In situ microbial treatment of landfill leachate using aerated lagoons

Wastewater treatment in lagoons: A systematic review and a meta-analysis

This study has carried out a systematic review of 36 scientific papers (reporting 63 case studies) published in the last 15 years about the treatment of industrial, agri-food and municipal wastewater in lagoons. A concentration of studies from a few countries (Italy, Algeria and Iran) and about municipal wastewater (70% of papers) was revealed by the bibliographic analysis. Aeration was supplied in more than 50% of case studies; the storage capacity of lagoons (adopted as a measure of size) was extremely variable (over seven orders of magnitude), while their depth was generally lower than a few metres. The efficiency of lagoon treatments at removing COD was in a wide range (25-98%). Very few studies analysed the energy intensity of treatments in lagoons. The meta-analysis applied to a further selection of 10 papers with 29 case studies revealed significant differences in pH and dissolved oxygen concentration, due to aeration or type of treated wastewater. Treatment efficiency was higher in aerated lagoons compared to non-aerated systems, and did not depend on the type of treated wastewater. Based on the analysis of the reviewed papers, an urgent research need on this topic arises, mainly due to the oldness of most analysed studies. Practical suggestions are given to optimise the depuration performances of lagoons: (i) application of intermittent and night aeration; (ii) reduced air flow rates; (iii) adaptation of microbial biomass to high contents of inhibiting compounds in wastewater; (iv) construction of baffles to keep the planned hydraulic retention time avoiding short-circuit; (v) integration of lagoons with other treatments (e.g., constructed wetlands); (vi) ferti-irrigation of crops with lagoon effluents rather than disposal into water bodies.

A new treatment step of bioelectrochemically treated leachate using natural clay adsorption towards sustainable leachate treatment

Standalone and combined leachate treatment mechanisms suffer from low treatment efficiencies due to leachate's complex, toxic, and recalcitrant nature. Bioelectrochemical system (BES) was used for the first time to investigate the treatment of leachate mixed wastewater (WW) (i.e., diluted leachate, DL) (DL ≈ L:WW = 1:4) to minimize these complexities. A natural clay (palygorskite) was used as adsorbent material for further treatment on the BES effluent (EBES) while using two different masses and sizes (i.e., 3 g and 6 g of raw crushed clay (RCC) and 75 μ of sieved clay (75 μSC)). According to bioelectrochemical performance, BES, when operated with low external resistance (Rext = 1 Ω) (BES 1), showed a high removal of COD and NH3-N with 28% and 36%, respectively. On the other hand, a high Rext (100 Ω, BES 100) resulted in low removal of NH3-N with 10% but revealed high COD removal by 78.26%. Moreover, the 6 g doses of 75 μSC and RCC showed the maximum COD removals of 62% and 38% and showed the maximum removal of NH3-N with an average range of 40% for both sizes. After efficient desorption, both clay sizes resulted in regeneration performance which was observed with high COD (75%) and NH3-N (34%) on EBES. Therefore, when BES and clay adsorption technique sequentially treated and achieved with combined removal of ~ 98% for COD and ~ 80% of NH3-N, it demonstrated an efficient treatment method for DL treatment.

A sequential aerated electrocoagulation and peroxicoagulation process for the treatment of municipal stabilized landfill leachate by iron and graphite electrodes

