| Summary: | Even though heavy metals are naturally occurring compounds, in recent years, anthropogenic activities have introduced them in excessive quantities to different environmental matrices, imposing severe threats to the ecosystem. This chapter is focused on the occurrence of heavy metals in Malaysia, reviewing their potential sources, their existence in water, sediment, and aquatic life. However, despite the contents of heavy metals found in water, sediment, and aquatic life, they remain within the permissible limit. Heavy metals are known to be nondegradable and hence can lead to bioaccumulation in humans or animals. Avoiding heavy metals from entering the environment is, therefore, critical. From the literature survey undertaken in this chapter, it appears that the leading cause of heavy metal pollution in rivers is from industrial establishments and perhaps from the inadequate treatment of heavy metal–polluted wastewater discharging into rivers. Therefore treating wastewater is essential to ensure that no heavy metal ions are released into the environment. In undertaking this initiative the initial step is by having a proper detection device such as having sensors that can monitor the concentration of different types of heavy metal ions found in wastewater. Among the various technologies that are available, sensors utilizing nanostructured transition metal oxide are seen as an effective technique for the detection of various metal ions. The removal of heavy metal ions from wastewater can be accomplished in several ways of which metal oxide has been used for removal purposes. Clay and traditional oxides have also been used as an effective absorbent for highly concentrated heavy metal ions in wastewater, whereas nanostructured metal oxide semiconductors can be used to absorb and reduce the minute amount of heavy metal ions via photocatalysis process. © 2020 Elsevier Inc. All rights reserved.
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