Biological Treatment Of Landfill Leachate Research Articles

Effect and mechanism of Mn2+ on urease activity during anaerobic biological treatment of landfill leachate.

As a crucial hydrolytic enzyme, urease plays a vital role in anaerobic biological treatment. It is well-known that manganese ions are abundant in landfill leachate, but their concentration fluctuates significantly. However, few studies have investigated the effect and mechanism of different concentrations of Mn2+ on urease activity during anaerobic biological treatment of landfill leachate. This paper aimed to investigate the effects and mechanisms of different concentrations of Mn2+ on urease activity. The results showed that an appropriate amount of Mn2+ could significantly enhance urease activity, while a high concentration of Mn2+ could inhibit it. Insight into the mechanisms behind this phenomenon, various methods such as Zeta potential, particle size, ultraviolet spectroscopy, fluorescence spectroscopy, Fourier transform infrared spectroscopy, and statistical analysis were employed in our study. Research suggested that, on one hand, Mn2+ may form hydrogen bonds with the side chain amino or carboxyl groups of urease amino acid residues, affecting the structure of urease through hydrogen bonding. Additionally, Mn2+ also binds to urease through hydrophobic interactions. On the other hand, the C-OH and C-N functional groups in urease have a strong affinity for Mn2+, and changes in these functional groups can greatly enhance the activity of urease. Furthermore, under the action of high concentrations of Mn2+, while the structure of urease becomes more stable, there is also a steric hindrance phenomenon that affects the substrate from entering the catalytic center. Therefore, studying the mechanism of Mn2+ affecting urease activity has significant biological significance and provides a new perspective for exploring the impact of metals on anaerobic bioprocessing of landfill leachate.

Sustainable approach of biological treatment of landfill leachate by Anaerobic Ammonium Oxidation: A review

An upsurge in living standards, rising industrialization and urbanization, the protection of water environment has become a priority. Anaerobic ammonium oxidation process has drawn a lot of attention since it demonstrated substantial advantages over conventional nitrogen removal techniques, including a 100% reduction in the amount of organic carbon required, a 60% reduction in the amount of aeration needed, and a 90% reduction in the amount of sludge produced. Effective treatment of landfill leachate is extremely important as leachate is a threat to the environment. Municipal waste management is still a challenging situation in developing countries. Uncontrolled waste disposal results in greenhouse gases emissions which worsens climate change as the leachate will pollute water bodies, soil and a significant air pollution which impacts on human health will be released. This paper reviewed several published research works in Scopus dealing with the leachate treatment by Anammox process combined with some other systems and highlighted some common challenges found with the application of this new technology. Treating landfill leachate resulted in an excellent ammonium NH4 +-N removal efficiency. However, it has been highlighted that most of the research reviewed reported some limitations of the technology on a small scale such as the low start-up time affecting the growth of bacteria in the reactors and the instability of the system when pH and temperature decrease. Biological treatment, Anammox method included, offers a cost-effective, eco-friendly, and an effective solution for nitrogen removal.

Different Fenton treatments on diverse landfill organics: Discover the underestimated effect of derived-DOM

Fenton is one of the most promising processes for the removal of dissolved organic matter (DOM). It has always been highly suspected that derived-DOM would be generated during Fenton reaction, but there is lack of direct evidence at the molecular level. The present study explored the molecular properties of the derived-DOM of five common Fenton technologies for degradation of nine landfill organics including leachates and concentrates based on UPLC Orbitrap MS/MS analysis. The comparative results confirmed that DOM derivation was essential for Fenton technologies, with the DOM derivation rate as high as 17.3%–70.3%. The derived-DOM are dominated by trace organic contaminants (CHON-DOM), and typical new contaminants (PPCPs, flavors, etc.). Heterogeneous Fenton had significantly lesser derived-DOM (35.1% ± 16.9%) than other Fenton technologies. Among all landfill organics, medium leachate was most likely to derive DOM (51.4% ± 13.9%), while unexpectedly old leachate had the lowest derivation rate (32.0% ± 5.3%). In the overall membrane treatment process, the secondary membrane concentrate is more susceptible to DOM derivation (43.4% ± 5.5%–49.6% ± 3.8%) than the primary membrane concentrate (40.7% ± 14.1%), and the elements and subcategories composition and molecular property indexes of the derived-DOM become more complex. On the contrary, the DOM derivatization rate of the biological treatment effluent after Fenton treatment was much lower than that of the various concentrates after Fenton treatment and the molecular property are simpler. Therefore, Fenton may replace the membrane process directly as a deep treatment process after biological treatment of landfill leachate. These information would help the selection and application of Fenton technologies.

