Leachate Properties Research Articles

Variation in chemical property of asphalt immersed in varying aqueous solutions and its leachate property

The pavement asphalt properties are susceptible to deterioration under environmental factors, and the deterioration product will affect its surrounding aqueous environment. For this reason, the idealized asphalt-aggregate mixture was treated with coupled temperature, ultraviolet and aqueous solutions based on self-made multifactorial coupled simulation device. Subsequently, the deterioration of asphalt chemical properties was analyzed by fourier transform infrared spectroscopy and saturate-aromatic-resin-asphaltene tests. Meanwhile, the effect of environmental factors on leachate properties was explored based on organic matter contents and chemical elements. Based on that, the grey correlation method was adopted to correlate asphalt chemical properties and leachate properties. The results clearly showed that environmental factors increased the sulfoxide and carbonyl group content of asphalt and transformed the chemical components within it into polar substances. The asphalt chemical properties were gradually improved when coupling ultraviolet with sodium carbonate, sodium chloride and distilled water sequentially. Compared to neutral solution, alkaline solution exacerbated the effect of asphalt precipitates on leachate properties. The environmental factors increased the organic matter contents and chemical elements of leachate with time. The interaction mechanism between asphalt and aqueous environment involved the deterioration of asphalt properties caused by the presence of water, as well as the release of precipitates from aged asphalt into surrounding aqueous environment.

Devolatilization characteristics of a bio-residue (potato stems) with high contents of alkali metals and non-structural components – Influences of the washing pretreatment severity

A bio-residue (potato stems), rich in alkali metals and non-structural components, is subjected to hot (353 K) or acidic (0.1 mol/L hydrochloric acid) water washing. The acidic pretreatment is more effective for the demineralization, with alkalis reduced by 99 (powders) or 90 (particles) %, corresponding to organic matter dissolution around 35 or 17 wt%, respectively. The latter figures remain approximately the same for hot water washing (38 and 19 wt%) but alkalis are reduced only by 78 or 64 %. The leachate properties are significantly dependent on the solvent type and the residue granulometry, as indicated by thermogravimetric and SEM-EDX analysis. Washed bio-residues decompose at temperatures and with rates progressively increasing as the pretreatment becomes more severe (fine granulometry and acidic water washing). Multi-step global kinetics, previously developed for the untreated material and properly revisited to incorporate washing effects, reveals trends with important compositional changes. Despite starch dissolution, volatile product yields for the absolute peak rate zone increase by about 40–65 %, testifying augmented cellulose contents. The pectin compounds are almost eliminated, to the advantage of the shoulder rate zone, representing hemicellulose decomposition, with an increase in the volatile product yields around 22–78 %.

Using landfill leachate to indicate the chemical and biochemical activities in elevated temperature landfills

Landfill leachate properties contain important information and can be a unique indicator for the chemical and biochemical activities in landfills. In the recent decade, more landfills are experiencing elevated temperature, causing an imbalance in the decomposition of solid waste and affecting the properties of the landfill leachate. This study analyzes the properties of leachate from two landfills that were experiencing elevated temperature (ETLFs), samples were collected from both elevated temperature impacted and non-impacted areas in each landfill. The accumulation of volatile fatty acids (VFA) in leachates from elevated temperature impacted areas of both landfill sites revealed that methanogenesis was inhibited by the elevated temperature, which was further confirmed by the more acidic pH, higher H/C elemental ratio, and lower degree of aromaticity of the elevated temperature impacted leachates. Also, carbohydrates depletion indicated possible enhancement of hydrolysis and acidogenesis by elevated temperature, which was supported by compositional comparison of isolated acidic species by negative-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICRMS) at 21 T derived from both elevated temperature impacted and non-impacted areas in the same landfill site. Furthermore, leachate organics fractionation showed that leachates not impacted by elevated temperature contain less hydrophilic fraction and more humic fraction than elevated temperature-impacted leachates for both ETLFs.

