New technique to sustain fish and crops output
A research project was conducted at SQU to examine the potential of producing crops in an aquaponics system using both fish waste and treated waste water. For this purpose, a team has evaluated the impact of treated wastewater on fish growth and how the effluent coming from fish tanks may affect grown crops.
Defining the research approach, Dr. Ahmed Al-Busaidi – Principal Investigator – said, “Nine tanks with dimensions of 80x40x40 cm were filled either with freshwater or a mixture of freshwater and treated waste water at 50:50 and 75:25 % ratios. Each tank was stocked with 25 pieces of Tilapia with an initial body weight of 49g each. Each tank was connected with another one of the same dimensions used to grow lettuce and bean crops on the top layer. Water was circulated between the two tanks. No fertilizer was added to all treatments and all the tanks got a similar amount of fish feed.”
The experiment results showed that tanks with treated wastewater got higher values of dissolved oxygen due to algae growth and greater salts content due to the minerals added from treated waste water compared to fresh water alone. Therefore, lettuce and bean growth was much better and got higher values of chlorophyll content compared to those in the control tanks. For heavy metal analysis, all waters had similar values, but in some samples, the concentration of B, Cu, Mn and Zn was higher in treated waste water compared to fresh water and that was reflected in the lettuce roots.
For the edible part, lettuce grown in treated waste water had a higher value of Fe and Ba compared to the control samples. Similar concentrations were found with bean plants with higher values in treated waste water compared to freshwater. However, low concentrations of heavy metals were found in the edible parts of all treatments which was within international standards.
Al-Busaidi pointed out that fish analyses suggested that all the tested heavy metals were within the safe limit. Moreover, applying such a technique in the farming system could help the environment by utilizing treated waste water and reducing fertilizer applications, he underlined, adding that farmer income would increase since both fish and crops would be produced with minimum resources.
He described the system as simple, applicable in a small area and environment friendly: “It helps in saving fresh water and maximizing the application of treated waste water with no or minimum need for chemical fertilizers. However, monitoring with good managements is required to avoid any health issues.”
He concluded his remarks by emphasizing the importance of achieving Sustainable Development Goal 12 of the United Nations 2030 Agenda for Sustainable Development. He said that: “GCC countries need to look for innovative and sustainable production of food for the local and expatriate population. Opportunities exist for this method of food production using limited but highly treated wastewater. A change to fish and vegetable production using treated waste water will contribute to sustainable consumption and production in the region.”