Plastic pollution and degradation pathways: A review on the treatment technologies

Abstract

In recent years, the production of plastic has been estimated to reach 300 million tonnes, and nearly the same amount has been dumped into the waters. This waste material causes long-term damage to the ecosystem, economic sectors, and aquatic environments. Fragmentation of plastics to microplastics has been detected in the world's oceans, which causes a serious global impact. It is found that most of this debris ends up in water environments. Hence, this research aims to review the microbial degradation of microplastic, especially in water bodies and coastal areas. Aerobic bacteria will oxidize and decompose the microplastic from this environment to produce nutrients. Furthermore, plants such as microalgae can employ this nutrient as an energy source, which is the byproduct of microplastic. This paper highlights the reduction of plastics in the environment, typically by ultraviolet reduction, mechanical abrasion processes, and utilization by microorganisms and microalgae. Further discussion on the utilization of microplastics in the current technologies comprised of mechanical, chemical, and biological methods focusing more on the microalgae and microbial pathways via fuel cells has been elaborated. It can be denoted in the fuel cell system, the microalgae are placed in the bio-cathode section, and the anode chamber consists of the colony of microorganisms. Hence, electric current from the fuel cell can be generated to produce clean energy. Thus, the investigation on the emerging technologies via fuel cell systems and the potential use of microplastic pollutants for consumption has been discussed in the paper. The biochemical changes of microplastic and the interaction of microalgae and bacteria towards the degradation pathways of microplastic are also being observed in this review.

Keywords: Degradation; Microalgae; Microbial fuel cell; Microplastic.

Graphical abstract

Fig. 1

The degradation pathway of plastic to microplastic in nature [34,44,45].

Fig. 2

The degradation pathway of plastic to microplastic by microorganisms [53,54].

Fig. 3

Example of schematic design of single chamber microbial fuel cell [104].

Fig. 4

Example of schematic design of dual chamber microbial fuel cell [109].

Fig. 5

Illustration for dual chamber MFC separated by Proton Exchange Membrane (PEM).