COD In Leachate Research Articles

Analyzing performance and microbial mechanisms in an incineration leachate treatment after waste separation: Integrated metagenomic and metaproteomic analyses

The absence of food waste after separation poses a significant challenge to incineration leachate treatment, as it decreases the C/N ratio and COD of leachate, greatly impacting the biological treatment process. A one-year in-situ study was systematically conducted in an incineration leachate treatment plant that experienced waste separation, focusing on the variations in carbon and nitrogen removal performance as well as the involved microbial mechanism of the “anaerobic digestion (AD) + two-stage A/O” process. Results indicated that the biodegradability of leachate significantly decreased over time, with COD concentration decreasing by 10 times and the average C/N ratio decreasing from 12.3 to 1.4. The AD process was maintained stable, achieving a COD removal efficiency exceeding 92 %. The nitrification process also remained stable; while the denitrification process was significantly affected, and a nine-fold increase in external glucose addition was required to achieve a nitrogen removal efficiency of 85 %. Metagenomic analysis indicated that comammox Nitrospira (contributing 90 % to ammonia monooxygenase) occupied the dominant position over Nitrosomonas for nitrification due to the low NH4+-N concentration in A/O tanks (<35 mg/L), and Methanothrix was substituted by Methanosarcina for methanogenesis in AD unit. Metaproteomic results further elucidated that the expression of enzymes responsible for denitrification process, i.e., Nir, Nor, Nos (convert NO2− to N2), was decreased significantly, although the expression of enzymes related to glycolysis and TCA cycle were stimulated by glucose addition. The expression of Nar (convert NO3−-N to NO2−-N) remained stable, while the imbalance expression within denitrifying enzymes might have facilitated occurrence of partial denitrification, attributed to the low C/N ratio. The results prove that the function robustness and metabolic versatility were achieved in leachate treatment plant after waste separation but at the cost of the high external carbon resource addition, highlighting the urgent requirement for low-carbon nitrogen removal technologies.

Novel cost-effective oxygen-enriched melting method for MSWI fly ash

ABSTRACT Herein, a novel oxygen-enriched melting process for fly ash, which uses the biogas produced from the leachate of municipal solid waste incineration (MSWI) plants, is proposed to reduce the high cost of conventional fly ash – melting technology. The fly ash composition was estimated via X-ray fluorescence analysis; the six constituent elements detected in fly ash in the decreasing order of their content were calcium, chlorine, silicon, sulfur, sodium, and potassium. Based on literature and actual production data, the average yield of the leachate was 15% of the total waste entering the MSWI plants and the COD of leachate was 30,000–75,000 mg/L. The amount of biogas that can be used per ton of fly ash was calculated to be 62.0–157.0 m3. The analysis of melting thermal equilibrium revealed the amount of biogas required per ton of fly ash as 57.8 m3. The aforementioned research findings indicate that the biogas produced by MSWI plants can successfully meet the demands of the oxygen-enriched melting of fly ash produced in these plants. By establishing an oxygen-enriched-melting pilot platform, the pilot tests of melting were conducted on fly ash; the results revealed the good melting effects of fly ash. The X-ray diffraction analysis of the slag demonstrated that the content of the vitreous body met the technical requirements for glassy substances. Furthermore, the leaching toxicity test results revealed that heavy metals were well solidified in the slag. This study presents a novel fly ash – melting scheme for MSWI fly ash, namely, biogas oxygen-enriched melting strategy, which has the advantages of technical feasibility and cost-effectiveness. The proposed technique exhibits considerable prospects for widespread application in MSWI plants in China and can play an important role in the safe disposal of fly ash. Implications: In this paper, a low-cost melting method of municipal solid waste incineration(MSWI) fly ash is proposed. This method uses the biogas generated by MSWI plant itself as fuel for melting. Through research, it has been found that the production of biogas can meet the demand for fly ash melting. Adopting biogas as a molten fuel can significantly reduce the cost of melting, thereby significantly reducing the cost of fly ash melting. This study established a pilot scale platform for the melting of biogas and conducted pilot scale experiments on fly ash and additives. The experimental results showed that the melting system operated well and achieved the vitrification of fly ash. The leaching test results of the molten slag showed that heavy metals were well solidified in the slag. The research results can be extended to the MSWI plant for application, which can significantly reduce the cost of fly ash melting disposal, and has broad application prospects.

