Pretreatment Of Landfill Leachate Research Articles

Revamping of a Full-Scale Membrane Plant for Landfill Leachate Pretreatment Using Partial Nitritation.

This paper describes a case study involving a revamping of a full-scale membrane bioreactor that treats landfill leachate and other liquid wastes. The main change was the introduction of nitritation/denitritation in alternating cycles instead of the classic denitrification/nitrification process, together with the installation of fine bubble diffusers, a reduction in the volume of the biological compartment, and an increase in the equalization volume. The most significant results were obtained for the biological compartment, with a decrease in the specific energy consumption of 46.6%. At the same time, the removal efficiency of COD, BOD, and TN substantially remained the same before and after plant revamping, while the removal efficiency of TP increased over the years, reaching an average value of almost 71%. Regarding the ultrafiltration unit, the specific flux (or permeability) was characterized by an increasing trend. At the same time, the specific energy consumption of this section decreased by 9.4%. These results led to the conclusion that the changes introduced with the revamp led to a more stable process, a reduction in membrane fouling, and important energy savings.

Removal of pollutants from landfill leachate by adsorption with nano zero-valent iron particles: adsorption isotherms and kinetic studies

Abstract Nano zero-valent iron (nZVI) is an effective adsorbent for removing various organic and inorganic contaminants. In this study, nZVI particles, synthesized in our previous work, were used for landfill leachate pretreatment. The adsorption performance was tested at various adsorbent concentrations (50–500 mg Fe0/L), pH (3–8), and contact times (15–330 min). Chemical oxygen demand, dissolved organic carbon (DOC), nitrate (NO3-), and ammonium (NH4+) removal efficiency were approximately 75%, 60, 57, and 33%, respectively. The obtained data were fitted well by the Langmuir isotherm and adsorption kinetics of pseudo-second-order equations (R2 > 0.9). The adsorption capacities were found to be 29.62, 21.01, and 3.12 mg/g for DOC, NH4+, and NO3−, respectively, at Fe0 concentration of 50 mg Fe0/L, pH of 8, and contact time of 120 min, which was determined as the effective operational conditions in this work. The obtained removal levels were higher compared to the conventional activated carbon adsorption (72.3%). Results suggest that nZVI has the potential to create effective adsorption relevant to landfill leachate pretreatment, thereby providing more efficient biological treatment by decreasing important pollutants before biological treatment.

Pretreatment of Landfill Leachate Using Hydrodynamic Cavitation at Basic pH Condition

The leachate generated from a landfill can cause significant harm to the environment and human health, so it must be treated before being discharged. A biochemical method is effective to treat the landfill leachate, but it requires a physicochemical pretreatment to help reduce the organic load and improve the biodegradability of the landfill leachate. In this work, hydrodynamic cavitation was used to pretreat the landfill leachate due to it being cost-effective, without additional chemicals, and environmentally friendly. The pretreatment experiments were conducted under an inlet pressure of 0.4 MPa and a basic pH. The influence of operating parameters such as the orifice opening rate, the arrangement of orifices, and the reaction time on the chemical oxygen demand, ammonium nitrogen, and biochemical oxygen demand removal in landfill leachate was studied, and the energy efficiency was evaluated. The results showed that under the above conditions, the removal rate for the chemical oxygen demand of the orifice plate with an annular orifice arrangement was better than that of the orifice plate with a radiation orifice arrangement, and the orifice plate with an orifice opening rate of 0.0417 had the best effectiveness. The energy efficiency under these two optimization conditions was also the highest. When the optimal operation time was 60 min, the removal rate of the chemical oxygen demand was 22.63%. The biodegradability of the landfill leachate was significantly improved with BOD5/COD increasing by 57.27%. The study provides a theoretical basis and data support for the application of hydrodynamic cavitation as a low-cost and efficient treatment method in the pretreatment of landfill leachate.