Electrochemical treatment has emerged as a viable technology for the treatment of leachate due to its efficient removal of ammonaical nitrogen and other recalcitrant organics. The main technical issues that prevent its practical deployment are restricted performance of a single electrochemical process and the lengthy tertiary treatment time required to achieve the disposal quality standards. This study demonstrates the performance of electrochemical treatments such as peroxicoagulation (PC) and aerated electrocoagulation (A-EC) separately and also sequentially for the treatment of stabilized leachate. In aerated electro coagulation iron is used as both anode and cathode, whereas in peroxicoagulation, iron is used as anode and graphite as cathode. The area of electrode used for treatments was fixed as 12.5 cm2. The initial concentration of NH4-N, TN, COD, and TOC of the leachate was found to be 480 mg/L, 997 mg/L, 40,200 mg/L, and 9850 mg/L respectively. Removal efficiency of aerated electrocoagulation for NH4-N, TN, COD and TOC were 25.6%, 23.67%, 25.6% and 28.7% respectively, current density of 30 mAcm-2, electrolysis time of 60 min and pH 7.3. Meanwhile for peroxicoagulation, the removal efficiency was found to be 37.2%, 43%, 37.3%, and 45.6% for NH4-N, TN, COD, and TOC respectively, at an current density of 30 mAcm-2, electrolysis time of 120 min and a pH of 3. The sequential aerated electrocoagulation - peroxicoagulation process achieves a maximum removal efficiency of 63%, 68%, 78%, and 75% for NH4-N, total nitrogen, COD, and TOC respectively for a reaction time of 180 min. Removal of NH4-N, total nitrogen, COD and TOC from stabilized landfill leachate with a BOD/COD ratio less than 0.1 was very much effective with the sequential aerated electrocoagulation - peroxicoagulaton treatment. The results also indicate that for the treatment of leachate, a significant synergistic index of 1.22 exists between aerated electrocoagulation and peroxicoagulation.

Optimal pre-treatment of moderately old landfill leachate at the pilot-scale treatment plant using the combined aerobic biochemical and reagent method

Landfill leachates contain highly concentrated pollutants, and their uncontrolled discharge poses significant risks to the public health and environment. This study validated a pilot-scale two-stage aerobic biochemical and reagent method for the pre-treatment of moderately old landfill leachate at a pilot-scale treatment plant with a capacity of 400 L per day. The kinetic curves of key pollutants were described using two-factor dimensionless exponential equations, allowing for predicting maximally achievable treatment effects during the first aerobic biochemical stage. The optimal duration of aerobic biochemical pre-treatment was determined based on the concept of limiting pollutant content and minimizing operating costs for the two-stage process. Reagent-based leachate pre-treatment using the modified Fenton method was verified in a batch reactor. Optimal concentrations and dosages of reagent solutions, including polyacrylamide, aluminium sulphate, ferrous sulphate, and hydrogen peroxide, were found to comply with Ukrainian regulations for wastewater discharge into sewerage networks. Key pollution indicators of pre-treated leachate, such as NH₄⁺-N (13.4-15.5 mg × L^-1), TKN (25.7-30.2 mg × L^-1), BOD_tot (71.8-76.9 mg × L^-1), and COD (390-459 mg × L^-1), meet the required standards.

Pharmaceuticals in the Aquatic Environment: A Review on Eco-Toxicology and the Remediation Potential of Algae

The pollution of the aquatic environment has become a worldwide problem. The widespread use of pesticides, heavy metals and pharmaceuticals through anthropogenic activities has increased the emission of such contaminants into wastewater. Pharmaceuticals constitute a significant class of aquatic contaminants and can seriously threaten the health of non-target organisms. No strict legal regulations on the consumption and release of pharmaceuticals into water bodies have been implemented on a global scale. Different conventional wastewater treatments are not well-designed to remove emerging contaminants from wastewater with high efficiency. Therefore, particular attention has been paid to the phycoremediation technique, which seems to be a promising choice as a low-cost and environment-friendly wastewater treatment. This technique uses macro- or micro-algae for the removal or biotransformation of pollutants and is constantly being developed to cope with the issue of wastewater contamination. The aims of this review are: (i) to examine the occurrence of pharmaceuticals in water, and their toxicity on non-target organisms and to describe the inefficient conventional wastewater treatments; (ii) present cost-efficient algal-based techniques of contamination removal; (iii) to characterize types of algae cultivation systems; and (iv) to describe the challenges and advantages of phycoremediation.

