Identification of organic compounds in landfill leachate treated by advanced oxidation processes

Purposely Development of the Adaptive Potential of Activated Sludge from Municipal Wastewater Treatment Plant Focused on the Treatment of Landfill Leachate

Biological treatment is a key technology in landfill leachate treatment However, often its efficiency is not high enough due to the pollutants in concentrations above the critical ones. The present study aimed to investigate the adaptive responses that occur in activated sludge (AS) during landfill leachate purification. A model process with AS from a municipal wastewater treatment plant and landfill leachate in increasing concentrations was constructed. The data showed that when dilutions 25 and 50 times had been applied the structure of the AS was preserved, but the COD cannot be reduced below 209 mg O2/L. The feed of undiluted leachate destroyed the AS structure as SVI was reduced to 1 mL/g, biotic index to 1, floc size was greatly reduced and COD remained high (2526 mg O2/L). The dominant group of protozoa was changed from attached to free-swimming ciliates. An increase of the bacterial groups responsible for the xenobiotics elimination (aerobic heterotrophs, genera Pseudomonas, Acinetobacter, Azoarcus, Thauera, Alcaligenes) was registered. This was accompanied by a significant increase in free bacteria. The obtained data showed that for optimal treatment of this type of water it is necessary to include a combination of biological treatment with another non-biological method (membrane filtration, reverse osmosis, etc.).

Enhanced removal of refractory humic- and fulvic-like organics from biotreated landfill leachate by ozonation in packed bubble columns

Biotreated landfill leachate contains much refractory organics such as humic and fulvic acids, which can be degraded by O₃. However, the low O₃ mass transfer and high energy cost limit its wide application in landfill leachate treatment. Previous studies proved that packed bubble columns could enhance the O₃ mass transfer and increase the synthetic humic acids wastewater degradation, but the performance of packed bubble columns in real wastewater treatment has not been investigated. Therefore, this study aims to evaluate the feasibility of application of packed bubble column in the real biotreated landfill leachates treatment and provide insights into the transformation of organic matters in leachates during ozonation. Packed bubble columns with lava rocks or metal pall rings (LBC or MBC) were applied and compared with a non-packed bubble column (BC). At an applied O₃ dose of 8.35 mg/(L_{water sample} min), the initial COD (400 mg/L) was only removed for 26% in BC and 32% in MBC while this was 46% in LBC, indicating LBC has the best performance. GC-MS analysis shows that raw biotreated leachate contains potential endocrine disruptors such as di(2-ethylhexyl) phthalate (DEHP). 61% of DEHP was removed in LBC and the least intermediate oxidation products from humic- and fulvic-like organics was detected in LBC. The highest O₃ utilization efficiency (89%) and hydroxyl radical (OH) exposure rate (3.0 × 10^-10 M s) were observed in LBC with lowest energy consumption (E_EO) for COD removal of 18 kWh/m³. The enhanced ozonation efficiency in LBC and MBC was attributed to the improved O₃ mass transfer. Besides, LBC had additional adsorptive and catalytic activity that promoted the decomposition of O₃ to generate OH. This study demonstrates that a packed bubble column increases removal and decreases energy use when treating landfill leachate, thus promoting the application of ozonation.

Intensification of supercritical water oxidation (ScWO) by ion exchange with zeolite for the reuse of landfill leachates

