Comparison of hybrid wetland arrangements for dairy wastewater treatment

NOCETTI, E.; HADAD, H.R.; DI LUCA, G.A.; MUFARREGE, M.M.; MAINE, M.A.

Bruges

Simposio; 10th International Symposium on Wetland Pollutant Dynamics and Control, WETPOL; 2023

Ghent University

The aim of this work was to compare the performance of two pilot-scale hybrid wetland systems to assessthe best arrangement for the treatment of dairy wastewater. The hybrid wetland 1 (HW1) was composedof a first stage of three parallel vertical flow (VF) wetland units followed by a second stage of a horizontalsubsurface flow (HSSF) wetland unit. The hybrid wetland 2 (HW2) was composed of a first stage of threeparallel VF wetland units followed by a second stage of a free water surface (FWS) wetland unit. Coarsesand, river stones, and sediments were the substrates used in VF, HSSF, and FWS, respectively. Typhadomingensis was planted in all wetland units. The HW1 and HW2 received 0.170 m3-1 d of dairy wastewater which was previously treated by a dissolved air diffusion and an aerobic pound. Wastewater,plants, and sediments samples were taken from each wetland unit. COD, BOD, TKN, NO2--, NO3, and TP were determined in all wastewater samples. TN was estimated as TN = TKN + NO2---N + NO3-N. TKN and TP concentrations also were determined in plant and sediment samples. The removal percentages of mainpollutants in each wetland unit were calculated. Mean chemical composition of the inlet wastewater was:COD = 1211.9 mg O2 L-1, BOD = 238.9 mg O2 L-1, TN =96.4 mg N L-1, and TP =32.1 mg P L-1. Figure 1 shows COD, BOD, TN, and TP removal percentages in stage 1, stage 2, and full system for HW1 and HW2. COD,TN, and TP removals did not show significant differences between HW1 and HW2. However, COD and TPremovals from the VF stage of HW1 were significantly higher than HW2. BOD removal showed significantdifferences between HW1 and HW2, due to BOD removal in FWS was lower compared to HSSF. N and Pconcentrations in plant tissues increased during the treatment in HSSF and FWS wetlands while in VF stageof HW2 TN and TP removals in were correlated to low concentrations of nutrients in plant tissues,indicating a significant plant uptake. Nutrient concentrations in the sediment from FWS wetland did notshow a significant increase. Both the HW1 and HW2 were efficient for the treatment of dairy wastewater.The obtained results suggest that uptake by plants could be a key process for N and P removal from thewastewater