Leachate Chemical Oxygen Demand Research Articles

Absorbent mixtures optimisation for COD and Ammonia Nitrogen reduction in stabilised leachate

This paper describes the optimisation of mixed media for Chemical Oxygen Demand (COD) and Ammonia Nitrogen (NH3-N) removal from stabilised leachate by feldspar (FE), zeolite (ZE), activated carbon (AC), and cockle shells (CS) mixtures using D-optimal mixture design. Linear equations characterised the optimal mixture. The optimum mitigation of COD and NH3-N in landfill leachate was favourable at 12.5 mg/L, 9.72 mg/L, 6 mg/L, and 11.79 mg/L of adsorbent mixed dosage for FE, ZE, AC, and CS, respectively, with the desirability value of 0.886. The predicted R-squared values for NH3-N (0.9839) and COD (0.8972) were in close agreement with the adjusted R-squared values of 0.9940 and 0.9900 for COD and NH3-N, respectively, which validates the obtained regression models. The Lack of Fit F-values of 0.6015 (COD) and 0.4565 (NH3-N) are insignificant, indicating that the models accurately predict the removal. The Fourier transform infrared spectroscopy (FTIR) revealed that the predominant hydroxyl group consisted of –OH at spectra 3306.18 and 3338.74. The study also revealed that the D-optimal mixture design has extremely high application potential as it produces a good mixture design based on the remediation of contaminants from stabilised leachate.

Analysis of particle size distribution of organic carbon for landfill leachate—implications for sustainable treatment

AbstractBACKGROUNDLandfill leachate has a complex composition requiring experimental support to formulate a sustainable treatment strategy. This study utilized the particle size distribution (PSD) of the chemical oxygen demand (COD) content to assess the profile of biodegradable and inert COD fractions; it also emphasized the functions and benefits of ultrafiltration and nanofiltration modules coupled to an activated sludge process. The evaluation profited from the field data of a landfill site in Istanbul, where the leachate was actually treated in a membrane bioreactor (MBR) plant.RESULTSCOD and total nitrogen levels fluctuated between 10 100–31 200 mg L−1 and 1150–2800 mg L−1, respectively. PSD analysis for COD, conducted at two extremes, displayed similar results, where the majority of the COD was observed to accumulate at the low extremity of the particle size, 70–72% below 2 nm. Therefore, direct membrane filtration of leachate yielded low COD removals that were limited to 9% with ultrafiltration and to 31–35% with nanofiltration. COD fractionation indicated a ratio of 5% for the inert COD in leachate. The permeate COD of ultrafiltration in the existing plant was 2000 mg L−1, much higher than the inert fraction ratio, which was further reduced to 266 mg L−1 by nanofiltration.CONCLUSIONPSD analysis was an integral complement of respirometry for establishing the size‐biodegradation relationships of different COD fractions. It located the majority of soluble COD fractions below 0.55 nm, thus implying the necessity of a biological process. PSD also identified the generation of soluble residual metabolic products, indicating that residual COD escaping treatment would be equally significant to the removal potential of the biodegradable substrate. © 2023 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

Acid leaching of hydrothermally carbonized sewage sludge: phosphorus recovery and hydrochar characteristics

The options for managing sewage sludge and its utilization as fertilizer are becoming progressively limited as a result of stringent environmental regulations imposed by the European Union over the past 10 years. The limitation of moisture present in sewage sludge that affects conventional treatment options like incineration can be obviated by using the hydrothermal carbonization (HTC) process. This research investigates the acid leaching of hydrochar produced by hydrothermally carbonizing sewage sludge. The objective is to investigate and compare the effects of formic acid (HCOOH), sulfuric acid (H2SO4), and acetic acid (CH3COOH) at varying pH levels on total phosphorus (TP) mobilization and hydrochar properties. The impact of independent parameters such as carbonization temperature of hydrochar, acid type, acid concentration, and acid leaching retention time on the TP mobilization, chemical oxygen demand (COD) of the leachate, and the fuel characteristic of the hydrochar was explored. A quadratic and cubic model was proposed to correlate the effects of independent parameters on TP and ortho-P mobilization, acid need, COD of leachate, and fuel characteristics of hydrochar using Design of Experiments and Response Surface Modeling. This approach was chosen in order to maximize the amount of data from a constrained number of experimental trials. The outcome of the study indicated a fractional amount of H2SO4 was enough to reach and maintain the lower pH in hydrochar slurry compared to HCOOH and CH3COOH. TP mobilization from solid to liquid is highly favorable in the presence of H2SO4 at lower pH compared to HCOOH and CH3COOH under similar reaction conditions. In addition, it was discovered that lowering the pH using HCOOH and H2SO4 to acid-leach the hydrochar boosted the caloric value of the hydrochar. However, CH3COOH has a contradictory effect.