Pre-treatment of landfill leachate via coagulation-flocculation: Optimization of process parameters using response surface methodology (RSM)

Wastewater treatment is achieved mainly through the regeneration of resources and energy from wastewater, especially using pre-treatment technologies. In this study, coagulation pre-treatment of landfill leachate was performed using polymeric iron sulfate (PFS) as coagulation. Moreover, the whole experimental process was divided into two parts. In the first phase, the effects of PFS dosing, initial pH and PAM dosing on the removal of chemical oxygen demand (COD), total phosphorus (TP) and UV254 from the leachate were assessed using one factor one experiment (OFAT); In the second phase, the individual and interactive effects of parameters on COD%, TP%, and UV254% were evaluated using response surface methodology (RSM). Numerical multiple response optimization was conducted using RSM to maximize COD%. The COD%, TP%, and UV254% at optimum condition (PFS dose of 12.18 g/L, initial pH of 8.12, and PAM dosage of 11.29 mg/L) reached 62.30 %, 95.79 %, and 83.45 %, respectively. The 3D-EEM showed the effluent from the leachate after mixing. The chemical properties significantly changed, and the concentration of hard-to-degrade substances, such as humic acid, decreased. FTIR and ESM-EDX were used to delineate the intrinsic mechanism of contaminant removal, demonstrating that hydroxyl bonds are crucial in the extraction of leachate and the aggregation of folcs.

Removal of recalcitrant organic matter of landfill leachate by adsorption onto biochar from sewage sludge: A quali-quantitative analysis

Sewage sludge is a byproduct of sewage treatment, whereas landfill leachate is a complex wastewater generated by the decomposition of solid waste. These byproducts require adequate management, and one option for the sludge is the thermal treatment by pyrolysis to produce biochar. The resulting biosolid can be used as an adsorbent to treat landfill leachate. The main objective of this research was to remove recalcitrant organic matter from landfill leachate by adsorption onto biochar produced from sewage sludge. Aerobic and anaerobic sludges were pyrolyzed at 450, 650 and 850 °C, under residence times of 60, 90 and 120 min. Temperature had a positive and more significant impact on the characteristics of the biochars produced, and consequently on the adsorption of recalcitrant organic matter. However, the impact of residence time was less intense and, in some cases negative. Biochars produced from both aerobic and anaerobic sludge pyrolyzed at 850 °C for 120 and 60 min, respectively, showed higher specific surface areas (114.4 m2g-1 and 104.2 m2g-1, respectively) compared with those pyrolyzed at 450 °C and 650 °C. The biochar from anaerobic sludge produced at 850 °C and 60 min showed the best performance regarding the adsorption process, with chemical oxygen demand (COD), dissolved organic carbon (DOC), and color removals from the leachate of 32%, 36%, and 41%, respectively. The results of adsorption capacity for this biochar from anaerobic sludge were 26.1 mg g−1 for COD and 7.9 mg g−1 for DOC. The adsorption of recalcitrant organic matter from leachate was evidenced by the decrease in the UV–Vis absorbances and fluorescence intensities. It indicates that recalcitrant and humic substances were removed mainly by biochars pyrolyzed at 850 °C. Thus, the results allow to stress that the pyrolysis of sewage sludge to produce biochar is a promising alternative to sludge treatment, and the biochar may be applied as a pre-treatment of landfill leachate since it successfully removed the recalcitrant organic matter.

Algae-based treatment of a landfill leachate pretreated by coagulation-flocculation

Landfill leachate (LL) management is an urgent issue at recently closed Sisdol Landfill Site (SLS) used to dispose of solid waste generated in Kathmandu (Nepal) as untreated leachate is flowing directly to the nearby Kolpu River causing environmental and health concerns. This study aims to assess the potential of algae-based treatment of LL pretreated by optimized coagulation-flocculation (CF) for the removal of conventional pollutants such as biological oxygen demand (BOD5), chemical oxygen demand (COD), ammonia, nitrate, and phosphate. Response Surface Methodology (RSM) was used to optimize the operating variables (dose and pH) during the pretreatment of leachate by the CF process using ferric chloride (FeCl3.7H2O), alum (Al2(SO4)3.6H2O) and commercial poly aluminium chloride (PAC) as coagulants using a jar test apparatus. The pretreated LL was subjected to algal treatment using the mixed microalgae culture isolated and enriched from the wastewater collection pond and grown in artificial light. The combined physicochemical and algal treatment of LL from SLS achieved 62.93–72.43%, 74.93–75.55% and 87.58–93.40% and 73.63–86.73% removal for COD, BOD5, ammonium-nitrogen and phosphate, respectively. Thus, this research has proven the feasibility of a combined physiochemical and algae-based treatment of LL and also offers an exciting alternative to current treatment practices for LL.

