Strength Leachate Research Articles

Development of fuzzy leachate pollution index for treatability-based classification of solid waste landfills.

The fuzzy leachate pollution index (FLPI) was established to classify the landfill sites on the basis of their leachate pollution potential by considering the limitations of traditional methods. The FLPI was developed adopting 9 critical input parameters, i.e., TDS, pH, Cl, Cu, Pb, Cr, Zn, BOD, and COD, from 22 major landfill sites across India. Using these critical parameters, 3 groups, i.e., inorganic leachate strength (INLS), organic leachate strength (ORLS), and heavy metal leachate strength (HMLS), were generated to estimate the FLPI. The regression analysis, ANOVA, and sensitivity analysis were also performed to determine the significance and uncertainty of the index. The results showed that among all MFs, the triangular with overlapping open ends (TOO) MF was best fitted (R = 0.90) for FLPI estimation. Accordingly, 41% of the landfill sites showed less treatment while the others (59%) required moderate degree of treatment. The regression (R2 = 0.92) and ANOVA (F value = 15.003, p = 0.000031) analyses described that the developed tool was significant (p < 0.05). The sensitivity analysis showed that Zn (R = 0.99) was the most influencing factor followed by BOD > COD > pH > Cr > Cu > Cl > Pb > TDS. The study provides an important tool that can also be used by researchers and scientists for investigating and evaluating various environmental problems.

A ‘Concentrate-&-Destroy’ technology for enhanced removal and destruction of per- and polyfluoroalkyl substances in municipal landfill leachate

Per- and polyfluoroalkyl substances (PFAS) are ubiquitous in landfill leachate due to their widespread applications in various industrial and consumer products. Yet, there has been no cost-effective technology available for treating PFAS in leachate because of the intrinsic persistency of PFAS and the high matrix strength of landfill leachate. We tested a two-step ‘Concentrate-&-Destroy’ technology for treating over 14 PFAS from a model landfill leachate through bench- and pilot-scale experiments. The technology was based on an adsorptive photocatalyst (Fe/TNTs@AC), which was able to selectively adsorb PFAS despite the strong matrix effect of the leachate. Moreover, the pre-concentrated PFAS on Fe/TNTs@AC were effectively degraded under UV, which also regenerates the material. The presence of 0.5 M H2O2 during the photocatalytic degradation enhanced the solid-phase destruction of the PFAS. Fresh Fe/TNTs@AC at a dosage of 10 g/L removed >95% of 13 PFAS from the leachate, 86% after first regeneration, and 74% when reused three times. Fe/TNTs@AC was less effective for PFBA and PFPeA partially due to the transformation of precursors and/or longer-chain homologues into these short-chain PFAS. Pilot-scale tests preliminarily confirmed the bench-scale results. Despite the strong interference from additional suspended solids, Fe/TNTs@AC removed >92% of 18 PFAS in 8 h under the field conditions, and when the PFAS-laden solids were subjected to the UV-H2O2 system, ~84% of 16 PFAS in the solid phase were degraded. The ‘Concentrate-&-Destroy’ strategy appears promising for more cost-effective removal and degradation of PFAS in landfill leachate or PFAS-laden high-strength wastewaters.

Phytoaccumulation of heavy metals from municipal solid waste leachate using different grasses under hydroponic condition

Grasses have been used widely to remediate contaminants present in domestic wastewater, but leachate generated from municipal solid waste that usually contain some concentrations of heavy metals has never been reported to be treated with grasses, especially Rhodes grass. A series of experiments was performed to investigate the contaminant uptake from municipal solid waste leachate by Chloris gayana (Rhodes grass) grown in combination with two commonly available grass varieties namely Vetiveria zizanioides (Vetiver grass) and Pennisetum purpureum (Elephant grass). Leachate used for the experiments had high values for chemical oxygen demand (5 g/L), pH (8.5), electrical conductivity (9.0 mS/cm), nitrates (182.1 mg/L), phosphates 6.4 mg/L along with heavy metals i.e. copper, zinc and manganese. Different dilutions of leachate ranging from 0 to 100% were applied in batches and their result showed that collectively all the grasses reduced overall contaminant concentrations. These were reported for chemical oxygen demand, electrical conductivity, nitrates, and phosphates reduced up to 67, 94, 94, and 73%, respectively. Metals uptake by grasses also showed a significant decrease in applied dose i.e. zinc (97%), copper (89%), and manganese (89%). Plant analysis showed that all grasses showed preference to heavy metals uptake e.g. Rhodes grass favoured up taking zinc, Elephant grass for copper and Vetiver grass preferred manganese. Overall growth performance of Rhodes grass was better in dilute leachate, whereas in more concentrated leachate, Rhodes grass did not perform better and production of biomass decreased. In Vetiver grass, root and shoot lengths decreased with increasing leachate strength, but the biomass did not change significantly.

