RESUMEN

Landfill leachate contains many complex components that have a negative impact on the environment when improperly discharged. This study is the first to treat landfill leachate (after continuous flow sequencing bed biofilm reactor (CF-SBBR) bio-digested) using electrocoagulation (EC) combined with persulfate (PS) on Al and Fe electrodes. The effect of some of the key parameters on the COD, Color, TOC and TN removal efficiencies as part of the EC-PS process were studied using the PS concentration, reaction time, initial pH, current density, and aeration rate. The results show that a PS concentration of 3 g/L improved the COD removal efficiency by 9.0 ± 1.3 % at the Al electrode and 16.0 ± 2.6 % at the Fe electrode. Aeration also improved the COD, TOC and color removal efficiencies by about 10.0 ± 2.3 %, 8.0 ± 1.7 % and 3.0 ± 0.5 % at an optimal aeration rate 3.3 L/min. The optimal operation conditions for the EC-PS process were a PS concentration of 3 g/L, a pH of 2.0 (Al electrode), a pH of 4.0 (Fe electrode), a reaction time of 70 min, a current density of 35 mA/cm2 and an aeration rate of 3.3 L/min. The highest COD, color, TOC and TN removal efficiencies were 46.5 ± 1.8 %, 95.8 ± 2.4 %, 83.5 ± 1.7 %, and 40.9 ± 1.6 % at Al electrode and 54.4 ± 2.3 %, 98.5 ± 2.1 %, 78.6 ± 1.5 % and 57.9 ± 1.1 % at the Fe electrode. The EC-PS working mechanisms involve co-precipitation, an advanced oxidation process (AOPs) using oxidation radicals (HO, SO4-) and flotation. EC-PS is a promising method to treat bio-digested landfill leachate.

Asunto(s)

Contaminantes Químicos del Agua , Biopelículas , Electrocoagulación , Electrodos , Oxidación-Reducción , Contaminantes Químicos del Agua/análisis

RESUMEN

Landfill leachate contains many pollutants that have a negative effect on the environment when improperly discharged. Thus the treatment of landfill leachate is a crucial issue, especially in the bigger cities in developing countries. In this study, landfill leachate is treated using a continuous flow sequencing biofilm batch reactor (CF-SBBR) with different biocarriers (non-carrier (NC), kaldness K1 (K1), mutag biochip 30™ (MB), and sponge polyurethane (SP)). The results show that the best COD, TOC, and NH4+-N removal efficiencies were 79.6 ± 0.8%, 78.1 ± 1.9% and 77.5 ± 3.9% in the MB biocarriers tank with an aeration/mixing ratio of 1.3, a cycle time of 9 h and an organic loading rate (OLR) of 1.74 kgCOD/m3.d. The TN removal efficiencies was decreased when there was an increase in the biocarrier's surface area (NC > K1 > MB > SP). At the highest it was 46.1 ± 6.4%, where the aeration/mixing ratio was 1.3, the cycle time was 9 h, and the OLR was 1.52 kgCOD/m3.d. The higher the surface area of the biocarriers, the greater the anti-shock organic loading capacity of the biocarriers due to the formation of biofilm layers. The microbial communities in the CF-SBBR tanks were abundant with common phylum bacteria as in a conventional activated sludge system. Anammox candidatus bacteria was found to total 0.5%. This study concluded that CF-SBBR is an efficient method to treat landfill leachate.

Asunto(s)

Contaminantes Químicos del Agua , Biopelículas , Reactores Biológicos , Nitrógeno , Eliminación de Residuos Líquidos

RESUMEN

Swine wastewater contains high concentrations of organic compounds, nutrients (nitrogen and phosphorus), heavy metals, and residual antibiotics, amongst others, that have negative impacts on the water environment. The main aim of this work was to remove nutrients from anaerobically digested swine wastewater using an intermittent cycle extended aeration system (ICEAS). The effects of operational parameters such as cycle time, organic loading rate, C/N ratio, and aeration/mixing ratio on the pollutant removal efficiencies of ICEAS were studied and compared with the performance of a conventional sequencing batch reactor (SBR). The following optimal conditions were obtained: cycle time, 6 h; organic loading rate, 0.86 kg COD m-3 day-1; C/N ratio, 2.49-2.82; and aeration/mixing ratio, 1.57. The pH was maintained in the range of 6.0-8.0. The total organic carbon (TOC), total nitrogen (TN), ammonium (NH4 +), total phosphorus (TP), and color removal efficiencies of ICEAS were higher than those of the conventional SBR, with removal efficiencies of 95.22, 88.29, 97.69, 85.81, and 97.84%, respectively, compared to 94.34, 81.16, 94.15, 77.94, and 96.95%, respectively, observed in the SBR. TOC, TN, NH4 +, TP, and the color removal efficiencies of ICEAS were higher by 0.88, 7.13, 3.54, 7.87, and 0.95%, respectively, than the conventional SBR. The good results from this study show that ICEAS is a promising technology for the removal of organic contaminants and nutrients from anaerobically digested swine wastewater and that the effluent water quality meets the Vietnamese discharge standard (QCVN 62-MT:2016/BTNMT) for swine wastewater effluents.