Discovering dominant ammonia assimilation: Implication for high-strength nitrogen removal in full scale biological treatment of landfill leachate

Landfill leachate containing high-strength nitrogen is generated in domestic waste landfilling. The integration of anoxic and aerobic process (AO) based on nitrification and denitrification, has been a mainstream process of biological nitrogen removal (BNR). But the high-strength organics as well as aerobic effluent reflux might change the biochemical environment designed and operated as AO. In view of the nitrogen balance in a full scale landfill leachate treatment plant with two-stage AO, we found that approximately 90% removal of total nitrogen (TN) and ammonia (NH4+-N) focused on primary anoxic and aerobic stage. Meanwhile, the less nitrate and nitrite in the aerobic effluent were incapable of sustaining denitrification or anaerobic ammonia oxidation (anammox). The high reflux flow from aerobic to anoxic process enabled the similar microbial community and functional genes in anoxic and aerobic process units. However, the functional genes involving ammonia assimilation in all process units showcased the highest abundance compared to those correlated with other BNR pathways, including nitrification and denitrification, assimilatory and dissimilatory nitrate reduction, nitrogen fixation and anammox. The ammonia assimilation dominated the removals of TN and NH4+-N, rather than other BNR mechanism. The insight of dominant ammonia assimilation is favorable for illustrating the authentic BNR mechanism of landfill leachate in AO, thereby guiding the optimization of engineering design and operation.

An assessment of the UV/nFe0 /H2 O2 system for the removal of refractory organics in the effluent produced by the biological treatment of landfill leachate.

The removal efficiency and mechanism of the ultraviolet/nanoscale Fe0 /H2 O2 (UV/nFe0 /H2 O2 ) system for refractory organics in membrane bioreactor effluent were investigated. The most effective removal of organics was achieved at initial pH = 3.0, H2 O2 dosage = 50 mM, nFe0 dosage = 1.0 g/L, and UV power = 15 W, with a reaction time of 60 min. Under these conditions, the absorbance at 254 nm, chromaticity, and total organic carbon removal efficiencies were 65.13%, 79.67%, and 61.51%, respectively, and the aromaticity, humification, molecular weight, and polymerization of organics were all significantly reduced. The surface morphology and elemental valence analysis of nano zero-valent iron (nFe0 ) before and after the reaction revealed the formation of iron-based (hydrated) oxides, such as Fe2 O3 , Fe3 O4 , FeOOH, and Fe (OH)3 , on the surface of the nFe0 . Refractory organics were removed by Fenton-like reactions in the homogeneous and heterogeneous adsorption-precipitation of iron-based colloids. At the same time, UV radiation accelerated the formation of Fe2+ on the nFe0 surface and promoted the Fe3+ /Fe2+ redox cycle to a certain extent, enhancing the removal of refractory organics. The results provide a theoretical basis for the application of the UV/nFe0 /H2 O2 system to remove refractory organics in the effluent produced by the biological treatment of landfill leachate. PRACTITIONER POINTS: The UV/nFe0 /H2 O2 process is effective in refractory organics removal in leachate treatment. Humus in leachate was largely destroyed and mineralized by the UV/nFe0 /H2 O2 process. Active nFe0 material participated in the Fenton-like process and was promoted by UV. The effects of nFe0 material and UV introduction were investigated.