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.

Low-cost treatment method for organic matter and nutrients in landfill leachate.

In this study, the ability of low-cost composite adsorbents to treat organic compounds in terms of chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) was investigated. The composite adsorbents were composed of washed sea sand (WSS), dewatered alum sludge (DAS), zero-valent iron (ZVI), and granular activated carbon (GAC). The removal efficiency of COD in landfill leachate by a composite adsorbent (composed of WSS (40%), DAS (40%), ZVI (10%), and GAC (10%) in weight) was 79.93 ± 1.95%. The corresponding adsorption capacity was 8.5 mg/g. During batch sorption experiments, the maximum COD removal efficiencies given by DAS, WSS, ZVI, and GAC were 16, 51.3, 42, and 100.0%, respectively. The maximum removal efficiencies of the above composite adsorbent for TN and TP were 84.9 and 97.4%, respectively, and the adsorption capacities were 1.85 and 0.55 mg/g, respectively. The Elovich isotherm model gave the best fit for COD, TN, and TP adsorption. This composite adsorbent can treat more than one contaminant simultaneously. The application of DAS and ZVI to make an efficient adsorbent for wastewater treatment would be a good re-use application for them, which would otherwise be landfilled directly after their generation.

Impact of leachate on quality of ground water around Chunga Landfill, Lusaka, Zambia and possible health risks

We report the characteristics and possible impact of leachate on quality of groundwater in the Chunga Landfill area of Lusaka, Zambia. Water and leachate samples were collected within and around the landfill for analysis. The pH, biological oxygen demand (BOD), chemical oxygen demand (COD), nitrates, sulphates, chlorides for the leachate and groundwater samples were (6.6 ± 0.1 to 8.7 ± 0.0), (1.7 ± 0.3 to 1,569.6 ± 4.9 mg/L), (4.0 ± 0.0 to 10,378.5 ± 59.2 mg/L), (8.0 ± 0.0 to 37.7 ± 0.4 mg/L), (11.7 ± 0.0 to 273.1 ± 1.7 mg/L), (43.0 ± 1.2 to 974.2 ± 0.8 mg/L) respectively. Heavy metal concentration ranges were cadmium (0.004 ± 0.000 to 1.149 ± 0.021 mg/L, chromium (0.007 ± 0.000 to 2.699 ± 0.039 mg/L), copper (0.013 ± 0.002 to 0.246 ± 0.005 mg/L), lead (0.062 ± 0.005 to 2.591 ± 0.065 mg/L) and zinc (0.008 ± 0.001 to 2.032 ± 0.017 mg/L). The pH of the leachate (8.5 ± 0.0 to 8.7 ± 0.0) meant the landfill was in the methane fermentation phase. An indexing approach was used with the leachate pollution index (LPI) of 30.173, heavy metal pollution index (HPI) of 3,938.92. The heavy metal index (HMI) for copper, lead, chromium, cadmium and zinc were found to be 0.92, 1,124.19, 47.20, 994.17 and 1.48 respectively. Principal component analysis (PCA) showed that anthropogenic activities contributed to pollution with high loading values. Ash from continuous burning of the waste may provide alkalinity which reduces leachate BOD and COD. Results showed that the landfill has outgrown the designed cells capacity as not all leachate was collected by the under-drainage. Results also showed that lack of adequate landfill cover significantly increases rainfall infiltration thereby increasing volumes of leachate produced with a, hence potential for underground water contamination and a human health and environmental problem.

