Academic literature on the topic 'Treatment of landfill leachate- Carbon and nitrogen derivatives'

Landfill leachate has the characteristics of high ammonia nitrogen content, high concentration of organic matter and low carbon nitrogen ratio. Traditional biological treatment technology is difficult to meet the increasingly stringent emission standards. Ammonia nitrogen is the main pollutant in landfill leachate. The ammonia-nitrogen-rich leachate not only poses a threat to the surrounding environment, but also has adverse effects on the subsequent biological treatment of leachate. Anaerobic ammonium oxidation (Anammox) is a new biological denitrification technology, which has the advantages of high denitrification capacity and low energy consumption, and is suitable for the treatment of landfill leachate. This article from the process type, inhibiting factors and microbiology at home and abroad are reviewed in three aspects: the anaerobic ammonia oxidation treatment, the research progress of landfill leachate by analyzing the national environmental protection agency of leachate quality related data in the database, and combining previous research results, reveals the infiltration drain liquid ammonia nitrogen in the different conditions of concentration variation characteristics, for anaerobic ammonia oxidation treatment of landfill leachate to provide the reference for engineering applications.

With the development of economy and the improvement of people’s living standard, landfill leachate has been increasing year by year with the increase in municipal solid waste output. How to treat landfill leachate with high efficiency and low consumption has become a major problem, because of its high ammonia nitrogen and organic matter content, low carbon to nitrogen ratio and difficult degradation. In order to provide reference for future engineering application of landfill leachate treatment, this paper mainly reviews the biological treatment methods of landfill leachate, which focuses on the comparison of nitrogen removal processes combined with microorganisms, the biological nitrogen removal methods combined with ecology and the technology of direct application of microorganisms. In addition, the mechanism of biological nitrogen removal of landfill leachate and the factors affecting the microbial activity during the nitrogen removal process are also described. It is concluded that the treatment processes combined with microorganisms have higher nitrogen removal efficiency compared with the direct application of microorganisms. For example, the nitrogen removal efficiency of the combined process based on anaerobic ammonium oxidation (ANAMMOX) technology can reach more than 99%. Therefore, the treatment processes combined with microorganisms in the future engineering application of nitrogen removal in landfill leachate should be paid more attention to, and the efficiency of nitrogen removal should be improved from the aspects of microorganisms by considering factors affecting its activity.

Abstract Three management options for the treatment of leachate from landfilled domestic solid waste have been evaluated. Research results show that leachate can be treated effectively in aerobic systems, with high organic carbon and ammoniacal nitrogen removals of >90% and >85% respectively. Optimum SRT of about 10 days is required. Anaerobic treatment (UASB) with HRT's of between 1.0 and 4.0 days results in COD destruction of about 85% with high methane production (400-600 mg/g COD removed) and provides an intermediate effluent suitable for polishing to a high standard. Recirculation of leachate through the landfill by itself cannot provide a complete treatment, although significant reductions in volume and strength of leachate can be obtained.

The microorganism-attached activated carbon fluidized bed (MAACFB) process was applied to treat a landfill leachate containing refractory organics and a high concentration of ammonium nitrogen. The MAACFB process removed about 60 % and 70 % of refractory organics and nitrogen, respectively, from the landfill leachate simultaneously and steadily over a more than 700 days of operation period. A mass balance on organics around the MAACFB process revealed that more than 90 % of the removed organics may be biodegraded. It was suggested that the MAACFB process is highly effective in biodegrading the refractory organics in landfill leachate.