Optimization of stabilized anaerobic landfill leachate treatment using ozonation with metallic compound using response surface methodology.

Malaysia encounters a consistent rise in the generation of solid waste and leachate on a daily basis. It should also be noted that leachate has a low degree of biodegradability (BOD5 /chemical oxygen demand [COD]), as shown by its BOD5 /COD ratio. Its high toxicity levels significantly threaten the environment, water bodies, and human well-being. High concentrations of COD, color, and ammoniacal nitrogen (NH3 -N) in leachate prevent this wastewater from being allowed to be discharged directly into the water body. Therefore, an effective process to remove the pollutant is desired. The aims of this study are to investigate the performance of ozonation with two metallic compounds, ZrCl4 and SnCl4 , and optimize their performance using response surface methodology (RSM). In this study, the performance of ozonation with ZrCl4 (O3 /ZrCl4 ) recorded better pollutant removals compared with the ozonation with tin tetrachloride (O3 /SnCl4 ), as seen in the removals of 99.8%, 93.5%, and 46.3% for color, COD, and NH3 -N, respectively. These removals were achieved by following the experimental model (optimum experiment condition) generated by RSM at O3 dosage of 31 g/m3 , COD and ZrCl4 dosage ratio (COD, mg/L/ZrCl4 , mg/L) of 1:1.35, with the pH solution of 8.78 and reaction time of 89 min. The R2 of each parameter for this model was recorded as 0.999 (COD), 0.999 (color), and 0.998 (NH3 -N), respectively. These data indicated that the model is well fitted as the predicted data by statistical calculation and in good agreement with the actual data. PRACTITIONER POINTS: The performance of O3 /ZrCl4 and O3 /SnCl4 was examined for remediate stabilized landfill leachate. The performance of O3 /ZrCl4 and O3 /SnCl4 was optimized using RSM, and a set of experimental models was generated and tested. O3 /ZrCl4 recorded the higher removal of COD, color, and NH3 -N compared with O3 /SnCl4 . At best condition, both methods recorded removal as 89% to 99.8% of pollutants in leachate and product clear effluent. This finding gives a new approach to treat landfill leachate effectively and efficiently.

Distribution, removal and ecological risk assessment of antibiotics in leachate from municipal solid waste incineration plants in Shanghai, China

Leachate from Municipal Solid Waste (MSW) incineration plants contains multiple antibiotics. However, current knowledge of antibiotics in such leachate is very limited compared to landfill leachate. In this study, the distribution, removal and ecological risks of 8 sulfonamides (SAs), 4 quinolones (FQs), and 4 macrolides (MLs) antibiotics in leachate from three MSW incineration plants in Shanghai were investigated. The results showed that 12 types of target antibiotics were detected at high concentrations (7737.3–13,758.7 ng/L) in the fresh leachate, exceeding the concentrations reported for landfill leachate. FQs were the dominant antibiotics detected in all three fresh leachates, accounting for >60 % of the total detected concentrations. The typical “anaerobic-anoxic/aerobic-anoxic/aerobic-ultrafiltration” treatment process removed the target antibiotics effectively (89.0 %–93.4 %), of which the anaerobic unit and the primary anoxic/aerobic unit were the most important antibiotic removal units. Biodegradation was considered to be the dominant removal mechanism, removing 78.11 %–92.37 % of antibiotics, whereas sludge adsorption only removed 1.02 %–10.89 %. Antibiotic removal was significantly correlated with leachate COD, pH, TN, and NH3-N, indicating that they may be influential factors for antibiotic removal. Ecological risk assessment revealed that ofloxacin (OFX) and enrofloxacin (EFX) in the treated leachate still posed high risks to algae and crustaceans. This research provides insights into the fate of antibiotics in leachate.