Treatment of fresh leachate by anaerobic membrane bioreactor: On-site investigation, long-term performance and response of microbial community

This study proposed fresh leachate treatment with anaerobic membrane bioreactor (AnMBR) based on the on-site investigation of the characteristics of fresh leachate. Temperature-related profiles of fresh leachate properties, like chemical oxygen demand (COD), were observed. In addition, AnMBR achieved a high COD removal of 98% with a maximum organic loading rate (OLR) of 19.27 kg-COD/m3/d at the shortest hydraulic retention time (HRT) of 1.5 d. The microbial analysis implied that the abundant protein and carbohydrate degraders (e.g., Thermovirga and Petrimonas) as well as syntrophic bacteria, such as Syntrophomonas, ensured the effective adaptation of AnMBR to the reduced HRTs. However, an excessive OLR at 36.55 kg-COD/m3/d at HRT of 1 d resulted in a sharp decrease in key microbes, such as archaea (from 37% to 15%), finally leading to the deterioration of AnMBR. This study provides scientific guidance for treating fresh leachate by AnMBR and its full-scale application for high-strength wastewater.

The reducing effect of aglime onN2OandCO2emissions balance from an acidic soil: A study on intact soil cores

AbstractThe functioning of the nitrous oxide (N2O) reductase enzyme involved in the last step of denitrification is pH sensitive, with an optimum of 6.8. A solution to mitigate N2O emissions would be to bring soil pH close to neutrality by adding agricultural liming products (aglime). Nevertheless, the influence of aglime on the soil greenhouse gas (GHG) balance (CO2–N2O) is a subject of debate, particularly when considering the fate of the carbon (C) derived from carbonates. Our objective was to investigate the results of the effect of calcium carbonate (CaCO3) aglime on the CO2–N2O balance. Sixteen cylinders of undisturbed acidic soil were taken from a sandy loam profile and incubated at 20°C for 107 days in anaerobic conditions (water‐filled pore space >60%). Eight limed treatment cylinders received 1.45 g of aglime on the soil surface (2 t NV ha−1) and 0.08 g of N (100 kg of N ha−1). Eight control treatment cylinders received only 0.08 g of N. N2O and CO2fluxes were measured and converted into CO2equivalents to perform a GHG balance calculation. Furthermore, soil and leachate properties were measured. Aglime application triggered a reduction of N2O emissions, probably due to an increase in soil pH at the beginning of the experiment, which would have led to the N2O reductase activation. High ‐N content in the soil may inhibit the high N2O reduction potential in the limed treatment. CO2emissions were unexpectedly lower in the limed treatment. Aglime addition did not enhance C mineralisation, which may be explained by the possible stabilisation of soil organic carbon. A significant 11.3% reduction of GHG emissions was observed in the limed treatment. Overall, our results show that a strategy of liming acidic agricultural soil could be implemented for its potential in GHG mitigation. Nevertheless, future in‐depth research is necessary to better understand the fate of the C brought about by aglime.

Irrigation water quality, gypsum, and city waste compost addition affect P dynamics in saline-sodic soils

The amendments used for sodicity reclamation also profoundly influence P dynamics and leaching losses. This study characterized the effect of irrigation water quality on P dynamics and leaching from saline-sodic soil during reclamation utilizing gypsum alone or in combination with manure and city compost. Changes in properties of unleached and leached soils were fitted with labile P pools using redundancy analysis. The relation between leachate properties and P loss was explained by means of monitoring leachate properties up to ten pore volumes. During incubation, the water-extractable P (PH2O) concentration was greater than Olsen's P (PNaHCO3) in all treatments. The PNaHCO3 decreased in proportion to the amount of gypsum applied. Applying the organics with gypsum increased the PNaHCO3, PH2O, and organic P concentration compared to gypsum alone. The labile P pools in soil were positively correlated with HCO3− content (r = 0.39–0.77; P < 0.05) of leached and unleached soils. Adding gypsum and compost caused a 10–14% decrease in cumulative P leaching. The cumulative P leaching were greater with rainwater compared to saline water of SAR (sodium adsorption ratio) 5 and 15. The CO32−, HCO3−, pH, and SO42–content of the leachate explained about 71% variability in total P leaching (adj. R2 = 0.71; P < 0.001). This study concludes that low electrolyte water had a greater risk of P leaching and associated environmental pollution. Leaching of the saline–sodic soil amended with gypsum and city waste compost with low SAR saline water can reduce P leaching compared to good quality rainwater.