Sorptive removal of per- and polyfluoroalkyl substances (PFAS) in organic-free water, surface water, and landfill leachate and thermal reactivation of spent sorbents

This study evaluated the performance of five commercially available granular activated carbons (GACs) derived from different sources for the removal of short-chain and long-chain per- and polyfluoroalkyl substances (PFAS) from raw and pretreated landfill leachate using ozonation to break down organic substances. The adsorption isotherms of PFAS on GAC in organic-free water and surface water were also established to understand the effect of water chemistry. The results demonstrated that bituminous GACs have the highest adsorption capacity compared to GACs made from coconut shells and lignite coal. The GAC adsorption of PFAS in landfill leachate was two orders of magnitude lower than that in surface water. Pretreatment of leachate by ozonation moderately increased the adsorption of PFAS on GAC. This is the first time that PFAS isotherm data are available for mainstream GACs in raw and pretreated landfill leachate samples. Such data can be used to design a GAC treatment system for removing PFAS from leachate. Furthermore, our results showed that GAC contaminated with PFAS in landfill leachate could be effectively regenerated using conventional muffle and tube furnaces, indicating that the presence of other substances in the leachate has no significant impact on the reactivation of the GAC. Lastly, the results indicate that induction heating is an efficient and rapid method for thermally reactivating GAC contaminated with various PFAS.

Improving organic matter and nutrients removal and minimizing sludge production in landfill leachate pre-treatment by Fenton process through a comprehensive response surface methodology approach

Landfill leachate (LL) represents a very complex effluent difficult to treat and to manage which usually requires a chemical pre-treatment. In this study, response surface methodology (RSM) was used to identify the optimum operating conditions of the Fenton process as a pre-treatment of LL in order to reduce the high organic content and simultaneously optimize the BOD5:TN:TP ratio. The dosages of Fenton process reagents, namely Fe2+ and H2O2, were used as variables for the implementation of RSM. Chemical oxygen demand (COD), five-days biochemical oxygen demand (BOD5), total nitrogen (TN), total phosphorus (TP) removals (and simultaneously BOD5:TN:TP ratio), sludge-to-iron ratio (SIR) and organic removal-to-sludge ratio (ORSR) were selected as target responses. This approach considered the SIR and ORSR parameters which are a useful tool for assessing sludge formation during the process along with organic matter removal. The variables (H2O2 and Fe2+ concentrations) significantly affected the responses, as the role of oxidation mechanism is dominant with respect to coagulation one. The pH for the process was fixed to 2.8 while the treatment time was set to 2 h. The optimum operational conditions obtained by perturbation and 3D surface plot, were found to be 4262 mg/L and 5104 mg/L for Fe2+ and H2O2, respectively (H2O2/Fe2+ molar ratio = 2) with COD, BOD5, TN and TP removals of 70%, 67%, 84% and 96% respectively, while SIR and ORSR final values were 1.15 L/mol and 33.79 g/L respectively, in accordance with models-predicted values. Moreover, the initial unbalanced BOD5:TN:TP ratio (9:1:1) was significantly improved (100:6:1), making the effluent suitable for a subsequent biological treatment. The investigated approach allowed to optimize the removal of organic load and nutrients as well as to minimize the sludge formation in Fenton process, providing a useful tool for the operation and management of LL pre-treatment.