Co-composting poultry carcasses with wood-based, distillers’ grain and cow manure biochar to increase core compost temperatures and reduce leachate's COD

Composting has been recognized as a viable method to dispose of animal carcasses. Common concerns related to the composting process include low core temperatures, leachate generation, and ammonia emissions. This study tested co-composting full-size poultry carcasses with commercially available biochars at an aeration rate of 0.8 L∙min−1. Biochars prepared by gasifying wood pallets, distillers’ grains, and cow manure were added to the composting bins at the 13% rate (by volume). Results showed that poultry carcasses with wood-based and cow manure biochar increased temperatures by 2.0 to 3.3 °C. All biochar-amended bins met the time–temperature criteria to eliminate avian influenza (H7N1) viruses, which could not be achieved without biochar addition. Wood-based biochar amendment lowered the cumulative chemical oxygen demand of the leachate samples by 87% (P = 0.02). At the rate studied, the biochar amendment did not significantly affect ammonia emissions (P = 0.56). BET surface area of wood-based biochar was 1.4 and 28 times greater than that of cow manure and distillers’ grain biochar, respectively. Compared to no biochar addition, wood-based biochar resulted in significantly higher compost temperatures (P = 0.02), lower leachate COD values (P = 0.02), and a higher total nitrogen content (P = 0.01) while it did not cause an increase in sodium content (P = 0.94) of the finished compost. In conclusion, amending the poultry carcass composting process with wood-based biochar (13% by volume) is recommended, especially to eliminate disease-causing agents.

Experimental Study on the Treatment of Landfill Leachate by Electro-Assisted ZVI/UV Synergistic Activated Persulfate System

To solve the problem of the poor treatment of high concentration landfill leachate, an electro-assisted ultraviolet (UV)/zero-valent iron (ZVI) synergic activated persulfate (PS) system was used to treat landfill leachate. The effects of PS and ZVI dosage, initial pH value, and current density on the removal efficiency of COD and NH3-N in landfill leachate were investigated. The treatment effects of single PS, single electrochemical, UV/PS, electro-assisted ZVI activated PS, and electro-assisted ZVI/UV co-activated PS were compared. At the same time, UV-visible and three-dimensional fluorescence spectroscopy were performed on the landfill leachate before and after treatment. The results show that under the optimal conditions of initial pH = 3, the dosage of PS/12COD = 1, ZVI = 1.5 g/L, current density 62.5 mA/cm2, and t = 6 h, most of the macromolecular organic substances such as humic acid and fulvic acid were removed. Removal efficiencies of COD, NH3-N, and Chroma reached 81.99%, 89.90%, and 99.75%, respectively. The BOD5/COD value increased from 0.23 to 0.46. In addition, the radical identification results showed that the degradation of COD was due to the combined action of sulfate radicals (SO4•−) and hydroxyl radicals (•OH) and that SO4•− was dominant. The combined means of synergistic activation of PS for landfill leachate treatment was significantly better than that of single means of PS activation, confirming that electrically assisted ZVI/UV synergistic activation of PS is a promising method for landfill leachate treatment.