Sustainable strategy on microbial fuel cell to treat the wastewater for the production of green energy

Microbial fuel cell (MFC) is one of the promising alternative energy systems where the catalytic conversion of chemical energy into electrical energy takes places with the help of microorganisms. The basic configuration of MFC consists of three major components such as electrodes (anode and cathode), catalyst (microorganism) and proton transport/exchange membrane (PEM). MFC classified into four types based on the substrate utilized for the catalytic energy conversion process such as Liquid-phase MFC, Solid-phase MFC, Plant-MFC and Algae-MFC. The core performance of MFC is organic substrate oxidation and electron transfer. Microorganisms and electrodes are the key factors that decide the efficiency of MFC system for electricity generation. Microorganism catalysis degradation of organic matters and assist the electron transfer to anode surface, the conductivity of anode material decides the rate of electron transport to cathode through external circuit where electrons are reduced with hydrogen and form water with oxygen. Not limited to electricity generation, MFC also has diverse applications in different sectors including wastewater treatment, biofuel (biohydrogen) production and used as biosensor for detection of biological oxygen demand (BOD) of wastewater and different contaminants concentration in water. This review explains different types of MFC systems and their core performance towards energy conversion and waste management. Also provides an insight on different factors that significantly affect the MFC performance and different aspects of application of MFC systems in various sectors. The challenges of MFC system design, operations and implementation in pilot scale level and the direction for future research are also described in the present review.

Progress and prospects in mitigation of landfill leachate pollution: Risk, pollution potential, treatment and challenges

The escalating loads of municipal solid waste (MSW) end up in open dumps and landfills, producing continuous flows of landfill leachate. The risk of incorporating highly toxic landfill leachate into environment is important to be evaluated and measured in order to facilitate decision making for landfill leachate management and treatment. Leachate pollution index (LPI) provides quantitative measures of the potential environmental pollution by landfill leachate and information about the environmental quality adjacent to a particular landfill. According to LPI values, most developing countries show high pollution potentials from leachate, mainly due to high organic waste composition and low level of waste management techniques. A special focus on leachate characterization studies with LPI and its integration to treatment, which has not been focused in previous reviews on landfill leachate, is given here. Further, the current review provides a summary related to leachate generation, composition, characterization, risk assessment and treatment together with challenges and perspectives in the sector with its focus to developing nations. Potential commercial and industrial applications of landfill leachate is discussed in the study to provide insights into its sustainable management which is original for the study.

Treat-ability of Manihot esculenta Peel Extract as Coagulant Aid for Stabilised Leachate

Agro-waste can be commercialised into another useful product such as natural coagulant for wastewater treatment. The purpose of this study was to quantify the ability of agro-waste (Manihot esculenta peel extract (MEP)) as an aid alongside the utilisation of chemical coagulant (polyaluminium chloride (PAC)) based on the removal percentages of selected parameters at the optimum coagulant dosage and pH of stabilised leachate. Series of jar tests were used to compare the leachate treatments using single and the dual coagulant of PAC and MEP with respective standard methods to analyse the removal parameters, i.e., Colorimetric (APHA Method:5220 C, HACH Method:8000) for chemical oxygen demand (COD), Conductimetric (APHA Method: 4500-N, HACH Method: 8038) for ammonia nitrogen (AN), Nephelometric (APHA Method:2130) for turbidity, Spectrophotometric (APHA Method: 2120 B, HACH Method: 8025) for colour, and Gravimetric (APHA Method:2540 D, HACH Method:630) for suspended solids (SS). Leachate treatment using the application of single PAC coagulant at the optimum conditions of 3,750 mg/L dosage and pH 6.0 of leachate managed to remove about 54.1%, 28%, 91.1%, 98%, and 98% for COD, AN, turbidity, colour, and SS, respectively. Meanwhile, by using dual coagulant at the optimum dosages of 3,500 mg/L (PAC) and 250 mg/L (MEP), and pH 7.0 of leachate, the treatment achieved higher removal except for the colour parameter. The final removal outcomes of this study were 58.3% of COD, 34% of AN, 96.9% of turbidity, 92.1% of colour, and 99% of SS. The application of MEP as coagulant aid also managed to reduce the aluminium (Al) content in PAC dosage from 577.5 mg/L to 539.0 mg/L without affecting much of its efficiency.