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.

Biologically induced mineralization in anaerobic membrane bioreactors: Assessment of membrane scaling mechanisms in a long-term pilot study

Herein, we report on a mechanism of inorganic fouling observed in a pilot-scale anaerobic membrane bioreactor (AnMBR) treating high strength leachate from domestic food waste. Long-term operation (around 700 days) of the AnMBR encountered frequent, sudden irreversible fouling events driven by biologically induced mineral scaling which required intense chemical cleaning to recover membrane permeability. Mineral scale formation occurred on the surface and within pores of 100kDa ultrafiltration (UF) membranes. The UF membrane rejected phosphorus, calcium and magnesium up to 97%, 92% and 60%, respectively, which suggests that these ions either precipitated ahead of the UF membranes and existed in a colloidal state and/or precipitated and were retained within UF membrane pores. Microscopic and spectroscopic analyses combined with geochemical modeling confirmed hydroxyapatite, dolomite and struvite were the prevailing mineral precipitates coming from the methanogenic digester; these minerals were embedded in the cake layer and found within membrane pores. Geochemical modeling suggests that slower-growing minerals such as dolomite might precipitate within the membrane pore structures possibly causing membrane pore constriction and/or blocking. Combined use of HOCl (to oxidize and remove organic matter) and citric acid (to dissolve minerals and chelate divalent ions) proved the most effective cleaning regime to recover membrane permeability.

Management of landfill leachate: The legacy of European Union Directives

Landfill leachate is the product of water that has percolated through waste deposits and contains various pollutants, which necessitate effective treatment before it can be released into the environment. In the last 30years, there have been significant changes in landfill management practices in response to European Union (EU) Directives, which have led to changes in leachate composition, volumes produced and treatability. In this study, historic landfill data, combined with leachate characterisation data, were used to determine the impacts of EU Directives on landfill leachate management, composition and treatability. Inhibitory compounds including ammonium (NH4-N), cyanide, chromium, nickel and zinc, were present in young leachate at levels that may inhibit ammonium oxidising bacteria, while arsenic, copper and silver were present in young and intermediate age leachate at concentrations above inhibitory thresholds. In addition, the results of this study show that while young landfills produce less than 50% of total leachate by volume in the Republic of Ireland, they account for 70% of total annual leachate chemical oxygen demand (COD) load and approximately 80% of total 5-day biochemical oxygen demand (BOD5) and NH4-N loads. These results show that there has been a decrease in the volume of leachate produced per tonne of waste landfilled since enactment of the Landfill Directive, with a trend towards increased leachate strength (particularly COD and BOD5) during the initial five years of landfill operation. These changes may be attributed to changes in landfill management practices following the implementation of the Landfill Directive. However, this study did not demonstrate the impact of decreasing inputs of biodegradable municipal waste on leachate composition. Increasingly stringent wastewater treatment plant (WWTP) emission limit values represent a significant threat to the sustainability of co-treatment of leachate with municipal wastewater. In addition, the seasonal variation in leachate production poses a risk to effective co-treatment in municipal WWTPs, as periods of high leachate production coincide with periods of maximum hydraulic loading in WWTPs.

Leachability of Self-Compacting Concrete (SCC) Incorporated with Fly Ash and Bottom Ash by Using Toxicity Characteristic Leaching Procedure (TCLP)

The process of combustion in coal fired power plant generates ashes, namely fly ash (FA) and bottom ash (BA). In addition, coal ash generated from coal combustion generally contains heavy metals within their compositions. These metals are toxic to the environment as well as to the human health. Fortunately, treatment methods are available for these ashes and the use of FA and BA in concrete mix is one of the few. As such, this study presents the work in determining the leachability of self-compacting concrete (SCC) incorporated with FA and BA. The ashes were obtained from Kapar Energy Ventures power plant in Kapar, Selangor. SCC mixtures incorporated with 10%, 20% and 30% FA (replacing cement) and BA (replacing sand) respectively was formulated and casted. The samples were then crushed to be extracted using Toxicity Characteristic Leaching Procedure (TCLP) and heavy metals content within the samples were identified accordingly using Atomic Absorption Spectrometry (AAS). From the results, it was found that incorporation up to 30% of the ashes were safe as the leached heavy metals concentration did not exceed the regulatory levels, except for arsenic (As). On the other hand, incorporation of 20% FA and BA each in SCC provided the most economically viable product, with high strength and low leachate concentrations. In conclusion, this study will serve as a reference which suggests that FA and BA are widely applicable in concrete technology and its incorporation in SCC constitutes a potential means of adding value with appropriate mix and design.

