Anaerobic ammonia oxidation (anammox) is a promising biological wastewater treatment process. It has been widely implemented in many industries due to lower oxygen consumptions besides being an environmental friendly method for wastewater treatment. However, there are several challenges in the process for potential application such as low anammox bacterial abundance and slow growth rate that lower the efficiency of the reaction. Therefore, several factors are being considered during operation of the anammox process. There are various anammox bacteria, which may be enriched using special techniques. Lower nitrogen content of influent brings great challenges for anammox performance due to inhibition caused by ammonium-oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) in nitrification process. This review highlighted the anammox process in various industry as well their anammox bacteria morphology, mechanism and strategies to enrich the bacteria. Coupled anammox process with low strength domestic wastewater requires more research to enable potential application in wastewater treatment.

Improper Solid Waste Management leads to the generation of landfill leachate at the landfills. To reduce the negative impacts of highly toxic and recalcitrant leachate on the environment, several techniques have been used. A lot of research is conducted to find suitable methods for the treatment of landfill leachate such as biological processes, chemical oxidation processes, coagulation, flocculation, chemical precipitation, and membrane procedures. The biological process is still being used widely for the treatment of leachate. The current system of leachate treatment consists of various unit processes which require larger area, energy and cost. In addition, the current aerobic treatment is not able to treat entirely the pollutants which require further treatment of the leachate. Anaerobic wastewater treatment has gained considerable attention among researchers and sanitary engineers primarily due to its economic advantages over conventional aerobic methods. The major advantages of anaerobic wastewater treatment in comparison to aerobic methods are: (a) the lack of aeration, which decreases costs and energy requirements; and (b) simple maintenance and control, which eliminates the need for skilled operators and manufacturers. Several anaerobic processes have been used for leachate treatment such as up-flow anaerobic sludge blanket (UASB) reactor, anaerobic filter, hybrid bed reactor, anaerobic sequencing batch reactor and Anaerobic baffled reactor. The following chapter provides an insight to the solid waste management at the landfills, generation of leachate and details of some of the highly efficient anaerobic treatment systems that are used for the overall treatment of landfill leachate.

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Anaerobic ammonium oxidation (Anammox) process is a type of biological nitrogen removal technology which is known to directly convert ammonium and nitrite to nitrogen gas. The freshwater ‘Candidatus Kuenenia stuttgartiensis’ anammox under the phylum of Planctomycetes is used to study the parameters that affect the anammox development and the metabolic pathways alongside the associated enzymes. These observations were made using state-of-the art techniques for detecting anammox bacteria based on their small-subunit ribosomal RNA genes, functional genes and unique reaction pathways. This review systematically summarizes up-to-date studies on the parameters affecting the growth of the anammox bacteria and metabolic networks driving anammox bacterial anabolism and mixotrophy beyond genome-based predictions. The K. stuttgartiensis survives in summer and winter conditions besides in the aerobic zones (dissolved oxygen >2 mg/L), which consequently contribute to better nitrogen removal in the wastewater treatment. Furthermore, the K. stuttgartiensis utilizes the Wood–Ljungdahl pathway to directly assimilate extracellular formation instead of oxidising it completely to CO2 prior reassimilation.