Prospects of integrating algae technologies into landfill leachate treatment

Landfilling of municipal waste, an environmental challenge worldwide, results in the continuous formation of significant amounts of leachate, which poses a severe contamination threat to ground and surface water resources. Landfill leachate (LL) is generated by rainwater percolating through disposed waste materials and must be treated effectively before safe discharge into the environment. LL contains numerous pollutants and toxic substances, such as dissolved organic matter, inorganic chemicals, heavy metals, and anthropogenic organic compounds. Currently, LL treatment is carried out by a combination of physical, chemical, and microbial technologies. Microalgae are now viewed as a promising sustainable addition to the repertoire of technologies for treating LL. Photosynthetic algae have been shown to grow in LL under laboratory conditions, while some species have also been employed in larger-scale LL treatments. Treating leachate with algae can contribute to sustainable waste management at existing landfills by remediating low-quality water for recycling and reuse and generating large amounts of algal biomass for cost-effective manufacturing of biofuels and bioproducts. In this review, we will examine LL composition, traditional leachate treatment technologies, LL toxicity to algae, and the potential of employing algae at LL treatment facilities. Emphasis is placed on how algae can be integrated with existing technologies for biological treatment of LL, turning leachate from an environmental liability to an asset that can produce value-added biofuels and bioproducts for the bioeconomy.

Recent advances in municipal landfill leachate: A review focusing on its characteristics, treatment, and toxicity assessment

Nowadays, sanitary landfilling is the most common approach to eliminate municipal solid waste, but a major drawback is the generation of heavily polluted leachates. These leachates must be appropriately treated before being discharged into the environment. Generally, the leachate characteristics such as COD, BOD/COD ratio, and landfill age are necessary determinants for selection of suitable treatment technologies. Rapid, sensitive and cost-effective bioassays are required to evaluate the toxicity of leachate before and after the treatment. This review summarizes extensive studies on leachate treatment methods and leachate toxicity assessment. It is found that individual biological or physical-chemical treatment is unable to meet strict effluent guidelines, whereas a combination of biological and physical-chemical treatments can achieve satisfactory removal efficiencies of both COD and ammonia nitrogen. In order to assess the toxic effects of leachate on different trophic organisms, we need to develop an appropriate matrix of bioassays based on their sensitivity to various toxicants and a multispecies approach using organisms representing different trophic levels. In this regard, a reduction in toxicity of the treated leachate will contribute to assessing the effectiveness of a specific remediation strategy.

Removal of ammoniacal nitrogen from municipal landfill leachate with floating Typha domingensis (Typhaceae)

 A promising method for the treatment of effluents is the use of floating macrophytes. Ammoniacal nitrogen is a typical compound present in urban landfill leachates and its removal is important due its toxicity to several organisms. Therefore, the study evaluated Typha domingensis survival and nitrification potential artificially floating in domestic solid waste leachate. Plants were exposed for 35 days to leachate (100, 75 and 50 %) and to rainwater with N:P:K (control). Dissolved oxygen (DO) of the treatments was periodically measured, and ammoniacal nitrogen, nitrite and nitrate were analyzed before and after exposure. At the end of the experiment, plant survival rate was calculated. After two weeks, DO increased twice in the control, three times in 50 % leachate, four times in 75 % leachate, and eight times in 100 % leachate. At the end of the experiment, ammoniacal nitrogen was no longer detected, there was a significant reduction of nitrite, and a significant increase of nitrate in the treatments containing leachate. Plant survival was higher in those individuals exposed to 100 % leachate and decreased at lower leachate concentrations: 98 %, 94 %, 92 %, and 86 %. The study demonstrated that the ammoniacal nitrogen concentration of the leachate was not toxic to T. domingensis, and that it was efficient in the removal of this compound from the effluent, indicating that the species may be used artificially floating for the removal of this contaminant from domestic solid waste landfill leachate when in low concentrations.