Insights into the landfill leachate properties and bacterial structure succession resulting from the colandfilling of municipal solid waste and incineration bottom ash

Four simulated bioreactors were loaded with only MSW, 5 % BA + MSW, 10 % BA + MSW and 20 % BA + MSW to investigate the leachate property and bacterial community change trends during the colandfilling process. The results showed that with increasing BA addition proportion (5 %∼20 %), the leachate oxidation–reduction potential (ORP) was lower, the leachate pH quickly entered the neutral stage, and the chemical oxygen demand (COD), volatile fatty acids (VFA), NH4+-N, Ca2+ and SO42− presented faster downward trends. The leachate SUVA254 and E300/400 confirmed that BA can accelerate the leachate humification process. BA can quickly increase bacterial diversity, and the higher the addition proportion of BA, the more significant the change in microbial community structure during the landfilling process. The leachate pH and COD greatly influenced the bacterial community structure. A low BA proportion can increase metabolism pathway abundance during the initial stage, but a high BA proportion had an inhibitory effect on the metabolism pathway.

Impregnation of zinc oxide nanoparticles on activated carbon synthesised from corncob for appraisal of leachate chemical oxygen demand removal potential

ABSTRACT An agro-waste corncob was used to prepare activated carbon and loaded with ZnO nanoparticles by using the impregnation method. The FTIR band at 492 cm−1 of zinc oxide nanoparticle-loaded corncob activated carbon (ZnO@CCAc-7) shows the spreading vibrational modes of ZnO. The crystallinity and crystal structure of different prepared materials were analysed using X-ray diffraction (XRD). The specific surface area of ZnO@CCAc-7 was observed to be 148.3 m2/g, which was nearly two times larger than that of efficient corncob activated carbon. The fundamental peaks of carbon, oxygen and ZnO nanoparticle with their atomic percent of C 66.66, O 27.10 and ZnO 6.24 were observed in the SEM-EDX spectrum. The thermal stability of the prepared adsorbent was also analysed using thermogravimetric analysis (TGA). The maximum COD reduction using ZnO@CCAc-7 adsorbent was obtained to be 76.4% at the peak values of pH 6, dose 1.50 g/50 mL, time 160 minutes and temperature 30 ͦC. The various adsorption models Hill, Khan, Redlich–Peterson, Toth, Koble–Corrigan and Freundlich were found close-fitted to the adsorption process. It was observed that the COD removal adsorption technique ensued to a pseudo-first-order rate of kinetics. The negative value of Gibb’s free ΔG0 and positive values of the enthalpy change (∆H° = 25.64 kJmol-1) indicates that the process of COD removal using ZnO@CCAc-7 adsorbent was spontaneous and endothermic in nature. Furthermore, response surface methodology with a subset of Central composite design was also studied in detail to optimise the COD removal efficiency.

A novel process for landfill leachate pretreatment using hydrodynamic cavitation combined with potassium ferrate oxidation

AbstractBACKGROUNDEfficient pretreatment is key to improving landfill leachate biodegradability. This is the first study to combine hydrodynamic cavitation (HC) and potassium ferrate (K2FeO4) for the treatment of landfill leachate, using chemical oxygen demand (COD) and UV absorbance at a wavelength of 254 nm (UV254) as the main test indicators. The feasibility of HC combined with K2FeO4 as a mature leachate pretreatment method was explored.RESULTSThe HC experiment used 40 L of mature landfill leachate raw water, with optimal reaction conditions of: pH 4, 70 min continuous cavitation and K2FeO4 dosage of 1.5 g/L. The leachate COD decreased from 3812.64 mg/L to 1833.8 mg/L (51.69% removal), while UV254 decreased from 20.44 to 6.14 (65.14% removal) and total organic carbon decreased from 1489 to 915.3 mg/L (38.53% removal). After HC/K2FeO4 treatment, the biochemical oxygen demand after 5 days (BOD5)/COD (0.61) was greatly improved compared to the raw leachate (0.362), with effluent reaching the standard (BOD5/COD >0.6) required to be considered fully biodegradable. Studies have shown that HC can accelerate the reaction rate of Fe(VI) with pollutants, while also forming a Fenton‐like system with the products of Fe(VI) reduction. FT‐IR analysis results showed that HC/K2FeO4 treatment achieved the removal of complex high molecular weight compounds, by carbonization or decomposition into more biodegradable substances.CONCLUSIONCompared with the traditional pretreatment process, HC/K2FeO4 exhibits strong oxidation and coagulation performance, achieving the significant removal of leachate humus and effectively improving biodegradability, while also being suitable for large‐scale applications, such as landfill leachate treatment. © 2022 Society of Chemical Industry (SCI).

