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

More and more stringent requirements for pollution control and the implementation of the new discharge standard for landfill leachate make the development and application of landfill leachate treatment a research focus. The aim of the review is to determine appropriate technique for effective treatment of landfill leachate. In the paper, various leachate treatment technologies are presented and summarized, the key control parameters and some main problems are discussed from a technological point of view. It is proposed that the improvement of existing technical and the development and industrial application of a new treatment for landfill leachate are necessary. The development and application of integrated leachate treatment process of different physical, biological and chemical technologies could be a suitable option to reduce the contamination levels of leachate. Particularly, advanced oxidation technologies and an efficient integration between physical–chemical processes and biochemical processes are indicated as a significant research direction of new technology development.

The present status of landfill leachate treatment and its development trend from a technological point of view

Facile preparation of N-doped activated carbon produced from rice husk for CO2 capture.

Palm oil mill effluent (POME) is generated from the sterilization, condensation and hydrocycloning of palm oil in mills. If the effluent is discharged into the aquatic and terrestrial ecosystem without treatment, it could lead to high biological oxygen demand (BOD), chemical oxygen demand (COD) and acidic pH of the receiving waters. Biogas consisting mostly of methane, carbon dioxide, and to a lesser hydrogen has been produced through anaerobic treatment of this toxic effluent. The process of biogas production involves microbial synthesis involving hydrolysis, acidogenesis, acetogenesis and methanogenesis. Biogas is formed during anaerobic degradation of POME by indigenous microbial communities. This review updates the current state of art of biogas production through anaerobic digestion of POME using different configurations of reactors such as fluidized bed reactor, anaerobic filtration, up-flow anaerobic sludge blanket (UASB) reactor, anaerobic contact digestion, up-flow anaerobic sludge fixed-film (UASFF) reactor, modified anaerobic baffled bioreactor (MABB), anaerobic baffled bioreactor (ABR), continuous stirred tank reactor (CSTR), expanded granular sludge bed (EGSB) reactor, Ultrasonicated membrane anaerobic system (UMAS), Ultrasonic-assisted Membrane Anaerobic System (UAMAS), membrane anaerobic system (MAS)and upflow anaerobic sludge blanket reactor (UASBR). The factors that influences biogas yield during treatment include pH, temperature (environmental factors), organic loading rate (OLR), hydraulic retention time (HRT), mixing rate, pressure, equilibrium, nutrient and microbial activities (Internal factors). Based on this study, UAMAS is the best configuration for methane production from POME during anaerobic treatment. Biogas from POME could contribute to energy sources of oil palm producing nations, while preventing the attendant environmental impacts associated with its disposal.

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A review of biogas production from palm oil mill effluents using different configurations of bioreactors

It is noteworthy to highlight that ammonia nitrogen contamination in wastewater has been reported to pose a great threat to the environment. This conventional method of remediating ammonia nitrogen contamination in wastewater applies the packed bed tower technology. Nevertheless, this technology appears to pose several application issues. Over the years, researchers have tested various types of ammonia stripping process to overcome the shortcomings of the conventional ammonia stripping technology. Along this line, the present study highlights the recent development of ammonia stripping process for industrial wastewater treatment. In addition, this study reviews ammonia stripping application for varied types of industrial wastewater and several significant operating parameters. Furthermore, this paper discusses some issues related to the conventional ammonia stripper for industrial treatment application. Finally, this study explicates the future prospects of the ammonia stripping method. This review, hence, contributes by enhancing the ammonia stripping treatment efficiency and its application for industrial wastewater treatment.

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Recent Development in Ammonia Stripping Process for Industrial Wastewater Treatment

An old landfill leachate was pre-treated in a pilot-scale aerated packed tower operated in batch mode for total ammoniacal nitrogen (TAN) removal. The stripped ammonia was recovered with a 0.4 mol L−1 H2SO4 solution, deionized water and tap water. Ca(OH)2 (95% purity) or commercial hydrated lime was added to the raw leachate to adjust its pH to 11, causing removal of colour (82%) and heavy metals (70–90% for Zn, Fe and Mn). The 0.4 mol L−1 H2SO4 solution was able to neutralize 80% of the stripped ammonia removed from 12 L of leachate. The effectiveness of the neutralization of ammonia with deionized water was 75%. Treating 100 L of leachate, the air stripping tower removed 88% of TAN after 72 h of aeration, and 87% of the stripped ammonia was recovered in two 31 L pilot-scale absorption units filled with 20 L of tap water.