Microbial nitrate removal efficiency in groundwater polluted from agricultural activities with hybrid cork treatment wetlands

Agricultural practices have raised the level of nutrients reaching aquifers. In Europe, nitrate pollution is considered as one of the main threats for the quality of groundwater in agricultural areas. Treatment wetlands (TWs), also known as Constructed Wetlands, are used for groundwater treatment in areas with an important concentration of nitrogen compounds; total nitrogen removal depends on the type and operation scheme. Cork by-product from the industry has shown clear adsorbent properties to remove organic pollutants. The work is focused on the characterization of microbial communities involved in the nitrate‑nitrogen removal process in groundwater polluted from agricultural activities. The experimental design allowed the comparison of nitrate removal efficiency depending on the filter media material, cork by-product or gravel, used in two hybrid TWs (a vertical flow cell followed by a horizontal subsurface flow cell), installed in areas close to two irrigated agricultural plots at the Lleida plain area (Spain). Both physicochemical and microbial results were consistent and confirm the nitrate removal efficiency using cork as a filter media. A significant (p = 0.0025) higher removal in Bellvís TW using cork compared with the Vilanova de la Barca gravel system was observed, achieving a removal rate from 80 to 99% compared to the 5-46%, respectively. Regarding the community composition of the two different TWs, microorganisms were mainly related to the phylum Proteobacteria, and included members found to be key players in the nitrogen cycle, such as ammonia and nitrite oxidizers, as well as denitrifiers. Also, the group Bacteroidetes turns to be another abundant phylum from our bacterial dataset, whose members are suggested to be strongly involved in denitrification processes. Some groups showed to prevail depending on the type of media (cork or gravel); Firmicutes and Delta and Epsilonproteobacteria had a significant higher abundance in the TW with cork, while Acidobacteria and Planctomyces were prevalent in gravel. Therefore, cork could be an alternative material used by treatment wetlands to minimize the impact in the environment caused by nitrogen pollution in groundwater bodies.

Landfill leachate treatment by sorption in magnetic particles: preliminary study

Leachates are still an open issue in environmental protection. Many of the applied methods for their treatment present low efficiency and thus need to be used collectively. In practice reverse osmosis is mostly used, as it is the most effective option, regardless of its cost. Magnetic methods to treat effluents have been used for water and wastewater treatment by the use of magnetic particles together with magnetic separation for the removal of contaminants. However, large-scale applications are few or even non-existent when we deal with complex contaminated media such as landfill leachates, for which not even research studies at laboratorial scale with real samples have been done yet. In this work, we apply for the first time magnetic sorption for the treatment of leachates, and close the full cycle by studying the regeneration and re-use of the magnetic particles; we also study the influence of the concentration of magnetic particles, the use of several pre-treatment methodologies and the type of particle used in the process, in real landfill samples from the waste treatment plant of Salamanca (Spain), for the removal of COD, NO₃^-, NO₂^-, NH₄⁺, Total-N, PO₄^3-, SO₄^2- and Cl^-. Regeneration of the magnetic particles after being used in the sorption stage is also studied, as well as their efficiency regarding their re-use. It is also determined the optimum number of batches for complete desorption and for regeneration of the particles, the effect of successive regeneration and re-use cycles, the use of two different regeneration methods, the efficiency of the desorption, the effect of the quantity of solvent and the influence of the time of sorption. Due to its innovative character and the complexity of the media, this work represents a first preliminary approach and, although some promising results have been obtained, further studies are required to completely understand and evaluate the proposed treatment process.

Challenges in the application of microbial fuel cells to wastewater treatment and energy production: A mini review

Wastewater is now considered to be a vital reusable source of water reuse and saving energy. However, current wastewater has multiple limitations such as high energy costs, large quantities of residuals being generated and lacking in potential resources. Recently, great attention has been paid to microbial fuel cells (MFCs) due to their mild operating conditions where a variety of biodegradable substrates can serve as fuel. MFCs can be used in wastewater treatment facilities to break down organic matter, and they have also been analysed for application as a biosensor such as a sensor for biological oxygen which demands monitoring. MFCs represent an innovation technology solution that is simple and rapid. Despite the advantages of this technology, there are still practical barriers to consider including low electricity production, current instability, high internal resistance and costly materials used. Thus, many problems must be overcome and doing this requires a more detailed analysis of energy production, consumption, and application. Currently, real-world applications of MFCs are limited due to their low power density level of only several thousand mW/m². Efforts are being made to improve the performance and reduce the construction and operating costs of MFCs. This paper explores several aspects of MFCs such as anode, cathode and membrane, and in an effort to overcome the practical challenges of this system.

