Now that we’ve covered how to select the right polyacrylamide — the molecular weight, charge density, and ion type decisions that make or break your treatment program — the next critical step is making sure you’re dosing it correctly. And that’s exactly what jar testing is for.
I’ve worked with operators who treat jar testing like an optional extra, something the chemical vendor does once during startup and then nobody thinks about again. That’s a mistake that costs real money. Water chemistry in the Permian changes constantly — new zones coming online, blending ratios shifting, seasonal temperature swings, saltier production as fields mature. The PAM program that worked perfectly six months ago might be underperforming today, and without jar testing, you’ll never know why.
Think of jar testing as your cheapest insurance policy. A few hours of bench work can save weeks of troubleshooting and thousands of dollars in chemical waste, disposal costs, and equipment downtime.
What You Need Before You Start
You don’t need a laboratory to run a proper jar test. Most of what you need is either already on-site or inexpensive to source. Here’s the basic kit:
- Six-paddle jar test apparatus (a standard flocculator unit with variable RPM)
- 1-liter or 2-liter graduated beakers — at least four, preferably six
- Stopwatch or timer
- Turbidimeter or Imhoff settling cones (turbidimeter is better if you have access to one)
- Fresh water samples from your actual process stream
- Stock polymer solutions of each candidate PAM at 0.1–0.5% concentration
- Adjustable micropipettes or graduated syringes for accurate dosing
- pH meter and basic water quality test kit (TDS/conductivity meter helps too)
- A notebook — write everything down
[Suggested image: Jar test setup with beakers, paddle flocculator, and turbidimeter on a field workbench]
Alt text: Complete jar test setup for polyacrylamide dosing optimization in Permian Basin produced water treatment
The most important item on that list is the water sample itself. I’ll say it plainly: if your sample isn’t representative, your results aren’t worth the time you spent on them.
Collecting a Representative Sample — Don’t Skip This Part
Permian produced water and flowback are not consistent streams. Solids settle, oil stratifies, and chemistry varies throughout the day depending on what’s coming in from the field. I’ve seen operators pull a jar test sample from a quiet corner of a storage tank and wonder why their bench results never matched what happened in the clarifier. The clarifier is seeing a completely different water.
Collect your sample as close to your actual dosing point as possible, from a flowing line or an actively mixed vessel. Collect it in a clean, capped container and run your test within 30–60 minutes. Temperature matters — a sample that’s cooled down significantly from process temperature will give you slower settling times and can skew your dosage results. If your process water is running at 90–100°F, try to run the jar test at a similar temperature.
The Step-by-Step Jar Test Procedure
This is the sequence I’ve used for years, and it works whether you’re optimizing for a clarifier, a DAF unit, or a filter press feed program.
- Fill your beakers with equal volumes of representative water sample — typically 1 liter each. Label them clearly (Blank, Dose 1, Dose 2, Dose 3, Dose 4, Dose 5).
- Measure baseline water quality on each beaker: record pH, temperature, TDS/conductivity, and initial turbidity or Imhoff cone reading. This is your baseline — don’t skip it.
- Set your mixing speed to simulate rapid mix conditions — typically 100–150 RPM. This replicates the energy input at your inline mixer or pipe flocculator.
- Dose your polymer into each beaker at increasing concentrations. A typical Permian starting range might be 2 mg/L, 4 mg/L, 6 mg/L, 8 mg/L, and 10 mg/L. Adjust your range based on prior knowledge of your water.
- Rapid mix for 60–90 seconds — this simulates contact time at the dosing point.
- Drop to slow mix speed — 20–30 RPM — and continue mixing for 10–15 minutes. This is your flocculation phase. Watch what’s happening in each beaker. Note when floc first appears, how large it grows, and whether it’s staying cohesive or breaking apart.
- Stop mixing completely and let all beakers settle for 10–15 minutes undisturbed. Watch settling velocity — how fast does the clear/cloudy interface drop?
- Measure final turbidity or record Imhoff cone settled solids volume on each beaker. Compare to your baseline.
