Fingerlings of common carp, Cyprinus carpio, and golden carp, Carassius auratus, as tertiary treatment of a facultative pond effluent

Abstract

The treated waters from the effluent of a facultative lagoon used to the secondary treatment of domestic wastewaters from the Aurora II colony in the wastewater treatment plant Arturo Pazos Sosa, can be reused in a tertiary treatment by using common carp (Cyprinus carpio) and golden carp (Carassius auratus) fingerlings. In this articule, the results of the research are presented using a small-scale ponds system with common carp and golden carp fingerlings, configured in parallel where the flow coming from the effluent facultative lagoon of the secondary treatment was distributed equitably to each of the ponds, with a hydraulic retention time (HRT) design of approximately 76 minutes. Each pond contained 25 fingerlings per type, this in order to evaluate the removal efficiency of selected water quality parameters. Eight water quality sampling were determined at the input and at the output of tertiary treatment for 4 months. The simple or punctual samples were taken every fifteen days, for a total of thirty-two samples. To evaluate the removal efficiency of the tertiary treatment were selected three main parameters, being the biochemical oxygen demand (DBO5), total phosphorus and fecal coliforms. The removal efficiency of the common carp fingerlings was of 8.86% to DBO5, 7.13% to total phosphorus and 7.46% to fecal coliforms. The removal efficiency of the golden carp fingerlings was of 7.69% to DBO5, 7.97% to total phosphorus and 8.47% to fecal coliforms. The efficiency in the removal of the parameters evaluated by the presence of the fingerlings were less than 10.0%, for this reason the use of fish as tertiary treatment is not recommended, however, they can be used as bioindicators capable of demonstrate that the water quality in the effluents of the facultative lagoon is good.