Removal of Pollutants in Different Landfill Leachate Treatment Processes on the Basis of Organic Matter Fractionation

A combination of processes was required for the proper treatment of old landfill leachate, as it contained a high concentration of pollutants. Humic substances comprised half of the total organic carbon in the raw leachate. Mobility of di(2-ethylhexyl) phthalate (DEHP) and metals could depend on the fate of these substances. Characterization of carbon in raw leachate and effluent of the membrane bioreactor, biofiltration, electro-oxidation, electro-coagulation, and nanofiltration showed complete removal of suspended solids and colloids. Physical processes could not remove the hydrophilic fraction due to its lower molecular weight. However, high removal of the hydrophilic fraction with a molecular weight <500 Da was expected in the biological process. In comparison with fulvic acid, larger sized humic acid resulted in complete removal by physicochemical processes. Because of DEHP partitioning on dissolved organic matter, especially on humic substances, its removal could be correlated with total organic carbon removal. Metals such as iron, aluminum, magnesium, and lead showed removal efficiency >80% in biological processes. Electro-deposition on the surface of an electrode and precipitation by hydroxide resulted in removal efficiencies >90 and >50% in electro-coagulation and electro-oxidation, respectively. Rejection of metals by nanofiltration was >80% and depended on the size and charge of cation. All in all, a combination of membrane bioreactor and nanofiltration seems to be the optimal process configuration for efficient treatment of old landfill leachate.

Treatment of mature landfill leachate using hybrid processes of hydrogen peroxide and adsorption in an activated carbon fixed bed column

In this study, the treatment of mature landfill leachate is evaluated by oxidation with hydrogen peroxide (H₂O₂) combined with adsorption in a granular activated carbon (GAC) fixed bed column to determinate the increase in the biodegradability index, the reduction of chemical oxygen demand (COD) as well as the increase in the useful life of the GAC bed. The sample leachate from Loma de Los Cocos Landfill (Cartagena de Indias, Colombia) has a very low biodegradability ratio ranging from 0.034 to 0.048 that makes it difficult to meet the required water quality level according to the regulations. The COD removal is initially monitored in the H₂O₂ oxidation treatment process. The operating conditions such as pH, H₂O₂ dosage, and the reaction time are optimized in this process based on the percentage of COD removal. A maximum COD removal of 29.9% is achieved at an initial H₂O₂ concentration of 5000 mg L^-1 with a pH of 8 and the reaction time of 60 min. The hybrid treatment by H₂O₂-GAC achieved 97.3% COD removal and 116% increase in the biodegradability ratio (from 0.072 to 0.134) while this ratio was increased by 6.5% with H₂O₂ alone. Moreover, the useful life of the GAC bed is increased from 45 min in the column fed with raw leachate to 170 min in the column fed with pretreated leachate and 5000 mg L^-1 of H₂O₂ at pH of 8 that subsequently increased the activated carbon adsorption capacity. An adsorption model for leachate treated with H₂O₂ is also developed.

Performance evaluation of a hybrid-passive landfill leachate treatment system using multivariate statistical techniques

