Watercalcs
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Premium feature

This part of the Jar Test Designer is included with a Watercalcs Premium subscription ($49/month).

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v2.6
i Quick guide to Plant Match mode

What Plant Match is. A full jar test designed around your actual plant. Instead of using fixed bench settings, the tool works out paddle speeds, mixing times and settle times that reproduce your plant's conditions in a 1 L jar — so what works on the bench should work on the plant.

How it differs from Quick Test. Quick Test is one page with a fixed protocol — good for a fast "which dose is best" comparison, clarification only. Plant Match adds the things Quick Test leaves out: mixing matched to your plant, filtration simulation, pH adjustment with acid/base estimation, custom stock strengths, full reporting, and the optional floc strength test. Use Quick Test for routine dose checks; use Plant Match when you want the jar to genuinely represent your plant, or when your test involves filtration or pH work.

How to navigate. The tabs across the top run in order — work left to right, or use the Next button at the bottom of each tab:

  • Setup (this tab) — your jar tester, water temperature, and plant type.
  • Plant Match — describe your plant's mixing, clarifier and filters.
  • Jar Mixing — check the computed bench paddle speeds.
  • Solutions — stock recipes for coagulant, polymer, acid and base.
  • Regime — set what each jar gets, and get your run protocol.
  • Observations — record floc size during the test.
  • Results — enter measurements; the tool finds the optimum.
  • Reports & Save — PDF, CSV, and save/load.

Each tab has its own Quick guide (collapsed, like this one) if you want more detail. + Floc Strength is an optional extra test, outside the main sequence.

Demo Data

See the tool fully populated with a worked example

Test Information

Plant Configuration

What treatment train are you simulating?

Coagulant Dose Unit

How you want to talk about dose throughout the test

Jar Apparatus

mm
Vertical paddle dimension. Phipps & Bird standard: 25 mm.
mm
Horizontal sweep dimension. Standard: 75 mm.
Set in Settings (calibration value). Standard ≈ 0.75.

Water Conditions

°C
°C
Used to flag if the jars warm up during the test.
i Quick guide

This tab is where you describe the plant — flow rates, tank sizes, paddle speeds, hydraulic loading rates. You just enter what's on the plant's design drawings or what the SCADA tells you it's running at. The tool does the conversion.

Behind the scenes, the tool works out the mixing intensity at each stage — how vigorously the water is being stirred. It then figures out what jar paddle speed gives the same intensity in a 1 L jar. That's what makes the bench test a meaningful copy of the plant.

It does the same thing for the rest of the plant: the clarifier rise rate, the filter rate. All of these get translated into bench-scale settings on the next tabs.

If you don't have plant data — or you're just exploring — you can switch to Generic mode below and set the jar mixing intensity directly using typical values for a conventional plant.

① Rapid Mix (Coagulation)

② Flocculation

③ Clarification

Hydraulic loading rate is all we need

Clarifier type doesn't matter for the jar test. What matters is the rise rate — the m/h that floc has to settle faster than to be removed. Set it from your plant's design or operating data.

m/h

④ Filtration

Filter rate + media — selects the jar test filter

For a meaningful filter step in the jar test, the tool needs the plant filter rate (to scale the analogy) and the media type (to pick a Whatman / membrane that mimics the bed cut-off). The jar test won't reproduce filter runtime — but it will give you a clean filtrate sample for analysis comparable to your downstream water.

m/h
mm
Used to estimate EBCT (not critical for jar sim).
Tool suggests a Whatman / membrane that approximates your plant filter cut-off.
Essential for low-DOC / UV₂₅₄ work.
mL
200 mL is enough for full filtrate analysis.
i Quick guide

This tab tells you what to dial into your jar tester. The tool has already worked everything out from the Plant Match tab — the green panels are the numbers you set on the bench: paddle speed (rpm) and how long to run each stage.

The white fields (target G, stage times) are already filled in from your plant data. You only need to touch them if you deliberately want to test different mixing — most people never do.

If a green panel turns amber, the required speed is outside what a jar tester can do (over ~250 rpm or under ~10). That usually means the paddle dimensions in Setup don't match your actual bench paddle.

Nothing to enter here for most tests. The green panels show what to set on your jar tester — rpm and time for each stage. The white fields are pre-filled from Plant Match; only change them to deliberately test different mixing.

