetics and sizing results — suitable for spreadsheet review.
JSON save / load is the round-trippable design state. This is the only place in the tool that handles saving and exporting.
Select tabs to include:
Tip: in the print dialog, select "Save as PDF" as the destination, and disable "Headers and footers" under More settings for the cleanest layout.
A flat row-per-quantity CSV of all inputs, derived parameters, oxidant doses, kinetics, and sizing results.
Save the complete design state to a JSON file. Includes all inputs, settings, the active oxidant choice, and sizing options.
Restore a previously-saved design from a JSON file.
Reset all inputs and settings to defaults. This clears the locally-saved design from this browser too.