Removal of COD and colour from young municipal landfill leachate by Fenton process

Study of the Water Quality Index and Polycyclic Aromatic Hydrocarbon for a River Receiving Treated Landfill Leachate

Rising solid waste production has caused high levels of environmental pollution. Population growth, economic patterns, and lifestyle patterns are major factors that have led to the alarming rate of solid waste production. Generally, solid wastes such as paper, wood, and plastic are disposed into landfills due to its low operation and maintenance costs. However, leachate discharged from landfills could be a problem in surfaces and groundwater if not adequately treated. This study investigated the patterns of the water quality index (WQI) and polycyclic aromatic hydrocarbons (PAH) along Johan River in Perak, Malaysia, which received treated leachate from a nearby landfill. An artificial neural network (ANN) was also applied to predict WQI and PAH concentration of the river. Seven sampling stations were chosen along the river. The stations represented the upstream of leachate discharge, point of leachate discharge, and five locations downstream of the landfill. Sampling was conducted for one year starting July 2018. Physicochemical parameters, namely pH, biological oxygen demand, chemical oxygen demand, ammoniacal nitrogen, total suspended solids, and dissolved oxygen, were used to compute the water quality index (WQI). PAH concentrations were determined by liquid–liquid extraction of water samples followed by an analysis using gas chromatography. Results showed that WQI of Johan River was under Class III where intensive treatment was required to make it suitable for drinking purposes. The highest recorded PAH concentrations were fluoranthene (333.4 ppb) in the dry season and benzo(a) pyrene (93.5 ppb) in the wet season. A correlation coefficient (Rp) for a model prediction based on WQI-ANN and TEC-ANN (toxicity equivalent concentration) in the wet and dry seasons was 0.9915, 0.9431, 0.9999, and 0.9999, respectively. ANN results showed good model performance with Rp ≈ 0.9. This study suggested that ANN is a useful tool for water quality studies.

Remedial Technologies for Aniline and Aniline Derivatives Elimination from Wastewater

BACKGROUND

Aniline and its derivatives are widely used as intermediate chemicals in the pharmaceutical and dye industries and are present in their wastewaters. These chemicals are of concern due to their potential detrimental effects on public health and aquatic species in the environment.

OBJECTIVES

Various available remedial technologies presented in the literature were investigated to determine the most suitable technology for the elimination of aniline and aniline derivatives from waste streams.

METHODS

The related literature was collected electronically from ScienceDirect, Google Scholar, the International Agency for Research on Cancer (IARC), ResearchGate and Wiley Online Library for systematic review. The search terms included 'aniline', 'aniline degradation', 'advanced oxidation processes (AOPs)', 'aniline derivatives' and 'Fenton's reagent'.

DISCUSSION

Aniline and its derivatives are a serious issue in the effluents of dye and pharmaceutical industries, but a number of efficient treatment methods using biological, physical and AOPs have been presented in the literature.

CONCLUSIONS

Comparison of the available technologies showed that AOPs were the most cost effective and efficient technologies for eliminating aniline and its derivatives from wastewater.

COMPETING INTERESTS

The authors declare no competing financial interests.

Electro-catalytic ozonation for improving the biodegradability of mature landfill leachate

Landfill leachate contains complex, resistant, and diverse compounds that are considered as an environmental health problem. This study aims to investigate the efficacy of integrated homogeneous catalytic ozonation and electrochemical process for improving the biodegradability of landfill. This experimental study was conducted on real landfill leachate on the laboratory scale. The variables were current density (O₃/H₂O₂-42.1 mA/cm²), ozone concentrations (100-400 mg/h), the initial pH (3-9), and the reaction times (1-6 h). The optimum operating condition was obtained at 1.42 mA/m², 400 mg/h of ozone concentration, initial pH of 3, during 3 h. In the proposed integrated catalytic ozonation-electrochemical process, the chemical oxygen demand (COD) and biochemical oxygen demand (BOD) concentrations were removed to 3381.9 and 1521.8 mg/L, respectively. Under the optimum condition, the biodegradability index increased from 0.27 to 0.45. The results showed that the electro-catalytic ozonation process has a significant effect on the biodegradability index and could improve the removal efficiency of landfill leachate treatments.