ChemInform Abstract: Determinants of Optimal Aerobic Bioreactor Landfilling for the Treatment of the Organic Fraction of Municipal Waste

AbstractReview: 85 refs.

Performance Assessment of Gravel–Tire Chips Mixes as Drainage Layer Materials Using Real Active MSW Landfill Leachate

Potential of clogging for rubber tire chips, gravel and their relative performance for transmitting high strength leachate when arranged in proportionate layers of relative thickness and in random state mixes of various percentage compared to the case of used alone were studied through column experiments. Comparative hydraulic performance of gravel and tire chips in their different combinations with percentage change (reduction) in COD, TSS, Ca-hardness and TDS concentration levels for the real active high strength MSW landfill leachate with time were investigated. Experiments were performed to simulate conditions occurring at the base of all active MSW landfills, in an attempt to replicate reasonably worst case conditions. Results clearly showed that the combinations ds (scrap tire chips layer thickness)/dg (gravel layer thickness) = 0.25, 0.50 (arranged by relative thickness) and Ws:Wg = 1:3 (25 % tire chips:75 % gravel; mixed by weight friction of each component) were good in term of obtaining initially relatively free drainage. Minor reduction in hydraulic conductivity for fairly longer duration, due to lesser clogging and small reduction in COD, TSS and Ca-hardness concentration levels were observed for these combinations. These experimental findings may prove to be very useful for the proper design, long term performance and service life of all tire chips–gravel made drainage layers of all the active MSW landfill leachate collection and removal systems.

Monitoring transitory profiles of leachate humic substances in landfill aeration reactors in mesophilic and thermophilic conditions

The presence of humic substances (HS) in landfill leachate is of great interest because of their structural stability and potential toxicity. This study examined the effects of temperature and waste age on the transformation of HS during in situ aeration of bioreactor landfills. By establishing aerobic conditions, dissolved organic carbon (DOC) rapidly accumulated in the bioreactor leachate. Fractional analysis showed that the elevated concentration of humic acids (HAs) was primarily responsible for the increment of leachate strength. Further structural characterization indicated that the molecular weight (MW) and aromacity of HS were enhanced by aeration in conjunction with thermophilic temperature. Interestingly, elevation of HAs concentration was not observed in the aeration reactor with a prolonged waste age, as the mobility of HAs was lowered by the high MW derived from extended waste age. Based on these results, aeration may be more favorable in aged landfills, since dissolution of HAs could be minimized by the evolution to larger MW compared to young landfills. Moreover, increased operation temperature during aeration likely offers benefits for the rapid maturation of HS.

A comparative examination of MBR and SBR performance for the treatment of high-strength landfill leachate

The management of landfill leachate is challenging, with relatively limited work targeting high-strength leachate. In this study, the performance of the membrane bioreactor (MBR) and sequencing batch reactor (SBR) technologies are compared in treating high-strength landfill leachate. The MBR exhibited a superior performance with removal efficiencies exceeding 95% for BOD5, TN, and NH3 and an improvement on SBR efficiencies ranging between 21 and 34%. The coupled experimental results contribute in filling a gap toward improving the management of high-strength landfill leachate and providing comparative guidelines or selection criteria and limitations for MBR and SBR applications.ImplicationsWhile the sequencing batch reactor (SBR) technology offers some flexibility in terms of cycle time and sequence, its performance is constrained when considering landfill leachate associated with significant variations in quality and quantity. Combining membrane separation and biodegradation processes or the membrane bioreactor (MBR) technology improved removal efficiencies significantly. In the context of leachate management using the MBR technology, more efforts have targeted low-strength leachate with limited attempts at moderate to high strength leachate. In this study, the SBR and MBR technologies were tested under different operating conditions to compare and evaluate their feasibility for the management of high-strength leachate from a full-scale operating landfill. Such a comparison has not been reported for high-strength leachate.