The disposal of solid residues in sanitary landfills results in the formation of a complex, variable, and recalcitrant wastewater, known as leachates. Supercritical water oxidation (ScWO) can be applied to treat leachates although most studies are based on removing the most relevant contaminants, such as organic matter and ammonia. Therefore, comprehensive analysis of this process is essential for large-scale applications. In this study, we investigated a system composed of ScWO and ion exchange using zeolite (ScWO/zeolite) for the reuse possibilities of treated leachates based on different regulations for municipal wastewater reuse. This system was applied to both raw leachate (RL) and leachate treated via conventional processes at the studied landfill (PL). The continuous ScWO reactor operated under a pressure of 23 MPa at 600 °C without the addition of oxidants. A commercial zeolite (clinoptilolite) in a fixed-bed glass column was used for ion exchange. The intensified system significantly improved the characteristics of RL by removing 89% of COD and 99% of NH₃-N. Moreover, the contaminant concentrations of PL were within the limits for discharge and reuse, except arsenic and molybdenum contents. The unexpected high concentrations of arsenic in RL and PL necessitated the requirement of further investigation of the complex and toxic characteristics of leachates. Nevertheless, the intensified process was conducted without the addition of oxidants or auxiliary substances and resulted in a less expensive and more environmentally -friendly process that can be applied for the treatment of leachates with similar characteristics.

Efficient fungal and bacterial facilitated remediation of thiencarbazone methyl in the environment

Triazole herbicide, Thiencarbazone-methyl (TCM) applied on different crops for weedicidal activity is associated with an inherent toxicity towards bladder and urinary functionality. TCM has been first time explored for its biodegradative behavior utilizing microbes, previously isolated from soils. Simulated bio-transformation assemblies of five fungal strains; Aspergillus flavus (AF), Penicillium chrysogenum (PC), Aspergillus niger (AN), Aspergillus terrus (AT), Aspergillus fumigatus (AFu) and two bacterial strains: Xanthomonas citri (XC), Pseudomonassyringae (PS), were utilized. 10 mg/L TCM concentration was set up utilizing each microbe and analysed for 42 days. TCM bio-degradation was evaluated by UV-Visible spectrophotometery and gas chromatography mass spectroscopy. Aspergillus terrus (R² = 0.86) and Penicillium chrysogenum (R² = 0.88) exhibited highest capability to metabolize TCM while forming intermediate metabolites including; 2,4-dihydro-[1,2,4] triazol-3-one, semicarbazide and urea, methyl 4-isocyanatosulfonyl-5-methylthiophene-3-carboxylate. TCM degradation by all strains AF, AFu, AN, PC, AT, PS and XC was found to be 74, 74, 81, 95, 98, 90 and 95%, respectively after 42 days elucidating the effectiveness of all the utilized strains in degrading TCM. Current investigations can impact vital bioremediation approaches for pesticides mitigation from the ecological compartments. Furthermore, present research can be extended to the optimization of the bio-deteriorative assays to be employed on the practical scale for the successful management of environment through sustainable and cost effective ways.

Intensification of supercritical water oxidation (ScWO) process for landfill leachate treatment through ion exchange with zeolite

Over the past few years, supercritical water oxidation (ScWO) has shown great potential for application to landfill leachate treatment, providing substantial organic matter degradation in terms of biochemical oxygen demand (BOD), chemical oxygen demand (COD), and total organic carbon (TOC). However, the conversion of ammonia, which is present at high concentrations in leachates, is the rate-limiting step during ScWO and usually requires large amounts of oxidants, the addition of catalysts, or severe operating conditions. Aiming at proposing a treatment system that effectively removes both organic matter and ammonia from leachate, this paper evaluates the intensification of the ScWO process through ion exchange with zeolite. Thus, ScWO was operated under a pressure of 23 MPa at 600 and 700 °C, without the addition of oxidants. The zeolite (clinoptilolite) was used without any modification inside a glass column. The ScWO (600 °C)/zeolite system removed 90% ammoniacal nitrogen (NH₃-N), 100% nitrite (NO₂-N), 98% nitrate (NO₃-N), color, and turbidity, 81% TOC, and 74% COD, suggesting that this system is a promising alternative for leachate treatment. However, the final NH₃-N and COD values were slightly above the limits (20 and 200 mg L^-1, respectively) stipulated by the Brazilian environmental legislation. These results suggest that further improvements are still required for the application of the intensified ScWO to be feasible. Notably, ammonium-saturated clinoptilolite is amenable for regeneration or can be applied to soil as a slow-release fertilizer.