Landfill leachate pretreatment effects on nanofiltration and reverse osmosis membrane performance

The present study investigates the effects of landfill leachate pretreatment by coagulation-flocculation (C/F) on the performance of nanofiltration (NF) and reverse osmosis (RO) membranes by comparing permeate flux, fouling resistance, and leachate quality. Pretreated leachates were produced by applying the C/F with ferric chloride (FeCl3) and alum sulfate (Al2(SO4)3), named P1 and P2 leachates. Raw leachate (RL), P1, and P2 samples were treated using five different polymeric membranes termed NP030, NP010, XN45, BW30, and X201. The C/F pretreatment with FeCl3 or Al2(SO4)3 increased XN45's permeate flux by more than 80%. In this case, fouling median resistance values were 2.13e+ 08, 0.96e+ 08, and 1.02e+ 08 m−1 for RL, P1, and P2, respectively. Kruskal-Wallis test showed a significant difference between RL and pretreated leachate groups (p-value < 0.05). No significant difference between P1 and P2 was identified by the Dwass-Steel-Critchlow-Fligner test run for pairwise comparisons. These results indicate that the leachate pretreatment reduced membrane fouling by more than 50%, independently of the coagulant employed. Although higher removals of organic contaminants were, on average, obtained by membrane treatment for RL than for P1 and P2 samples, membranes that operated for RL treatment presented the worst performance in terms of permeate flux and fouling resistance. Therefore, NF and RO processes are not advisable as a single step in a landfill leachate treatment train, and a pretreatment step is recommended. This research makes a major contribution to the field by providing quantitative data for the conceptual premise that leachate pretreatments mitigate membrane fouling. Our findings help elucidate pretreatment effects on membrane performance and determine the preferable leachate treatment layout.

Process of landfill leachate pretreatment using coagulation and hydrodynamic cavitation oxidation.

Landfill leachate poses a threat to the environment and human health, and its complex composition made it difficult to treat. Among the methods for treating landfill leachate, the physicochemical combination method is considered to have significant effectiveness, low cost, and application potential. In this study, we propose a new method of coagulation and hydrodynamic cavitation/chlorine dioxide (HC/ClO2) for treating landfill leachate. The optimal conditions for coagulation and HC/ClO2 treatment were investigated experimentally. Under the optimal conditions for coagulation, the COD removal rate was 60.14%. Under the optimal HC/ClO2 treatment conditions, the COD removal rate was 58.82%. In the combined coagulation and HC/ClO2 process, the COD removal rate was 83.58%. Thus, the proposed method can significantly reduce the organic load before subsequent biological treatment processes, thereby reducing the operation cycles and cost of biological treatment.

Comparative analysis of sorbents within the landfill leachate pretreatment process

Comparative analysis of sorbents within the landfill leachate pretreatment process

Integrated membrane electrochemical reactor-membrane distillation process for enhanced landfill leachate treatment

Treatment of recalcitrant landfill leachate (LFL) induces huge energy consumption and carbon emissions due to its complex composition. Although membrane distillation (MD) exhibits good potential in LFL treatment with waste heat utilization, membrane fouling and ammonia rejection are still the major problems encountered that hinder its application. Herein, membrane electrochemical reactor (MER) was coupled with MD for simultaneous membrane fouling control and resource recovery. LFL pretreatment with membrane-less electrochemical reactor (EO) and without pretreatment were also purified by MD for comparison. Results showed that the MER-MD system rejected almost all CODCr, total phosphorus, metal salts, and ammonia nitrogen (increased by 33.5%–43.5% without chemical addition), and recovered 31% of ammonia nitrogen and 48% of humic acid in the raw LFL. Owing to the effective removal of hardness (61%) and organics (77%) using MER, the MER-MD system showed higher resistance to the membrane wetting and fouling, with about 61% and 14% higher final vapor flux than those of the MD and EO-MD systems, respectively, and the pure water flux could be fully recovered by alkaline solution cleaning. Moreover, SEM-EDS, ATR-FTIR and XRD characterization further demonstrated the superiority of the MD membrane fouling reversibility of the MER-MD system. Energy consumption and carbon emissions analysis showed that the MER-MD system reduced the total energy consumption/carbon emissions by ∼20% and ∼8% compared to the MD and EO-MD systems, respectively, and the ammonia nitrogen recovered by MER could offset 8.25 kg carbon dioxide equivalent. Therefore, the introduction of MER pretreatment in MD process would be an option to decrease energy consumption and reduce carbon emissions for MD treatment of LFL.

