Nitrogen and phosphorus pollution in water bodies primarily result from agricultural runoff, wastewater discharge, and industrial waste. These nutrients contribute to the increase in biochemical oxygen demand BOD levels in water bodies by promoting the growth of microorganisms, particularly algae and bacteria, which consume dissolved oxygen during their metabolic processes.When nitrogen and phosphorus are present in high concentrations, they lead to eutrophication, a process where excessive nutrients cause rapid growth of algae, also known as algal blooms. As these microorganisms grow and die, they are decomposed by aerobic bacteria, which consume dissolved oxygen in the process. This leads to a depletion of dissolved oxygen in the water, causing an increase in BOD levels. High BOD levels indicate poor water quality, as it can lead to the death of aquatic life due to oxygen depletion.To remove nitrogen and phosphorus from polluted water, several chemical and biological processes can be employed:1. Nitrification and denitrification: These are biological processes that involve the conversion of nitrogen compounds by bacteria. Nitrification is the oxidation of ammonia NH3 to nitrite NO2- and then to nitrate NO3- , carried out by nitrifying bacteria. Denitrification is the reduction of nitrate to nitrogen gas N2 by denitrifying bacteria, which is then released into the atmosphere. This process helps in removing nitrogen from water bodies.2. Phosphorus precipitation: Chemical precipitation is a common method for removing phosphorus from water. This involves the addition of metal salts, such as aluminum sulfate alum or ferric chloride, which react with dissolved phosphates to form insoluble metal phosphates. These precipitates can then be removed by sedimentation or filtration.3. Enhanced biological phosphorus removal EBPR : This is a biological process where specific bacteria, known as polyphosphate-accumulating organisms PAOs , take up and store phosphorus as polyphosphate granules within their cells. These bacteria are then separated from the treated water and removed, along with the stored phosphorus.4. Adsorption: This process involves the use of adsorbent materials, such as activated carbon or natural zeolites, which can bind and remove nitrogen and phosphorus compounds from water. The adsorbent materials can then be regenerated or replaced to maintain their effectiveness.5. Membrane filtration: Advanced filtration techniques, such as ultrafiltration, nanofiltration, and reverse osmosis, can effectively remove nitrogen and phosphorus compounds from water by passing it through a semi-permeable membrane that retains these pollutants.By employing these processes, nitrogen and phosphorus pollution can be reduced, leading to a decrease in BOD levels and an improvement in water quality.