Effect of hydraulic parameters of leachate treatment process on di(2-ethylhexyl) phthalate removal from aged leachate

ABSTRACT The effect of hydraulic parameters of an anaerobic/anoxic/oxic leachate treatment reactor on the removal of di(2-ethylhexyl) phthalate (DEHP) from aged landfill leachate was studied. The mean DEHP removal efficiencies were 79.5%, 87.1%, 89.7% and 87.8% at hydraulic retention times of 6, 4.5, 3 and 2 d, respectively. The removal efficiency of DEHP was significantly higher when the internal reflux ratio was 200% than others. There was no significant difference among the DEHP removal efficiencies at different external reflux ratios of the reactor. Due to the overall efficiency of the reactor, hydraulic retention time 3 d, internal reflux ratio 200% and external reflux ratio 60%, were considered the optimal hydraulic parameters for DEHP removal from aged leachate. The removal efficiency of DEHP was significantly improved (from 75.7% to 89.1%) after the optimization of hydraulic parameters of the reactor. The removal percentages of DEHP in the anaerobic, anoxic, and oxic units of the reactor were 42.8%, 17.6%, and 15.3%, respectively. The oxic microcosms in the reactor had little effect on DEHP removal. The correlation between DEHP and leachate pollutants indicated that DEHP removal was strongly correlated with leachate COD and NH4 +–N.

Evaluating the impacts of leachate co-treatment on a full-scale municipal wastewater treatment plant in Canada.

The objective of this study was to evaluate the impacts of leachate co-treatment on a full-scale municipal WWTPby comparing plant performance at varying levels of leachate contributions and hydraulic loadings.Leachate BOD:COD ratio was 0.08±0.07 and indicated a stabilized, old matrix and concentrations of zinc, iron, aluminum, chloride and sulfate were 0.174, 38, 1.47, 1803 and 119.1mg/L, respectively. The average volumetric leachate ratio (VLR%) was approximately 0.01% corresponding to a daily volume of 30m3 but reaching a maximum of 270m3(VLR% = 0.1%) and fluctuating on a daily-basis. A cluster analysis revealed 5 VLR% groupings that were used for subsequent analyses:no leachate, 0<Low≤0.001, 0.001<Medium≤0.02, 0.02<High≤0.05, 0.05<Very high≤0.2. Treated effluent concentrations of TKN, ammonia, fecal coliforms (FC),E. coli(EC), TSS and TP experienced atrend where effluent quality was improved at low and medium VLR%compared to no leachate addition, but deteriorated in high and very high VLR%.Treated effluent UVT% and EC were not statistically significantly different at varying VLR%, but FC was.Plant hydraulic had a significant impact on removal rates.Ammonia removals and nitrite concentrations improved inhigh flow conditions, whileTP, BOD and cBODremovals deteriorated. Finally,VLR%, leachate COD, TKN ammonia, chloride and arsenic had significant relationships with plant performance. Thus,for leachate with comparable age and strength, VLR% should not exceedlow to medium contributions(0 and 0.02%)during co-treatment at this WWTP.

Enhanced Cod and Ammonium-N Removal of Old Landfill Leachate by Peroxodisulfate-Activated Electro-Oxidation and Electro-Coagulation in a Two Anodes Electrochemical System

Enhanced Cod and Ammonium-N Removal of Old Landfill Leachate by Peroxodisulfate-Activated Electro-Oxidation and Electro-Coagulation in a Two Anodes Electrochemical System

Correlation analysis of leachate in final disposal sites on groundwater and surface water quality

The Final Disposal Site (TPA) is where waste is disposed of at the end of its life cycle. The contamination of groundwater and surface water caused by leachate is one type of pollution generated by TPA. The goal of this research is to determine the level of groundwater and surface water pollution, as well as the correlation of leachate to groundwater and surface water in West Lombok’s Final Disposal Site, which is located in Kebon Kongok Hamlet, Suka Makmur Village, Gerung District. The analysis method utilized in this research is the pollution index method and the analysis which consists of a correlation test. The results of the analysis of groundwater pollution levels from samples of resident wells were classified as adequate condition, lightly polluted, and moderate polluted. Meanwhile, surface water is classified as moderately polluted. The results of the TSS correlation test analysis on groundwater turbidity have a positive direction and a strong correlation with a value of 0.643. The results of leachate TSS analysis against surface water TSS have a positive direction and a moderate correlation with a value of 0.357 as well as the COD of leachate against COD of surface water with a value of 0.257. The results of the analysis of leachate BOD to surface water BOD indicate that there is a moderate correlation with a value of 0.475. This is in line with the pollutant index which has a moderate polluted value. Referring to the findings, it is recommended that the urgency of zero waste should be implemented by all parties, not only the government but also all levels of society.

