Mature Leachate Research Articles

Effect of chloride ions on the reactive species change pathway and removal performance in the MW/Co2+/PMS process

Efficient removal of refractory organic matter is the focus of research in the treatment of actual wastewater with Peroxymonosulfate-based advanced oxidation processes(PMS-AOPs). However, the high concentration of chloride ions (Cl−) ubiquitously present in wastewater changes the reactive species (RS) present in the process, and the mechanism of this change is still not clear. This study investigated the effects of Cl− on the transformation behavior of RS and treatment performance under microwave (MW) combined with cobalt ions (Co2+)-activated PMS. The results showed that increasing the Cl− concentration can enhance the removal performance of the MW/Co2+/PMS process for ammonia (NH4+-N), accompanied by the production of nitrate nitrogen (NO3-N), monochloramine (NH2Cl) and dichloramine (NHCl2), which was related to the transformation of existing reactive oxygen species (ROS, •OH and SO4•−) into reactive chlorine species (RCS), with hypochlorous acid (HClO) as an important intermediate. Cl− can generate HClO through free radical oxidation (•OH and SO4•−) dominance and non-free radical oxidation (PMS and Co3+) promotion, and the heat transferred by MW can further trigger conversion between HClO and PMS, thereby changing the distribution of RS. Increasing the dosage of PMS and the dosage of Co2+ promoted the transformation of Cl− to reactive species in the MW/Co2+/PMS process. At MW power=160 W, [Co2+]=17.5 μM,[PMS]=10 mM, and [Cl−]=17 mM, the maximum cumulative [HClO] reached 1910.97 μM, and the decay rate was 0.1815 min−1.The macromolecular organic matter in aqueous environment competes with ammonia for the RCS. Through regulating [Cl−] in mature leachate, RCS has a certain oxidation effect to organic matter, but its limited oxidation ability leads to a decrease in the mineralization effect.

The Influence of Groundwater Migration on Organic Matter Degradation and Biological Gas Production in the Central Depression of Qaidam Basin, China

For insight into the productive and storage mechanisms of biogas in the Qaidam Basin, efforts were made to investigate the groundwater recharge and the processes of hydrocarbon generation by CDOM-EEM (fluorescence excitation-emission matrix of Chromophoric dissolved organic matter) spectrum, hydrogen and oxygen isotopes, and geochemical characters in the central depression of the Qaidam Basin, China. The samples contain formation water from three gas fields (TN, SB, and YH) and surrounding surface water (fresh river and brine lake). The results indicate that modern precipitation significantly controls the salinity distribution and organic matter leaching in the groundwater system of the central depression of the Qaidam Basin. Higher salinity levels inhibit microbial activity, which leads to organic matter degradation and to gas generation efficiency being limited in the groundwater. The inhabitation effect is demonstrated by the notable negative correlation between the extent of organic matter degradation and its concentration with hydrogen and oxygen isotopes. The conclusion of this study indicated that modern precipitation emerges as a crucial factor affecting the biogas production and storage in the Qaidam Basin by influencing the ultimate salinity and organic matter concentration in the formation, which provides theoretical insight for the maintenance of modern gas production wells and the assessment of gas production potential.

Refractory organic matter removal from mature leachate by bipolar electrocoagulation-electrooxidation reactor configurations

In this study, mature leachate treatment with combined electrochemical processes was investigated to benefit from the advantages of electrocoagulation (EC) and electrooxidation (EO) simultaneously. First, control experiments were conducted, the most effective anode-cathode combination for EO was selected as Ti/IrO2-Gr, the number of Al electrodes for EC was determined as 3 and the number of Fe electrodes was determined as 5. Optimization of process parameters of the combined system with Al and Fe electrodes was conducted with Box-Behnken design (BBD). With BBD, the effect of the process parameters (initial pH, current density, and reaction time) on the system responses (COD, UV254, and color removal efficiencies) was determined. The suitability of the created model in the study was analyzed statistically and the results of quadratic models were found compatible with experimental studies. The model's capacity for prediction was also confirmed by validation experiments under optimum conditions. By implementing the optimum conditions, COD, UV254, and color removal efficiencies were determined as 71.5 %, 60.2 %, and 93.2 %, respectively for the combined process with Al electrodes and 79.5 %, 68.0 %, and 97.7 %, respectively for the combined process with Fe electrodes. Correlation of actual and predicted data showed that BBD is reliable for optimizing process parameters of combined processes with Al and Fe electrodes. The obtained results showed that combined processes are more effective than hybrid processes, based on both pollutant removal efficiencies and energy consumption.