Plant Targets

Read-only

Rapid Mix

Pre-filled from plant
s⁻¹
s
Set jar tester to

Jar Geometry

Read-only, from Setup
Jar
Paddle
Viscosity (μ)

Bench Run Sheet

The whole mixing sequence at a glance
The default SG and % active for every coagulant product, and the default polymer stock strength, can be adjusted in Settings (gear icon, top right). Values you set there apply to all tests. Overrides made on this tab apply to this test only.
i Quick guide

This tab gives you the recipe for each stock solution you'll dose from. There are four of them:

  • Coagulant stock — a diluted version of your plant's neat product, made at a strength that gives you syringe-friendly volumes (a few mL per jar).
  • Polymer stock — 1 g of polymer made up to 1 L with deionised water, aged 30 minutes before use.
  • Acid stock — for lowering pH (typically 0.5 N sulphuric acid).
  • Base stock — for raising pH if you need to (sodium hydroxide or sodium carbonate).

The tool tells you exactly what to weigh out (or measure with a pipette) and what volume to make up to. Make coagulant and polymer stocks fresh each day — they age and lose strength.

The simple rule: 1 mL of a 1 g/L stock added to a 1 L jar gives 1 mg/L dose. Everything else scales from there.

Coagulant

mg active / mL
5 mg/mL works for most plants. Higher for very low doses; lower for high doses.
% w/v
Auto-filled from product. Override with the supplier's COA value.
g/mL
Liquid coagulants only.
mL
🧪
Make-up recipe:
i Quick guide

Polymer

g/L
1 g/L standard. Higher for very low doses.
mL
1 L volumetric is the bench standard.
🧪
Recipe:

pH Adjustment

mL
mL
Acid:

Base:
i Quick guide

This is where you decide what each jar gets. The auto-fill buttons populate a sensible ladder based on what test you're running — vary one thing at a time so the results are interpretable.

Typical sequence:

  1. Coag dose screen first — hold pH constant, vary coag dose across the jars.
  2. pH optimisation next — at the best dose, vary pH around the suspected optimum.
  3. Polymer trial last — at the best (dose, pH), test polymer addition.

About acid and base doses: The tool can estimate how much acid (or base) you need to reach a target pH, using the raw water alkalinity from the Results tab. Click Estimate acid/base to populate the columns. The estimate accounts for the alkalinity that the coagulant itself consumes, but it's a starting point — not a precise prediction. Always measure the actual pH of the first jar and adjust your dosing accordingly. If you don't enter raw alkalinity, the columns stay empty and you'll need to set the volumes manually based on a pre-titration.

Sampling Configuration

Inherited from Plant Match
m/h
Change in Plant Match tab.
mm
Auto-set from sample method; override if your tap is at a different height.

Dose Timing

When chemicals enter the jar

Coagulant & Stock Solutions

Pick your product, make these before you start

The "Stock to add (mL)" column in the ladder below is the volume of this stock solution to add to each jar. Switch to Plant Match mode for different stock strengths, acid/base stocks, and full recipes.

Per-Jar Dose Ladder

Operator Protocol

Generated from everything above — print or save from the Reports tab
i Quick guide

During the flocculation phase, watch each jar and note the floc size class at each timepoint. The size chart below is your reference card — match what you see in the jar to a class number.

Two things that make the observations reliable:

  • Same method every time. Hold the jar against a white background with even overhead light — floc looks bigger in shadow and smaller in glare. Any operator can do the sizing; what matters is that everyone uses the same background, lighting and reference chart.
  • Look in the bulk of the jar, not at the surface or against the walls. Floc concentrates near the top meniscus and looks bigger there than it really is. Ideally, observe while the paddle is still turning slowly.

Floc behaviour tracks faster than any analytical result, and weak or slow-forming floc is usually the first sign that the chemistry isn't right.

Size Reference Chart

The visual standard for d-class sizing

Edit midpoints in Settings if your bench reference differs. The chart on the right is rendered at on-screen scale — print the true-scale comparator from the Floc Strength tab when you need a bench card.

Per-Jar Floc Observations

Comma-separated. Default 5/10/15/20/30 min.

Floc Growth Read-Out

Trend interpretation from your recorded size classes
i Quick guide

This is where the analytical numbers go. There are two samples to measure from each jar:

  • The clarified water (what you drew off the top after settling), and
  • The filtrate (what comes through the GF/C paper, simulating the plant filter).

The tool shows whichever columns make sense for your plant — both if you're doing clarification + filtration, just one if you're doing clarification only or direct filtration.

What to measure:

  • Turbidity — always. Clarified turbidity tells you how well the floc settled; filtrate turbidity tells you how well the filter is polishing.
  • Organics — pick one parameter (UV₂₅₄ absorbance, True Colour, DOC, or SUVA) and measure it on both clarified and filtrate. Turbidity alone isn't enough for a proper assessment.
  • pH and alkalinity — read on the clarified water, before any chlorination.
  • Residual metal — total in the clarified, dissolved in the filtrate.