A pilot-scale hybrid-passive treatment system operated at the Merrick Landfill in North Bay, Ontario, Canada, treats municipal landfill leachate and provides for subsequent natural attenuation. Collected leachate is directed to a hybrid-passive treatment system, followed by controlled release to a natural attenuation zone before entering the nearby Little Sturgeon River. The study presents a comprehensive evaluation of the performance of the system using multivariate statistical techniques to determine the interactions between parameters, major pollutants in the leachate, and the biological and chemical processes occurring in the system. Five parameters (ammonia, alkalinity, chemical oxygen demand (COD), "heavy" metals of interest, with atomic weights above calcium, and iron) were set as criteria for the evaluation of system performance based on their toxicity to aquatic ecosystems and importance in treatment with respect to discharge regulations. System data for a full range of water quality parameters over a 21-month period were analyzed using principal components analysis (PCA), as well as principal components (PC) and partial least squares (PLS) regressions. PCA indicated a high degree of association for most parameters with the first PC, which explained a high percentage (>40%) of the variation in the data, suggesting strong statistical relationships among most of the parameters in the system. Regression analyses identified 8 parameters (set as independent variables) that were most frequently retained for modeling the five criteria parameters (set as dependent variables), on a statistically significant level: conductivity, dissolved oxygen (DO), nitrite (NO2(-)), organic nitrogen (N), oxidation reduction potential (ORP), pH, sulfate and total volatile solids (TVS). The criteria parameters and the significant explanatory parameters were most important in modeling the dynamics of the passive treatment system during the study period. Such techniques and procedures were found to be highly valuable and could be applied to other sites to determine parameters of interest in similar naturalized engineered systems.

Landfill leachate treatment as measured by nitrogen transformations in stabilization ponds

The treatment performance and nitrogen mass balance of a pilot-scale landfill leachate treatment system was evaluated. The system was comprised of a series of three ponds and a rock filter and was fed a continuous flow (200 L d(-1)) during 111 weeks. Three different operational conditions were investigated: conventional operation (stage I), aeration (stage II) and aeration/recirculation (stage III). The system was able to treat landfill leachate with soluble chemical oxygen demand and ammonia removal between 35-82% and 75-99%, respectively, and the highest removal occurred during the recirculation stage. The nitrogen balance was calculated using total nitrogen applied load and the main transformation processes within the ponds. The main form of nitrogen transformation/removal was by dead/inert algae settle (64-79%), followed by volatilization (12-27%) and algae assimilation (1-6%). Nitrification/denitrification occurred in only stage II. Analyses of the phytoplankton community showed that the Chlamydomonas genera were dominant in the photosynthetic ponds.

Research Progress of Landfill Leachate Treatment

The aim of our research was to find the better treatment progress for landfill leachate. It elaborated the source and the quality variation law with time change and harm to human body of the leachate. Listed all kinds of treatment methods, including physical, chemical, biological. Thought the development trends of landfill leachate treatment was the combination of multiple progress.

Pilot-scale comparison of two hybrid-passive landfill leachate treatment systems operated in a cold climate

Hybrid-passive landfill leachate treatment systems employ active pretreatment to remove dissolved inorganic constituents and decrease the oxygen demand of the leachate prior to treatment in a passive system. In a 1-year pilot-scale study, two passive treatment systems - a peat and wood shaving biological trickle filter and a sand and gravel constructed wetland - were installed to treat leachate from the Merrick Landfill in North Bay, Ontario, Canada. Leachate was pretreated in a fixed-film aerobic reactor, which provided reductions in COD (26%), and masses of ammonia (21%), Al (69%), Ca (57%), Fe (73%) and Sr (37%). A comparison of the performance of the hybrid-passive treatment systems indicated different extents of heterotrophic nitrification; the peat and wood shaving filter removed 49% of the ammonia and nitrified 29%, while the constructed wetland removed 99% of the ammonia and nitrified 90%. Hybrid-passive landfill leachate treatment was determined to be feasible in cold climates.

Microbial nitrogen transformation potential in surface run-off leachate from a tropical landfill