Efficient Pretreatment of Landfill Leachate by Loading Sulfonated Cobalt Phthalocyanine Catalyst: Optimization, Regeneration and Mechanisms

Efficient Pretreatment of Landfill Leachate by Loading Sulfonated Cobalt Phthalocyanine Catalyst: Optimization, Regeneration and Mechanisms

Adsorption studies using natural palygorskite for the treatment of real sanitary landfill leachate

The efficiency of a naturally occurring palygorskite as an adsorbent for the simultaneous removal of color, dissolved chemical oxygen demand (d‐COD) and ammonium nitrogen (NH4+-N) from real, untreated sanitary landfill leachate (SLL) was investigated. Saturation and desorption studies of palygorskite were also performed for all three pollutants simultaneously. Optimal adsorption conditions were attained at palygorskite dosage of 133 g L−1 and suspension pH 8. In these conditions, color removal efficiency reached 85.4 ± 1.4% within just 2.5 min of contact time with the natural palygorskite, while d-COD and NH4+-N removal was 54.7 ± 0.6% and 41.9 ± 0.5%, respectively, for 180 min residence time. Limited reuse of palygorskite for color uptake was possible. NH4+-N uptake on palygorskite was irreversible, while d-COD and color uptake were reversible. The combination of natural palygorskite with natural zeolite in series, in any order, doubled the overall removal efficiency of NH4+-N from raw SLL. Solid characterization of palygorskite confirmed the adsorption of NH4+-N, aromatic and aliphatic organic compounds. BET specific surface area (SSA) analysis showed significant changes of the solid upon saturation. Zeta potential measurements of the suspended particles after SLL treatment in combination with FTIR and XPS analyses suggested that SLL decolorization was due to the adsorption of anionic aliphatic and aromatic compounds. The results of this study indicate that adsorption on natural palygorskite is a viable option for the pre-treatment of untreated landfill leachate.

Approach to a fungal treatment of a biologically treated landfill leachate

White-rot fungi (WRF) have the ability to synthetize extracellular enzymes that could degrade recalcitrant pollutants. The aim of this work was to evaluate the use of P. chrysosporium to treat a biologically and physically pre-treated landfill leachate which high load of refractory compounds (COD>1000 mg/L, BOD5<50 mg/L) in order to reduce COD and colour. Batch tests were carried out at 26 °C and 135 rpm for 15 days. The soluble chemical oxygen demand (sCOD), soluble biological oxygen demand (sBOD5) and colour, as well as the lignin peroxidase (LiP) and manganese peroxidase (MnP) enzymatic activities were analysed. Besides, the effects of different operating conditions, i.e., pH control, permeate dilution and supplementation, on treatment efficacy were investigated.The control of pH was shown to be key for fungal treatment. In addition, it was found that the addition of carbon and nitrogen sources improved the enzymatic synthesis and the removals of sCOD and colour. Data here obtained open the possibility of using fungi for reducing the amount of recalcitrant pollutants still present in treated landfill leachates or similar effluents.

Advanced Reduction Processes for Degradation of Refractory Organics in Landfill Leachate

