Traditionally we see water supply, pollution control, and agricultural resource management as independent problems to be solved separately. However, it is becoming more and more apparent that interconnections among cycles of water, nutrients, and carbon offer the possibility of integrated solutions. These cycles can be simultaneously exploited by management strategies that foster the multiple functions of these overlapping systems. Applying a Nexus Approach could optimize resource use to provide services for human communities, while improving ecosystem health. Properly designed and operated, constructed wetlands for the treatment of wastewater is a prime example of such a management strategy. They can provide functions that include safe sanitation in decentralized settings, shelter for biodiversity, and cleansing of polluted sites.
Globally over 80 % of wastewater worldwide is not collected or treated, and urban settlements are the main source of pollution. Urban areas are both producers and consumers of large amounts of wastewater. Wastewater management is quite advanced in large cities with centralised treatment plants. These use traditional engineering systems that required expensive construction and costly maintenance and operation. The decentralisation of small treatment plants is one solution with the potential to give access to clean water and reduce environmental pollution in rural areas. Each decentralised wastewater treatment plant (d-WWTP) can be tailor-made to suit local climatic conditions, aesthetic requirements, water quality and usage. As an example of d-WWTPs, constructed wetlands have been extensively used in sanitation and pollution control. They provide a low-cost, low-maintenance alternative to traditional wastewater treatment. The objective of this work is to develop and test a methodology for optimal design and respective criteria of constructed wetlands in order to obtain effluent quality that sustains food security producing high yields of good quality crops.