Characterization of Solid Waste Leachateand Its Impact on Surface Water Quality: A Case Study at Rajbandh, Khulna, Bangladesh

The present study was carried out to characterize leachate from waste dumping site and its impact on surrounding surface water quality at Rajbandh in Khulna. For this purpose, surface water samples (10) and leachate samples (5) were taken from the site during two season the monsoon season and post monsoon respectively. The samples were taken during the daytime from 9 a.m. to 1 p.m because at midday the temperature rises and the physico-chemical parameters of the water are modified. Some physico-chemical parameters such as pH, Electrical conductivity (EC), Total dissolved Solids (TDS), Dissolve Oxygen (DO), Chloride (Cl-), Magnesium (Mg2+), Calcium (Ca2+), Sodium (Na+), Potassium (K+), Biological Oxygen Demand (BOD5), Chemical Oxygen Demand (COD), Iron (Fe2+), Phosphate (PO43-), Sulfate (SO42-), Nitrate (NO32-) were analyzed in the laboratory in accordance with standard laboratory procedure. As well as some heavy metals such as Cadmium, Chromium, Lead, Manganese, Iron and Zinc were also analyzed in the laboratory. It is observed that, the physicochemical characteristics of surface water and leachate samples vary among the parameters in two seasons throughout the study period. The concentration of TDS and EC were found to be high in leachate compare to surface water samples that might be caused due to the existence of high-level various anions and soluble salts with other inorganic components. In monsoon the TDS values ranged from 3227 ± 2357 for leachate and 737 ± 498 for surface water samples whereas in post-monsoon the variation followed by 4640 ± 1790 and 803 ± 232 for surface water and leachate respectively. In case of EC for leachate it varied from 3630 ± 1397 and 4900 ± 1734 for monsoon and post-monsoon seasons correspondingly but varied from 1473 ± 498 in monsoon and 1627 ± 473 in post-monsoon for surface water samples. The high concentration of BOD (3.91 ± 1.54 in monsoon and 6.25 ± 3.27 in post- monsoon) and COD (117.80 ± 58.31 in monsoon and 229.39 ± 166.55 in post-monsoon) value were found in surface water samples compared to leachate samples. In case of Cr for leachate it varied from 0.081 ± 0.029 and 0.070 ± 0.026 for monsoon and post-monsoon seasons correspondingly. As well as the concentration of Cd (0.023± 0.006 in monsoon and 0.087±0.068 in post monsoon) and Pb (0.35±0.109 in monsoon and 0.025±0.013 in post monsoon) varied greatly during both season. The concentration of heavy metals such as Pb, Zn, Cr and Mn in surface water samples was also greater than 0.001mg/l. Further for leachate COD was very strongly correlated with TDS and cadmium. Magnesium was significantly correlated with potassium. For surface water sample TDS was significantly correlated with EC and pH. Chloride was significantly correlated with Cd and pb was correlated with calcium. This study recommended that the authority should take proper steps for the management of waste as well as give emphasis on the leachate collection.

An overview of comparing chemical oxygen demand removal methods from landfill leachate

Aims: Landfill leachate contains many pollutants including chemical oxygen demand (COD), biological oxygen demand, ammonia nitrogen, organic matter, minerals, and toxins. Given the importance of COD removal from landfill leachate, this study was conducted to evaluate and compare different methods used for the removal of COD from leachate. Materials and Methods: This study was conducted as a narrative review using keywords of leachate, COD, landfill in related journals issued in scientific databases such as Web of Science, PubMed, SID, and Google Scholar. We reviewed different aspects of COD removal from leachate to find better options in this respect. Results: The highest rate of COD removal was observed for batch reactor methods of anaerobic and aerobic granular activated carbon and electro Fenton by 98.4% COD removal, and the lowest one was 22.7% for the electro-Fenton method. The most commonly used methods for removing COD from solidwaste leachate have been physical and chemical methods. Conclusion: This study showed that a wide range method has been used to remove COD from leachate. It seems that combined methods are more effective to reduce the content of leachate COD. Besides, methods such as Fenton and absorption are more preferable because of simple application and low energy consumption.