- Record everything — dose, floc appearance, settling rate, final turbidity, and anything unusual you noticed.
[Suggested image: Before and after jar test flocculation showing clear supernatant vs. untreated turbid sample]
Alt text: Jar test results showing flocculation before and after optimal polyacrylamide dosing in Permian produced water
How to Read What You’re Seeing
Here’s a simple guide to interpreting your results:
| What You Observe | What It Likely Means |
|---|---|
| Small, weak, slow-settling floc | Underdosing — increase polymer concentration or try higher MW |
| Large, fast-settling floc, clear supernatant | Good range — this is your target |
| Fluffy floc that breaks apart during slow mix | Too much shear or MW too high for your conditions |
| Turbid supernatant even at high doses | Wrong ion type, or need coagulant pre-treatment |
| Good floc forms then restabilizes (turbidity increases) | Overdosing — charge reversal, back off the dose |
| No floc formation across all doses | Significant chemistry mismatch — reassess PAM type entirely |
That last row — no floc formation — is something I’ve walked into at a facility that was using a high-charge-density anionic product on very-high-TDS brine. The salt was essentially neutralizing the polymer activity before it could do anything. Switching to a low charge density product and adding a coagulant pre-step fixed it within a day.
Common Mistakes That Throw Off Your Results
Mixing speed errors are probably the most common. Running your rapid mix too fast shears apart the floc as it’s forming and makes every product look like it’s underperforming. Too slow and you don’t get adequate polymer distribution. Match your RPM to what’s actually happening in your process — if you’re not sure, 120 RPM rapid mix and 25 RPM slow mix is a reasonable middle-ground starting point for most Permian applications.
Not waiting long enough during the settling phase is another one. Operators get impatient, read results at three minutes, and miss the fact that one of the doses would have produced excellent clarity at twelve minutes. Slow settling isn’t always a failure — it might just mean you need a longer retention time in your clarifier.
Ignoring temperature is a bigger deal than most people realize. Cold water increases viscosity, slows polymer hydration, and significantly reduces settling rates. If your facility runs in winter conditions, test at winter temperatures. I’ve seen facilities optimize their summer program perfectly and then struggle all through December and January wondering why performance dropped. The chemistry didn’t change — the temperature did.
Using old or improperly stored polymer stock for your test solutions will also give you bad data. PAM degrades in solution over time, and heat accelerates that. Make fresh stock solutions for each testing session.
Scaling Jar Test Results to Full-Scale Operations
Jar test results don’t translate directly to your full-scale dosage — there’s always a scaling factor involved, and it varies by equipment type.
For clarifiers and settling tanks, bench-scale optimal dose typically scales up by a factor of 1.0–1.3x, depending on your mixing energy and contact time in the full-scale unit. For filter presses and belt presses, expect to run somewhat higher doses in the field because the dewatering demand is greater than what a settling jar test captures — the bench test gives you direction, not an exact number.
For centrifuges, jar testing is still useful for product selection and rough dosage direction, but you really need piloting or direct optimization on the centrifuge itself, because the high shear environment is very different from what a beaker can replicate.
The other thing worth remembering: run jar tests regularly, not just at startup. Quarterly is a minimum in my book, and more frequently when you’re onboarding new source water, changing blending ratios, or adding new well pads to the system.
What Proper Jar Testing Actually Gets You
When you take jar testing seriously, the results show up fast and they show up where it matters — lower chemical spend, cleaner effluent, drier dewatered cake, and operators who aren’t constantly chasing performance problems they can’t explain. That directly connects back to what we talked about in the Real Operator Cost Savings with Optimized Polyacrylamide in the Permian Basin 2026 article: optimized PAM programs in the Permian Basin aren’t magic, they’re just disciplined chemistry management. Jar testing is how you stay disciplined as your water keeps changing.
Get the bench work right, and the full-scale program takes care of itself. (For more on selecting the right polymer before you even start testing, see our recent post on the Polyacrylamide Selection Guide.)