Characterization and spatiotemporal variations of fluorescent dissolved organic matter in leachate from old landfill-derived incineration residues and incombustible waste.

Dissolved organic matter (DOM) influences the bioavailability and behavior of trace metals and other pollutants in landfill leachate. This research characterized fluorescent dissolved organic matter (FDOM) in leachate from an old landfill in Japan during a 13-month investigation. We employed excitation-emission matrix (EEM) fluorescence spectroscopy with parallel factor analysis (PARAFAC) to deconvolute the FDOM complex mixture into three fluorophores: microbial humic-like (C1), terrestrial humic-like (C2), and tryptophan-like fluorophores (C3). These FDOM components were compared with findings from other studies of leachate in landfills with different waste compositions. The correlations among EEM-PARAFAC components, dissolved organic carbon (DOC) concentration, and ultraviolet-visible and fluorescence indices were evaluated. The FDOM in leachate varied spatially among old and extended leachate collected in the landfill and leachate treatment facility. The FDOM changed temporally and decreased markedly in August 2019, November 2019, and April 2020. The strong positive correlation between HIX and %C2 (r = 0.87, ρ = 0.91, p < 0.001)) implies that HIX may indicate the relative contribution of terrestrial humic-like components in landfill leachate. The Fmax of C1, C2, and C3 and the DOC concentration showed strong correlations among each other (r > 0.72, ρ > 0.78, p < 0.001) and positive correlations with leachate level (r > 0.41, p < 0.001), suggesting the importance of hydrological effects and leachate pump operation on FDOM.

Improved greywater quality after biofiltration with a fibre-biofilter derived from plantain pseudo stem

In this study, we addressed the prevalent issue of untreated greywater discharge into waterbodies in many developing countries, despite the associated public health risks. Our approach involved utilizing fibers extracted from plantain pseudo-stems to enhance the quality of greywater through simple biofiltration setups. Greywater sourced from the GETFund Hostel of the University of Energy and Natural Resources in Sunyani, Ghana, served as the focal point of our investigation. Through the application of this biofilter, we achieved notable reductions in two crucial parameters for assessing greywater quality: biochemical oxygen demand (BOD) and chemical oxygen demand (COD), averaging at 30.4 % and 28.67 %, respectively. Furthermore, we conducted comparative analyses between the efficacy of plantain pseudo-stem fibers and carbonized coconut shell adsorbent, both individually and in composite form as biosorbents. While certain combinations of biofilters led to slight increases in conductivity, pH, and total dissolved solids (TDS) in the treated greywater, these variations were anticipated and attributed to potential organic matter leaching during the biofiltration process. Employing Fourier-transform infrared (FT-IR) spectroscopy, we detected significant spectral changes indicative of successful organic matter removal from the greywater. Specifically, we observed an intensified phenolic hydroxyl (OH) peak at 3300 cm⁻¹, which shifted marginally to 3335 cm⁻¹ post-biofiltration. Additionally, the emergence of a carboxylic hydroxyl stretch at 2850 cm⁻¹ post-biofiltration provided strong evidence supporting the efficacy of our approach in mitigating organic contaminants in greywater.

Characterization and differentiation of dissolved organic matter in leachate derived from an old Japanese landfill site through Orbitrap mass spectrometry

Elucidating the characteristics of dissolved organic matter (DOM) is crucial to assessing its impact on the bioavailability and mobility of pollutants in landfill leachate. This study reports a comprehensive 5–month investigation into the characteristics of DOM in leachate from an old Japanese landfill, collected at six different sampling points. The molecular composition, chemical properties, and structural characteristics of DOM were assessed using Orbitrap mass spectrometry and spectral analysis. The leachate DOM mainly consisted of CHO-containing molecules (58.5–88.9%), low-oxygen unsaturated phenolic compounds (40.5–54.0%), and aliphatic compounds (19.4–47.3%), with slight variation among sampling points. A significant portion of the nominal oxidation state of carbon was in the reduced zone (76.2–95.4%). The results underscore the distinct molecular composition of DOM in mature Japanese landfill leachate compared to young and mature leachates from other countries. Two of six sampling points, with notable differences in molecular characteristics, were compared and elucidated. The composition of landfill waste, rather than landfill age, was the main factor affecting the characteristics and differentiation of leachate DOM.