A systematic assessment of aeration rate effect on aerobic degradation of municipal solid waste based on leachate chemical oxygen demand removal

Aeration is one mainstream technique to accelerate municipal solid waste (MSW) degradation in landfills. The determination of an appropriate aeration rate is critical to the design and operation of a landfill aeration system. In this study, we analyze 132 waste degradation tests reported in forty one studies in the literature. We use L min−1 kg−1 dry organic matter (L min−1 kg−1 DOM) as the uniform unit to quantify the aeration rates in all tests. The first order rate coefficient for chemical oxygen demand (COD) removal in leachate (kCOD) is selected as the parameter to characterize MSW degradation process. We further divide aerobic tests into five aerobic groups base on the respective aeration rates, i.e., <0.02, 0.02–0.1, 0.1–0.3, 0.3–1, and >1 L min−1 kg−1 DOM. With an increase in the aeration rate, the kCOD increases first and then decreases. The aeration rate between 0.1 and 0.3 L min−1 kg−1 DOM has the best enhancement on the kCOD. The kCOD values are not much higher than the anaerobic and semi-aerobic tests when the aeration rates are <0.1 L min−1 kg−1 DOM, because such aeration rates may be lower than the actual oxygen consumption rates. An aeration rate >0.3 L min−1 kg−1 DOM reduces the kCOD likely due to excess water evaporation and ventilation cooling. Among the analyzed results, the aeration rate is the most related to the kCOD in principal component analysis than the other factors, including liquid recirculation and addition, waste total density, waste degradation level, and waste initial temperature.

Photocatalytic treatment of landfill leachate using cascade photoreactor with immobilized W-C-codoped TiO2 nanoparticles

Landfill leachate is categorized as recalcitrant wastewater and its treatment is a necessary measure for environmental protection. Recently, photocatalytic treatment of recalcitrant wastewaters using N-, P-, and N-P-type TiO2 nanoparticles under visible light irradiation has attracted researchers’ attention. This study aims at investigating the photocatalytic removal efficiency of leachate chemical oxygen demand (COD) using tungsten (W)-Carbon (C)-codoped titanium dioxide (TiO2) nanoparticles under visible light irradiation. A cascade photoreactor with immobilized W-C-codoped TiO2 nanoparticles was applied to overcome the limitations of mass transfer and aeration in immobilized photocatalytic treatment processes. The effect of operating parameters such as coating surface density, light intensity, leachate recirculation flow rate, and initial leachate COD on the COD removal efficiency was experimentally investigated. Based on the results, 84 % of leachate COD was removed after 40 h treatment under the conditions of 550 mg.L−1 initial leachate COD, 40 W light intensity, 10.59 g.m-2 coating surface density, and 1 L.min−1 leachate flow rate. In addition, the COD removal efficiency of leachate with 550 mg.L−1 initial COD under 40 h sunlight irradiation, which was 46 %, was equal to that under 40-W light irradiation. The photocatalytic COD removal efficiency of leachate with high initial COD (10,100 mg.L−1) was 32 % after 60 h treatment. The findings of this research offer new insights about efficient photocatalytic treatment of landfill leachate using cascade photoreactor under visible light irradiation on a modest and large scale.

Brominated flame retardants and perfluoroalkyl substances in landfill leachate from Ireland

Between June and November 2017, leachate samples were collected from 40 landfills across the Republic of Ireland. Concentrations of perfluoroalkyl substances (PFASs), polybrominated diphenyl ethers (PBDEs), and hexabromocyclododecane (HBCDD) determined in these samples were within the range previously reported in other countries. Average concentrations of PFASs exceeded those of PBDEs and HBCDD; likely due to the higher water solubility of PFASs. Log-transformed concentrations of BDEs-47, 100, 153, and 183, as well as perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA) and perfluorobutane sulfonate (PFBS) were significantly (p < 0.05) higher in leachate from newer, lined landfills than in samples from unlined landfills. These higher concentrations in lined landfills are likely related to the fact that lined landfills are found to retain organic matter leading to a higher organic content of leachate from such landfills. This is evidenced by the significant (p < 0.05) correlation between log-transformed concentrations in leachate of most of the same contaminants and those of chemical oxygen demand (COD). Concentrations of the less water-soluble, higher molecular weight BDE-209 were not correlated with leachate COD, nor landfill age or the presence of a landfill liner. This suggests that the presence of BDE-209 in landfill leachate is driven more by physical abrasion of particles and fibres from waste articles, than dissolution into the aqueous phase. The higher concentrations of some PFASs and PBDEs in leachate from lined landfills present a challenge with respect to leachate disposal, when leachate is sent to wastewater treatment plants that do not necessarily have mechanisms in place to remove or destroy these chemicals prior to discharge into the environment. Moreover, the presence of these persistent organic chemicals in leachate from unlined landfills raises concerns about releases to the environment including groundwater over the lifetime of such landfills and beyond.

