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

Landfill leachate contains a large amount of organic matter and ammoniacal nitrogen. As such, it has become a complex and difficult issue within the water treatment industry. The activated sludge process has been found to be a good solution with low processing costs and is now therefore the core process for leachate treatment, especially for nitrogen removal. This paper describes the characteristics and treatment of leachate. Treatment of leachate using the activated sludge process includes the removal of organic matter, ammoniacal nitrogen, and total nitrogen (TN). The core method for the removal of organic matter involves anaerobic treatment supplemented with an aerobic process. Ammoniacal nitrogen is commonly removed using a conventional aerobic treatment, and advanced TN removal is achieved using endogenous denitrification or an anaerobic ammonium oxidation (ANAMMOX) process. Since biological processes are the most economical method for TN removal, a key issue is how to tap the full potential of the activated sludge process and improve TN removal from leachate. This complex issue has been identified as the focus of current scholars, as well as an important future direction for leachate research and development.

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Treatment of Landfill Leachate Using Activated Sludge Technology: A Review.

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

A review of aerobic granular sludge (AGS) treating recalcitrant wastewater: Refractory organics removal mechanism, application and prospect

A huge amount of hazardous organopollutants, often persistent and toxic, is pro‐ duced annually over the world and may contaminate soil, water, ground water, and air. Being from various sources such as wastewater, landfill leachates, and solid residues, xenobiotics include phenols, plastics, hydrocarbons, paints, dyes, pesticides and insecticides, paper and pulp mills, and pharmaceuticals. Among biological processes for degradation of xenobiotics, fungal ones, being eco-friendly and cost cheap, have been investigated extensively because most of basidiomycetes are more tolerant to high concentrations of pollutants. Fungal bioremediation is a promising technology using their metabolic potential to remove or reduce xenobiotics. Basidiomycetes are the unique microorganisms that show high capacities of degrading a wide range of toxic xenobiotics. They act via the extracellular ligninolytic enzymes, including laccase, manganese peroxidase, and lignin peroxidase. Their capacities to remove xenobiotic substances and produce polymeric products make them a useful tool for bioremedia‐ tion purposes. During fungal remediation, they utilize hazardous compounds, even the insoluble ones, as the nutrient source and convert them to simple fragmented forms. The aim of this chapter is to elucidate the ability of basidiomycetes to degrade xenobiotics. This is an overview to present the importance of extracellular enzymes for efficient bioremediation of a large variety of xenobiotics.

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White-Rot Fungi and their Enzymes as a Biotechnological Tool for Xenobiotic Bioremediation

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

Arbuscular mycorrhizal fungi (AMFs) and biochar are two common alternatives to chemical fertilizers applied to soil to improve crop growth. However, their interactive effects on maize (Zea mays L.) growth, nutrient absorption, and physiological properties remain poorly understood. In this study, maize plants were grown in pots treated with biochar and AMFs Diversispora eburnea, alone or in combination. The results showed that the individual application of AMFs or biochar increased maize growth and mineral contents in shoots and roots (including P, K, Ca, Na, Mg, Fe, Mn, and Zn). The chlorophyll a, chlorophyll b, and total chlorophyll contents in AMF-treated leaves were significantly higher than those in the control treatment group. However, AMFs had no synergistic effects with biochar on maize growth, nutrient absorption, nor photosynthetic pigments. The application of biochar to the soil significantly reduced mycorrhizal colonization by 40.58% in the root tissues, accompanied by a significant decline in mycorrhizal dependency from 80.57% to −28.67%. We conclude that the application of biochar and AMFs can affect maize growth, nutrient uptake, and physiological properties. Our study can provide vital information for further resource use optimization in agroecosystems.

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Effects of Arbuscular Mycorrhizal Fungi and Biochar on Growth, Nutrient Absorption, and Physiological Properties of Maize (Zea mays L.)

This research investigated the treatment of landfill leachate using aerobic granular sludge (AGS). The AGS was cultivated from a lab-scale sequencing batch reactor (SBR). Leachate was gradu...

Landfill Leachate Treatment Using Aerobic Granular Sludge

The landfill leachate has high concentration of COD, ammonia and other recalcitrant composition compounds. The amount of eachwhich is mainly largely dependent on the age of the landfill. The conventional leachate treatments can be classified as chemical-physical treatments and biological treatments. Using fungi to treat leachate is an emerging research topic. Fungi, with their excellent recalcitrant compound degradability, have been used to treat industrial wastewater that contains toxic or recalcitrant compound. Due to the complex composition and toxicity of landfill leachate, fungi have showed shown better removal efficiency in terms of COD, toxicity and color removal than the conventional leachate treatment. White rot fungi species and yeast are so far the two species that have been studied in treating landfill leachate. Future research should be extended to the other fungi species as well asand also on the impact of ammonia in landfill leachate on the fungi treatment process.

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Yanan Ren

Papers

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

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

Effects of Arbuscular Mycorrhizal Fungi and Biochar on Growth, Nutrient Absorption, and Physiological Properties of Maize (Zea mays L.)

Landfill Leachate Treatment Using Aerobic Granular Sludge

Fungi in Landfill Leachate Treatment Process