Constructed wetlands for final polishing of slaughterhouse effluent

SANCHEZ, G.C; MAINE, M.A.; CAFFARATTI, S.E.; PEDRO, M.C.

Brugges

Simposio; Symposium on Wetland Pollutant Dynamics and Control, WETPOL.; 2023

The slaughterhouse industry represents an important economic sector in Argentina. Cattle slaughter generates significant volumes of effluents that require treatment before final disposal. Constructed wetlands (CWs) constitute a consolidated technology for the treatment of sewage and have been used successfully for different industrial wastewater depuration. However, slaughterhouse wastewater is complex and has a high organic strength. The aim of this study was to evaluate the feasibility of using constructed wetlands for the final treatment of this effluent.The performance of free water surface (FWS) and horizontal subsurface flow (HSSF) wetlands were compared in greenhouse experiences. CWs were planted with Typha domingensis and Canna Indica. The raw effluent receives a primary treatment through a separation chamber, followed by a system of anaerobic, facultative and aerobic ponds. In the latter pond, COD and BOD tend to increase when temperatures rise and algae develop. To evaluate the feasibility of replacing the aerobic pond with a CW, the inlet wastewater of this pond was used in the study.Plants tolerated the effluent. Both CWs were efficient in the final effluent treatment. N-NH4+ and TKN mean removal were 99.1 and 89.5%, respectively, not presenting significant differences between FWS and HSSF wetlands. TN removals did not present significant differences between CWs (78.1- 80.8%), while in controls (without macrophytes) they were 23.6% (FWS control) and 51.3% (HSSF control). Regarding nitrate, there were not significant differences between initial and final concentrations in both wetlands. Comparing the FWS and HSSF controls, it was observed that nitrate increased in both controls, indicating the plant role in these systems. Nitrate concentration was higher in FWS controls, probably because its conditions did not favor denitrification, which implies less NT removal in controls. The mean removal of COD, BOD and TP were 71.2; 80.7 and 68.3, respectively for FWS with T. domingensis. In HSSFs, COD and BOD removal did not present significant differences between the two species (65.2 and 66.4, respectively) while TP removal was higher in HSSF planted with C. glauca (75.2%) than those planted with T. domingensis (54.7%) The highest removal efficiencies were achieved in FWS wetlands. T. dominguensis and C. glauca were tolerant and efficient species in the effluent treatment. FWS wetlands are the best option for this case, taking into account not only the efficiency in effluent treatment, but also the lower cost of construction and operation.