Mature landfill leachate is a complex and highly polluted effluent with a large amount of ammonia nitrogen, toxic components and low biodegradability. Its COD/N and BOD5/COD ratios are low, which is not suitable for traditional nitrification and denitrification processes. Anaerobic ammonia oxidation (anammox) is an innovative biological denitrification process, relying on anammox bacteria to form stable biofilms or granules. It has been extensively used in nitrogen removal of mature landfill leachate due to its high efficiency, low cost and sludge yield. This paper reviewed recent advances of anammox based processes for mature landfill leachate treatment. The state of the art anammox process for mature landfill leachate is systematically described, mainly including partial nitrification–anammox, partial nitrification–anammox coupled denitrification. At the same time, the microbiological analysis of the process operation was given. Anaerobic ammonium oxidation (anammox) has the merit of saving the carbon source and aeration energy, while its practical application is mainly limited by an unstable influent condition, operational control and seasonal temperature variation. To improve process efficiency, it is suggested to develop some novel denitrification processes coupled with anammox to reduce the inhibition of anammox bacteria by mature landfill leachate, and to find cheap new carbon sources (methane, waste fruits) to improve the biological denitrification efficiency of the anammox system.

Leachate is a high concentration organic wastewater, and microbial fuel cell (MFC) is capable of decomposing and treating organic pollutants directly. Single-chamber MFC using landfill leachate as anolyte was built to get rid of BOD and ammonia-nitrogen organic pollutant in leachate. The use of MFC led to the treatment of the biodegradable organic pollutant of municipal solid waste leachate and the production of electricity. The biofilm was detected on the MFC anode carbon felt, the voltage and power output were achieved 292.7± 5 mV and 2375.1mW.m-2. The suitable running time was about 10 days, when the BOD and ammonia-nitrogen removal efficiencies were achieved about 93.0% and 84.1 %, respectively.

The management of the liquid fraction of digestate produced from the anaerobic digestion of biodegradable municipal solid waste is a difficult affair, as its land application is limited due to high ammonium concentrations and the municipal waste that water treatment plants struggle to treat due to high pollutant loads. The amount of leachate and the pollutant load in the leachate produced by landfills usually decreases with the time, which increases the capacity of landfill leachate treatment plants (LLTPs) to treat additional wastewater. In order to solve the above two challenges, the co-treatment of landfill leachate and the liquid fraction of anaerobic digestate in an industrial-scale LLTP was investigated along with the long-term impacts of the liquid fraction of anaerobic digestate on biocoenosis and its impact on LLTP operational expenses. The co-treatment of landfill leachate and liquid fraction of anaerobic digestate was compared to conventional leachate treatment in an industrial-scale LLTP, which included the use of two parallel lanes (Lane-1 and Lane-2). The average nitrogen removal efficiencies in Lane-1 (co-treatment) were 93.4%, 95%, and 92%, respectively, for C/N ratios of 8.7, 8.9, and 9.4. The average nitrogen removal efficiency in Lane-2 (conventional landfill leachate treatment), meanwhile, was 88%, with a C/N ratio of 6.5. The LLTP’s average chemical oxygen demand (COD) removal efficiencies were 63.5%, 81%, and 78% during phases one, two, and three, respectively. As the volume ratios of the liquid fraction of anaerobic digestate increased, selective oxygen uptake rate experiments demonstrated the dominance of heterotrophic bacteria over ammonium and nitrite-oxidising organisms. The inclusion of the liquid fraction of anaerobic digestate during co-treatment did not cause a significant increase in operational resources, i.e., oxygen, the external carbon source, activated carbon, and energy.

Nitrified leachate recirculation represents a promising strategy for a more sustainable landfill management. Our objective was to determine the reactions involved in nitrate reduction in municipal solid waste batch biodegradation tests. Anaerobic digestion of waste in the three control reactors showed a good reproducibility. In two test reactors, nitrate was added at various moments of the waste degradation process. We observed that: (1) H2S concentration controlled the nitrate reduction pathway: above a certain threshold of H2S, dissimilatory nitrate reduction to ammonium (DNRA) replaced denitrification. (2) N2O/N2 ratio varied with the organic carbon concentration: the lower the easily biodegradable carbon concentration, the higher the N2O/N2 ratio. (3) N2 was consumed after denitrification. The possibility of a nitrogen fixation reaction in the presence of NH4+ is discussed. Nitrified leachate recirculation during acidogenesis should be avoided because of higher H2S production which could induce DNRA.