Ammonia removal from landfill leachate by air stripping and absorption

Co-treatment of landfill leachate and domestic wastewater using a submerged aerobic biofilter.

The treatment of young landfill leachate was investigated using two 3 L sequencing batch reactors (SBR) with different biomass: aerobic granular sludge (GSBR) and the suspended growth activated sludge (ASBR). According to the nature of aerobic granular sludge, high settling velocities were expected in the GSBR and it was confirmed with 60 ml/g VSS of 5-min sludge volume index (SVI5). However, the activated sludge required 30 min for the ASBR to achieve a SVI of 42 ml/g VSS. Compared to the ASBR, the GSBR was also more efficient in nitrogen and carbon removal. During the steady period of the experiment, 99% of total ammonium nitrogen (TAN) was removed through nitritation and nitrification in the GSBR with an average influent TAN concentration of 498 mg/L. With high influent TAN concentration, the GSBR could achieve a full nitrification efficiency of 56 ± 12% without accumulating nitrite. On the contrary, complete nitrification was not achieved in the ASBR as it was exposed to high concentrations of free ammonia (FA) and free nitrous acid (FNA), 16 and 0.2 mg/L respectively. Partial nitrification (nitritation) with the efficiency of 77 ± 10% was observed in the ASBR. The GSBR also presented higher efficiency in denitrification compared to the ASBR. 23% denitrification was observed in the GSBR during the anaerobic phase. Moreover, higher chemical oxygen demand (COD) removal efficiency was observed in GSBR than ASBR. Phosphorus removal efficiency was almost identical in both reactors. Overall, compared with the activated sludge, the aerobic granular sludge showed the best nutrients removal performance and higher tolerance to toxic compounds in young landfill leachate.

Comparing young landfill leachate treatment efficiency and process stability using aerobic granular sludge and suspended growth activated sludge

Leachate/domestic wastewater aerobic co-treatment: A pilot-scale study using multivariate analysis.

Aerobic granular sludge has become an attractive alternative to the conventional activated sludge due to its high settling velocity, compact structure, and higher tolerance to toxic substances and adverse conditions. Aerobic granular sludge process has been studied intensively in the treatment of municipal and industrial wastewater. However, information on leachate treatment using aerobic granular sludge is very limited. This study investigated the treatment performance of old landfill leachate with different levels of ammonium using two aerobic sequencing batch reactors (SBR): an activated sludge SBR (ASBR) and a granular sludge SBR (GSBR). Aerobic granules were successfully developed using old leachate with low ammonium concentration (136 mg L−1 NH4
 +-N). The GSBR obtained a stable chemical oxygen demand (COD) removal of 70% after 15 days of operation; while the ASBR required a start-up of at least 30 days and obtained unstable COD removal varying from 38 to 70%. Ammonium concentration was gradually increased in both reactors. Increasing influent ammonium concentration to 225 mg L−1 N, the GSBR removed 73 ± 8% of COD; while COD removal of the ASBR was 59 ± 9%. The GSBR was also more efficient than the ASBR for nitrogen removal. The granular sludge could adapt to the increasing concentrations of ammonium, achieving 95 ± 7% removal efficiency at a maximum influent concentration of 465 mg L−1 N. Ammonium removal of 96 ± 5% was obtained by the ASBR when it was fed with a maximum of 217 mg L−1 NH4
 +-N. However, the ASBR was partially inhibited by free-ammonia and nitrite accumulation rate increased up to 85%. Free-nitrous acid and the low biodegradability of organic carbon were likely the main factors affecting phosphorus removal. The results from this research suggested that aerobic granular sludge have advantage over activated sludge in leachate treatment.

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Fernanda M. Ferraz

Papers

Ammonia removal from landfill leachate by air stripping and absorption

Co-treatment of landfill leachate and domestic wastewater using a submerged aerobic biofilter.

Comparing young landfill leachate treatment efficiency and process stability using aerobic granular sludge and suspended growth activated sludge

Leachate/domestic wastewater aerobic co-treatment: A pilot-scale study using multivariate analysis.

Treatment of old landfill leachate with high ammonium content using aerobic granular sludge.