Determinants of Optimal Aerobic Bioreactor Landfilling for the Treatment of the Organic Fraction of Municipal Waste

Historically, municipal solid waste landfills have been designed and operated as disposal facilities with suboptimal degradation under anaerobic conditions, resulting in slow waste stabilization and generation of landfill gas rich in methane and high strength leachate. Recently, aerobic bioreactor landfilling is being promoted as a promising method that enhances waste stabilization while producing a relatively weaker leachate and no methane generation. The authors review transformation processes and benefits associated with aerobic bioreactor landfilling. Factors affecting the operation of aerobic bioreactor landfills were detailed and performance indicators were defined with technical and operational considerations. The article emphasizes conditions for economic viability of the technology and concludes with outlining existing gaps and future research needs to improve the understanding and performance of aerobic bioreactor landfilling.

A study of shear strength properties of municipal solid waste in Chongqing landfill, China.

The aim of this study is to analyze the effect of biodegradation on the shear strength of municipal solid waste (MSW), leachate, and biogas production. The direct shear (DS) test shows that the shear strength of waste in the initial stages is mainly depended on its composition and inter-structure. After the waste has been in a landfill for 30 days, the waste's increased biodegradation exhibited a great influence on the waste's shear strength. The increase of moisture content in the waste mass might cause a decrease of its shear strength. Tri-axial tests under consolidation-drained (CD) condition show that the shear strength of the cohesion and friction angle for degraded samples increased when the defined axial strain increased from 5 to 20 %. The cohesion varied from 35.90 to 66.42 kPa and the drained friction angle ranged between 29° and 38°. The measurements of shear strength properties are utilized to assess the slope stability of landfills.

Environmental pollutants removal from composting leachate using anaerobic biological treatment process

Aims: The main purpose of this study was to make an initial assessment on the possibility of anaerobic treatment of an extremely high strength leachate streams generated at Isfahan composting plant. Materials and Methods: In this interventional study, the pretreated composting leachate was fed intermittently to a anaerobic sequencing batch reactor (ASBR) at increasing steps of 6 g chemical oxygen demand (COD)/l.day (hydraulic retention time [HRT] =23 h), 33 g COD/l.day (HRT = 18 h), and finally 36.5 g COD/l.day (HRT = 12 h) for about 10 months. Reactor performance was investigated by measuring pH, total suspended solids (TSS), electrical conductivity, biogas production, COD, and TSS removal twice a week. Results: In pretreated composting leachate, biochemical oxygen demand 5/COD ratio was ranged 0.64-0.8. The pH value in ASBR was between 7.47 and 8.15 without any pH adjustment throughout the study. Conclusion: Although in loading rate of 11 g/l.day, most of the pollutants were decreased significantly, but aerobic process is required to ensure achieving national standard values for discharge in receiving waters.

A bench-scale assessment of ozone pre-treatments for landfill leachates

Leachate from stabilized landfill can pose unique challenges to conventional biological wastewater treatment. Ozone-based advanced oxidation processes have garnered recent consideration as an option to reduce the organic strength and recalcitrance of aged landfill leachate. With a bench-scale investigation, the reported work examines the potential for leachate conditioning for further biological treatment by treatment with low-mg/L doses of ozone (0–7.5 mg/L O3). While not sufficient for significant organics mineralization, the tested ozone doses could potentially produce both selective and non-selective oxidation of recalcitrant leachate organic compounds leaving bio-available products in the pre-treated leachate. Leachate conditioning by O3 or O3/H2O2 was assessed via monitoring of three anthropogenic organic leachate contaminants(tris-(2-chloroethyl) phosphate, tris-(butoxyethyl)-phosphate and 17β-estradiol (E2)) with ozonation, and ozonation followed by anaerobic incubation. In addition, chemical oxygen demand (COD) and BOD5 analysis of the ozonated leachate, and methane and total gas formation during the anaerobic incubation were used to assess the degree of leachate conditioning. When treated with O3 alone, 58% removal of E2 was observed with an ozone dose of 4.5–5.4 mg/L. Direct oxidation of the three leachate contaminants was limited with O3/H2O2 pre-treatment. However, this pre-treatment was observed to have significantly improved degradation of E2 during anaerobic incubation of ozonated leachates (removal rate of E2 was 53.7% with 15 days of incubation), indicating the potential for ozone synthesized co-metabolism. However, overall anaerobic microbial activity was not significantly impacted by the applied ozone pre-treatments, as measured by methane formation, total gas formation, and COD removal during incubation.

