Surface Water Nitrogen Load Due to Food Production-Supply System in South Asian Megacities: A Model-based Estimation

Food production and supply system contributed more than 90% of the nitrogen originated in south
Asian megacities that pollute the surface water. Five megacities of three South Asian countries were
considered in this study. These countries are developing and their population is increasing
tremendously. All the five megacities are very densely urbanized. A numerical model has been used
to calculate the anthropogenic nitrogen load on the environment. FAO statistics on fertilizer
consumption and food balance data sheet has been used to calculate the nitrogen load. Human waste
plays the vital role in nitrogen production of south Asian megacities. So, in these contexts the nitrogen
load for all the study areas extremely harmful for environment and ever increasing population also
increased the load of nitrogen on surface water produced from human waste which also very awful for
the environment. So, a proper sewage treatment facility is compulsory for all the study areas. Four
findings has been identified are; (1) for all three countries, rice and wheat production-supply produce
the maximum amount of nitrogen. (2) Though the amount of nitrogen due to fertilizer input more or
less same among the countries but amount of produced nitrogen due to human waste is huge in
Bangladesh. (3) Moreover, in city scale, the amount of nitrogen due to fertilizer input is maximum in
Delhi city and negligible in Kolkata due to an insignificant amount of farmland. (4) Interestingly, the
maximum amount of nitrogen load in surface water is in Kolkata city due to human waste but Mumbai
and Dhaka shows a medium amount of nitrogen load. This can give the estimation for city wise
untreated nitrate content and this is necessary for the capacity development of existing sewerage
treatment plant as well as the establishment of new plants.