Development of an electrochemical separation-Rhodopseudomonas palustris electrolysis cell-coupled system for resourceful treatment of mature leachate landfill

Electrochemical technology is a promising technique for separating ammonia from mature landfill leachate. However, the accompanying migration and transformation of coexisting pollutants and strategies for further high-value resourceful utilization of ammonia have rarely received attention. In this study, an electrochemical separation-Rhodopseudomonas palustris electrolysis cell coupled system was initially constructed for efficient separation and conversion of nitrogen in mature landfill leachate to microbial protein with synchronously tracking the transport and conversion of coexisting heavy metals accompanying the process. The results revealed that ammonia concentration in the cathode increased from 40.3 to 49.8% with increasing the current density from 20 to 40 mA/cm2, with less than 3% of ammonia transformation to NO2−-N and NO3−-N. During ammonia separation, approximately 95% of HM-DOMs (Cr, Cu, Ni, Pb, and Zn) were released into the anolyte due to humus degradation and further diffused to the cathode. A significant correlation was observed between the releases of HM-DOMs. Cu-DOMs accounted for 70.2% of the total Cu content, which was the highest proportion among the heavy metals (HMs). Among the HMs in anolyte, 57.4% of Pb, 52.5% of Ni, and 50.6% of Zn diffused to the cathode, and most of the HMs were removed in the form of hydroxide precipitations due to heavy alkaline catholyte. Compared with the open-circuit condition, the utilization efficiency of NH4+-N in the R. palustris electrolysis cell increased by 445.1% with 47% and 50% increases in final NH4+-N conversion rate and R. palustris biomass, respectively, due to bio-electrochemical enhanced phototrophic metabolism and acid generation for buffering the strong alkalinity of the electrolyte to maintain suitable growth conditions for R. palustris.

Biochar and vegetation effects on discharge water quality from organic-substrate green roofs

Green roofs have been increasingly used to improve stormwater management, but poor vegetation performance on roof systems, varying with vegetation type, can degrade discharge quality. Biochar has been suggested as an effective substrate additive for green roofs to improve plant performance and discharge quality. However, research on the effects of biochar and vegetation on discharge quality in the long term is lacking and the underlying mechanisms involved are unclear. We examined the effects of biochar amendment and vegetation on discharge quality on organic-substrate green roofs with pre-grown sedum mats and direct-seeded native plants for three years and investigated the key factors influencing discharge quality. Sedum mats reduced the leaching of nutrients and particulate matter by 6–64% relative to native plants, largely due to the higher initial vegetation cover of the former. Biochar addition to sedum mat green roofs resulted in the best integrated water quality due to enhanced plant cover and sorption effects. Structural equation modeling revealed that nutrient leaching was primarily influenced by rainfall depth, time, vegetation cover, and substrate pH. Although biochar-amended sedum mats showed better discharge quality from organic-substrate green roofs, additional ecosystem services may be provided by native plants, suggesting future research to optimize plant composition and cover and biochar properties for sustainable green roofs.

Leaching of biochar at different stages of anaerobic digestion: Leaching behaviors, leachate chemodiversity and effects

