Treated wastewater application in urban agriculture
Ahmed Al-Busaidi1*, Mushtaque Ahmed1, Wenresti Gallardo2, Waad Al-Aghbari1
1Department of Soils, Water and Agricultural Engineering, Sultan Qaboos University,
2Department of Marine Science and Fisheries, College of Agricultural & Marine Sciences, P.O. Box 34, Al-Khoud 123, Muscat, Oman
https://doi.org/10.5004/700007
ABSTRACT
Waste management is one of the most crucial challenges for the governments to control the worst impacts in terms of public health, environmental resources (water and food) and climate change. Therefore, in order to achieve Sustainable Development Goal (SDG) 12, water deficit countries need to look for innovative and sustainable production of food using integrated circular approach (reduce, reuse, recycle) in modern agriculture such as hydroponic and aquaponics systems. Circulating water in a close hydroponic system with fish and vegetable production (aquaponics system) using treated wastewater will contribute to sustainable consumption and production (SCP) in the region. Therefore, the objective of the study was to evaluate the effect of tertiary treated wastewater on plant growth and production using aquaponics system. This approach will enhance the saving of freshwater and used fertilizer in similar agriculture systems. Nine tanks with dimensions of 80×40×40 cm were filled either with freshwater or a mixture of freshwater and treated wastewater at (50:50 and 75:25% ratios). Each tank was stocked 25 pieces of Tilapia with an initial body weight of 49 g. Each tank was connected with another tank of same dimensions that was used to grow lettuce and bean crops on the top layer. Water was circulating between two tanks. No fertilizer was added to all treatments and all tanks got similar amount of fish feed. It was found that tanks with treated wastewater got higher values of metal content due to minerals added from treated wastewater compared to fresh water alone. Therefore, lettuce and bean growth were much better and got higher values of chlorophyll content compared to control tanks. For heavy metal analysis, all waters got similar values with small increase in some elements found in treated wastewater. For the edible part, lettuce grown in treated wastewater got higher value of Fe and Ba compared to control. Similar concentrations were found with bean plants with higher values in treated wastewater compared to freshwater. However, low concentrations of heavy metals were found in the edible parts of all treatments and it was within the international standards. Fish analyses showed that all tested heavy metals were within the safe limit. However, applying this technique in the farming system will help the environment by utilizing treated wastewater and reducing fertilizer applications. Moreover, farmer income will increase since both fish and crops will be produced with minimum resources.
Keywords: Hydroponics; Aquaponics; Fish; Heavy metal; Plant quality