Municipal solid waste leachate treatment using ultrasonication microwave & Ozonation combined Fenton process

ABSTRACT This work focus on the effect of Microwave power, Ozonation and Fenton reagent in microwave coupling Ozonation and Fenton oxidation process for the disintegration of COD of leachate. The experimental parameters like pH, COD, temperature, Oxidant dosage, microwave power and reaction time were varied. The results showed that 70% of COD removal efficiency was achieved at 450 W within 10 minutes interval in microwave process, 57.4% of COD removal efficiency was achieved at 60 minutes, ozone dosage 159 mg/L, pH 11. In Fenton Process, 52.91% COD removal efficiency at 60 minutes with H2O2 66.47 mµ/L and Fe2+ 80 mµ/L. Individual process showed an adverse reaction time consumption. On comparison of three processes, microwave achieved higher COD removal with shorter reaction time. In O3+ Fe process 83% COD removal was achieved at 75 minutes of reaction time. The experiment revealed the combined process of M+ O3+ Fe induces to the disintegration of COD in Leachate with a shorter reaction period.

Experimental study on advanced treatment of landfill leachate by ultraviolet catalytic persulfate

Landfill leachate is characterized by complex composition and difficult degradation. In this paper, we compared the effects of advanced treatment of ultraviolet (UV) system, persulfate (PS) system and ultraviolet/persulfate (UV/PS) system on landfill leachate. The results showed that the UV/PS system had the best removal efficiency. When the initial concentration of humic acid was 200 mg/L, the dosing of PS was 25 mmol/L, and the initial pH was 4, the maximum removal rates of UV 254 and TOC were 89.62% and 76.17%. Namely, the value of SUVA 254 decreased to 7.6603 L/(m ⋅ mg). It follows that the UV/PS system is effective in the removal of humic acid in the landfill leachate. In addition, this paper investigated the effects of temperature, initial pH and dosing ratio of chemicals on the treatment of leachate by UV/PS system. It was found that the optimal process conditions were 35 °C, pH = 4, dosing ratio = 2, and 24 h of operation. Under these conditions, the maximum removal rates of COD and TOC were 82.64% and 66.69%. The removal capacity of the system was in accordance with the pseudo-second-order kinetic equation. Therefore, this paper can provide a reference for the advanced treatment of landfill leachate. • An advanced oxidation technology for the removal of landfill leachate after biochemical treatment was presented. • Humic acid was used as a model for organic matter. The value of SUVA 254 decreased to 7.660315 L/ (m ⋅ mg) under the optimum conditions. • Under the optimal conditions, the removal rates of COD and TOC of landfill leachate after biochemical treatment reached 82.64% and 66.69%. • SR-AOPs are more efficient, economical and widely applicable compared to other technologies for deep treatment of landfill leachate.

Analysis of the Landfill Leachate Treatment System Using Arima Models: A Case Study in a Megacity

Leachate has been reported as the most significant source of landfill pollution. Predicting the characteristics of untreated and treated leachate may be useful during optimal scheduling of leachate treatment systems. The objective of this paper is to show an analysis of the operation of a landfill leachate treatment system in a Latin American megacity (Bogota, Colombia) by means of auto-regressive integrated moving average (ARIMA) models. A comparative analysis of the leachate treated with respect to reference legislation is carried out. The influence of climate variables during the operation of the treatment system is also considered. The results suggest that the concentrations of heavy metals (HMs), BOD5, and COD in untreated leachate do not follow the same annual cycles observed for the quantity of solid waste disposed within the landfill. This difference is possibly associated with the hydraulic retention time (HRT) of the leachate inside the conduction and pre-treatment system (storage/homogenization ponds). The ARIMA analysis suggests an HRT of up to one month (AR = 1) for the HMs identified as indicators of untreated leachate (Cu, Pb, and Zn). It is noted that the removal efficiency of HM indicators of the operation of the leachate treatment plant (Fe and Ni) is probably conditioned by operations carried out over a period of one month (AR = 1). The high input concentration of these HM indicators may prevent changing their ARIMA temporal structure during leachate treatment. This is reflected in the low removal efficiencies for all HMs under study (average = 26.1%).

