Use of tilapia, Oreochromis Niloticus, as a tertiary treatment in effluents from a facultative pond

Abstract

The tertiary treatment of wastewater from the facultative pond effluent through the use of tilapia fry is an alternative for reuse and maximum utilization of wastewater. In this article, the performance of a pond system with tilapia fry Oreochromis niloticus in series for the treatment of the effluent of the facultative ponds of the Arturo Pazos treatment plant was evaluated at pilot scale. The system constructed at the exit of the facultative lagoons consisted of three ponds in series; each of them with 25 tilapia fry and with a hydraulic retention time of 75 minutes. The evaluation was performed in the dry season on a fortnightly basis, obtaining a total of 32 samples of the removal efficiency generated by tilapia. The percentages of removal of physical characteristics, total solids and dissolved oxygen, ranged from 3,7% to 12,5%; the content of DQO and DBO5 reached an average removal of almost 10,0%. On the other hand the removal efficiencies obtained in parameters such as fecal coliforms, hydrogen potential, total phosphorus and total nitrogen were: 6,0%, 3,5%, 7,9% and 4,5%, respectively. With only three ponds of tilapia fry and with the effluent of the lagoons even without optimum removal efficiencies, it can be seen that the proposed tertiary treatment presents relatively low removal results, however tilapia can be implemented as a bioindicator capable of surviving in these waters in process of treatment.