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Micropollutants in Water
By Shawna Nemesia Rebello

Micropollutants are low concentration substances that are not naturally present in the environment. Composed of various materials such as pesticides, pharmaceuticals, cosmetics, flame retardants, perfumes, waterproofing agents, plasticisers and insulating foams, micropollutants are usually organic contaminants that are slowly released into the environment through wastewater from industry, households, or agriculture. Although they may be partly degraded in treatment plants or in water bodies, conventional water treatment methods are not capable of handling complex soluble organic chemicals. Thus, micropollutants spread throughout the water ecosystem, where they persist and keep accumulating. The most frequently detected micropollutants in water are pharmaceuticals and endocrine disrupting chemicals. Given the myriad of micropollutants, barely any of them are required to have their concentrations in water regulated by law.

Sources and environmental pathways of micro-pollutants


Impacts
After being taken up by organisms via contaminated water or food, micropollutants are transported to different tissues. They exert toxic effects through the following three modes:
  • Disruption of the structure/ function of biological membranes
  • Interference through binding with specific receptors on cells
  • Reaction with nucleic acids and proteins

Routine ingestion of micropollutants can lead to severe health problems such as mutagenicity, estrogenicity, and genototoxicity in humans as well as other organisms, which can in turn disrupt biological cycles. An example is the feminisation of male fish, caused due to the fish population being exposed to Endocrine Disrupting Compounds (EDCs).

Even when released at low levels, the continuous discharge of EDCs into the environment may cause reproductive and development abnormalities in highly sensitive species.

Another major impact is the continuous release and bioaccumulation of antibiotics in the environment. Due to the extensive use of stronger antibiotics for curing seemingly common illnesses, levels of these antibiotics in wastewater have increased over the past few decades. This in turn causes microorganisms to develop a resistance against the antibiotics, which then leads to diseases that become harder to cure. The lower stock of antibiotics and even their cost exacerbates the problem in developing and under developed nations.

Micropollutant Group Example Compound Main Adverse Effect
Pharmaceuticals - antibiotics Ciprofloxacin Bacterial resistance
Additives for enhancing growth of livestock Arsenic roxarsone Toxic,Carcinogenic
Personal care products – antimicrobials in cosmetics Triclosan Endocrine disruption , Persistent degradation products
Biocides - insecticides Carbaryl Toxic
Industrial chemicals - incineration products Dioxins Endocrine disruption , Mutagenic,Carcinogenic

Mitigation

Use of environmentally friendly manufacturing methods incorporating non-hazardous ingredients and substances with good biodegradability, and legislation for regulating product use are source control measures which prevent micropollutant release into the environment. Removal of micropollutants from discharge streams however, requires treatment facilities to be upgraded so as to employ advanced water treatment methods – such as filtration and reverse osmosis membrane processes, activated carbon and ozonation. Future removal methods include direct photolysis, electrochemical treatment and use of Fenton reactions.

Treatment Technique Mode of Micropollutant Removal
Membrane processes As water flows under a driving force through porous media, particle micropollutants are selectively retained
Activated carbon Micropollutants adhere to granular surfaces or become trapped in pores while passing through activated carbon filters
Ozonation Ozone forms radicals in water which cause the breakdown of micropollutants, thereby making them more susceptible to biological degradation
Photolysis Micropollutant breaks down on absorption of particular wavelengths of light
Electrochemical methodsI Radicals formed at electrodes cause the mineralisation of micropollutants into less harmful compound
Fenton reactions Micropollutants are mineralised at room temperature and atmospheric pressure through radicals generated in reactions of hydrogen peroxide in the presence of iron

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