Phytoremediation of landfill leachate using Ipomoea aquatica and Pistia stratiotes

Aim: In this study, Ipomoea aquatica and Pistia stratiotes were used to remove total suspended solids, chemical oxygen demand and ammoniacal nitrogen (NH3-N) from the landfill leachate collected at Ampar Tenang Closed Landfill (ATCL) site in Dengkil, Selangor, Malaysia. Methodology: The physico-chemical characteristics of landfill leachate (pH, temperature, NH3-N, dissolved oxygen, biochemical oxygen demand, chemical oxygen demand, total dissolved solids, total suspended solids, salinity, electrical conductivity and nitrite as well as selected heavy metals were determined before phytoremediation treatment. Results: The physico-chemical properties of leachate samples were found to be lower as compared to the standards set by the government, except for COD (&gt;100 mg l-1). Heavy metals content, Na, Mg and Fe was high in leachate. It was found that the concentrations of NH3-N, COD and TSS in leachate decreased by 57.64%, 26.85% and 62.05% after treatment with Ipomea aquatica, respectively. Whereas, 61%, 32% and 74.7% removal rate was observed for NH3-N, COD and TSS, post-treatment by Pistia stratiotes. One-way ANOVA analysis for Ipomoea aquatica revealed insignificant difference (p&gt;0.05) but for Pistia stratiotes there was a significant difference (p&lt;0.05) in the reduction of TSS, COD and NH3-N concentrations. Interpretation: Based on the findings, Pistia stratiotes was found more effective than Ipomea aquatica for reducing TSS, COD and NH3-N concentrations from landfill leachate.

Temporal variation of leachate pollution index of Indian landfill sites and associated human health risk.

The present study investigated the variation in leachate pollution index (LPI) of four municipal solid waste (MSW) dumping sites: non-engineered (Okhla, Ghazipur, Bhalswa) and engineered (Narela-Bawana) of Delhi, India. A review of 142 screened studies from Google Scholar database was done for synthesis of information on LPI parameters. Further, the rate constant determination and human health risk assessment for various leachate parameters was done. Results showed the following LPI trends: Okhla landfill: irregular with exceedance to threshold value; Bhalswa landfill: exponential increase; and Narela-Bawana landfill: linear increase. Parameters such as pH, dissolved solids, copper, nickel, zinc, and chromium of Bhalswa landfill, exhibited an exponential decay with LPI variation. Whereas, for Narela-Bawana's leachate BOD and COD parameters, an exponential decay in LPI vs zinc and linear increase for LPI vs lead was observed. For all dumping sites, a positive correlation was observed between heavy metals and LPI. In case of human health risk assessment, order of oral risk posed by Okhla's metals was cadmium > chromium > nickel > lead, with maximum hazard quotient (HQ) of 1.61 for cadmium. For Ghazipur and Bhalswa landfills, cancer risk values for both adult and child sub-populations were observed to be maximum for cadmium followed by nickel, chromium, and minimum for lead. For Narela-Bawana landfill, the order of cancer risk was as follows: chromium > nickel > lead. HQ for Pb-contaminated groundwater exceeded the threshold limit in Ghazipur and Bhalswa landfills. For dermal groundwater exposure, cadmium for Okhla (adult 2.3 × 10-4 and child 1.4 × 10-4), Ghazipur (adult 9 × 10-5 and child 5.2 × 10-5), and Bhalswa (adult 1.5 × 10-4 and child 8.6 × 10-5) was observed to have maximum cancer risk. The analyzed year-wise LPI trend, calculated rate constants, and human health risk values from present study provide a basis to waste managers and regulators for understanding various waste sources.