Transformation of dissolved organic matter in landfill leachate during a membrane bioreactor treatment

In this study, a cutting-edge mass spectrometry (MS) technique, Orbitrap fusion MS with ultrahigh resolution, was used to analyze the molecular composition, chemical properties, formation mechanism, and environmental impact of refractory dissolved organic matter (rDOM) in leachate. The results showed that the bioavailable DOM (bDOM) and rDOM constituents varied substantially during the biological treatment of landfill leachate. Compared with bDOM, the rDOM in leachate had a higher degree of unsaturation, aromaticity, and oxidation, and a larger molecular weight, and contained more organic matter with benzene ring and biphenyl structures. Using high-throughput 16S rRNA sequencing, metagenomics, the Kendrick mass defect (KMD), and a mass difference network (MDiN), it was found that rDOM in leachate is generated through carboxylation (+COO), dehydro-oligomerization (-H2), and chain scission (-CH2) pathways due to the activity of microbes such as Patescibacteria, Chloroflexi, and Proteobacteria. Compared with Suwannee River fulvic acid (SRFA), the rDOM in leachate contained more organics with nitrogen, sulfur, benzene rings, and biphenyls. If the rDOM in leachate enters the environment it will affect the composition of the original organic matter, and its biogeochemical transformation and environmental fate will then need to be monitored and may require special attention.

Discovering Dominant Ammonia Assimilation: Implication for High-Strength Nitrogen Removal in Full Scale Biological Treatment of Landfill Leachate

Discovering Dominant Ammonia Assimilation: Implication for High-Strength Nitrogen Removal in Full Scale Biological Treatment of Landfill Leachate

Enhanced landfill leachate treatment in sequencing batch biofilm reactors (SBBRs) amended with zeolite and biochar

AbstractBACKGROUNDBiological treatment of landfill leachate is inhibited by high concentrations of ammonia and recalcitrant organic matter. This study investigated the addition of natural adsorbent materials, zeolite (clinoptilolite) and biochar, to enhance biological treatment of landfill leachate in sequencing batch biofilm reactors (SBBRs). Three bench‐scale SBBRs were set up with varying types of biofilm support media: (i) lightweight expanded clay aggregate (LECA) as a control (C‐SBBR); (ii) LECA + zeolite (CZ‐SBBR); and (iii) LECA + zeolite + biochar (CZB‐SBBR). SBBRs were operated with alternating anoxic and aerobic stages to promote total nitrogen (TN) removal via nitrification/denitrification.RESULTSExcellent TAN removal (>99%) was achieved in all three SBBRs throughout the study, most likely as a result of the favorable environmental conditions and long hydraulic retention time (HRTs) applied (nine or more days). Biochar addition in CZB‐SBBR resulted in significantly higher chemical oxygen demand (COD) (61–83%) and color (82–95% as UV456) removals compared with C‐SBBR (42–44% for COD and 28–33% for color) and CZ‐SBBR (34–45% for COD and 20–35% for color). High effluent nitrate (NO3−) concentrations initially were observed in CZB‐SBBR, most likely due to limited organic carbon availability for denitrification. However, after >1 year of operation, NO3− accumulation declined and TN removal of 81% was achieved, indicating that the main nitrogen removal pathway shifted from simultaneous nitrification/denitrification to partial nitritation/anammox.CONCLUSIONSZeolite/biochar amended SBBRs are a promising approach for enhanced landfill leachate treatment. © 2021 Society of Chemical Industry (SCI).

Kinetic study of real landfill leachate treated by non-thermal plasma (NTP) and granular sequential batch reactors (GSBR)

The biological treatment of landfill leachate is a challenging process due to the high concentration of chemical oxygen demand (COD), nitrogen compounds, and other toxic compounds. Furthermore, nitrification inhibition may occur in landfill leachate due to the high concentration of free ammonia and inhibitors, such as poisonous compounds. Accordingly, this study aimed to use non-thermal plasma and aerobic granules to reduce organic loading rate and heavy metals of landfill leachate. We used a plasma reactor with a working volume of 0.5 l, quartz material for the pretreatment process. According to the results, the plasma reactor was most efficient in removing metals as well as d quasi-metals (e.g., arsenic, antimony, selenium, cobalt, iron, strontium, and silver) and least efficient in the removal of nickel, zinc, aluminum, and manganese. Our findings indicated that the COD removal efficiency decreased from 100% to 98%, from 93.5% to 89.18%, and from 92% to 88%, for 20%, 50%, plus 100% leachate, and three hydraulic retention times (6, 4.5, and 2.1 h), respectively. The amount of organic matter removal was a function of concentration and followed the second-order kinetic (R2 > 0.9) and Stover-Kincannon models (R2 > 0.97). Thus, it could be concluded that aerobic granules could effectively reduce e the organic load, COD, and heavy metals entering a GSBR reactor. Due to the good efficiency of the plasma reactor and GSBR, so we proposed full- scale studies at the landfill site for heavy metal and organic loading reduction. It also presents a new subject of research and concludes with an outlook on future investigation topics, such as different contaminants in leachate of landfills from different areas.