When picking the optimum jar, don't just go for the lowest number. Check that the dose one step lower is nearly as good (it's cheaper), and that the floc looked robust in your observations. A flat plateau is more reliable than a knife-edge.

Dissolved Organics Parameter

Pick one for the entire test
All four are valid surrogates for natural organic matter. UV₂₅₄ absorbance is the most common bench measurement; True Colour is operator-friendly; DOC is the cleanest analytical truth; SUVA combines both.

Raw Water

Organics measurements are optional, but you need at least one for a proper performance assessment. Turbidity alone tells you only about the particle phase — coagulation also drives dissolved organic carbon removal, and your dose optimum is often set by organics, not turbidity. Pick a parameter above and include it in raw water and treated samples.

Per-Jar Results

Removal Performance

Enter results to identify optimum
i Quick guide

Four ways to get your work off the tool:

  • PDF report — to print and bring to the bench, or send to a colleague. Choose which sections to include below. Use your browser's "Save as PDF" option in the print dialog, and turn off Headers and footers for a clean output.
  • CSV export — for opening in Excel. The doses, observations, results, and floc strength data all come out as tables.
  • Save JSON — a complete snapshot of everything: setup, plant config, doses, observations, results. Use this to re-open the test later, or to send to a colleague using the same tool.
  • Load JSON — restore a previously saved test. This replaces everything currently in the tool, so save your current work first if you want to keep it.

Plant Name

Appears on the report title
Optional. Leaves the report title generic if blank.

Sections to Include

One selection — applies to both the PDF report and the CSV export

PDF Report

In the browser print dialog: set Destination to Save as PDF, and untick Headers and footers for a clean output.

CSV Export

Exports the tables from your selected sections above (dose ladder, observations, results, floc strength) with test details at the top. Sections without tabular data appear in the PDF only.

Save / Load JSON

Complete test snapshot
Includes all settings, doses, observations, results, and floc strength log.
⚠ Loading replaces everything. Save first if you want to keep current.
i Quick guide Optional

This is a follow-on test that answers a question the standard jar test can't: how robust is the floc? You make the floc, take a size reading, then shear it hard for a short burst, take another reading, let it reform, and take a third reading.

Two chemistries can give the same clarified turbidity but behave very differently downstream. Weak floc shears in the filter inlet and packs tightly at the surface, giving fast headloss rise and short filter runs. Floc that can't reform after a shock will punch through the bed and cause early turbidity breakthrough. Strong, reformable floc rides through flow swings and dose drift without complaint.

The tool gives you two numbers:

  • Strength Factor (Sf) — how much of the floc survived the shear. Higher is stronger.
  • Recovery Factor (Rf) — how well the broken floc reformed. Higher is more forgiving.

Run this to compare two coag/polymer combinations that look equivalent on clarified turbidity, to verify a polymer actually toughens the floc, or to diagnose filter breakthrough.

① Test Condition

Carry over from main test, or set manually
Pick a jar to inherit its dose / pH.
mg/L
mg/L

② Breakage & Reformation

s⁻¹
s
s⁻¹
min

③ Bench Protocol

④ Record Observations

⑤ Results & Interpretation

Strength Factor (Sf)
Resistance to breakage. Higher = stronger floc.
Recovery Factor (Rf)
Ability to re-aggregate after shear. Higher = more forgiving.

Settings

Default coagulant for new tests

PACl 10% Al₂O₃ medium basicity and Alum 14H₂O equivalent are flagged as Common in NZ.

Coagulant properties

Default SG and % w/v active for each liquid product. Override if your supplier's COA differs. Changes apply globally to new and existing tests.

Default polymer

g/L
1 g/L is the bench standard (1 g in 1 L volumetric).

Bench paddle calibration

Default ≈ 0.75 for typical jar paddles. 1.0 for plant paddles. Calibrate against a known G if you have one.
mm
mm

Phipps & Bird standard: 25 × 75 mm. Per-test paddle dimensions live in Setup.

Floc size comparator scale

Used in Observations and Floc Strength. Edit the midpoints if your bench reference card uses different sizes.

Equipment guide

A practical inventory of the gear you need to actually run a jar test. Brand examples are illustrative — equivalents are fine.