Abstract This review deals with low-cost nanoporous zeolites for the treatment of sanitary landfill leachate. Organic contaminants and ammoniacal nitrogen are significant parameters in landfill leachate treatment. Adsorption processes are regarded as promising alternative treatment options in this respect. Zeolites are aluminosilicate materials that are widely used in separation, filtration, adsorption and catalysis. Natural zeolite is a low-cost and readily available form of zeolite and is a promising candidate to be used as an ion-exchange material for ammonia and other inorganic pollutant removal from landfill leachate. In this review, adsorption isotherms and kinetic models in batch systems are evaluated and adsorption design parameters of the fixed-bed system are presented. Studies on ammonia removal from landfill leachate via zeolites have been thoroughly investigated. Leachate treatment systems combined with zeolites are presented. Cost of zeolites are also reported in comparison with other adsorbents. The investigated studies demonstrate that activated zeolite can improve the removal of chemical oxygen demand, NH3-N and colour significantly compared to the case where raw zeolite is used. Moreover, the composite of activated carbon and zeolite is also favorable for ammonia removal according to reported findings, where best adsorptive removal is attained on the composite media (24.39 mg/g).

Landfill leachate is a high-strength wastewater that is most difficult to deal with because the fluctuating of composition and quality as well as high concentration of specific pollutants (PAH, PCBs, heavy metals) and very high ammonia nitrogen and COD concentrations. So, after a pre-treatment as electrocoagulation, over 73% of COD has been treated from Nam Son landfill leachate, however the output value of COD still exceeds the QCVN 40:2011/BTNMT, column B. So, an electro-fenton process was employed to secondarily treat Nam Son landfill leachate, after an electrocoagulation pre-treatment. This electro-fenton system used a Pt gauze anode and a commercial carbon felt cathode to electrogenerate in situ hydrogen peroxide and regenerate ferrous ion as catalyst. In this study, the effects of various operating conditions such as initial pH, concentration of Fe2+ catalyst, current applied on reduction of COD in Nam Son landfill leachate were examined. At the optimal condition: applied current of 1A, pH 3, Fe2+ concentration of 0.1m M, Na2SO4 concentration of 0.05 M, 77.2% COD reduction can be reached within 60 min and the output value of COD is 130.9 mg.L-1, according to QCVN 40:2011/BTNMT, column B. The research results indicated that electro-fenton process can promise as a potential method in practice for secondary treatment of landfill leachate.