Insights into the landfill leachate properties and bacterial structure succession resulting from the colandfilling of municipal solid waste and incineration bottom ash

Four simulated bioreactors were loaded with only MSW, 5 % BA + MSW, 10 % BA + MSW and 20 % BA + MSW to investigate the leachate property and bacterial community change trends during the colandfilling process. The results showed that with increasing BA addition proportion (5 %∼20 %), the leachate oxidation–reduction potential (ORP) was lower, the leachate pH quickly entered the neutral stage, and the chemical oxygen demand (COD), volatile fatty acids (VFA), NH4+-N, Ca2+ and SO42− presented faster downward trends. The leachate SUVA254 and E300/400 confirmed that BA can accelerate the leachate humification process. BA can quickly increase bacterial diversity, and the higher the addition proportion of BA, the more significant the change in microbial community structure during the landfilling process. The leachate pH and COD greatly influenced the bacterial community structure. A low BA proportion can increase metabolism pathway abundance during the initial stage, but a high BA proportion had an inhibitory effect on the metabolism pathway.

Treatment of wastewater using black soldier fly larvae, under different degrees of biodegradability and oxidation of organic content

The biological treatment process based on the metabolism of Black Soldier Fly (BSF) larvae proved to be a highly promising technique for the treatment of high organic content (HOC) wastewater, such as sewage from food industries, leachate from municipal solid waste (MSW) landfill, etc. The present study was aimed at achieving a better understanding of how biodegradability and degree of oxidation of organic content might influence treatment performance and biomass quality. Six leachates characterised by similar COD (Chemical Oxygen Demand) but different BOD5/COD (Biochemical Oxygen demand/COD) and TOC/COD (Total Organic Carbon/COD) ratios were tested. By combining these ratios, the BOD5/TOC ratio was introduced to take into account the effect of both leachate properties (biodegradability and oxidation degree). Process treatment performance was significantly influenced by the quality of organic substances. Higher BOD5/TOC values (higher biodegradability and lower oxidation degree) resulted in a greater and faster larvae growth, with final wet weight of between 49.2 and 91.9mg/larva; lower mortality between 5 and 32%; higher prepupation percentages ranging from 4 to 21% and higher specific substrate consumption rate with values varying from 0.051 to 0.063 mgTOC/mg larva/d, up to 3-fold higher than values obtained using conventional activated sludge based on COD consumption. Conversely, no significant differences were detected in larvae protein and lipid contents, including the profiling of fatty acids.

Geotechnical properties of fresh municipal solid wastes with different compositions under leachate exposure

This paper investigates the geotechnical properties of a type of synthetic municipal solid waste (MSW). The tests were conducted on five groups of synthetic MSW compositions, based on the field characterization of fresh MSW samples collected from Mugga Lane landfill site, ACT, Australia. Compaction, hydraulic conductivity, compression, drained and undrained shear properties of the MSWs with water and leachate addition to the field moisture content were studied. The study shows that adding leachate could increase the maximum dry density of the MSWs under given moisture contents and compaction energies. The hydraulic conductivity of the MSWs could decrease by 100-fold when the confining pressure increases from 15 kPa to 240 kPa. The shear behaviours of the MSW samples follow the strain hardening behaviours of loose sand. The cohesion of the MSWs decreases but the friction angle of the MSWs increases with leachate addition due to the change in the surface tension and viscosity of the pore liquids and the loss of cementitious components. The addition of leachate increases the compression ratios of the MSWs by around 10% to 30% due to the change in the pH of the pore liquids. The most significant components affecting the shear and compression behaviours of the MSW were paper and wood. The effects of leachate exposure on the geotechnical properties of the MSWs is not very significant. It is important to consider the variation of MSW properties to the leachate properties (viscosity, pH and surface tension) in the large body of MSWs in the landfills.

