Wastewater generation is a current environmental and public health problem. Some international organizations point out that 80% of the wastewater produced worldwide does not receive an adequate treatment (UNESCO, 2014). In Latin America the picture is similar, since it is estimated that 70% of wastewater is returned to rivers without prior treatment (Yee-Batista, 2013). In Ecuador, the volume of water consumed is close to 414,000,173 m3/year and the total volume of wastewater that receives treatment corresponds to 61,928,393 m3/year corresponding to 15%. It is worth mentioning that 75% of the treated water in Ecuador comes from the urban area (INEC, 2013).
Artificial wetlands have proven to be a good alternative to remove organic matter and dangerous substances present in wastewater. These natural systems act as ecological reactors that retain suspended solids and favor biological and physicochemical processes that produce the elimination of nitrogen and phosphorus (López, 2016)
Two wetlands were built on a laboratory scale, consisting of a one series system. Each system consisted of a VFAW and an HFAW. The dimensions of the wetland were 0.4 m in length, 0.2 m in width, and 0.2 m in height. Concrete with a diameter of ¾ to 1 inch was used as support medium, occupying a height of 15 cm.
The hybrid wetland system was divided into two stages: The first stage was a system with oxygenation under conditions of a vertical subsurface flow wetland, with a retention time of 3 days. The second stage was made up of a horizontal subsurface flow wetland with a retention time of 4 days.
Each wetland has two individuals of Canna indica and two individuals of Racinaea fraseri. The vertical wetland was fed with 3.5 liters of wastewater, that is, to a height of approximately 0.10 m. After 3 days, the water was removed from the VFAW with the help of plastic garden faucets and the resulting effluent was fed to the HFAW. In addition, the two wetlands were lined with a black plastic sheath to prevent light from entering the concrete and thus prevent the proliferation of harmful algae
The design of hybrid subsurface-flow artificial wetlands with the species Canna indica and Racinaea fraseri reduces the contamination of domestic wastewater
Based on the analyzes carried out in the pilot system of the artificial hybrid wetland, the removal of COD had an efficiency of 81.80%, that of suspended solids of 69.95% and that of phosphates of 95.17%, and a decrease in nitrates and ammoniacal nitrogen obtaining values that are within the current environmental regulations for the discharge of fresh and marine water.
The practical application of the pilot system with wastewater from the Universidad de las Américas presented similar efficiencies to those applied with synthetic wastewater; hence, it would be feasible to use these unconventional systems in rural areas.
The water treated with this technology can be used again in irrigation activities for tall-stem, ornamental plants.
Concrete can be considered as an alternative to use it as a support material in subsurface wetlands, since it is a residue that can be reused and has a high phosphate adsorption capacity.
Finally, artificial wetlands with concrete support medium and Canna indica and Racinaea fraseri plants can be used in rural areas due to their low investment costs of 59.73 USD/inhab and operating costs of 23.86 USD/inhab.year.
Project videoThis is how I came up with the idea for this project:
My inspiration to develop this project was born in the Yahuarcocha lagoon, located in the same province of Imbabura, since it is in an environmental emergency due to the wastewater problematic. Therefore, the search for suitable and adaptable alternatives for rural areas is a priority.