Large quantities of nutrients in aquatic environment, such as nitrates and phosphates can lead to eutrophication. Two important sources of those nutrients are wastewater effluent and untreated sewage. The contribution of nitrogen and phosphorous per person is approximately 10.8 g/day N and 2.2 g/day P. Nitrogen is one of the most important water pollutants, creating problems of toxicity to aquatic organisms in addition to environmental changes. Phosphorus can be found in various chemical forms in urban wastewater, which represents about 30‐50% of the its total discharge. Phosphorus in wastewater discharged in the aqueous natural environment leads to an excessive development of algae and, generally, to a pH increase, thus corresponding to eutrophication. It represents a significant renewable source, contributing to both agricultural and industrial development. This is the reason why it is not eliminated but recovered, in order to use it as a fertiliser. The following paragraph explains the process of eutrophication, to show the effect of nitrogen and phosphate in wastewater effluent. The high level of nutrients in the run‐off causes phytoplankton to grow and reproduce more rapidly, resulting in algal blooms. This bloom of algae disrupts normal ecosystem functioning and causes many problems. The algae may use up all the oxygen in the water, leaving none for other marine life, which results in the death of many aquatic organisms such as fish, which need the oxygen in the water to live. Since they are in the surface, this bloom of algae may also block sunlight from other photosynthetic marine plants under the water surface. Some algae even produce toxins that are harmful to higher forms of life. This can cause problems along the food chain and affect any animal that feeds on them.

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