Introduction

Polychlorinated Biphenyls (PCBs) are synthetic industrial compounds which have been banned in many countries due to their toxic nature, persistence in the environment and bioaccumulation in the food chain. PCBs enter the environment through various sources such as waste water discharges from industries and landfills, and can contaminate water bodies. Water treatment plants are responsible for ensuring that potable water is safe for consumption, however, they face the challenge of removing PCBs from water.

Properties of PCBs

PCBs are highly stable, lipophilic and hydrophobic compounds. They are resistant to breakdown by heat, water, air and most chemical reactions. They can dissolve in organic solvents and accumulate in the fatty tissues of living organisms. These properties make it difficult to remove PCBs from water using traditional water treatment methods.

Water treatment methods

Water treatment plants use a combination of physical, chemical and biological processes to remove contaminants from water. These methods include coagulation and flocculation, sedimentation and filtration, disinfection and activated carbon adsorption. While these methods are effective in removing many contaminants from water, they have limited ability to remove PCBs.

Activated carbon adsorption

Activated carbon is a commonly used adsorbent in water treatment plants due to its ability to remove organic compounds from water. PCBs are adsorbed onto the surface of the activated carbon, however, the adsorption capacity is limited by the hydrophobic nature of PCBs. Additionally, the effectiveness of activated carbon adsorption is reduced in the presence of other organic compounds, such as humic acids, which compete for adsorption sites on the activated carbon.

Biological processes

Biological processes such as biodegradation and bioremediation have been used to remove PCBs from the environment. These processes involve the use of microorganisms which can break down PCBs into less toxic compounds. However, these processes are slow and require specific environmental conditions to be effective. Additionally, the presence of other contaminants can inhibit the effectiveness of biological processes.

Conclusion

Water treatment plants face the challenge of removing PCBs from water due to their unique properties. While traditional water treatment methods can remove many contaminants from water, they have limited ability to remove PCBs. Activated carbon adsorption and biological processes have been used to remove PCBs from water, but their effectiveness is limited by the hydrophobic nature of PCBs and the presence of other contaminants. Further research is needed to develop more effective methods for removing PCBs from water and protecting public health.