Enzymatic Wastewater Treatment

A Biological Solution to a Growing Crisis

Water, much like air, is fundamental to all life forms. Without it, neither humans nor ecosystems can survive. The increasing global scarcity of clean water has become so acute that experts warn future conflicts may be fought not over land or oil—but over water. Unfortunately, our water bodies—rivers, lakes, seasonal streams, and ponds—are being overwhelmed with pollutants. These include industrial discharge, untreated sewage, pharmaceutical residues, chemical run-off from tanneries, and indiscriminately discarded waste. The lack of public concern and action towards this environmental degradation is nothing short of alarming.

In response to this escalating crisis, numerous technologies have emerged to treat wastewater. Physical and chemical methods such as coagulation, flocculation, and activated carbon adsorption have long been employed. Advanced techniques including reverse osmosis, ion exchange, nanofiltration, photolysis, and advanced oxidation processes have also shown promise. However, these methods tend to be costly, energy-intensive, and often impractical for large-scale or municipal deployment, limiting their use primarily to small-scale drinking water purification.

In contrast, biological approaches—particularly those involving enzymes—are gaining traction as more sustainable, cost-effective, and scalable alternatives. Enzyme-based wastewater treatment is not only easy to implement but also capable of breaking down harmful contaminants completely, transforming them into less hazardous or even biodegradable substances. One class of enzymes, oxidoreductases, stands out for its versatility. These enzymes facilitate oxidation-reduction (redox) reactions and possess broad substrate specificity, meaning they can interact with a wide variety of pollutants.

In lay terms, oxidoreductases are capable of reacting with numerous chemical compounds, breaking down their structure and transforming them into safer forms. Their ability to catalyse reactions in multiple directions—thanks to traits like regioselectivity and enantioselectivity—makes them highly effective for treating persistent organic pollutants such as industrial dyes, phenolic compounds, and other hazardous materials.

Unlike conventional chemical oxidisers that fully mineralise their target compounds, oxidative enzymes often generate free radicals. These radicals react with other molecules, forming larger, less toxic and more biodegradable compounds. This enzymatic approach to biological oxidation provides a powerful tool for removing toxins from wastewater.

Among oxidative enzymes, three major categories are typically used for environmental remediation: oxygenases, peroxidases, and polyphenol oxidases, including tyrosinases and laccases. Let’s examine how each of these plays a role in wastewater treatment.

A. Oxygenases

Oxygenases are intracellular enzymes essential for various metabolic and biosynthetic pathways. They are uniquely capable of introducing atomic or molecular oxygen into pollutant structures, transforming hydrophobic (water-repelling) molecules into more water-soluble forms. This transformation makes it easier to isolate and eliminate these pollutants from water sources.

Due to their high specificity and versatility—attributes such as stereoselectivity, enantioselectivity, and regioselectivity—oxygenases can degrade a wide range of environmental toxins. These enzymes are particularly effective in neutralising petroleum-based pollutants and other residues from fossil fuels, which are among the most persistent and damaging environmental contaminants. What sets oxygenases apart is their use of atmospheric oxygen—a universally available and eco-friendly oxidising agent—as opposed to synthetic chemical oxidants.

B. Peroxidases

Peroxidases are haem-containing enzymes (metalloproteins) found in virtually all living organisms. In plants, they protect against oxidative stress and support tissue integrity. In the context of wastewater treatment, peroxidases catalyse the breakdown of organic peroxides like hydrogen peroxide and facilitate the oxidation of toxic compounds.

Peroxidases operate by transferring electrons to pollutant molecules, effectively dismantling them into harmless byproducts. There are four principal reactions associated with peroxidase activity: oxidative halogenation, dehydrogenation, oxygen transfer, and the decomposition (disproportionation) of hydrogen peroxide. These reactions are particularly effective for treating industrial and domestic effluents containing dyes, phenols, and other aromatic substances.

C. Polyphenol Oxidases

Polyphenol oxidases (PPOs) are copper-containing enzymes known for their role in the natural browning of fruits, vegetables, and even certain wines. Commercially, they are used to enhance the flavour of beverages like coffee, cocoa, and tea. Their environmental value lies in their ability to degrade phenolic pollutants in wastewater.

PPOs achieve this by hydroxylating aromatic rings in phenolic compounds, which are then oxidised to form quinones—highly reactive molecules. These in turn polymerise or interact with other substances to form insoluble pigments, which can be easily separated from the water. PPOs are omnipresent in nature and can be further categorised into two main types used in bioremediation: tyrosinases and laccases.

Tyrosinases

These are copper-based enzymes primarily responsible for melanin production in animals and humans. In wastewater treatment, tyrosinases convert toxic phenolic compounds into non-soluble agglomerates, which are far less harmful and more manageable. However, they have some limitations: their relatively low redox potential and the instability of the resulting byproducts may allow pollutants to recombine or persist, reducing the long-term effectiveness of treatment.

Laccases

First discovered in 1883, laccases are widely distributed in fungi, plants, insects, and even bacteria. They serve many biological functions, including protection against oxidative stress and UV radiation. In wastewater treatment, laccases break down phenolic and aromatic compounds through oxidation, transforming harmful substances into less toxic forms or rendering them inert.

Their ability to work across a range of substrates, coupled with their low environmental impact, makes laccases a promising tool for large-scale water treatment initiatives.

A Greener Future Through Enzyme Innovation

Environmental pollution is a growing concern, but water and air contamination remain at the forefront of this crisis. Enzymatic treatment of wastewater offers an innovative and eco-conscious alternative to traditional chemical methods. These biological processes are not only more sustainable but also often more effective at degrading complex pollutants into non-toxic, biodegradable forms.

As the global demand for clean water intensifies, enzyme-based treatment technologies present a scalable, affordable, and environmentally responsible solution. With continued research and investment, biological oxidation using enzymes could become a cornerstone of water purification strategies—paving the way for a cleaner, healthier world.

Bioglobe offer Enzyme pollution remediation for major oil-spills, oceans and coastal waters, marinas and inland water, sewage and nitrate remediation and also agriculture and brown-field sites, globally.

For further information:
BioGlobe LTD (UK),
22 Highfield Street,
Leicester LE2 1AB
Phone: +44(0) 116 4736303| Email: info@bioglobe.co.uk