Mohd Nordin Adlan

Statistical optimization of process parameters for landfill leachate treatment using electro-fenton technique.

Mature landfill leachate is typically non-biodegradable and contains high concentration of refractory organics. The aim of this research was to optimize operating parameters in electro-Fenton process, for the removal of recalcitrant organics from semi-aerobic landfill leachate using response surface methodology (RSM). Effectiveness of important process parameters H(2)O(2)/Fe(2+) molar ratio, current density, pH and reaction time were determined, optimized and modeled successfully. Significant quadratic polynomial models were obtained (R(2)=0.9972 and 0.9984 for COD and color removals, respectively). Numerical optimization based on desirability function were employed; in a 43 min trial 94.07% of COD and 95.83% of color were removed at pH 3 and H(2)O(2)/Fe(2+) molar ratio 1, while current density was 49 mA/cm(2). The results indicate that E-Fenton process was an effective technology for semi-aerobic landfill leachate treatment.

Removal of ammoniacal nitrogen (N-NH3) from municipal solid waste leachate by using activated carbon and limestone.

The presence of ammoniacal nitrogen (N-NH3) in leachate is one of the problems normally faced by landfill operators. Slow leaching of wastes producing nitrogen and no significant mechanism for transformation of N-NH3 in the landfills causes a high concentration of ammoniacal nitrogen in leachate over a long period of time. A literature review showed that the removal of ammoniacal nitrogen from leachate was not well documented and to date, there were limited studies in Malaysia on this aspect, especially in adsorption treatment. The main objective of the present study was to investigate the suitability of activated carbon, limestone and a mixture of both materials as a filtering medium, in combination with other treatments capable of attenuating ammoniacal nitrogen which is present in significant quantity (between 429 and 1909 mg L-1) in one of the landfill sites in Malaysia. The results of the study show that about 40% of ammoniacal nitrogen with concentration of more than 1000 mg L-1 could be removed either by activated carbon or a mixture of carbon with limestone at mixture ratio of 5: 35. This result shows that limestone is potentially useful as a cost-effective medium to replace activated carbon for ammoniacal nitrogen removal at a considerably lower cost.

Removal of copper from water using limestone filtration technique: determination of mechanism of removal

This paper discusses heavy metal removal from wastewater by batch study and filtration technique through low-cost coarse media. Batch study has indicated that more than 90% copper (Cu) with concentration up to 50 mg/l could be removed from the solution with limestone quantity above 20 ml (equivalent to 56 g), which indicates the importance of limestone media in the removal process. This indicates that the removal of Cu is influenced by the media and not solely by the pH. Batch experiments using limestone and activated carbon indicate that both limestone and activated carbon had similar metal-removal efficiency (about 95%). Results of the laboratory-scale filtration technique using limestone particles indicated that above 90% removal of Cu was achieved at retention time of 2.31 h, surface-loading rate of 4.07 m3/m2 per day and Cu loading of 0.02 kg/m3 per day. Analyses of the limestone media after filtration indicated that adsorption and absorption processes were among the mechanisms involved in the removal processes. This study indicated that limestone can be used as an alternative to replace activated carbon.

Optimization of stabilized leachate treatment using ozone/persulfate in the advanced oxidation process

The objective of this study was to investigate the performance of employing persulfate reagent in the advanced oxidation of ozone to treat stabilized landfill leachate in an ozone reactor. A central composite design (CCD) with response surface methodology (RSM) was applied to evaluate the relationships between operating variables, such as ozone and persulfate dosages, pH, and reaction time, to identify the optimum operating conditions. Quadratic models for the following four responses proved to be significant with very low probabilities (<0.0001): COD, color, NH3-N, and ozone consumption (OC). The obtained optimum conditions included a reaction time of 210 min, 30 g/m(3) ozone, 1g/1g COD0/S2O8(2-) ratio, and pH 10. The experimental results were corresponded well with predicted models (COD, color, and NH3-N removal rates of 72%, 96%, and 76%, respectively, and 0.60 (kg O3/kg COD OC). The results obtained in the stabilized leachate treatment were compared with those from other treatment processes, such as ozone only and persulfate S2O8(2-) only, to evaluate its effectiveness. The combined method (i.e., O3/S2O8(2-)) achieved higher removal efficiencies for COD, color, and NH3-N compared with other studied applications. Furthermore, the new method is more efficient than ozone/Fenton in advanced oxidation process in the treatment of the same studied leachate.

Influence of Fenton reagent oxidation on mineralization and decolorization of municipal landfill leachate

This study evaluated the effectiveness of Fentons technique for the treatment of semi-aerobic landfill leachate collected from Pulau Burung Landfill Site (PBLS), Penang, Malaysia. The Fe2 + or Fe3 + as catalyst and H2O2 as oxidizing agent are commonly used for the classical Fentons reaction. In present study, the effect of operating conditions such as pH, reaction time, molar ratio, agitation rate, feeding mode and Fenton reagent concentrations which are important parameters that affect the removal efficiencies of Fenton method were investigated. Under the most favorable conditions, the highest removals of 58.1 and 78.3% were observed for COD and color, respectively. In general, the best operating conditions were pH = 3, Fe = 560 mg L−1, H2O2 = 1020 mg L−1, H2O2/Fe2 + molar ratio = 3, agitation rate = 400 rpm and reaction time = 120 minutes. The results highlighted that stepwise addition of Fentons reagent was more effective than adding the entire volume in a single step. Excessive hydrogen peroxide and iron have shown scavenging effects on hydroxyl radicals and reduced degradation of refractory organics in the landfill leachate.