Tese de doutoramento em Engenharia Química e Biológica
Sanitary landfilling is the most used and accepted method to eliminate municipal solid waste worldwide due to its economic advantages. The generation of leachate is an inevitable consequence of this practice. Landfill leachate is a high-strength wastewater with great chemical complexity and diversity. In order to avoid discharges to the environment causing negative impacts to the biota or public health, it must be properly collected and treated before being discharged. In Portugal, in many leachate treatment plants, the leachate after withstanding a series of biological and physico-chemical processes, still presents very high concentrations of nitrate (NO3-). The main objective of this work was to evaluate the removal of nitrate from a landfill leachate with high NO3- load by denitrification in an anoxic rotating biological contactor (RBC). Accordingly, the study began by assessing the denitrification process in an anoxic RBC, for the treatment of synthetic wastewater, under two carbon to nitrogen ratios (C/N) (1.5 and 3). For the tested conditions, the ratio C/N=1.5 was the most advantageous. The anoxic RBC showed a very high performance in reducing the nitrate concentration working with a relatively short hydraulic retention time. Moreover, the increase of carbon-acetate and nitrogen-nitrate influent concentrations had only a slight negative effect in terms of substrate removal. As the biofilm structure and activity are determinant to the reactor performance, at the end of the continuous experiment, biofilm characteristics, composition and activity were evaluated. It was verified that, in spite of a lower thickness, the biofilm grown under a carbon/nitrogen ratio of 1.5 was more active than the biofilm grown at C/N=3. After that, the denitrification performance of the biofilm grown on the reactor disks using pretreated landfill leachate with high nitrate load was evaluated and the effect of initial nitrate load, phosphorus concentration and C/N ratio assessed. Under a C/N=2, the reactor achieved NNO3- removal efficiencies above 95% for nitrate loads up to 100 mg N-NO3-!L-1. The highest observed denitrification rate was 55 mg N-NO3-!L-1!h-1 at a nitrate load of 560 mg N-NO3-!L-1. Although the reactor has revealed a very good performance in terms of denitrification, effluent chemical oxygen demand (COD) concentrations were still high for direct discharge. The results obtained in a subsequent experiment at constant nitrate load (220 mg N-NO3-!L-1) and lower C/N ratios (1.2 and 1.5) evidenced that the organic matter present in the leachate was nonbiodegradable. A phosphorus concentration of 10 mg P-PO43-!L-1 promoted autotrophic denitrification, revealing the importance of phosphorus concentration on biological nitrate removal processes. In order to improve the biodegradability of the pre-treated landfill leachate, Fenton’s oxidation (Fe2+/H2O2) and different ozone-based Advanced Oxidation Processes (AOPs) (O3, O3/OH- and O3/H2O2) were also tested. The effect of initial pH, oxidant agents concentration and reaction time on the performance of each AOP tested was evaluated in terms of COD, total organic carbon (TOC), BOD5, nitrogenous compounds and aromaticity. The results indicated that Fe2+/H2O2, O3/OH- and O3/H2O2 processes, comparatively to ozone at natural and neutral pH values, resulted in higher COD, TOC and UV254 removal efficiencies and improvement of landfill leachate biodegradability. These results confirm the enhanced production of hydroxyl radical under such conditions. Although Fe2+/H2O2 is the most economical system to treat the landfill leachate, for practical purposes O3/OH- was chosen for further work. Finally, the performance of the sequence of treatments, leachate ozonation followed by RBC denitrification was analyzed. The pre-ozonation led to a TOC removal of 28%. The global system did not affect the denitrification efficiency, which remained close to 100%. In fact, it was possible to attain a denitrification rate of 123 mg N-NO3-!L-1!h-1. The moderate decrease in the carbon load of the final effluent indicated that some recalcitrant compounds were still present after ozonation. These results were confirmed by the denitrifying activity tests carried out at the end of the continuous experiment. From the experiments performed with landfill leachate, considering the nitrate load applied, nitrate removal efficiencies and the negligible accumulation of intermediates, the anoxic rotating biological contactor showed to be extremely efficient and constitutes a promising technology for removing nitrate from landfill leachate.