Sequential coagulation/flocculation and microwave-persulfate processes for landfill leachate treatment: Assessment of bio-toxicity, effect of pretreatment and cost-analysis

The possibility of landfill leachate treatment in a coupled microwave-persulfate (MW-PS) system with and without pretreatment, i.e. coagulation-flocculation (C-F) was investigated. The C-F pretreatment with alum and FeCl₃ has reduced the turbidity from 90 NTU to 43 NTU and 10 NTU, respectively, at the optimized coagulant dosage. Moreover, 73% COD and 86% color removal was observed in C-F pretreatment with FeCl₃. The application of MW-PS system (at 10 g/L of PS dosage) for pretreated leachate (FeCl₃ dosage 1 g/L and pH 5.5) has produced a final COD removal of 89%. Similarly, alum pretreatment (dosage 1.6 g/L, pH 8.2) coupled with MW-PS system has achieved a total COD removal of 62%. In MW-PS system, the ratio of initial PS dosage to initial COD ratio has shown significant effect on leachate treatment. However, slightly lesser ammonia removal was observed in MW-PS (93%) compared to MW alone (97%) owing to reduction in pH of the system. The comparison of bio-toxicity (i.e. inhibition to aliivibrio fischeri) of treated samples from MW-PS and MW alone after pretreatment, i.e. 12.1 mg/L and 6.8 mg/L of equivalent ZnSO₄ toxicity, indicated that MW-PS treated sample were found to be more toxic than MW alone treatment and raw leachate (7.6 mg/L and 7.2 mg/L of equivalent ZnSO₄ toxicity, respectively) due to sulfate ion. This indicates that C-F followed by MW alone would be an ideal option for leachate treatment. The cost and energy estimation of MW and MW coupled systems well supported the above findings.

Unraveling complex removal behavior of landfill leachate upon the treatments of Fenton oxidation and MIEX® via two-dimensional correlation size exclusion chromatography (2D-CoSEC)

The complex removal behavior of stabilized landfill leachate was explored for the treatments of Fenton oxidation (FnO) and magnetic ion exchange (MIEX^®) resin using two-dimensional correlation size exclusion chromatography (2D-CoSEC) and fluorescence excitation emission matrix-parallel factor analysis (EEM-PARAFAC). The overall removal rates of the bulk parameters (∼45% for dissolved organic carbon and ∼78% for UV absorbance) were similar between the two treatment options, while distinct differences were found with respect to different molecular sizes and chemical composition. The resin treatment eliminated humic substances (HS) and low molecular weight acid (LMWA) fractions to a greater extent than other fractions (i.e., HS: 62% and LMWA: 99%), while low molecular weight neutral (LMWN) and biopolymers (BP) fractions were more effectively treated by the FnO with the removal rates of 56% and 92%, respectively. The 2D-CoSEC further revealed that the sequential or preferential changes of different size fractions with increasing the resin or H₂O₂ were opposite between the two treatment options in the order of HS → LMWA → LMWN → BP for MIEX^®. Due to their complementary roles in treating leachate, the combined processes removed a wider ranges of different molecular sizes compared to the single operation.

Exploring the fate and oxidation behaviors of different organic constituents in landfill leachate upon Fenton oxidation processes using EEM-PARAFAC and 2D-COS-FTIR

In this work, the changes of different organic constituents in landfill leachate were tracked in Fenton oxidation processes with different operation parameters including H₂O₂ doses, pH, and the ratios of [H₂O₂]/[Fe] via fluorescence excitation emission matrix - parallel factor analysis (EEM-PARAFAC) and two-dimensional correlation spectroscopy (2D-COS). One tryptophan-like (C1), one fulvic-like (C2), and one humic-like (C3) components were identified in the leachates. The removal behaviors of the individual fluorescent components were dependent upon the operation conditions, suggesting the existence of unique characteristics with respect to the responses to the oxidation mechanisms, which were likely altered by different operation conditions. For all tested conditions, a greater extent of removal was consistently found for C3 versus C1 and C2 except for the relatively high pH ranges (>6.0), in which C2 presented the highest removal rates. 2D-COS combined with synchronous fluorescence spectra exhibited the preferential oxidation sequence in the order of C3 > C1 > C2 with higher H₂O₂ doses. 2D-COS coupled with Fourier transform infrared (2D-COS-FTIR) showed that aromatic functional groups were initially oxidized, followed by the removal of carboxylic groups and the formation of inorganic functional groups and aldehyde or ketonic groups. Hetero 2D-COS maps further revealed the close association between the aromatic groups and C3, and between the carboxylic groups and C1. This study utilizing 2D-COS provided new insights into the dynamic behavior of heterogeneous landfill leachate in Fenton oxidation processes under varying operation conditions.

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.

Optimization of Fenton treatment process for degradation of refractory organics in pre-coagulated leachate membrane concentrates

Untreated leachate membrane concentrates are a threat to the environment. In our study, effective removal of contaminants in pre-coagulated leachate membrane concentrates was achieved using the Fenton process. The Fenton process was optimized using the response surface method, and the maximum total organic carbon (TOC), chemical oxygen demand (COD), and chromaticity reduction efficiencies reached 68.9%, 69.6%, and 100% under the conditions pH 2, H₂O₂ concentration 1mol/L, and Fe²⁺ concentration 17.5mmol/L. The COD concentration was reduced from 1120 to 340mg/L. The H₂O₂ concentration was the key factor affecting the TOC removal efficiency. Slow, continuous addition of the Fenton reagents improved the H₂O₂ utilization rate, which improved the TOC removal efficiency. Fourier-transform infrared and three-dimensional fluorescence spectroscopy showed that the majority compound of the removed organic material was humic acid. Our study provides guidelines for the treatment of leachate membrane concentrates in engineering applications.

