Waste Becomes a Solution, Biochar from Activated Sludge Tackles Antibiotic Pollution

Antibiotics are lifesavers in fighting infectious diseases. But who would have thought that antibiotic waste is now becoming a new threat to the environment? One of the most commonly used antibiotics, tetracycline (TC), often does not fully break down in the human body. As a result, up to 90% of its residue is excreted through urine and feces, ending up in sewage systems and eventually leaking into the environment.

Antibiotics that escape wastewater treatment plants can contaminate rivers, soil, and even the food chain. This leads to ecosystem disruption, the emergence of super-resistant bacteria, and ultimately, risks to human health.

Turning Waste into a Filter: Solving Two Problems at Once

Imagine if activated sludge from wastewater treatment plants could be transformed into a pollutant-absorbing material. In other words, waste being used to tackle waste. That’s the idea behind biochar technology from activated sludge.

Through a process of heating without oxygen (pyrolysis), sludge is converted into a special type of charcoal called sludge biochar. However, regular biochar still has a weakness: its ability to adsorb antibiotics remains relatively low.

KOH: The Key to Boosting Biochar’s Absorption

Researchers have tested various methods to enhance biochar’s ability to capture tetracycline—from acids and oxidants to alkaline treatments. The winner? Potassium hydroxide (KOH).

So, what makes KOH-modified biochar (biochar-KOH) so powerful?

• More porous → larger surface area to trap pollutants

• More oxygen-based functional groups → makes bonding with tetracycline easier

• π-π interactions → helps bind with the aromatic ring structures of antibiotics

Impressive Numbers

• Biochar-KOH can adsorb up to 243.3 mg of tetracycline per gram at 25°C—over six times more effective than regular biochar!

• Still efficient even after 3 reuse cycles, losing only about 6% of its capacity

• 4.5 times stronger than regular biochar even after repeated use

• Works well even with the presence of ions like Cl⁻, NO₃⁻, and SO₄²⁻

• Slight performance drop with ions such as HCO₃⁻, PO₄³⁻, Ca²⁺, and Mg²⁺—something to consider depending on water conditions

How Does Biochar Capture Tetracycline?

Several mechanisms are at play:

• Ion exchange: swapping charges with pollutants

• Hydrogen bonding: pulling water molecules and pollutants to the surface

• Pore filling: trapping tetracycline inside tiny pores

• Electrostatic forces and π-π interactions: like magnets, but for molecules

A New Hope for Clean Water

By turning waste into a solution, this technology tackles two issues at once: managing activated sludge waste and removing antibiotic pollution from water. It is eco-friendly, efficient, and scalable without creating new contamination.

Imagine if all 90 million tons of activated sludge generated globally each year could be turned into antibiotic-absorbing biochar. Not only would wastewater become cleaner, but the problem of sludge buildup would also shrink.

With KOH-modified biochar, the future of wastewater treatment looks brighter—and cleaner.

Discover more about SAWA’s Innovative Biochar production and its impact on sustainable farming.

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