Occurrence of per- and polyfluoroalkyl substances (PFAS) in municipal solid waste landfill leachates from western China.

Landfill leachate has been documented as a significant source of trace organic pollutants, comprising an expansive family of per- and polyfluoroalkyl substances (PFAS). This study presents the findings on the distribution of 13 perfluoroalkyl carboxylates (PFCAs) and 4 perfluoroalkyl sulfonates (PFSAs) in leachates from 6 municipal solid waste (MSW) landfills in western China. The total concentrations of 17 PFAS in sampled leachates ranged from 1805 to 43,310ng/L, and 15 compounds were detected in all samples. The short-chain compounds perfluorobutane sulfonate (PFBS, mean mass fraction 23.1%) and perfluorobutyric acid (PFBA, mean mass fraction 20.6%) were dominant. There were higher PFAS concentrations in leachates from operating landfills (mean: 12,194ng/L) compared to closed landfills (mean: 2747ng/L), but there was no significant difference between young (< 10years) and old landfills (> 10years). Moderate to weak correlations were observed between PFAS concentrations and leachate properties, e.g., TN, NH4+-N, TOC, and pH. This is the first report on the distribution of PFAS in landfill leachates from western China. The results have identified landfill leachate as an underestimated source of PFAS in the environment and have contributed to a more comprehensive evaluation on PFAS presence across China.

Leachate characteristics: Potential indicators for monitoring various phases of municipal solid waste decomposition in a bioreactor landfill

Leachate is a contaminated liquid generated during the bio-chemical decomposition processes of municipal solid waste (MSW) that occurred at semi-solid or solid-state in a bioreactor landfill (BLF). Conceptually, leachate from a BLF is analogous to the urine generated in the ‘human body’, on which the medical practitioners rely to diagnose and remediate ailments. In line with this practice, to monitor the complex MSW decomposition processes, prolonged investigations were performed to establish the temporal variation of different chemical parameters (such as pH, electrical conductivity, chemical oxygen demand, organic- and inorganic carbon, nitrate- and ammonium-nitrogen, sugars and volatile fatty acids) of the leachate collected from different cells (age≈ 6–48 months) of a fully functional BLF in Mumbai, India. Furthermore, to understand the effect of the climate, MSW composition and landfill operating conditions on the rate of the decomposition process, chemical parameters of the leachate obtained from a landfill located in the central part of Poland were compared with the BLF. The study reveals that the chemical parameters, except for the pH, evince a rapid reduction with time and attain a constant value, which indicates the ‘stabilized MSW’. Also, native microorganisms that are an integral part of MSW consume volatile fatty acids within a year in the BLF, which facilitate the rapid transformation of the decomposition process from acidogenesis and acetogenesis to the methanogenesis phase. It is worth iterating here that based on the long-term field study, a convenient and efficient methodology, which is currently missing from the literature, has been established to understand the kinetics of different phases of anaerobic decomposition. This study would be very helpful to the landfill operators, who are interested in accelerating MSW decomposition by augmenting leachate properties.

Low-carbon treatment of zinc contaminated iron tailings using high-calcium geopolymer: Influence of wet-dry cycle coupled with acid attack

Zinc contaminated iron tailings can be stabilized by an environmentally friendly high-calcium geopolymer as a new filler material for clean reutilization. The durability and toxic leaching of stabilized materials are vital for sustainable engineering applications, especially when exposed to complex environments. This study comprehensively studied the strength and leaching performance of four types of high-calcium geopolymer stabilized tailings (M series and C series; M1, M2, C1, and C2) subjected to the erosion of the Wet-Dry cycles coupled with Acid rain (WDA). Tests including unconfined compression test, apparent integrity, and mercury intrusion test were carried out to evaluate the strength and durability of stabilized tailings. These results showed that the erosion resistance of the C series was worse than that of the M series. Meanwhile, the leachate properties, e.g., pH, electrical conductivity, and typical ion (calcium, magnesium, and zinc) leaching concentrations, were examined to evaluate the leaching durability of the stabilized tailings. The relationships between chemical properties and ion leaching concentration were analyzed, which helped understand the erosion and leaching mechanisms. These results reflected that the occurrence of erosion is due to the coupling effect between the structural damage and hydration reaction. Furthermore, the stabilized materials after the WDA erosion were investigated the mechanisms of immobilization, erosion, and leaching via the X-ray diffraction and scanning electron microscope-energy dispersive spectroscopy tests. The mechanisms of zinc immobilization were precipitation, adsorption and solid-solution structure, and physical encapsulation. After the WDA erosion, the number of hydration products would decrease, but the zinc-sulfate precipitates would increase to reduce zinc leaching. Therefore, the increase of zinc leaching concentration was related to zinc desorption and damage of physically encapsulated zinc. The paper deepens the understanding of the durability of these stabilized materials under wet-dry and acid erosion, improving the reuse reliability of clean and green materials.

