A review on the scope of remediating chlorinated paraffin contaminated water bodies and soils/sediments.

ABSTRACT

Chlorinated paraffins (CPs) involve a wide range of complex mixtures of chlorinated alkanes. The versatility of their physicochemical properties and their wide range of use has turned them into ubiquitous materials. This review covers the scope of remediating CP-contaminated water bodies and soil/sediments via thermal, photolytic, photocatalytic, nanoscale zero-valent iron (NZVI), microbial and plant-based remediation techniques. Thermal treatments above 800 °C can lead to almost 100 % degradation of CPs by forming chlorinated polyaromatic hydrocarbons and thus should be supported with appropriate pollution control measures leading to high operational and maintenance costs. The hydrophobic nature of CPs lowers their water solubility and reduces their subsequent photolytic degradation. However, photocatalysis can have considerably higher degradation efficiency and generates mineralized end products. The NZVI also showed promising CP removal efficiency, especially at lower pH, which is challenging to achieve during field application. CPs can also be bioremediated by introducing both naturally occurring bacteria and also by engineered bacterial strains which are capable of producing specific enzymes (like LinA2 and LinB) to catalyze CP degradation. Depending on the type of CP, bioremediation can even achieve a dechlorination efficiency of >90 %. Moreover, enhanced degradation rates can be achieved through biostimulation. Phytoremediation has also exhibited CP bioaccumulation and transformation tendencies, both at lab-scale and in field-scale studies. The future research scope can include developing more definitive analytical techniques, toxicity and risk assessment studies of CPs and their degradation products, and technoeconomic and environmental assessment of different remediation approaches.