Predictive model of limestone scaling in ammonia stripping towers and its experimental validation on a treatment plant fed by MSW leachate-polluted groundwater

Groundwater pollution by municipal solid waste (MSW) landfill leachate is a global concern. Stripping towers are one of the most implemented techniques for the removal of ammonia pollution. This study presents a predictive computational model to estimate calcium carbonate precipitation in ammonia stripping towers. The model considers the Ca²⁺ super-saturation condition due to the water pH, temperature and salinity. The results have been validated through experimental data obtained from a plant fed with MSW landfill leachate-polluted groundwater. The plant consisted of two parallel lines composed of a coagulation-flocculation stage at high pH followed by a stripping tower. Six combinations of water pH and temperature conditions were tested. Maximum precipitation was 1,400 kgCaCO₃ after a period of 120days, observed at inlet pH and temperatures of 10.5 and 38 °C The maximum removal efficiency of ammonia was reported as 91%, 87% and 80% respectively. Finally, a good relationship between the loss of efficiency in ammonia removal and the increase of precipitating CaCO₃ to the tower plain area ratio, valid for all water pH and temperatures, has been found.

Power generation and nitrogen removal of landfill leachate using microbial fuel cell technology

Microbial fuel cell (MFC) technology has been practised in the treatment of landfill leachate. However, it is a big challenge for the usage of MFCs to treat landfill leachate with high ammonium content. The purpose of this study was to design and test two MFC reactors, i.e. an ammonium oxidation/MFC reactor and an MFC/Anammox reactor for the treatment of landfill leachate with high ammonium content in terms of power generation and nitrogen removal. Using the ammonium oxidation/MFC reactor, the landfill leachate collected from Leon County Landfill of Northwest Florida generated a power density of 8 mW/m2 together with 92% of nitrogen removal. For the MFC/Anammox reactor, a power density of 12 mW/m2 was achieved with 94% of nitrogen removal. Compared with the ammonium oxidation/MFC reactor, 50% more energy was generated because in the MFC/Anammox Reactor, nitrite served as the electron acceptor; while in the Ammonium Oxidation/MFC reactor, nitrate served as the electron acceptor. In this research, power generation was also found to be directly linked to the microbial species that were involved in organic decomposition, i.e. the greater the microbial concentration, the more the power generated.

Municipal leachate treatment by Fenton process: effect of some variable and kinetics

Due to complex composition of leachate, the comprehensive leachate treatment methods have been not demonstrated. Moreover, the improper management of leachate can lead to many environmental problems. The aim of this study was application of Fenton process for decreasing the major pollutants of landfill leachate on Kermanshah city. The leachate was collected from Kermanshah landfill site and treated by Fenton process. The effect of various parameters including solution pH, Fe²⁺ and H₂O₂ dosage, Fe²⁺/H₂O₂ molar ratio, and reaction time was investigated. The result showed that with increasing Fe²⁺ and H₂O₂ dosage, Fe²⁺/H₂O₂ molar ratio, and reaction time, the COD, TOC, TSS, and color removal increased. The maximum COD, TOC, TSS, and color removal were obtained at low pH (pH: 3). The kinetic data were analyzed in term of zero-order, first-order, and second-order expressions. First-order kinetic model described the removal of COD, TOC, TSS, and color from leachate better than two other kinetic models. In spite of extremely difficulty of leachate treatment, the previous results seem rather encouraging on the application of Fenton's oxidation.

Toxicity assessment of tannery effluent treated by an optimized photo-Fenton process

In this work, an optimized photo-Fenton process was applied to remove pollutants from tannery industrial effluent (TIE) with its final toxicity level being assessed by a lettuce-seed-based bioassay test. A full 33 factorial design was applied for the optimization of long-term photo-Fenton experiments. The oPtimum conditions of the photo-Fenton process were attained at concentration values of 0.3 g Fe(2+) L(-1) and 20 g H2O2 L(-1) and pH3, for 120 min UV irradiation time. Reactor operating parameter (ROP) effects on the removal of chemical oxygen demand, colour, turbidity, total suspended solids and total volatile solids were evaluated, suggesting that a broad range of ROP values are also suitable to give results very near to those of the photo-Fenton experiments under optimal conditions. Based on the low calculated median lethal dose (LD50) values from a lettuce-seed-based bioassay test, we suggest that recalcitrant substances are present in treated TIE samples. A possible cause of the high toxicity level could partly be attributed to the nitrate concentration, which was not completely abated by the photo-Fenton process. Apart from this, the photo-Fenton process can be used as a part of an industrial effluent treatment system in order to abate high organic pollutant loads.