A deposição final de resíduos sólidos urbanos em aterro sanitário é o método de tratamento mais usado e aceite em todo o mundo devido às suas vantagens económicas. A produção de lixiviado é uma consequência inevitável deste método. O lixiviado de aterro sanitário é uma água residual com elevada carga poluente e com grande complexidade química. Para evitar descargas que causem impactos negativos ao ambiente ou à saúde pública, o lixiviado deve ser recolhido e tratado adequadamente antes da descarga. Em Portugal, em muitas estações de tratamento de águas lixiviantes, tem-se verificado que o lixiviado tratado, após suportar uma série de processos biológicos e físico-químicos, continua a apresentar elevadas concentrações de nitrato (NO3-). O objectivo principal do trabalho experimental conducente a esta dissertação consistiu em avaliar a remoção de nitrato de um lixiviado de um aterro sanitário com elevada carga de NO3- por desnitrificação num reactor anóxico de discos biológicos rotativos. Com este propósito, começou-se por estudar o processo de desnitrificação no reactor anóxico para o tratamento de uma água residual sintética, sob duas razões carbono/azoto (C/N) (1.5 e 3). Para as condições testadas observou-se que a razão C/N=1.5 era a mais vantajosa. O reactor apresentou uma grande eficácia na redução da concentração de nitrato num tempo de retenção hidráulico baixo e o aumento das concentrações de carbono-acetato e azoto-nitrato do influente tiveram apenas um ligeiro efeito negativo em termos de remoção de substrato. Como a estrutura e a actividade do biofilme são determinantes para o desempenho do reactor, no final da experiência em contínuo, tanto as características do biofilme como a sua actividade foram avaliadas. Constatou-se que, apesar de uma espessura menor, o biofilme desenvolvido com uma razão C/N=1.5 era mais activo do que o biofilme crescido a C/N=3. Seguidamente, estudou-se o desempenho desnitrificante do reactor usando lixiviado prétratado com elevada carga de nitrato e foram avaliados os efeitos da carga inicial de nitrato, da concentração de fósforo e da razão C/N. Com uma razão C/N=2, o reactor atingiu eficiências de remoção de N-NO3- acima de 95% para cargas superiores a 100 mg N-NO3-!L-1. A maior taxa de desnitrificação observada foi de 55 mg N-NO3-!L-1!h-1 para uma carga de nitrato de 560 mg N-NO3-!L-1. Embora o reactor tenha demonstrado um desempenho muito bom em termos de desnitrificação, as concentrações da carência química de oxigénio no efluente eram ainda elevadas para descarga directa. Os resultados obtidos numa experiência posterior, com uma carga constante de nitrato (220 mg N-NO3-!L-1) e valores inferiores de C/N (1.2 e 1.5), evidenciaram que a matéria orgânica presente no lixiviado era não-biodegradável. Uma concentração de fósforo 10 mg P-PO43-!L-1 estimulou a desnitrificação autotrófica, revelando a importância da concentração de fósforo nos processos de remoção biológica de nitrato. De forma a melhorar a biodegradabilidade do lixiviado pré-tratado foram estudados, o processo de oxidação de Fenton (Fe2+/H2O2) e vários processos de oxidação avançada com ozono (O3, O3/OH- e O3/H2O2). O efeito do pH inicial, concentração dos agentes oxidantes e tempo de reacção no desempenho de cada um dos processos foi analisado em termos de carência química de oxigénio, carbono orgânico total, biodegradabilidade, compostos azotados e aromaticidade. Os resultados indicaram que os processos Fe2+/H2O2, O3/OH- e O3/H2O2, comparativamente com ozonização a pH natural ou neutro, resultaram em eficiências de remoção superiores e aumentaram a biodegradabilidade do lixiviado. Estes resultados confirmam o aumento da produção do radical hidroxilo em tais condições. Apesar do sistema Fe2+/H2O2 ser o mais económico, por motivos práticos o processo O3/OH- foi o escolhido para trabalho posterior. Por fim, analisou-se o desempenho da sequência de tratamentos: ozonização do lixiviado seguida de desnitrificação no reactor. A pré-ozonização removeu cerca de 28% do carbono orgânico total. O sistema global não afectou a eficiência de desnitrificação, que se manteve próxima de 100%. De facto, foi mesmo possível alcançar uma taxa de desnitrificação de 123 mg N-NO3-!L-1!h-1. A diminuição moderada na carga de carbono do efluente final indicou que alguns compostos recalcitrantes continuavam presentes após ozonização. Estes resultados foram confirmados pelos testes de actividade desnitrificante realizados no final da experiência em contínuo. Pelas experiências realizadas com lixiviado, considerando a carga de nitrato aplicada, as eficiências de remoção de nitrato e a acumulação insignificante de intermediários, o reactor anóxico de discos biológicos rotativos demonstrou ser extremamente eficiente e uma tecnologia promissora para a remoção de nitrato de lixiviados de aterros sanitários.
Fundação para a Ciência e Tecnologia (FCT) - Bolsa SRFH/BD/24715/2005