Physico-thermal, mechanical, and toxicity properties of stabilised interlocking compressed earth blocks made with produced water from oilfields

Inefficient wastewater management has been recognised as a major contributor to global water crises due to its potential for contaminating ecological resources. This study investigates the physico-thermal, mechanical, and leachate properties of stabilised interlocking compressed earth blocks (CEBs) produced from oil wastewater and soils from two major oilfields (Nimr and Marmoul) in Oman. An experimental testing programme was conducted to investigate compressive strength, thermal conductivity, and water absorption rate, including leachability properties of the CEBs. The X-ray fluorescence spectrometry (XRF), X-ray diffraction (XRD), and scanning electron microscope (SEM) analyses showed similar mineralogical composition and micro-structural properties of the soil samples. The findings from this study revealed that CEBs from both oil fields have shown good compressive strength values of about 4.5–7.3 MPa and 4.0–8.1 MPa at 7-and 28-curing days, respectively. The produced CEBs satisfy the Omani standard for blocks for both non-loadbearing and loadbearing masonry walls. The thermal conductivity properties of both Nimr (0.927 W/m.K) and Marmoul (1.001 W/m.K) CEBs agreed with the typical masonry concrete blocks (0.7–1.3 W/m.K) used in building construction. This study's water absorption rates were found to be slow, indicating that most of the pores found in the blocks showed moderate accessibility to water. Thus, the water absorption rates of the CEBs from both Marmoul (16%) and Nimr (17%) oilfields were moderate compared to similar studies found in the literature. Also, to determine the sustainable application of the produced CEBs, a leaching test revealed a low concentration of all the selected heavy metals, except chromium (3.73–3.14 mg/L), which was slightly high but yet was found below the United States Environmental Protection Agency (US EPA) standard of 5.0 mg/L for hazardous waste material, thereby posing low environmental threat to soil and aquatic systems.

Comparison of Landfill Leachate Properties by LPI and Phytotoxicity-A Case Study

The formation of leachate is one of the inevitable consequences associated with the operation of landfills. In addition to the study of physicochemical composition, toxicity is an important parameter taken into account, among others because of the need to subject leachate to treatment before discharge into the environment. The aim of this study was to determine the degree of leachate contamination using LPI and toxicity index. An analysis of the relationship between the toxic effect on plants and the calculated LPI values was also carried out to assess whether they could provide a measure of leachate toxicity when selecting a treatment method. The research conducted was to determine the degree of leachate contamination using LPI and toxicity index. An analysis of the relationship between the toxic effect on plants and the calculated LPI values was also carried out to assess whether they could provide a measure of leachate toxicity when selecting a treatment method. Calculated values of the leachate pollution index showed that leachates from selected Polish landfills are characterized by low and medium levels of LPI values. The variation in index values obtained was particularly evident between active and closed landfills and was related to the physicochemical composition of leachates. In closed landfills this value ranged from 7.4 to 11.1, while in active landfills from 12.9 to 15.9. The variation in index values obtained was particularly evident between active and inactive landfills and was related to the physicochemical composition of leachates. Phytotoxicity tests showed that leachate at low concentrations can promote plant growth. At higher concentrations (50 and 100%), leachates caused inhibition of root and shoot growth, which correlated with high LPI values. The results confirmed the relationship between the toxic effect on plants and the LPI values, so it can be considered as a reliable indicator of leachate toxicity.