Statistical modelling and assessment of landfill leachate emission from fresh municipal solid waste: A laboratory-scale anaerobic landfill simulation reactor study.

Quantification, measurement of quality, post-treatment, and leachate control has been a significant problem due to the dumping of waste in an unscientific manner across the globe, and especially in developing countries like India. In this context, the objective of this study was to investigate the degradation of fresh mixed municipal solid waste (MSW) in an anaerobic landfill reactor operated with rainfall addition in laboratory conditions. Experiments were carried out in a landfill reactor of 1 m length × 1 m width × 1.1 m height. The reactor was simulated with 50 years weighted average actual rainfall rate of India. It contained the waste composition of 73% wet waste (food and kitchen) and 27% dry waste (paper, plastic, wood, textiles, and others). The leachate parameters were continually monitored for 39 weeks. In the fresh MSW landfill reactor it was evident that concentrations of leachate parameters were high initially, and there was a significant decrease in BOD5 (7041-39310 mg L-1), COD (15692-71630 mg L-1) and TS (9077-33200 mg L-1) in leachate. Therefore, rainfall had a direct influence on leachate quality. The developed first-order decay models were used for BOD5, COD, and total solids with adjusted R2 of 0.83, 0.92, and 0.96, respectively. Therefore, this model can be applied for leachate strength estimation at any given time from the period of deposition of waste under similar rainfall and waste compositions, and is largely applicable in India and tropical areas. This study is expected to be a good simulation for cities with the waste composition of high wet waste (>70%) as the estimations of important design parameters such as BOD5, COD, VFA, and NH4+-N were studied in this research. As the importance of moisture (precipitation) has been established in this study, some moisture additions can be designed in areas with low rainfall, such as arid zones.

Photocatalytic landfill leachate treatment using P-type TiO2 nanoparticles under visible light irradiation

Landfill leachate treatment is a necessary measure for environmental protection and supporting sustainable development. Photocatalytic treatment method using N- or P-type TiO2 nanoparticles has been proposed as an efficient method for the treatment of recalcitrant pollutants. Since main oxidizing agents in the photocatalytic treatment by N- and P-type TiO2 are different, investigating their performance for the photocatalytic treatment of landfill leachate is necessary. Therefore, the purpose of this study is to evaluate the performance of P-type TiO2 nanoparticles for the photocatalytic treatment of landfill leachate under visible light irradiation. Silicon (Si) element was considered as TiO2 dopant, and Si-doped TiO2 nanoparticles were synthesized by sol–gel method. Four effective parameters on the photocatalytic treatment process, i.e., the dopant content of Si (Si wt.%), calcination temperature (T), pH, and exposure time, were considered as independent variables, and temporal normalized concentration of leachate residual COD was considered as dependent variable. Decision tree (M5P) model was applied for modeling the photocatalytic process of landfill leachate treatment using the data of 167 experiments. Based on the results, the optimum value of pH, calcination temperature, and dopant content for Si-doped TiO2 nanoparticles are 6, 500 °C, and 2.5 weight percentage, respectively, and the leachate COD removal efficiency at these conditions is about 85% for leachate with 600 mg/L initial COD. Therefore, Si dopant considerably enhances the photocatalytic activity of TiO2 nanoparticles under visible light irradiation. This photocatalytic process can be efficiently applied for landfill leachate treatment. Finally, the performance of Si-doped TiO2 nanoparticles as P-type TiO2 was compared with the performance of tungsten (W)-doped TiO2 nanoparticles as N-type TiO2 for leachate COD removal. Results showed that both types of nanoparticles have a similar performance for oxidizing the leachate COD, and there is no significant difference between them.

