AN INTERACTIVE FIELD GUIDE / UV + PAA
Explore the water, the chemistry, and the transformations that happen during treatment.
IN THIS FIELD GUIDE
01 START WITH THE WATER
Every drop of wastewater contains a mixture of substances. Some are pollutants that can harm ecosystems or human health, while others are dissolved organic matter (DOM), a mixture of complex, soluble organic molecules and colloids. To protect our oceans, we need to eliminate pollutants in wastewater before discharge.
Drag each sample into a bin, or select a sample and then choose a bin. Get all six right to finish.
THE SAMPLE TRAY
Choose a sample to get started.
Untreated wastewater contains both pollutants and dissolved organic matter. Pollutants must be removed before wastewater can be safely discharged to the environment.
02 A REACTIVE LITTLE REAGENT
Peracetic acid (PAA) is a powerful oxidant used in water treatment. An Advanced Oxidation Process (AOP) is a treatment method that produces highly reactive species capable of breaking down contaminants.
An atom is the basic building block of all matter in the universe. Atoms are linked together by chemical bonds (ionic, covalent) to form a compound. PAA is a covalent compound with carbon, hydrogen, and oxygen atoms linked together with covalent bonds.
PAA contains a peroxyacid group (−COOOH). Compared with ethanoic acid (CH₃COOH), PAA contains one additional oxygen atom and an oxygen-oxygen peroxide bond. This weak peroxide bond requires less energy to break and makes PAA much more reactive than ethanoic acid.
DRAG OR TAP AN ATOM INTO A BOX
CHOOSE A BOND
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Tap an atom, then tap a box to place it.
PAA differs from ethanoic acid because it contains one additional oxygen atom and a peroxide bond. This peroxide bond gives PAA stronger oxidative properties and makes it useful in wastewater treatment.
03 MAKE THE OXIDANT ACTIVE
UV/PAA treatment is an Advanced Oxidation Process. UV light supplies energy that activates PAA molecules. Activated PAA molecules break apart and generate radicals.
Radicals are highly reactive atoms or molecules that contain an unpaired electron. Because radicals are unstable, they quickly react with nearby substances, including pollutants in wastewater.
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CONTROL PANEL
Start the reactor, then drag UV photons to PAA molecules.
UV light activates PAA and generates radicals. These radicals are responsible for pollutant oxidation during UV/PAA treatment.
04 NOT EVERY RADICAL FINDS A POLLUTANT
Radicals and oxidants are limited resources. Both pollutants and dissolved organic matter can consume them. Therefore, competition occurs between DOM and pollutants, influencing treatment efficiency.
Set DOM, PAA, and UV from 0 to 100, then run the simulation. The simplified model shows how DOM competes for oxidants while PAA and UV increase their availability. Experiment to reach 80% removal.
ESTIMATED POLLUTANT REMOVAL
Adjust the sliders and run your first test.
DOM competes with pollutants for oxidants. High DOM concentrations generally reduce pollutant-removal efficiency.
05 CHANGE IS NOT THE SAME AS DISAPPEARANCE
Dissolved Organic Matter (DOM) molecules do not disapeear after reacting with radicals. Instead, they transform into other substances through oxygen addition and decarboxylation.
A model reaction turns HO–C₆H₄–COOH into C₆H₅–OH and CO₂. The carbon in CO₂ comes from the reactant’s carboxyl group. Which kind of reaction describes the loss of that group?
Select the transformation you see.
UV/PAA treatment changes DOM chemistry through oxygen addition and decarboxylation. These reactions produce new DOM structures and alter DOM composition.
06 ONE PROCESS, MANY CHANGES
Wastewater contain pollutants and dissolved organic matter (DOM). Peracetic Acid (PAA) is a strong oxidant that is used in wastewater treatment. In UV/PAA, PAA fragments into radicals, which could remove pollutants, under UV light. However, DOM could also react with radicals through oxygen addition and decarboxylation to form undesired products that might worsen the water quality. It means that DOM would compete with pollutants for the radicals, reducing the efficiency of pollutant removal.
Answer the five questions below as you scroll. Your score updates as you answer.
Choose one answer for each question.
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