Hydroxyl radicals generated from advanced oxidation processes (AOPs) are broadly applied to mitigation of refractory organics in landfill leachate. However, following treatment by AOPs, the wastewater still contains highly oxidized organics that are recalcitrant to further chemical oxidation, thereby providing a challenge to established wastewater-treatment technologies. This study aimed to validate whether advanced reduction processes (ARPs), an emerging chemical degradation process driven by highly reductive hydrated electrons (eaq−), can effectively decompose persistent and complex organics in a Fenton pretreated landfill leachate. Results showed that ARPs poorly cleave C-C bonds in the Fenton pretreated leachate organic matter (LOM) due to low reactivity of the mixed organics toward eaq−. However, eaq− and ultraviolet (UV) irradiation during the ARP treatment could attack certain chromophores to reduce UV254 absorbance by 53%. The transformation particularly occurred to the low-molecular-weight (<10 kDa) and hydrophobic LOM fractions. Meanwhile, the carboxylic content declined after the ARP treatment, whereas the phenolic concentration remained constant, suggesting that eaq− principally reacted with electron withdrawing groups rather than electron donating moieties on the Fenton pretreated LOM. This study highlights that ARPs can serve as a promising post-treatment after AOPs for treatment of refractory organic wastes in landfill leachate.

Electrochemical oxidation of pretreated landfill leachate nanofiltration concentrate in terms of pollutants removal and formation of by-products

This study compares the efficiencies of active (Ti/TiO2–RuO2–IrO2 (TIR)) and inactive (Ni/Boron Doped Diamond (BDD)) anodes in terms of pollutant treatment and by-product formation in pretreated (chemical coagulation) landfill leachate nanofiltration membrane concentrate (PLNC). PLNC has high chemical oxygen demand (COD:4900 mg/L), total organic carbon (TOC: 1874 mg/L), total Kjeldahl nitrogen (TKN: 520 mg/L), ammonium nitrogen (NH3–N: 21.35 mg/L), chloride (5700 mg/L) and sulfate (9000 mg/L – due to coagulant type). The parameters of COD, TOC, NH3–N, TKN, free and combined chlorine species, halogenated organic compounds (HOCs), adsorbable organic halogens (AOX), and nitrate at different current density (J: 111–555 A/m2) and initial pH (pHi:3.5–7) were compared for both anodes. The removal efficiencies at the optimum conditions (pHi 5.5, 333 A/m2 and 8 h) were obtained as 86.4% COD, 77.4% TOC, 93.4% TKN, 94.4% NH3–N with BDD and 34.3% COD, 27.3% TOC, 93.7% TKN, 97.4% NH3–N with TIR. According to gas chromatography-mass spectrometry (GC-MS) results obtained under optimum conditions, haloalkane/alkene, halonitroalkane, halonitrile, haloketone, haloalcohols, haloacids, haloaldehydes, haloamines/amides on both electrodes were detected as species of HOCs. In addition, the highest nitrate concentration was observed at the TIR anode, while the highest AOX concentration was observed at the BDD anode.

Leachate post-treatment by electrocoagulation process: Effect of polarity switching and anode-to-cathode surface area

In the electrocoagulation process, passivation or corrosion of the electrodes is one of the biggest challenges that cause a drop in treatment effectiveness. In this study, the effect of polarity switching was investigated, for the first time, in an attempt to enhance electrocoagulation treatment's ability to remove chemical oxygen demand (COD) and color from pretreated landfill leachate. Moreover, the ratio of the anode to cathode surface area and rotating electrode were examined in light of experimental results. The effect of different parameters, including the stirring speed, initial leachate pH, electrical current density, anode to cathode surface area ratio, and polarity switching time on system efficiency, was evaluated using the one-factor-at-a-time (OFAT) classical method. According to the results, polarity switching resulted in an almost 18% increase in COD removal, 14% increase in color removal, 13% decrease in electrical energy consumption (EEC), 51% decrease in the specific sludge production (TSS/COD), and improved electrode performance compared to non-polarity switching mode. The findings of this research showed the highest COD and color removal efficiencies, which were 34% and 67%, respectively, in a 120 min period, a stirring speed of 135 rpm, the initial leachate pH of 9, the current density of 14.4 mA/cm2, the anode/cathode surface ratio of 0.35, and the polarity switching time of 300 s.

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 &gt;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).

Optimization of coagulation-flocculation process conditions using the central composite design for pretreatment of Moroccan landfill leachate

Optimization of coagulation-flocculation process conditions using the central composite design for pretreatment of Moroccan landfill leachate