Mechanisms of clogging in granular drainage systems permeated with low organic strength leachate

Leachate drains in municipal solid waste (MSW) landfills are susceptible to biological and (or) chemical clogging. This paper describes clogging of drainage aggregates permeated with leachates representative of those from landfills containing wastes with a low organic content — such as low-level radioactive waste repositories — which may occur as a result of microbiological activity causing formation of bacterial biofilms (microbiological clogging) and precipitation of low-solubility inorganic salts (chemical clogging). The balance between these depends on the leachate composition. Biological deposits appeared to reach a pseudo steady state, proportional to the nutrient loading, for the range of conditions investigated and as such can be considered to be self-limiting and the clog material reasonably permeable. Harder inorganic deposits of calcium carbonate occurred if the Ca2+ concentration in the leachate exceeded the local solubility limit under the prevailing conditions, i.e., partial pressures of CO2 between 3.7 and 6 kPa and pH of 6.7–6.8. CaCO3 clog was observed to bind the granular aggregates together and be effectively impermeable, and was, unlike a pure microbial clog, observed not to be self-limiting. Hard CaCO3 clog could be reduced by not co-disposing wastes that are high in calcium with wastes having a high organic content, and generally keeping the Ca2+ concentration in the leachate low.

Modeling of Leachate Collection Systems with Filter Separators in Municipal Solid Waste Landfills

AbstractA numerical model is used to estimate the service life and clogging of gravel leachate drainage layers with a filter separator layer, such as those used in municipal solid waste landfills. A filter separator layer between the waste and the drainage layer is shown to reduce the leachate strength entering the gravel drainage layer and to extend the time that it takes to clog the drainage layer to the point when the leachate level exceeds the maximum design value (the service life). The filter layer is shown to have a far more significant effect in extending the service life when pea gravel (dg=6 mm) is used in the drainage layer, and less effect when coarse gravel (dg=27 mm) is used in the cases examined, although most of the benefit of a filter separator layer was achieved by using a 3-mm-thick needle-punched nonwoven geotextile. This geotextile may be sufficient for many practical purposes that are similar to those examined. The results from modeling leachate collection systems with filter separ...

Low flux submerged membrane bioreactor treating high strength leachate from a solid waste transfer station

A submerged membrane bioreactor was employed to treat high strength leachate generating from a solid waste transfer station. The reactor was operated at low fluxes of 1.2; 2.4; 3.8 and 5.1 LMH. The organic loading rate (OLR) ranged from 2 to 10 kg COD/m(3)day. Results show that 97% removal efficiency of COD at flux of 2.4 LMH. The highest removal of ammonia nitrogen and total nitrogen was 92.0 ± 1.5% and 88.0 ± 2.0% respectively at flux of 3.8 LMH. Fouling rates were observed to be 0.075; 0.121; 3.186 and 6.374 kPa/day for the fluxes of 1.2; 2.4; 3.8 and 5.1 LMH, respectively. Membrane fouled very slowly at low flux operation. The sustainable flux was identified to be less than 2.4 LMH for treating high strength leachate. It reveals less fouling was able to achieve for high strength wastewater by reducing the membrane flux.

Effect of grain size on service life of MSW landfill drainage systems

A numerical model “BioClog-2D” is used to examine the service life and clogging of leachate collection systems with granular drainage material of different grain sizes. The modelling shows that the leachate characteristics at the end of the drainage pipe are significantly different from those in the leachate entering the leachate collection system and this reduction in leachate strength corresponds to an accumulation of clog mass within the saturated drainage layer. The calculated clog mass within the saturated drainage layer is dominated by the inorganic material, which is in encouraging agreement with field-observed data. The service life of leachate collection systems is increased with an increase in the grain size of the drainage material and decreased with an increase in the length of the drainage path. The service life of the drainage layer is shown to vary from a few years to over 100 years depending on the design of the system. The results indicate that in addition to the particle size of the granular material, the infiltration rate and leachate strength history greatly affect the estimated service life of leachate collection systems.

Effects of sulphate addition and sulphide inhibition on microbial fuel cells

The effects of adding sulphate in: (i) standard activated sludge microbial fuel cells (MFCs) and (ii) larger-scale leachate-treating columns – both as individual units and as a system connected in cascade – are reported. S-replete power output was ∼2-fold higher than that of the S-deplete MFC. Furthermore, the effects of evolved sulphide (S2−) inhibition were investigated. The overall decrease in power output from the sulphide inhibitor (Na2MoO4) additions was 83% for the S-replete and 90% for the S-deplete. The second phase with the leachate treating units shows an improvement of 32–86% (depended on leachate strength) in current output as a result of adding sulphate. When leachate column MFCs were connected fluidically in series, the amount of Na2SO4 made available downstream was decreasing (increase in power was 99%, 40% and 12% for columns in cascade). Results demonstrated the beneficial effects of added sulphur sources to both activated sludge and leachate-treating MFCs.