Biochar addition is recognized as a promising way to increase the potential of anaerobic digestion. However, few studies have investigated the interaction between biochar leaching in complex, practical anaerobic digestion systems and the negative effects that biochar leachate may have on the anaerobic digestion process. The traditional measurement methods are relatively simple, but may underestimate the complexity of dissolved organic matter in biochar leachate. In this study, the leaching behaviors of biochar and the influence of biochar leachate on anaerobic digestion were studied at the molecular level by applying ultra-performance liquid chromatography online coupled with a hybrid quadrupole orbitrap mass spectrometer (UPLC Orbitrap MS/MS) test analysis and various molecular information-based analytical methods such as van Krevelen diagrams and by conducting a series of anaerobic digestion experiments. Dissolved organic matter leaching was higher in buffered saline solution and methanol than in ultrapure water and the dissolved organic matter mainly consisted of lipids and proteins. In the lactic acid solution, a large amount of dissolved organic matter was leached from the biochar, dominated by low molecular weight dissolved organic matter such as CHO and CHON, and the lower the pH, the more was leached, suggesting that lactic acid may have an inhibitory effect on anaerobic digestion. The maximum methane production amount and microbial abundance especially key methanogenic archaea such as Methanosaeta in the sample with biochar leachate addition were lower than those for the other samples. This meant that the dissolved organic matter in the biochar leachate might inhibit the growth of microorganisms and adversely affect the acetic acid methanogenesis process. The results from this study showed that a greater number of substances with more complex structures were leached out than had been detected in previous studies. When applying biochar to anaerobic digestion in the future, it is recommended that biochar is leached first to remove toxic and detrimental substances to prevent possible inhibitory effects.

Effects of biochar-amended soils as intermediate covers on the physical, mechanical and biochemical behaviour of municipal solid wastes

The effects of biochar-amended soils as landfill covers have been extensively studied in terms of liquid and gas permeability. However, the influences of biochar-amended soils on the performance of municipal solid wastes (MSWs) in bioreactor landfills have not been well understood. This paper investigates the potential application of biochar-amended soils as final and intermediate covers in landfills. The MSWs with biochar-amended soils as final and intermediate covers were recirculated with mature leachate in laboratory-scale bioreactors. The pH, chemical oxygen demand, ammonia and volatile fatty acids (VFAs) concentrations of leachates, mass reduction rates, settlement, methane, and total gas generations of MSWs were investigated. The results indicate that biochar-amended soils as intermediate landfill covers can provide pH-buffer capacity, increase the pH of leachate and decrease the accumulation of VFAs in the early stage of decomposition. The concentration of ammonia in the leachate with biochar-amended soils as intermediate cover is lower than that with natural soils. The application of biochar-amended soils as intermediate and/or final covers increases the biocompression ratios and settlement of MSWs. The application of biochar-amended soils as final cover slightly decreases the methane generation potential (L0). Biochar-amended soils as intermediate covers increase L0 by 10%, and biochar-amended soils as both intermediate and final covers enhance L0 by 25%. The increase in the ammonia removal, settlement, and methane yield indicates the viability of biochar-amended soils as intermediate landfill covers. Further studies can focus on the long-term behaviour of MSWs with soil covers with different biochar amendment rates and particle sizes.

Biochemical, hydrological and mechanical behaviors of high food waste content MSW landfill: Numerical simulation analysis of a large-scale experiment

The complex process of thermal-hydro-mechanical-biochemical (THMBC) coupled degradation in high food waste content (HFWC) municipal solid waste (MSW) is the main cause of intense heat, gas, and leachate generation in the landfills, which could lead to environmental disasters. A large-scale indoor experiment on HFWC MSW has been done with operations of loading, heated mature leachate recharging to study the rules of degradation. A THMBC coupled degradation model is used to analyze the results in the first 400 days drawn from the experiments, to explain how recharge of heated mature leachate accelerated degradation process and how was the portion of settlement led by intraparticle water release. The numerical simulation also calculated the landfill gas that was not collected in the experiment due to operational defects. The results show that recharging the heated mature leachate allows the stabilization process to occur at least six months earlier and settlement due to intraparticle water release accounts for half of the settlement in the first 60 days. The research indicates highly coupled THMBC model can be used to analyze the complex process in MSW degradation, make up for the shortcomings of physical experiments, and provide theoretical support for the design, construction, and management of landfills.

Microbial interactions and nitrogen removal performance in an intermittently rotating biological contactor treating mature landfill leachate

Developing efficient landfill leachate treatment is still necessary to reduce environmental risks. However, nitrogen removal in biological treatment systems is often poor or costly. Studying biofilms in anoxic/aerobic zones of rotating biological contactors (RBC) can elucidate how microbial interactions confer resistance to shock loads and toxic substances in leachate treatment. This study assessed the nitritation-anammox performance in an intermittent-rotating bench-scale RBC treating mature leachate (diluted). Despite the leachate toxicity, the system achieved nitritation with an efficiency of up to 34 % under DO values between 0.8 and 1.8 mg.L−1. The highest average ammoniacal nitrogen removal was 45.3 % with 10 h of HRT. The 16S rRNA sequencing confirmed the presence of Nitrosonomas, Aquamicrobium, Gemmata, and Plantomyces. The coexistence of these bacteria corroborated the selective pressure exerted by leachate in the community structure. The microbial interactions found here highlight the potential application of RBC to remove nitrogen in landfill leachate treatment.