Pepper cultivation on a substrate consisting of soil, natural zeolite, and olive mill waste sludge: changes in soil properties

The distribution of olive mill waste (OMW) in soil under specific conditions and restrictions seems to be an advantageous choice considering that it is a low-cost method and it recycles nutrients and returns organic carbon to the soil. In addition, it is regarded as a practice that contributes to climate change mitigation. The aim of this research was to investigate the potential of the natural zeolite clinoptilolite as a soil additive for using OMW sludge for vegetable cultivation and for eliminating the risk of soil and underground water degradation. For this purpose, a pot experiment was conducted under greenhouse conditions in which pepper seedlings were transplanted and grown onto different substrates containing combinations of 0%, 2.5%, and 5.0% zeolite and 0%, 2.5%, and 5.0% OMW sludge (v/v). The plants were irrigated twice a week, while leachates were collected on a weekly basis for testing. The results indicate that the use of OMW sludge improved soil properties. Moreover, the use of clinoptilolite as a substrate did not cause any significant variations in the cultivation process although this led to an increase in exchangeable Na at phytotoxic levels. However, it was determined that the substrate consisting of 2.5% clinoptilolite and 2.5% OMW sludge produced the best results in terms of substrate and leachate properties. The results are considered to be useful in effectively treating OMW when combined with natural zeolite additives as this process enhances the physicochemical characteristics of soil without leading to major irreversible negative consequences.

Behavior of Rejects from a Biological-Mechanical Treatment Plant on the Landfill to Laboratory Scale

This paper describes the laboratory-scale simulation of the behaviour of rejects from a biological-mechanical treatment (BMT) plant in Castellón (Spain). For this purpose, four lysimeters were built, with different densities. Simulations were carried out for 7 weeks and leachate recirculation was applied to two of them. The experimental results allowed us to determine: (i) dirt in fractions, which was relatively high (up to 15% in some fractions) due to biological processes; (ii) the field capacity for this waste with similar values to other works, which varied depending on the experiment; (iii) variation in the biomass percentage which lowered after experiments in all cases (59.5% lower on average), and the rejects’ calorific value was higher after experiments (28.2% on average); (iv) the evolution of leachate properties with or without recirculation, where percolation, in addition to the dragging of soluble materials, stabilised waste, which diminished its biological activity. Rejects’ increased calorific value will allow combustible material to be recovered in the future as a way to exploit the energy potential stored in landfills.

Laboratory Simulation of Aeration on Municipal Solid Waste from Barmshoor Landfill

This study was aimed to determine the influence of the aeration on some of the leachate properties and geotechnical aspects of the fresh municipal solid waste (MSW) in laboratory obtained from Barmshoor landfill, Iran. Two different bioreactors were filled with the same MSW in the laboratory and cured under anaerobic and aerobic conditions for 200 days. Temperature variation, the rate of leachate generation and its properties (pH, COD, BOD and organic content) as well as the shear strength parameters and settlement of the MSW for each bioreactor were measured in curing of the bioreactors. Aeration causes the temperature of the aerated sample to increase considerably. The temperature difference between the two bioreactors becomes about 7 °C after 200 days. For the aerated bioreactor, leachate volume decreased, then increased and finally, it reduced to the end of the experiment. The aerated sample produces less leachate compared to the blank sample. Aeration of MSW has significantly reduced COD of the generated leachate after 120 days. The COD/BOD ratio is remaining constant for the aerated sample (less than 1.6) during the experiment. However, it increases in the case of the blank sample after 60th day and reaches to more than 5 at the end of the experiment. Therefore, waste aeration can eliminate some complicated organic materials due to the presence of oxygen in the injected air. Comparing the results of the direct shear test of both bioreactors indicates that the aeration increases the shear strength at the end of the procedure.

