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Antimicrobial approaches for safe drinking water

Access to clean and safe drinking water is essential for human survival and environmental stability. However, water contamination continues to be a major threat, particularly in India, where pollutants like heavy metals – fluoride, arsenic, and nitrate – severely impact water quality. These contaminants not only harm human health but also disrupt ecosystems, degrade soil, reduce agricultural productivity, and contribute to water scarcity. Prolonged exposure to contaminated water can result in chronic health conditions, including kidney and liver damage, neurological disorders, and various types of cancer. Waterborne diseases have plagued societies throughout history, often claiming countless lives. Illnesses such as diarrhoea, cholera, typhoid, and dysentery continue to pose serious health risks today, especially in areas lacking proper sanitation and clean water access.

To protect against these risks, ancient communities developed traditional methods of water purification. Techniques like boiling water, sand filtration, storing water in copper vessels, and exposing water to sunlight were widely used to make water safer for consumption. These practices reflect an early understanding of the need for clean water and highlight how traditional knowledge played a role in public health.

Traditional Water Purification Methods: Limitations and the Need for Advanced Solutions

Traditional Water purification methods like boiling, storing water in copper vessels, sand filtration, etc. have been used for centuries.
Boiling kills harmful microorganisms, Copper vessels add antimicrobial properties and Sand filtration removes impurities at primary level.
However, these traditional methods have their limitations. While effective in eliminating microorganisms and basic impurities, they are not capable of removing more complex contaminants like,
  • Chemical Contaminants: Industrial pollutants, agricultural chemicals, and other dissolved impurities remain in the water.
  • Toxic Elements: Dangerous substances such as Arsenic, Fluoride, Nitrates, and Pesticide residues are not removed through boiling, copper vessels, or sand
  • Microbial Contaminants: Complex microbes are resistant to heat or physical filtration.
To address these challenges, modern chemical methods are necessary. Advanced purification technologies, such as activated carbon filtration, reverse osmosis, UV systems and chemical treatment, play a crucial role in removing complex contaminants, ensuring the water is safe and pure for consumption.
As we progress, integrating traditional and modern purification methods is essential to safeguarding water quality and public health.

(I) Chlorine in Water Treatment

An Overview of Chlorine

Chlorine has been a cornerstone of municipal water treatment for over a century, playing a pivotal role in combating waterborne diseases. As a potent disinfectant, chlorine neutralises a wide array of pathogens, viruses and protozoa. Its main advantage is its ability to maintain a residual presence in water, thereby ensuring ongoing protection as the water travels through various flows (eg; pipes to homes, schools, and businesses). This property alone makes chlorine indispensable in large-scale water distribution systems.

Chlorine’s versatility extends to its forms — gas, liquid, or solid — making it adaptable to various treatment needs. Its rapid action against pathogens ensures immediate water safety during emergencies. The three most common chlorine-containing substances used in water treatment are chlorine gas, sodium hypochlorite, and calcium hypochlorite. The choice depends on cost, available storage options and on the pH conditions required.

Mechanism of Action

When chlorine is added to water, it reacts to form hypochlorous acid (HOCl) and hypochlorite ions (OCl⁻). Hypochlorous acid, the primary disinfectant, penetrates microbial cell walls, disrupting critical processes like enzyme activity and DNA replication. This biochemical interference ultimately kills the pathogens, ensuring water safety.

The Advantages of Chlorine

  • Cost-Effectiveness and Accessibility: Chlorine is relatively inexpensive and widely available, making it the go-to solution for municipalities, especially in developing
  • Broad-Spectrum Efficacy: Chlorine demonstrates broad-spectrum efficacy, successfully targeting and eliminating various pathogens, including bacteria, viruses, and protozoa.
  • Residual Disinfection: Chlorine’s residual action protects water from recontamination during distribution, ensuring safety up to the point of use.
However, the use of Chlorine also bears a few challenges –

Challenges Associated with Chlorine

  • Formation of Harmful By-Products: Chlorine reacts with organic matter to form disinfection by-products (DBPs) such as trihalomethanes (THMs) and haloacetic acids (HAAs), which are linked to health risks like cancer.
  • Taste and Odour Challenges: Chlorinated water often has an unpleasant taste and
  • Corrosive Effects: Chlorine’s corrosive nature can damage pipes and infrastructure, leading to higher maintenance costs and potential damage.

While chlorine remains the predominant choice for municipal water treatment, these challenges have led researchers and engineers to explore alternative solutions.

Among these, silver has emerged as a promising option, particularly for specialized applications where chlorine’s limitations are most problematic.

(II) Silver as an Agent in Water Treatment

Overview of Silver

Silver’s use in water purification dates back centuries. Today, silver is emerging as a modern alternative for water disinfection due to its ability to eliminate microorganisms effectively without forming harmful by-products. Silver is extremely adaptable, especially in niche applications like hospitals and spacecraft, where ultra-pure water is critical.

Mechanism of Action

Silver ions (Ag⁺) exert their antimicrobial effect through several mechanisms. They bind to microbial proteins and nucleic acids, disrupting essential cellular functions like respiration and DNA replication. This interference ultimately kills the microorganisms.

Silver ions maintain their antimicrobial activity even after binding with bacterial proteins, making them highly efficient. Moreover, the unique properties of silver ions enable them to regenerate. Silver ions are effective even at low concentrations, such as 60 parts per billion (ppb). Silver can eliminate 99.99% of bacteria like Pseudomonas aeruginosa upon contact, demonstrating its potency and reliability

The Advantages of Silver

  • Zero Toxic Residue: Unlike chlorine, silver does not react with organic matter to produce toxic by-products, ensuring a safer and more environmentally friendly disinfection process.
  • Efficacy: Silver ions achieve potent antibacterial results at remarkably low concentrations, as low as 60 ppb.
  • Long-Lasting Antimicrobial Activity: Silver’s ability to regenerate and remain effective over time reduces the need for frequent application.

Some Challenges Associated with Silver

  • Higher Cost: Silver is significantly more expensive than chlorine, limiting its use in large-scale municipal systems.
  • Environmental Impact: High concentrations of silver can be toxic to aquatic life if
  • Aquatic Toxicity: Silver contamination in water bodies may pose a risk to

Conclusion

Advanced Chemical treatments are more impactful than traditional methods, offering a level of effectiveness and scalability that is hard to achieve with manual or physical approaches like filtration or boiling.
Chlorination continues to dominate municipal water treatment due to its affordability and broad-spectrum efficacy. However, its limitations, such as DBP formation and taste issues, highlight the need for safer alternatives, like silver.
It offers a promising option for niche applications, particularly where environmental sustainability and taste are priorities.

The choice between chlorine and silver hinges on factors like cost, scale, and public health priorities, ensuring consistent and large-scale disinfection. NICHEM has been working in the drinking water purification segment for more than 10 years to develop niche products.

References:

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