Factors affecting aerobic granule sludge formation in leachate treatment -a systematic review.

The biological treatment of landfill leachate due to high concentration of Chemical Oxygen Demand (COD), ammonia, and other toxic compounds is so difficult. One of the leachate treatment technology is the sludge biogranulation, that containing the two aerobic and anaerobic process. The aim of this study was conducted for determining the main factors affecting aerobic granule sludge formation in leachate treatment. In this study, all related papers in international databases were evaluated including Google Scholar, Science Direct, and PubMed, Also Open Access Journal Directory from 1990 until 2020 were investigated. The keywords used included Aerobic Granule Sludge (AGS), leachate treatment, Wastewater treatment, Granular Sequential Batch Reactors (GSBR), Formation Extracellular polymeric substance (EPS). Overall, 2,658 articles were retrieved of which 71 were selected after revising the titles and abstracts. Aerobic granulation has been only lately studied and a limited number of studies have been devoted to identification aspects of the process such as the organic source, and other factor affecting on formation granules. Some factors as shear stress, settling time, and the effluent discharge site have direct effect on the efficiency of aerobic granules reactor and other factors such as divalent metal ions, dissolved oxygen concentration, the ratio of height to diameter of the reactor, temperature affecting on the granulation process. If suitable conditions provide, the aerobic granule sludge process can be useful for leachate treatment.

Biological treatment of landfill leachate: efford landfill, Hampshire, UK - a case study

Demand for of on-site treatment schemes that are capable of treating landfill leachates to highstandards has grown substantially during the last two decades. Increasingly, plants are beingrequired to discharge high quality effluents directly into surface watercourses, or to provide ahigh degree of treatment prior to discharge into the public sewerage system. This trend is certainto continue - primarily driven in the United Kingdom in recent months by the requirements of theEU IPPC Directive, which demands the application of Best Available Techniques (BAT), and bythe EU Water Framework Directive.Aerobic biological treatment of leachate from domestic landfills has widely been shown to be themost appropriate, reliable and successful treatment technique to consistently meet stringentdischarge constraints with minimal operator input. The cost of this technology is also oftenfavourable, when compared with alternative processes. More than 50 plants of this type arecurrently operational in the United Kingdom, making it by far the most widely adopted on-sitetreatment technology, and many other examples exist overseas.This paper provides a detailed case study of the design, construction and commissioning of abiological, Sequencing Batch Reactor (SBR) leachate treatment plant for Hampshire CountyCouncil, at Efford Landfill Site in the New Forest in Hampshire, UK.Since plant commissioning was completed by the authors during early 2003, extensive anddetailed monitoring data have been collected. These are presented for the plant, which is capable 3 of treating up to 150 m /day of strong methanogenic leachate (ammoniacal-N from 600-1 000mg/1), and are compared with treatment performances achieved at other full-scale leachatetreatment plants. The paper shows 80D5 and ammoniacal-N removal efficiencies in excess of99%.Results also show the efficiency of polishing treatment in a reed bed, before discharge of finaleffluent to public sewer.