Jar test apparatus

  • Multi-station jar tester (4-jar or 6-jar) with variable speed 0–300 rpm (e.g. Phipps & Bird PB-700/PB-900, Stuart Flocculator SW6, Velp JLT). The bench paddle dimensions must match what's entered in Setup → Jar apparatus.
  • 4 × or 6 × 1 L square gator jars (or 2 L if you have them). Square cross-section matters — round jars create vortices that don't match plant floc-tank hydraulics.
  • Disposable plastic syringes — full set. 1 mL for polymer doses; 5 mL and 10 mL for coagulant, acid and base doses; 20–25 mL for drawing clarified or filtrate samples. Single-use disposables avoid cross-contamination between jars and remove the need for tubing — you can dose and sample directly with the syringe nozzle.
  • Stopwatch or phone timer. Protocol stage times need to be held to ±5 s for meaningful comparison between jars.

Measurement instruments

  • Turbidimeter reading 0–10 NTU at ≥ 0.01 NTU resolution (e.g. Hach 2100Q or TL2310, WTW Turb 430, HF Scientific Micro100). Calibrate with formazin or stabilised standards each test day.
  • pH meter with ±0.01 resolution and ATC (e.g. Hanna HI 5222, Mettler SevenCompact, YSI portable). Calibrate against pH 4.01 and 7.00 buffers (10.01 also if testing high-pH dosing).
  • Spectrophotometer for true colour at 456 nm (e.g. Hach DR1900 or DR3900). True colour is read on a 0.45 µm filtered sample.
  • Spectrophotometer for UV₂₅₄ if tracking organics. Many DR-series units cover both 254 nm and 456 nm. Use 1 cm quartz cuvettes — plastic does not pass UV.

Sample preparation

  • 0.45 µm syringe filters (PES or cellulose acetate, 25 mm). For true colour, UV₂₅₄ filtered, DOC, and dissolved metal analyses. Pair with the 20–25 mL disposable syringes — push the sample straight through into the cuvette.
  • Whatman GF/C glass-fibre filters (47 mm). For the filtrate sampling step that simulates rapid gravity filtration. Pre-rinse with ~250 mL DI before sampling.
  • Filter funnels (~75 mm, polypropylene or glass) to hold the GF/C papers. Mount these directly in the neck of the sample bottle so the filtrate collects there. Gravity flow is fine — no vacuum needed.
  • Sample bottles, 60–125 mL clean HDPE, one per jar.

Chemistry & stock preparation

  • Analytical balance, 0.01 g resolution. For weighing polymer (typically 1 g per stock) and verifying liquid chemical aliquots.
  • Volumetric flasks — Class A glass, 1 L, 500 mL, 100 mL. For preparing coagulant, polymer, acid and base stocks.
  • Calibrated micropipettes or graduated bulb pipettes spanning 100 µL to 10 mL. Variable-volume electronic pipettes are easiest; classical bulb pipettes work fine.
  • Magnetic stirrer and stir bars. For dissolving polymer (slow addition under shear) and homogenising acid/base dilutions.
  • 1 L amber HDPE bottles for stored stocks. Mark with date prepared — coagulant stocks degrade over weeks, polymer over days.

Reagents & consumables

  • Deionised or RO water, 5 L+ per test session. Tap water introduces alkalinity that biases acid/base demand.
  • pH calibration buffers (4.01, 7.00, 10.01).
  • Turbidity calibration standards (formazin or stabilised, traceable).
  • Polymer ageing vessel — any clean 1 L stoppered bottle. Polymer stock must age 30 min before use.
  • Disposable plastic cuvettes for visible measurements; quartz cuvettes for UV₂₅₄.

Safety

  • Lab coat, nitrile gloves, safety glasses. Concentrated coagulant and acid/base demand PPE.
  • Fume hood or well-ventilated area for concentrated acid/base dilutions. Always add concentrated acid to water — never the reverse.
  • Eye wash station accessible within 10 seconds of the bench.
  • SDS access for every chemical on the bench.

About this tool

What this tool is for

It helps you design, run, and report jar tests. There are two ways to use it:

Switch between modes with the selector at the top of the first tab — nothing you've entered is lost when you switch.

How it works (the short version)

Every mixing process — your plant's rapid mix, your plant's floc tanks, or a jar on the bench — can be described by a single number: the mixing intensity. In Plant Match mode the tool works out what that intensity is at each stage of your plant, then figures out what jar paddle speed gives the same intensity in a 1 L jar. It does the same translation for the clarifier (matching rise rate to settle time) and the filter (matching filter rate and media). In Quick Test mode the bench settings are fixed instead — simpler, and fine for comparing jars against each other.

What it can do

What it can't do

Tips that make a big difference

References

Version

v2.6.