Study of the effectiveness of a ZnO–TiO2 formulation in the degradation of humic substances in mature leachate by solar photocatalysis Brazil

Treatment of landfill leachate is an important environmental issue, especially in developing countries such as Brazil. Advanced oxidation processes (AOPs) have been considered interesting treatment alternatives. In this study, ZnO–TiO2 mixtures were incorporated into a paint polymer matrix and fixed onto supports. Paints were applied by overlapping coat layers on plates, resulting in high film thickness (600 ± 80 µm). Treatment of mature leachate by an AOP was conducted in a plug flow reactor connected to a stirred tank under solar irradiation. The objective was to evaluate the degradation of humic acid (HA) and fulvic acid + humins (FAH). The highest HA and FAH removal efficiencies were 62% ± 4.9% and 16% ± 4.2%, respectively. The kinetic model provided a coefficient of determination (R2) of 0.974. Rate constants for HA and FAH removal were 2.96 and 1.03 × 10−3 min−1, respectively. Statistical models for HA and FAH degradation had R2 values of 0.96 and 0.99, respectively. Both approaches indicated that HA degradation is greater at acidic pH and higher TiO2 concentrations. FAH degradation was favored by acidic pH and higher ZnO concentrations. Statistical models showed the same mean difference in conversion between replicate runs of HA and FAH, suggesting a uniform diffusion of fractions through catalysts.&#x0D; Keywords: heterogeneous photocatalysis, humic and fulvic acid, landfill leachate treatment, titanium dioxide, zinc oxide.

Nature based solutions applied to mature leachate treatment in the Latin American resource-poor environment

Some Latin American countries have implemented environmental policies which have enhanced a shift in domestic solid waste practices from open dumps to sanitary landfills, bringing about a serious challenge to the region in terms of leachate management both in the operation and the aftercare phases of landfills. This work looks at the viability of Nature based Solutions (NbS) in the Latin American resource-poor environment as a cost-efficient alternative for dealing with such a challenge. In particular, an experimental trial was carried out in order to evaluate the contaminants removal of four subsurface constructed wetlands at a pilot scale, for treating mature leachate with emphasis on nitrogen removal. The wetlands were set in two treatment lines: (1) a vertical flow wetland followed by a horizontal flow wetland and (2) two vertical flow wetlands in series. Each line was fed at a 173 L.d−1 rate of mature leachate. The wetlands were planted with a polyculture of the tropical plants Colocasia esculenta and Heliconia psittacorum in a random way and the support media used was composed of 3/8″ gravel and gross sand. Both treatment lines showed similar behaviours and it is important to highlight that ammoniacal nitrogen, that is the principal contaminant to treat, was significantly removed (40% approx.) considering the high loads the system was fed with (490 kg.d−1 TAN). It is considered that the removal mechanism of the ammoniacal nitrogen is a biological nitrification-denitrification process, due to the increase of nitrite and nitrate concentrations in the effluent, as well as the bicarbonate alkalinity consumption. These results suggest the system proposed as an NbS has promising potential for leachate treatment in Latin American countries.

Effect of the association of coagulation/flocculation, hydrodynamic cavitation, ozonation and activated carbon in landfill leachate treatment system

