Constructed wetlands use plants, microorganisms, and substrates to remove pollutants like organic compounds, nitrogen, and phosphorus. Organic pollutants are broken down by plants and microorganisms. Nitrogen is removed by plants, substrate adsorption, and microbial processes. Phosphorus is taken up by plants and adsorbed by substrates. Factors like oxygen levels and plant presence affect pollutant removal rates. Constructed wetlands are commonly used for treating industrial wastewater and sewage, but they can also be used for eutrophic water treatment and water resource protection.