Ultrasound-Assisted Treatment of Landfill Leachate in a Sequencing Batch Reactor

Purification of leachates is currently a big challenge due to their high variability in composition and amount. The complexity of the medium, namely leachates, makes new solutions highly sought after and finds the existing ones in need of optimization. The effects of ultrasound pretreatment (20 kHz, 12 µm) on biological treatment of landfill leachates in the form of processes carried out in two sequencing batch reactors were investigated. The experiment was divided into two stages. In the first stage, leachate was treated by an ultrasonic field at different sonication times (0.5, 1, 3, 5, 10 and 15 min). Next, leachates with and without conditioning were combined with municipal wastewater in the following ratios: 5, 10, 15 and 25% v/v. For optimal processing time (3 min), 16% removal of COD was achieved. In turn, the BOD5/COD ratio was 0.3, which is higher by approximately 270% than that of the non-conditioned sample. Further elongation of sonication time did not significantly affect both parameters. Also, pretreatment of leachate resulted in a maximum increase noted in the study of specific oxygen uptake rate and dehydrogenase activity of approximately 21 and 2 times compared to the non-conditioned sample. The implementation of a pretreatment step prior to the biological treatment was shown to result in higher pollutant removal efficiency. Depending on the share of leachates in the mixture, the removal enhancements of BOD, COD, and ammonium nitrogen for conditioned samples ranged from 6–48.5%, 4–48% and 11–42%, respectively. Furthermore, pretreatment of leachate allows for an increased (by up to 20%) share of leachate volume in the influent stream entering the reactor, while maintaining the quality of effluents in accordance with national regulation requirements. However, in scenarios without pretreatment, the leachate ratio cannot exceed 5% of the total wastewater due to poor quality of the effluents. The operational cost of ultrasound pretreatment of leachate was 22.58 €/(m3·g removed COD).

Simultaneous chemical oxygen demand removal, methane production and heavy metal precipitation in the biological treatment of landfill leachate using acid mine drainage as sulfate resource

Biological treatment played an important role in the treatment of landfill leachate. In the current study, acid mine drainage (AMD) was used as a source of sulfate to strengthen the anaerobic treatment of landfill leachate. Effects of chemical oxygen demand (COD) and SO42- mass concentration ratio on the decomposition of organic matter, methane production and sulfate reduction were investigated and the microbial community was analyzed using the high throughout methods. Results showed that high removal efficiency of COD, methane production and heavy metal removal was achieved when the initial COD/SO42- ratio (based on mass) was set at 3.0. The relative abundance of anaerobic hydrogen-producing bacteria (Candidatus Cloacamonas) in the experimental group with the addition of AMD was significantly increased compared to the control. Abundance of hydrogenotrophic methanogens of Methanosarcina and Methanomassiliicoccus was increased. Results confirmed that AMD could be used as sulfate resource to strengthen the biological treatment of landfill leachate.

Inhibitory effect of high calcium concentration on municipal solid waste leachate treatment by the activated sludge process.

This research focused on the inhibitory effects of Ca on the aerobic biological treatment of landfill leachate containing extremely high Ca concentrations. When the Ca concentration in leachate to be treated was more than 4500 mg l-1, the total organic carbon removal rate was significantly reduced and the processing time to achieve the same removal efficiency was 1.4 times that in the control treatment without added Ca. In contrast, the total nitrogen and ammonia nitrogen (NH4+-N) removal efficiencies were positively related to the Ca concentration, increasing from 65.2% to 81.2% and from 69.2% to 83.7%, respectively, when the dosage of added Ca increased from zero to 8000 mg l-1. During aerobic treatment, the reductions of solution Ca concentration were in the range of 1003-2274 mg l-1 and were matched with increases in the Ca content in the residual sludge. The inhibition threshold of Ca in the leachate treated by the activated sludge process appeared to be 4500 mg l-1, which could be realized by controlling the influent Ca concentration and using an appropriate sludge return ratio in the activated sludge process.

Removal of toxic metals during biological treatment of landfill leachates

Progressive implementation of the European Water Framework Directive has resulted in substantial changes in limits for discharges of heavy metals both to watercourses, and to sewer. The objective of this paper is to provide original, real, full-scale data obtained for removal of metals during aerobic biological leachate treatment, and also to report on studies carried out to look at further trace metal removal. Polishing technologies examined and investigated include; the incorporation of ultrafiltration (UF) membranes into biological treatment systems, the use of ion exchange, and of activated carbon polishing processes. Ultrafiltration was able to provide a 60 percent reduction in COD values in treated leachates, compared with COD values found in settled/clarified effluents. Removal rates for COD varied from 30.5 to 79.8 percent. Additionally, ultrafiltration of treated leachates significantly reduced both chromium and nickel concentrations of effluents by 61.6% and 34.3% respectively (median values). Despite mean reductions of chromium (9.7%) and nickel (13.7%) noted during the ion exchange trials, these results would not justify use of this technology for metals removal at full-scale. Further preliminary studies used pulverized activated carbon (PAC) polishing of UF effluents to demonstrate that significant (up to 80 per cent) removal of COD, TOC and heavy metals could readily be achieved by doses of up to 10g/l of suitable activated carbons. Additional evidence is provided that many trace metals are present not in ionic form, but as organic complexes; this is likely to make their removal to low levels more difficult and expensive.