Synergistically coupling membrane electrochemical reactor with Fenton process to enhance landfill leachate treatment

Landfill leachate is challenging to treat due to its complex composition. Advanced oxidation processes such as Fenton process can be effective to treat leachate. Herein, a previously developed membrane electrochemical reactor (MER) was coupled with Fenton oxidation through providing synergistic benefits with the low solution pH, reduced organics, and ammonia removal/recovery. This two-stage coupled system reduced the leachate COD by 88%, much higher than that from the standalone Fenton process treating raw leachate. In addition, the usage of chemical reagents has been greatly reduced. At a dimensionless oxidant dose of 1.0, the coupled MER-Fenton system reduced the consumption of both FeSO4⋅7H2O and H2O2 by 39%, H2SO4 by 100%, and NaOH by 55%. Consequently, the sludge production was reduced by 51% in weight and 12% in volume. Despite electricity consumption by the MER, the coupled system cost $4.76 per m3 leachate less than the standalone Fenton treatment. More notably, direct Fenton oxidation removed only 21% of ammonia; in comparison the MER-Fenton system removed ammonia by 98% with the possibility for recovery at a rate of 30.6–55.2 kg N m−3 reactor d−1. Those results demonstrate that coupling MER with Fenton process could mitigate some inherent drawbacks of Fenton oxidation such as ineffective ammonia removal, high acid and chemical reagents dose requirements, and a large amount of sludge generation. This system may be moved towards practical applications by addressing a few challenges such as using renewable energy to power MER.

Impact of Solid Waste Dumpsite on Groundwater Quality in the Neighbouring Communities

Leachate seepages into groundwater aquifer from solid waste dumpsites is likely to release toxic pollutants in groundwater which are hazardous to human health and local ecosystem. A study was conducted on the Physico-chemical parameters of dumpsite leachate and surrounding groundwater from Awotan Solid Waste Dumpsite, in Ibadan, Oyo State. The study was aimed at assessing the impact of the leachate from the dumpsite. The physicochemical analyses of the water samples were carried by standard analytical methods. The results obtained were compared with the WHO (World Health Organization) permissible limit of those parameters in drinking water. The Physico-chemical values obtained for the dumpsite leachate were generally higher than those of groundwater samples, suggesting that a source of contamination could be from the dumpsite leachate. The pH of groundwater samples ranged between 5.03 to 6.94, indicating that the groundwater was acidic. Results of Physico-chemical parameters of dumpsite leachate for Cl-, NO3, TH, Alk, BOD, COD exceeded the WHO limits for drinking water. The BOD and COD of dumpsite leachate and groundwater samples exceeded the WHO limits and hence not safe for drinking. The concentration of Cl- and TH in the groundwater closer to the dumpsite were higher than WHO permissible limits for drinking water. Also, concentrations of the analyzed parameters decreased with increasing distance from the dumpsite, thus implicating leachate seepage from the dumpsite into the groundwater. It is therefore recommended that dumpsites be located away from the human settlements to avoid drinking water contamination and local ecosystem &amp; biodiversity degradation.

Treatment of fresh leachate from a municipal solid waste incineration plant by combined radiation with coagulation process

In this study, the radiation technology was used for the advanced treatment of effluent of fresh leachate from a municipal solid waste incineration plant which was treated by membrane separation processes. The COD removal percentage of the effluent from the MBR treatment process was investigated by gamma irradiation combined with coagulation process. The experimental results showed that the removal percentage of COD could achieve 45.3% by gamma irradiation alone at the dose of 4 kGy. The COD removal percentage could be improved by the combination of coagulation with gamma irradiation. Particularly, the removal percentage of COD could increase to 55.2% at the dose of 1 kGy, when iron salt was used for the coagulation process. More researches are required in future study for further increasing the removal percentage of COD of leachate, for example, integrating radiation process into biological treatment process to enhance the COD removal.