Mature landfill wastewater is a complex effluent due to its low biodegradability and high organic matter content. Currently, mature leachate is treated on-site or transported to wastewater treatment plants (WWTPs). Many WWTPs do not have the capacity to receive mature leachate due to its high organic load leading to an increase in the cost of transportation to treatment plants more adapted to this type of wastewater and the possibility of environmental impacts. Many techniques are used in the treatment of mature leachates, such as coagulation/flocculation, biological reactors, membranes, and advanced oxidative processes. However, the isolated application of these techniques does not achieve efficiency to meet environmental standards. In this regard, this work developed a compact system that combines coagulation and flocculation (1st Stage), hydrodynamic cavitation and ozonation (2nd Stage), and activated carbon polishing (3rd Stage) for the treatment of mature landfill leachate. The synergetic combination of physicochemical and advanced oxidative processes showed a chemical oxygen demand (COD) removal efficiency of over 90% in less than three hours of treatment using the bioflocculant PGα21Ca. Also, the almost absolute removal of apparent color and turbidity was achieved. The remaining CODs of the treated mature leachate were lower when compared to typical domestic sewage of large capitals (COD ~ 600 mg L−1), which allows the interconnection of the sanitary landfill to the urban sewage collection network after treatment in this proposed system. The results obtained with the compact system can help in the design of landfill leachate treatment plants, as well as in the treatment of urban and industrial effluents which contains different compounds of emerging concern and persistence in the environment.

Optimisation of electrochemical oxidation process with boron doped diamond (BDD) for removing COD, colour, ammonium, and phosphate in landfill leachate

ABSTRACT This study investigated the electrooxidation (EO) of mature landfill leachate from the Brady Road Resource Management Facility, Winnipeg (Canada). EO using boron-doped diamond (BDD) electrodes were applied to treat real landfill leachate using a batch reactor. Response surface methodology (RSM) was used to determine the optimum process parameter levels. This research mainly focused on how different current densities (64, 95, and 125 mA/cm2) and operational time (30 min, 1, 1.5, 2, 2.5, and 3 hr.) influenced the optimisation of parameters such as chemical oxygen demand (COD), colour, ammonium, and phosphate removal in mature landfill leachate at varied pH. To attain a high percentage of removal for the parameters mentioned above, the optimal conditions were found to be a current density (J) of 125 mA/cm2 and a pH of 8. The optimum conditions resulted in removal percentages of 95.47%, 80.27%, 71.15%, and 47.15% for colour, NH4 +, COD, and PO4 3- respectively, with an energy consumption of 0.05 kWh/dm3. The removal is related to a mechanism of the decomposition of water molecules to hydroxyl radicals and by direct anodic oxidation where the pollutants are transformed to CO2 and H2O. The novelty of this research lies in the optimisation of BDD electrode-based treatment for the simultaneous removal of COD, ammonium, phosphate, and colour from mature leachate collected from a severely cold climatic region of Canada. The BDD electrode showed excellent removal efficiencies for the targeted contaminants with lower energy consumption, making it a feasible method for on-site landfill leachate treatment.

Performance evaluation of hybrid electrochemical processes in mature leachate treatment

AbstractBACKGROUNDRecently, hybrid treatment applications have gained attention in the treatment of high‐strength wastewater. In this study, the following hybrid applications were applied: electrocoagulation (EC)‐electrooxidation (EO) (EC‐EO), and EO‐EC. The single EC and EO processes were independently optimized and then hybrid EC‐EO and EO‐EC processes were applied under the optimized conditions. Firstly, the most effective electrode pairs were selected in both EC and EO processes concerning pollutant elimination performance and energy needs. Afterward, the optimum values of the system requirements (initial pH, applied current, inter‐electrode distance, and reaction time) of the EC and EO were determined.RESULTSAlAl in the EC process and a Ti/RuO2‐graphite anode–cathode combination in the EO process were the most effective electrodes. Under optimum conditions (EC process: pH 7, applied current 2 A, reaction time 60 min, and inter‐electrode distance 2 cm; EO process: pH 7, applied current 1 A, reaction time 120 min, and inter‐electrode distance 2.5 cm), the chemical oxygen demand (COD) yields for EC and EO processes were 56.6% and 45.6%, respectively. The hybrid EC‐EO and EO‐EC processes yielded 69.6% and 66.4% COD removal, respectively. Specific energy consumption values for the EC, EO, EC‐EO, and EO‐EC were calculated as 14.1, 41.8, 38.9, and 40.7 kWh kg−1 COD, respectively.CONCLUSIONBased on its pollutant removal efficiencies and energy usage values, the hybrid EC‐EO process was found to provide significant advantages in mature leachate treatment. © 2023 Society of Chemical Industry (SCI).