Vulnerability assessment of areas allocated for municipal solid waste disposal systems: a case study of sanitary landfill and incineration.

This study was conducted to assess the vulnerability of areas allocated for sanitary landfill in Nakhon Ratchasima and for incineration in Phuket, Thailand, and to investigate the factors contributing to their vulnerability. Analysis was conducted to develop a vulnerability index using a composite index approach and the Intergovernmental Panel on Climate Change (IPCC) framework approach, while correlation and t tests were applied to identify the relationships and differences between the two systems. Additionally, vulnerability indices were developed using the IPCC vulnerability definition. The results suggested that the vulnerability of the areas allocated for sanitary landfill and incineration were not significantly different. The factor that had the greatest impact on the vulnerability of the sanitary landfill was nuisance, while sub-component correlation analysis revealed that cadmium in groundwater was significantly negatively correlated with vulnerability (r = - 0.958, p < 0.05). Furthermore, the factor that had the greatest effect on vulnerability from incineration was leachate. Similarly, correlation analysis suggested that the chemical oxygen demand in leachate and solid waste residues was significantly positively correlated with vulnerability (r = 0.981, 0.975 respectively, p < .05). It is hoped that these findings can be used to establish measures for preventing environmental problems, as well as to prioritize and identify issues that need to be resolved urgently, and to help policy makers select appropriate systems for different regions of Thailand.

Efficiency of Combined Processes Coagulation/Solar Photo Fenton in the Treatment of Landfill Leachate

The combined coagulation-solar photo Fenton treatment of leachate from the sanitary landfill located in Atlantico-Colombia was investigated. Firstly, the efficiency of two alternative combined treatments for the reduction of chemical oxygen demand in leachate was assessed, coagulation with poly-aluminum chloride followed by solar photo-Fenton process (Treatment 1) and coagulation with FeCl3·6H2O followed by ferrioxalate-induced solar photo-Fenton process (Treatment 2). Afterwards, treatments 1 and 2 were compared with the treatment currently used in the sanitary landfill (only coagulation with poly-aluminum chloride), in terms of efficiency and costs. An optimization study of alternative treatments was performed combining central-composite experimental design and response surface methodology. The optimum conditions resulted in a chemical oxygen demand reduction of 73 % and 80 % for Treatment 1 and 2, respectively. Both alternative treatments for the leachate are more efficient than the treatment currently used in the sanitary landfill (chemical oxygen demand reduction of 20 %). In terms of costs, treatment 1 would be the most competitive to implement in the sanitary landfill, since this would have an increase of 13.3 % in the total unitary cost compared to an increase of 39.5 % of treatment 2.

Coupled experimental assessment of physico-biochemical characteristics of municipal solid waste undergoing enhanced biodegradation

Seven municipal solid waste (MSW) specimens with variable initial waste compositions were biodegraded in large (d = 300 mm, h = 600 mm) laboratory landfill simulators under leachate-recirculation-enhanced anaerobic biodegradation conditions to investigate changes in the biochemical and physical characteristics of solid waste, leachate and biogas during biodegradation. The evolution with time of the monitored characteristics of the three phases was presented and the characteristics empirically correlated. The impact of the initial composition of waste on the biodegradation process was quantified. Although removal of soluble compounds in leachate, and methane (CH4) generation from waste was practically completed after around 300 days, changes in vertical strain, total unit weight and volumetric moisture content of waste continued in decreasing rates even after 1000 days. Methane generation potential (L0) of the waste was correlated to the percentage of biodegradable waste prior to degradation expressed by parameter B0. Maximum methane generation rate (rCH4,max) increased with increasing L0 and maximum soluble chemical oxygen demand in leachate. Final strain (or settlement) of waste due to anaerobic biodegradation (εB,f) increased with increasing B0 and L0. The compression ratio was found to vary during the process, although it is commonly assumed to be constant. The maximum long-term compression ratio increased with increasing εB,f and rCH4,max. The total unit weight at submerged and field capacity states and volumetric moisture content of waste were also dependent on the initial composition and compression (quantified by strain) of waste. The trends presented in this study contribute to the quantitative understanding of coupled processes during enhanced biodegradation of MSW of variable waste composition.