Ammonium is one of the major toxic compounds and a critical long-term pollutant in landfill leachate. Leachate from the Jatibarang landfill in Semarang, Indonesia, contains ammonium in concentrations ranging from 376 to 929mgNL(-1). The objective of this study was to determine seasonal variation in the potential for organic nitrogen ammonification, aerobic nitrification, anaerobic nitrate reduction and anaerobic ammonium oxidation (anammox) at this landfilling site. Seasonal samples from leachate collection treatment ponds were used as an inoculum to feed synthetic media to determine potential rates of nitrogen transformations. Aerobic ammonium oxidation potential (<0.06mgNL(-1)h(-1)) was more than a hundred times lower than the anaerobic nitrogen transformation processes and organic nitrogen ammonification, which were of the same order of magnitude. Anaerobic nitrate oxidation did not proceed beyond nitrite; isolates grown with nitrate as electron acceptor did not degrade nitrite further. Effects of season were only observed for aerobic nitrification and anammox, and were relatively minor: rates were up to three times higher in the dry season. To completely remove the excess ammonium from the leachate, we propose a two-stage treatment system to be implemented. Aeration in the first leachate pond would strongly contribute to aerobic ammonium oxidation to nitrate by providing the currently missing oxygen in the anaerobic leachate and allowing for the growth of ammonium oxidisers. In the second pond the remaining ammonium and produced nitrate can be converted by a combination of nitrate reduction to nitrite and anammox. Such optimization of microbial nitrogen transformations can contribute to alleviating the ammonium discharge to surface water draining the landfill.

Cascade bioreactor with submerged biofilm for aerobic treatment of Tunisian landfill leachate

A bioreactor cascade with a submerged biofilm is proposed to treat young landfill leachate of jbel chakir landfill site south west from capital Tunis, Tunisia. The prototype was run under different organic loading charges varying from 0.6 to 16.3 kg TOC m(-3)day(-1). Without initial pH adjustment total organic carbon (TOC) removal rate varied between 65% and 97%. The total reduction of COD reached 92% at a hydraulic retention time of 36 h. However, the removal of total kjeldahl nitrogen for loading charges of 0.5 kg Nm(-3)day(-1) reached 75%. The adjustment of pH to 7.5 improved nitrogen removal to a rate of 85% for loading charge of 1 kg Nm(-3)day(-1). The main bacterial groups responsible for a simultaneous removal of organic carbon and nitrogen belonged to Bacillus, Actinomyces, Pseudomonas and Burkholderia genera. These selected isolates showed a great capacity of degradation at different leachate concentrations of total organic carbon.

Microbial fuel cell application in landfill leachate treatment

The feasibility of using microbial fuel cells (MFCs) in landfill leachate treatment and electricity production was assessed under high levels of nitrogen concentration (6033 mg NL(-1)) and conductivity (73,588 μS cm(-1)). An air-cathode MFC was used over a period of 155 days to treat urban landfill leachate. Up to 8.5 kg COD m(-3)d(-1) of biodegradable organic matter was removed at the same time as electricity (344 m Wm(-3)) was produced. Nitrogen compounds suffered transformations in the MFC. Ammonium was oxidized to nitrite using oxygen diffused from the membrane. However, at high free ammonia concentrations (around 900 mg N-NH(3)L(-1)), the activity of nitrifier microorganisms was inhibited. Ammonium reduction was also resulted from ammonium transfer through the membrane or from ammonia loss. High salinity content benefited the MFC performance increasing power production and decreasing the internal resistance.

Time-dependent evolution of olive mill wastewater sludge organic and inorganic components and resident microbiota in multi-pond evaporation system

The physico-chemical and microbiological characterizations of olive mill wastewater sludge (OMWS) were investigated in five OMW evaporation ponds of the open-pond system in Sfax (Tunisia), during the olive oil production period in 2004. Time-dependent changes in both physico-chemical parameters and the microbiota were investigated. Mathematical models and principal component analysis (PCA) were used to establish the correlations between the studied parameters. During the effluent time-dependent changes in the ponds, the result of OMWS analysis showed an increase of sludge index (SI), ash content, total solids (TS), volatile solids (VS), ethyl acetate extractive (EAE) and total phosphorus (Total P), as well as microbial flora especially the yeasts and moulds. The SI, TS, VS and Total P changes with time fit a simple linear equation, while EAE, phenols and NH(4)(+) fit a second-degree polynomial model. The PCA analysis exhibited three correlated groups. The first group included temperature, ash content, evaporation, SI, TS, VS, Total P, EAE, yeasts and moulds. The second group was made by bacteria and moisture; and the third group by NH(4)(+), oil and phenol. Such modelling might be of help in the prediction of OMW changes in natural evaporation ponds.