Removal of COD and colour in real pharmaceutical wastewater by photoelectrocatalytic oxidation method

In this study, TiO2/Ni photo-anode and multi-walled carbon nano-tubes (MWCNTs) air cathode were prepared by the dip-coating method, and the photoelectrocatalytic degradation of real pharmaceutical wastewater was investigated in the self-made reactor. The combination of the TiO2/Ni electrode and MWCNTs air cathode was adopted to treat the pharmaceutical wastewater by the process of photoelectrocatalysis. Various operational parameters to achieve optimum efficiency of this photoelectrocatalytic degradation system are presented, such as applied bias voltage, NaCl concentration, pH and different degradation methods. Under the optimal conditions, the removal of chemical oxygen demand (COD) and colour are 93.5% and 78.5% respectively. The possible roles of the anode-cathode on the reactions and the probable mechanisms of effect were also discussed. The photoelectrocatalytic technology can be used for the long-term treatment of real pharmaceutical wastewater.

Impact of human activities on the physico-chemical quality of surface water and groundwater in the north of Marrakech (Morocco)

The aim of this study was to assess the impact of three sources of pollution (landfill leachate, wastewater and mining activities) on the physico-chemical characteristics of surface water and groundwater in the northern region of Marrakech (Morocco). Numerous groundwater samples and surface water (Tensift River) samples were collected during the dry season and analysed. The groundwater samples had a high conductivity, which varied between 0.95 and 7.40 mS/cm; the conductivity of the surface water samples varied between 1.31 and 15.84 mS/cm. pH varied between 6.64 and 8.10 for groundwater and between 6.70 and 8.40 for surface water. The results showed that groundwater and surface water had a degraded quality in the region. Principal component analysis (PCA) enabled identification of the impact of pollution sources by combining the upstream and the downstream points. These results also showed that, in the study area, the effect of wastewater and the mine were dominated those of the landfill.

Using D-optimal experimental design to optimise remazol black B mineralisation by Fenton-like peroxidation

The mineralisation of remazol black B (RBB) was studied at concentrations ranging from 20-1000 mgL(-1). The work was aimed at investigating the Fenton-like peroxidation of RBB at a concentration typically obtained in Batik cottage industries. Other response parameters were degradation and colour removal efficiencies. The parameters that were measured included total organic carbon (TOC), chemical oxygen demand (COD) as well as absorbance for mineralisation, degradation and colour. To optimise the process, the interaction effects of several controlling variables on the treatment process were examined using dispersion matrix-optimal design and response surface analysis. Four specific variables: initial dye concentration (Dye)o; the molar ratio of oxidant to dye organic strength (H2O2):(COD); the mass ratio of the oxidant to the catalyst (H2O2):(Fe3+) and reaction time (t(r)), were observed. Three reduced empirical models, one for each response, were developed for describing the treatment process. For 20, 510 and 1000 mgL(-1), the optimum %TOC reduction and oxidation times were 44% for 95 min, 52% for 52.5 min and 68% for 10 min corresponding to 67, 81 and 75% COD reduction, respectively. The optimum COD reduction and oxidation times were 89% for 95 min, 91% for 10 min and 84% for 95 min for concentrations of 20, 510 and 1000 mg L(-1), respectively. For all concentrations, total colour removal was achieved. A comparison of the results obtained in this study with literature values for traditional Fenton, photo-Fenton and photo-Fenton-like oxidation indicated that the TOC reduction obtained using the Fenton-like process was satisfactory.

Effect of COD/SO4(2-) ratio on anaerobic treatment of landfill leachate during the start-up period

This study investigates the performance of an anaerobic baffled reactor (ABR) during the start-up period of raw young landfill leachate treatment at two chemical oxygen demand (COD) to SO4(2-) ratios of 20 and 4. The reactor was operated at ambient temperature and low organic loading rates (0.52, 0.76 and 1.05 kg COD/m3 per day). During the study, sulfate-reducing bacteria (SRB) activity increased at the lower ratio of COD/SO4(2-) producing higher levels of sulfide and alkalinity. The dissolved sulfide concentration reached an inhibitory level above 250 mg/L, which caused a sharp reduction in the total COD removal efficiency from 77-80% to 32%. Total volatile fatty acid (TVFA) production proceeded at a constant level despite increased organic loading. As the effluent total and organic COD concentrations increased, the inhibitory effect of the inborn sulfide was correlated to the limitation experienced in the hydrolysis/acidogenesis stages, and thus VFA production and organic matter removal.