Treatment of leachate from municipal solid waste of Mostaganem district in Algeria: Decision support for advising a process treatment.

The aim of this work is to propose a plan for the choice of a suitable process for the treatment of a young leachate from municipal solid waste. Classical processes were applied: Fenton process, the coupling coagulation-Fenton process and the adsorption on powdered activated carbon (PAC). The study involves synthesised leachates from three types of wastes collected from sanitary landfill (SL): leachate of putrescible fraction (Lp), paper-cardboard (Lpc), sawdust (Ls) and the one of landfill (Lsl). The optimal operating conditions have been determined for the three processes: Fenton: [H2O2] = 6.8 g L-1 and [Fe2+] = 2.8 g L-1, coagulation: [Fe3+] = 0.3 g L-1 and adsorption: [PAC] = 60 g L-1. The three processes gave reduction rates of chemical oxygen demand ranging from 50% to 85% for Lp, 87% to 97% for Lpc and 61% to 87% for Ls. Whereas for Lsl, it was of 45%, 56% and 80% for the Fenton, coagulation-Fenton and adsorption processes, respectively. A modelling study was conducted to calculate the chemical oxygen demand of leachate produced during 25 years for different thicknesses of waste. This predicted value is used to advise for the process treatment to apply and to assess the environmental impacts in the long term.

Evaluation of leachate dissolved organic nitrogen discharge effect on wastewater effluent quality

Nitrogen is limited more and more frequently in wastewater treatment plant (WWTP) effluents because of the concern of causing eutrophication in discharge waters. Twelve leachates from eight landfills in Florida and California were characterized for total nitrogen (TN) and dissolved organic nitrogen (DON). The average concentration of TN and DON in leachate was approximately 1146mg/L and 40mg/L, respectively. Solid-phase extraction was used to fractionate the DON based on hydrophobic (recalcitrant fraction) and hydrophilic (bioavailable fraction) chemical properties. The average leachate concentrations of bioavailable (bDON) and recalcitrant (rDON) DON were 16.5mg/L and 18.4mg/L, respectively. The rDON fraction was positively correlated, but with a low R2, with total leachate apparent color dissolved UV254, chemical oxygen demand (COD), and humic acid (R2 equals 0.38, 0.49, and 0.40, respectively). The hydrophobic fraction of DON (rDON) was highly colored. This fraction was also associated with over 60% of the total leachate COD. Multiple leachate and wastewater co-treatment simulations were carried out to assess the effects of leachate on total nitrogen wastewater effluent quality using removals for four WWTPs under different scenarios. The calculated pass through of DON suggests that leachate could contribute to significant amounts of nitrogen discharged to aquatic systems.

Evaluating the ability of artificial neural network and PCA-M5P models in predicting leachate COD load in landfills

Waste burial in uncontrolled landfills can cause serious environmental damages and unpleasant consequences. Leachates produced in landfills have the potential to contaminate soil and groundwater resources. Leachate management is one of the major issues with respect to landfills environmental impacts. Improper design of landfills can lead to leachate spread in the environment, and hence, engineered landfills are required to have leachate monitoring programs. The high cost of such programs may be greatly reduced and cost efficiency of the program may be optimized if one can predict leachate contamination level and foresee management and treatment strategies. The aim of this study is to develop two expert systems consisting of Artificial Neural Network (ANN) and Principal Component Analysis-M5P (PCA-M5P) models to predict Chemical Oxygen Demand (COD) load in leachates produced in lab-scale landfills. Measured data from three landfill lysimeters, including rainfall depth, number of days after waste deposition, thickness of top and bottom Compacted Clay Liners (CCLs), and thickness of top cover over the lysimeter, were utilized to develop, train, validate, and test the expert systems and predict the leachate COD load. Statistical analysis of the prediction results showed that both models possess good prediction ability with a slight superiority for ANN over PCA-M5P. Based on test datasets, the mean absolute percentage error for ANN and PCA-M5P models were 4% and 12%, respectively, and the correlation coefficient for both models was greater than 0.98. Developed models may be used as a rough estimate for leachate COD load prediction in primary landfill designs, where the effect of a top and/or bottom liner is disputed.