Tratamiento de lixiviados mezclados tipo I y tipo III mediante filtración y oxidación química

In Riobamba city from Ecuador, for more than thirty years solid urban waste was placed in an open dump, without gas and leachate control. In 2016, the landfill was technically closed and an emerging cell with the characteristics of a sanitary landfill was built nearby. The Environmental Health and Hygiene Management Department of the Riobamba Municipal Decentralized Autonomous Government monitors leachate generation, recording 19.24 m3/day of young leachate (Type I) from the emerging cell and 5.78 m3/day of mature leachate (Type III) from the old landfill. The two types of leachates are mixed in the main collection pipe that reaches a storage pool that receives 25.02 m3/day. The results of the physical-chemical analysis determine that the values of the parameters are outside the permissible limits. Turbidity is &gt;1000 NTU (Nephelometric Turbidity Unit), and the concentration of suspended solids is 1200 mg. L-1 and iron 135.85 mg. L-1. Calcium (1223 mg. L-1) and manganese (356.15 mg. L-1) were also evaluated, as these minerals are related to the 16,000 mg. L-1 of hardness. For the treatment of the mixed leachate, two phases are proposed: a) physical treatment by downward filtration in a granular bed to reduce the concentrations of suspended solids, and b) chemical treatment by oxidation using sodium hypochlorite. Laboratory results showed a 96.40% decrease in the concentration of suspended solids. Turbidity stabilized at 65 UTN. Iron, calcium, and manganese concentrations decreased by 95.60%, 96.28%, and 50.60%, respectively.

Simultaneous removal of organic and nitrogenous compounds in mature landfill leachate by a hybrid electro-oxidation-dialysis (EOD) system

ABSTRACT Electrochemical process has been widely applied to eliminate recalcitrant contaminants (i.e., organic and nitrogenous compounds) in landfill leachate. This study aimed to evaluate the performance of a hybrid electro-oxidation-dialysis (EOD) system to minimize organic and nitrogenous compounds through a synergistic process of electrochemical oxidation (EO) and electrodialysis (ED) as well as the dissolved organic matter was characterized in terms of fluorescent component and molecular weight distribution. The EOD was carried out using boron-doped diamond (BDD) and Pt alternately. The results have shown that pH adjustment to acidic conditions is beneficial to EO. At optimal pH (pH 4), BDD-based EO is superior to removing COD and NH 4 + up to around 56% and 64%, respectively. During EOD process, the lower current density at 20.83 mA cm−2 is preferred for the recovery of nitrogenous ions (i.e. NH 4 + and NO 3 – ), especially for BDD-EOD. In addition, the dominant humic acid-like (HAL) and soluble microbial products-like (SMPL) substances in the mature leachate are mostly degraded to smaller molecules from 105 Da to 103 Da in both EOD processes. Overall, BDD-EOD favours indirect oxidation and has a higher energy consumption efficiency than Pt-EOD induced by direct oxidation for simultaneous removal of organic and nitrogenous compounds. BDD-EOD requires a lower total operation cost of around $2.33/m3 compared to Pt-EOD. It is concluded that the hybrid BDD-EOD process is technically feasible as a powerful pre-treatment approach to mature landfill leachate for refractory organics degradation and nitrogenous nutrients recovery.

A Novel 4-Set Venn Diagram Model Based on High-Resolution Mass Spectrometry To Monitor Wastewater Treatment.

A 4-set Venn diagram model oriented to high-resolution mass spectrometry (HRMS) data was developed to decipher the fate of dissolved organic matters (DOM) in three-stage continuous wastewater treatment processes. In total, 24 typical wastewater treatment modes conceptualized into a combination of three stages were generalized so that this model can be applied to all common types of actual wastewater treatment processes. As a result, eight kinds of native DOM and seven kinds of wastewater-produced (WW-produced) DOM separately represented by each proper subset of the 4-set Venn diagram could be identified so as to offer a molecular profile of DOM transformation. The 15 proper subsets of the 4-set Venn diagram could then explain how different wastewater treatment units work. Transformation rates of each DOM molecular formula can be estimated as a semiquantitative result. We further discussed the relationship between the transformation rates and proper subsets. As a proof of concept, the 4-set Venn diagram model was successfully applied in a complicated full-scale mature leachate treatment process with nine treatment units. This model can help to overcome the challenging task of data mining when applying HRMS and reduce the workload of data screening in the subsequent structural annotation.