Heavy metal contamination in groundwater: sources and sustainable remediation approaches: a review

Groundwater has become a significant source of water for many countries. However, contamination by heavy metals has emerged as a serious global environmental issue, posing a threat to human health. Metals such as arsenic, lead, cadmium, and mercury are among the most prevalent toxins detected in groundwater, largely due to industrial activities and the effects of climate change. Heavy metals are toxic, mutagenic, carcinogenic, and prone to bioaccumulation in biological systems. Even at low exposure levels, they can damage various organs, including the nervous, cardiovascular, immune, and reproductive systems. Recent years have seen increased efforts to develop effective remediation methods. While some techniques can successfully remove heavy metal contaminants, their high operational costs may restrict their practical use. Numerous reviews have been published on the sources, toxicity, and remediation strategies for addressing heavy metal contamination in groundwater. Organic chelators like citric acid and EDTA in groundwater form complexes with heavy metals, making their removal difficult with conventional methods. Advanced oxidation processes (AOPs) are regarded as effective for decontaminating these heavy metal complexes. This review explores the sources of heavy metal contamination in groundwater, assessing their health risks and environmental impacts while highlighting recent advancements in low-cost, sustainable remediation strategies. It evaluates on-site and off-site approaches, including adsorption, ion exchange, membrane technologies, permeable reactive barriers, bioremediation, and AOPs, both as standalone and combined methods, discussing their benefits and limitations. The review also identifies research gaps, addresses current challenges, and proposes sustainable solutions for mitigating groundwater contamination.