MATRIX jar testing for chemical dosing optimisation.
Our Sectret Weapon
I’ve been optimising water treatment plants for 15 years… Usually with cracked beakers, on a flooded floor, surrounded by slippery polymer and the deafenning sound of jack hammers. Often in the pouring rain too as when you work in construction dewatering, you usually get the call out when the rains have flooded a site.
The best water treatment plants in the world can still be susceptible to a change in feed water, a worker that did an acid-wash upstream throwing pH out of whack, or the 5th 1 in 100 year rain event that happened that year (those statistics need updating for sure). If we had unlimeted budgets, there are many things I would do to help such as:
Large flow balance tanks to buffer abnormal inflows
Additional instrumentation such as turbidity and pH probes to add brains to your dosing system
A streaming current detector for automatic coagulant dosing and a floc analyser for automatic polymer dosing (I’ll try convince you to install these in a separate blog… it needs more explaining)
But when the above doesn’t happen, and your plant is dealing with new feed water, your operators are stuck turning to their only tool. Jar testing…
This is a nice jar-test setup
In a lab… Roof… Warm… Calibrated equipment… Maybe some music and coffee.
This is the field jar testing reality….
Rain. Cold. Mud. Manual equipment.
The problem is this. When your operater decides to do a field jar test to set their dose rate they will encounter the following problems:
They messed up their dilutions or they just werent accurate
Their beakers had slightly different levels of sample
Their mixing was nothing like the mixing in the process and it changed between their samples
They are using droppers/syringes and they aren’t very accurate or the operator didnt count the drops or see the level right
The timing they are using for their tests is slightly different
The sample has been sitting in bucket, collected half hour ago. Its paritially settled and needs stirring up. Its also been oxidising and the pH is changing too.
Even if you don’t have ANY of the issues above…. you are still relying on:
The dose you select being put into the settings correctly (did the commissioning engineer put the right density and concentration in? has that changed since commissioning? Is there a slightly different coagulant in your tanks?)
The dosing pump may not be calibrated and isn’t delivering the volumes you think it is.
The dosing line may be fully or partially blocked and you just aren’t getting the chemical dose you think you are
My MATRIX JAR TEST solves ALL of that.
Heres how it works:
Ensure your process has a sample point after coagulant/polymer/mixing.
Get say 12 small jars and label them.
Make a matrix dosing plan (I’ll show you one below). You will have tests 1 ot 12.
Run your process. Set your dosage to test 1. Take sample 1. (you can change settings to dose 2 after sampling).
Take a photo (on a white background) after 1 minute (or ideally your clarifiers “minimum effective” settling time)
Repeat the process 12 times. It probably takes 1 minute each test. You will be done in 12-15 minutes!
Now just compare your photo’s and the beakers. Pick the sample that worked best in your process and set your dosages accordingly! You CAN’T GO WRONG!
No operator error. No engineer error. No programming error. The process is doing exactly what you are seeing in your sample.
Matrix Jar Test Samples
Ok..ok… I didn’t label my beakers… and there is no white background. But I’ve been doing this for 15 years. I can smell the right one!
Some closing notes:
Water chemistry is complex. There is so much at play. Contaminants, concentrations, temperature, alkalinity, pH, mixing, timing, polymer age/degredation….
Sometimes the visual results don’t always present an obvious answer. “Lots of flock” doesn’t mean best supernatant. Sometimes extra flock is just extra coagulant/polymer and you are wasting money and producing extra sludge you will need to filter or dewater.
Sometimes (always?) an expert is cheaper in the long run. Let us visit and show you. We service Australia-wide, contact us below.
Here is an example of your matrix sheet. Typically you want to start with far-apart dosages when you start commissioning so you don’t miss the “sweet spot”.
Then narrow them down or use fewer rows/colums as you start getting a feel for your process.
Good luck and don’t hesitate to reach out if you need some assistance with chemicals / calculations or more.
Guardian Water Example Matrix Jar Test Sheet
Blank Matrix Jar Test Sheet