Heavy Metals in Environment Water Sources and Wastewater in Thailand: Harm, Measurement Methods, Detected Levels, and Removal Techniques

Abstract

                       Heavy metals are widely used in industry and agriculture today. As a result, heavy metals can enter the food chain of living organisms, including humans and animals. Long-term exposure to heavy metals, even at low concentration levels, can adversely affect health, lead to disabilities, diseases, or even life-threatening conditions. Therefore, studying the sources, chemical transformations, degradation processes, accumulation patterns of heavy metals, and methods for their removal is crucial to understanding and finding ways to control these issues. The techniques used to measure the concentrations of heavy metals must employ advanced methods due to the low levels of these metals present. Additionally, the accuracy and precision of the methods must be ensured at every stage, from sampling, sample preparation, contamination removal, to the measurement methods. Each technique has its own strengths and weaknesses, depending on the application, budget, and expertise of the operator, which must be considered when selecting a removal method. Recent research has indicated that heavy metal concentrations have been measured in various locations in Thailand, including the Port of Bangkok, Laem Chabang Port, the upper Gulf of Thailand coastline, the Chao Phraya river, Tha Thapao estuary, the Tha Chin estuary, and wastewater from hospitals and industries. Heavy metal contamination has also been detected in fishing communities in Narathiwat province, with measured levels in water sources reaching mgL^-1, and several areas exceeding standard limits. For instance, at the mouth of the Tha Thapao estuary in Chumphon province in 2011, cadmium, copper, lead, and nickel were found to exceed surface water standards. Similarly, in the Tha Chin estuary and its branches (from Nakhon Chai to the Tha Chin estuary) in 2013, arsenic levels exceeded surface water quality standards, and in the Mun River area in 2017, zinc, lead, cadmium, and copper were also found to exceed standard limits.

                     Regarding methods for removing heavy metals and developing effective and environmentally friendly removal techniques, extensive studies have been conducted worldwide, including ion exchange, chemical precipitation, electrochemical processes, adsorption, reverse osmosis, solvent extraction, and membrane filtration. Given that research reports on heavy metal contamination in the environment in Thailand are still limited, it should have more encouragement for research and publication.