A study on municipal leachate treatment through a combination of biological processes and ozonation

Landfill is the most commonly method of municipal solid waste disposal in many countries. This practice has great potential to produce highly polluted leachate in massive quantities, which can cause environmental contamination. Biological processes are known as a common method to treat municipal leachate however this process alone in is less effective, especially in reducing the concentration of organic pollutants (BOD5/COD ratio). Leachate properties are site-specific and greatly influenced by landfill age. This study focuses on the investigation of treatment methods that can increase the extent of leachate biodegradability by applying an ozone concentration of 2.5 mg/L with up to 360 minutes of contact time. In this study, batch reactors were used and operated in anaerobic and aerobic conditions. The leachate used here represents both young and old leachate. Several treatment combinations were compared: Variation I (a combination of biologically aerobic and anaerobic process), Variation II (ozonation included as a pre-treatment process), and Variation III (ozonation was included as a post-treatment process). The results suggest that the BOD5/COD ratios of young and old leachates were 0.58 and 0.21, respectively. The COD removal for a young and old leachate treatment by biological process alone was 96.8% and 50.8%, respectively. Meanwhile, a combination of anaerobic-ozonation-aerobic processes gave better COD removal. Ozonation had a significant effect on the old leachate treatment, where the COD removal rose from 50.8% to 75%. Ozonation is a type of technology that can be applied to a subsequence treatment of biological processes in order to elevate the COD removal efficiency.

Compressive Strength and Leaching Behavior of Mortars with Biomass Ash

This study investigated the use of a biomass ash produced by a fuel combination made with wood, corn stover, and corn cob as cement replacement for the production of mortar. Biomasses are now widely accepted as a substitute for conventional fuels and are becoming essential for cost-effective production of energy. This study aimed to provide an opportunity for the annual agricultural corn-crop residue, corn stover and cob, which is increasingly being used as fuel for its valuable energy content. Measurements of workability, compressive strength, and leachate properties (pH, salinity, heavy metals and calcium ion release) of mortar specimen, at different cement substitution levels and ages, were evaluated. The results obtained reveal definitive possibilities for such mixed biomass ash to be used in cement-based materials, such as mortars. Moreover, a multiple regression analysis has been reported between the mass of calcium ions leached and the mixture composition with the compressive strength. Data show that further confirmation, on a longer span of time and of other types of mechanical properties and environmental tests, would be necessary to fully implement the use of such biomass ashes in various types of cement-based construction materials, in order to divert them from landfill disposal.

Effect of some effective parameters on COD Removal from Nam Son Landfill Leachate by electrocoagulation

Leachate becomes ahead of wastewaters as being the most difficult to treat due to its complex and widely variable composition. In this research, the leachate treatment performance by electrocoagulation (EC) was studied. The samples of leachate were taken from Nam Son landfill in Hanoi. The effects of factors namely current intensity, electrolysis time, initial pH and anode materials on the EC performance were investigated via chemical oxygen demand (COD) removal efficiencies. The input leachate properties were obtained as COD, NH4+ and pH in the range of around 6247 ± 295, 1270 ± 38 mg/l and 8 ± 0.1, respectively. Mono-polar electrocoagulation unit was carried out in a batch system for leachate treatment with iron electrodes and approximately 1.8 litter of leachate. Firstly, with the increase in current (1 to 4A), the COD removal efficiencies increased from 50.00 to 78.57% (pH = 8 and operating time = 40 min). Secondly, by the increase in operating time, the treatment performance also went up significantly in first 40 min, then nearly level-off at above 73 % (pH=8, current intensity = 3A). In addition, the effect of pH in range of 5 to 10 on the electrocoagulation process was studied and showed the highest treatment efficiencies in neutral and mild alkaline medium, especially between 6 &lt; pH &lt; 8. Finally, the electrode materials made of iron and aluminum was investigated and the result indicated that when the iron anodes were replaced by aluminum, the COD removal efficiency experienced a considerable decline, from 70 to 37.93% (pH = 8 and operating time = 40 min). In combination of all experiments, the optimum operating conditions were achieved as iron electrodes, current intensity of 3A, electrolysis time of 40 min, the raw pH with iron electrodes, resulting the maximum COD removal efficiencies of 73.21%. As a result, the electrocoagulation can be applied to leachate pre-treatment.