Application of eco-friendly coagulants and pretreatment methods for reducing wastewater contaminants and improving water quality

Water pollution is a growing problem in freshwater systems in the United States of America (USA). Traditionally, chemical coagulants (such as aluminum sulfate) have been the main treatment agents; but, concerns about public health and the environment have made it necessary to seek out environmentally friendly alternatives, which has led to extensive research. This systematic review examines the different peer-reviewed studies, which studied the use of environmentally friendly coagulants and pretreatment techniques to minimize the pollutant load in wastewater systems of the USA. Plant, animal and microbial coagulants were compared to remove the turbidity, heavy metals and organic matter. The outcomes show that under optimized conditions plant derived coagulants such as Moringa oleifera, mucilage of the cactus and tannin-based extracts have the highest removal efficiency of the turbidity ranging from 75.2% to 99.8%. The removal rates of heavy metals by animal biocoagulants based on chitosan were the highest, reaching 92.1%. The use of coagulation aid pretreatment methods such as pH adjustment, rapid mixing and UV oxidation greatly improved coagulant performance. The statistical analysis of the data with SPSS version 26.0 indicated that the dose of coagulants, pH and settling time had significant interactions at p < 0.001. This review primarily focused on the possibility of using eco-friendly coagulants as a replacement or as an alternative to chemical coagulants at water treatment plants in America, and its impact on sustainability, regulatory standards, and public health.