Biological Treatment of Landfill Leachate at Elevated Temperature in the Presence of Polyurethane Foam of Various Porosity

Application of sequencing batch reactors (SBR) for treatment of leachate from old, stabilized landfills, could be still an economically viable solution, as far as nitrogen removal is concerned. Very low amounts of accesible organic compounds requires an unconventional approach to treatment technology. In this paper the authors proposed utilisation of polyurethane (PU) foam of various porosity as a biomass carrier, hydraulic retention time (HRT) extended to 2 days and temperature elevated to 37°C, to stimulate simultaneous nitrification and denitrification (SND). The porosity of PU carriers had no effect on the efficiency of organic compounds removal, whilst the ammonium nitrogen (N‐NH4+) removal efficiency was highest in the reactor (SBR2) equipped with PU cuboid‐shape carriers of 30 pores per inch (ppi), reaching 77.6%. In the reactor SBR3 filled with 15 ppi foam, the N‐NH4+ removal efficiency was much lower (54.2%), but still better than observed in reference reactor, SBR1, operated with suspended activated sludge only (46.3%). The average free ammonia concentration in the effluents ranged from 140.18 to 347.98 mg/L at pH 9.6, depending on the reactor. Neither nitrites nor nitrates were found in the effluents, and the kinetics of N‐NH4+ removal proceeded according to the first‐order reaction.

Unwanted metals and hydrophobic contaminants in bioreactor effluents are associated with the presence of humic substances

Biological treatment of landfill leachate is challenging due to the presence of complex compounds. Here, we treated an old landfill leachate using a membrane bioreactor under the following conditions: 24 h for hydraulic retention, 65 days of sludge retention and an average organic load rate of 1.71 ± 0.16 g/L/day. We observed a high removal of ammonia, phosphorous and some metals. However, removal of organic carbon was incomplete. Despite a major removal of suspended solids, hydrophobic and volatile hydrophilic compounds, high concentration of fulvic acid and hydrophilic contaminants was found in the effluent. Overally, we demonstrate that the presence of humic substances in the effluent is associated with the detection of arsenic, copper and chromium and di(2-ethylhexyl) phthalate.

Advanced nitrogen removal using bio-refractory organics as carbon source for biological treatment of landfill leachate

A combined system was developed to enhance the chemical oxygen demand (COD) and total nitrogen (TN) removal from landfill leachate. The system consists of an up-flow anaerobic sludge blanket (UASB), anoxic/aerobic (A/O) reactor, and the denitrifying UASB (DUASB). The influent used in our study was a mixture of 1:2 raw leachate and domestic wastewater. Because of the inhibitory effect of free ammonia (FA) on the nitrite-oxidizing bacteria (NOB), stable partial nitrification occurred, with a consistent nitrite accumulation ratio in the A/O reactor. In the DUASB, the nitrite and nitrate nitrogen (NOX−-N) were removed efficiently by denitrification by utilizing the carbon source of refractory organics under anoxic condition, which were likewise degraded. The organic matter, total nitrogen and ammonia nitrogen in the final effluent were 80–90, 39, and 14 mg/L, respectively, with respective removal efficiencies of 95, 98, and 95%. The respective COD removal efficiencies in the UASB, A/O and denitrifying-UASB were 76.8, 2.8, and 16.3%. The proposed process is an advanced technique that accomplishes the removal of organic matter and nitrogen in a single step.

Changes of the quality of activated sludge during the biological treatment of landfill leachate

Changes of the quality of activated sludge during the biological treatment of landfill leachate

Changes of the quality of activated sludge during the biological treatment of landfill leachate

Changes of the quality of activated sludge during the biological treatment of landfill leachate