Ammoniacal nitrogen and COD removal from semi-aerobic landfill leachate using a composite adsorbent: Fixed bed column adsorption performance

The performance of a carbon-mineral composite adsorbent used in a fixed bed column for the removal of ammoniacal nitrogen and aggregate organic pollutant (COD), which are commonly found in landfill leachate, was evaluated. The breakthrough capacities for ammoniacal nitrogen and COD adsorption were 4.46 and 3.23 mg/g, respectively. Additionally, the optimum empty bed contact time (EBCT) was 75 min. The column efficiency for ammoniacal nitrogen and COD adsorption using fresh adsorbent was 86.4% and 92.6%, respectively, and these values increased to 90.0% and 93.7%, respectively, after the regeneration process.

Application of psyllium husk as coagulant and coagulant aid in semi-aerobic landfill leachate treatment

Landfill leachate is a heavily polluted and a likely hazardous liquid that is produced as a result of water infiltration through solid wastes generated industrially and domestically. This study investigates the potential of using psyllium husk as coagulant and coagulant aid for the treatment of landfill leachate. Psyllium husk has been tested as primary coagulant and as coagulant aid with poly-aluminum chloride (PACl) and aluminum sulfate (alum). As primary coagulant, the optimum dosage and pH for PACl were 7.2 and 7.5 g/L, respectively, with removal efficiencies of 55, 80 and 95% for COD, color and TSS, respectively. For alum, the optimum conditions were 11 g/L alum dosage and pH 6.5 with removal efficiencies of 58, 79 and 78% for COD, color and TSS, respectively. The maximum removal efficiencies of COD, color and TSS were 64, 90 and 96%, respectively, when psyllium husk was used as coagulant aid with PACl. Based on the results, psyllium husk was found to be more effective as coagulant aid with PACl in the removal of COD, color and TSS as compared to alum. Zeta potential test was carried out for leachate, PACl, alum and psyllium husk before and after running the jar test to enhance the results of the jar test experiments.

The use of polyaluminium chloride for removing colour, COD and ammonia from semi-aerobic leachate

This research examined various experimental conditions for application of Polyaluminium Chloride (PAC) for removing colour, COD and ammonia from semi-aerobic. The removals of colour, COD and ammonia were up to 93%, 56% and 32%, respectively, at an optimum dosage of 2000 mg/L PAC. Rapid and slow mixing speed played only a minor role in the removal efficiencies for colour, COD and ammonia. The flocs size distribution for PAC coagulant shows an increase in floc size with increasing coagulant dosages. PAC also exhibited excellent settling characteristics, with majority of the flocs settled out in the initial 5 min of settling.

Application of the central composite design for condition optimization for semi-aerobic landfill leachate treatment using electrochemical oxidation

In the present study, Electrochemical Oxidation was used to remove COD and color from semi-aerobic landfill leachate collected from Pulau Burung Landfill Site (PBLS), Penang, Malaysia. Experiments were conducted in a batch laboratory-scale system in the presence of NaCl as electrolyte and aluminum electrodes. Central composite design (CCD) under Response surface methodology (RSM) was applied to optimize the electrochemical oxidation process conditions using chemical oxygen demand (COD) and color removals as responses, and the electrolyte concentrations, current density and reaction time as control factors. Analysis of variance (ANOVA) showed good coefficient of determination (R(2)) values of >0.98, thus ensuring satisfactory fitting of the second-order regression model with the experimental data. In un-optimized condition, maximum removals for COD (48.77%) and color (58.21%) were achieved at current density 80 mA/cm(2), electrolyte concentration 3,000 mg/L and reaction time 240 min. While after optimization at current density 75 mA/cm(2), electrolyte concentration 2,000 mg/L and reaction time 218 min a maximum of 49.33 and 59.24% removals were observed for COD and color respectively.

Optimization of semi-aerobic stabilized leachate treatment using ozone/Fenton's reagent in the advanced oxidation process

The objective of this study was to investigate the performance of employing Fentons reagent in the advanced oxidation of ozone to treat stabilized landfill leachate in an ozone reactor. A central composite design (CCD) with response surface methodology (RSM) was applied to evaluate the relationships between operating variables, such as ozone and Fenton dosage, pH, and reaction time, to identify the optimum operating conditions. Quadratic models for the following four responses proved to be significant with very low probabilities (<0.0001): chemical oxygen demand (COD), color, NH3–N, and ozone consumption (OC). The obtained optimum conditions included a reaction time of 90 min, 30 g/m3 ozone, 0.01 mol/LH2O2,0.02 mol/L Fe2+, and pH 5. COD, color, and NH3–N removal rates of 79%, 100%, and 20%, respectively, and 0.18 kg O3/kg COD OC were obtained. The predictions correspond well with experimental results (COD, color, and NH3–N removal rates of 78%, 98.5%, and 19%, respectively, and 0.29 kg O3/kg COD OC). This method reduces the treatment time and improves the treatment efficiency relative to a previously published method that used Fentons reagent prior to ozonation.