PCBs Polychlorinated Biphenyls

For their toxicity to humans and the environment and for their exceptional stability to chemical attack, polychlorinated biphenyls (PCBs) are very dangerous for living organisms. The pollution from PCBs is particularly alarming when it concerns agricultural areas. The PCBs, in fact, can reach humans through the food chain. The biological treatment (bioremediation) for the removal of PCBs from contaminated matrices represents the only possible way in terms of environmental and economic sustainability to solve diffused contamination of these hazardous chemicals.

Polychlorinated biphenyls (PCBs) represent a class of chlorine substituted aromatic compounds that have been heavily employed in various industrial sectors  especially  during the  ’60-’70. Today  their industrial synthesis is banned in most western countries because of their toxicity to humans and the environment. PCBs are highly persistent in the environment and  today vast areas near former production sites are still polluted. PCBs contamination results particularly alarming when impacting agricultural soil, since they effectively enter the food chain.

PCBs exist in 209 congeners, classified based on the number and relative position of the chlorine atoms on the biphenyls. 12 of these  209 molecules (which are coplanar) are characterized by a toxicity compared to that of dioxins and are defined dioxine-like PCBs.  These have serious  effects on human’s health, such as immune and endocrine system disruption, interference with fetal development , acute and chronic toxicity, carcinogenicity.

PCBs concentrate in soil and sediment but can also adsorb to small organic and mineral particles, therefore traveling far from the initial contamination site, carried by wind and water. Because they are so persistent and lipophilic, PCBs tend to accumulate in animals and human tissues.

Remediation System

Environmental remediation relying on biological degradation of PCBs is an efficient and cost-effective treatment.
The  standard design for an effective detoxification consists of the following steps:
– site characterization
– laboratory microcosm test
– field application

The laboratory test is the key step as it identifies the biological, chemical and physical conditions necessary for the degradation of the contaminants and is necessary for the formulation of the detoxifying solution later applied on field.

Soil Remediation

We have investigated the bioremediation approach for PCB in a project LIFE FreePCB, funded by the European Union and realized in collaboration with ARPA Lombardia (2003 – 2006). In this study we showed that  soil amendment with certain biological surfactants  were effective in the PCB degradation.

Recently, Biosearch Ambiente, in collaboration with the  University of Naples “Federico II”,  has developed a novel technique for the remediation of PCBs in soil,  consisting of two basic steps:

  1. an on site washing process of the polluted soil with a solution containing surfactants of natural origin, in particular humic acids.
  2. the stimulation of the autochtonus microbial community for the complete removal of PCB from the soil.

The first step allows the  PCB solubilization via the formation of complexes with the surfactants, thus removing the contaminant adsorbed to soil. This makes the PCB molecules readily available for microbial degradation. Advantages of this approach are:

  • a fast remediation time, with pollutant removed within 6-24 months
  • on-site operation (no soil is removed), therefore containing costs
  • versatility of the application: from emergency response to full-scale remediation

Biological Process

BioSoilWashing – Application of a natural surfactant solution to displace  the pollutants from the matrix, followed by the degradation of the PCB molecules operated by naturally occurring microorganisms.

Remediation System

On-site soil washing.

Treatment Time

6-24 months

Intervention Context

MISE, MISO, Full Remediation

case study