Strategy of rapid start-up and the mechanism of de-nitrogen in landfill bioreactor

Screening, identification, and application of anaerobic ammonia oxidizing bacteria in activated sludge systems: A comprehensive review

Anaerobic ammonium oxidation (Anammox) has garnered significant attention due to its ability to eliminate the need for aeration and supplementary carbon sources in biological nitrogen removal process, relying on the capacity of anaerobic ammonium oxidizing bacteria (AnAOB) to directly convert ammonium and nitrite nitrogen into nitrogen gas. This review consolidates the latest advancements in AnAOB research, outlining the mechanisms and enzymatic processes of Anammox, and summarizing the molecular biological techniques used for studying AnAOB, such as 16s rRNA sequencing, qPCR, and metagenomic sequencing. Additionally, it also overviews the currently identified AnAOB species and their distinct metabolic traits, while consolidating strategies to improve their performance. It further delineates coupled processes that utilize Anammox technology, offering practical insights for process selection. Eventually, the review concludes by suggesting future research directions and highlighting critical areas for further investigation. This review serves as a theoretical reference for the enrichment and cultivation of AnAOB, environmental impact management, and the selection of effective treatment processes.

Biostimulation accelerates landfill stabilization and resource utilization efficiency, providing feasible technical support for the overall lifecycle management of landfills

Although sanitary landfill is one of the principal municipal solid waste (MSW) treatment and disposal methods, its limitations, such as insufficient use of resources, long stability time, and high risk of environmental pollution, must be urgently resolved. The effect of multifunctional microbial community (MMC) inoculation on MSW landfill process was investigated using simulated anaerobic bioreactor landfill (ABL), and composition and microbial community structure of waste, leachate water quality, and gas production were monitored. MMC inoculation significantly accelerated lignocellulose degradation, and the (Hemicellulose content + Cellulose content)/Lignin content ((C + H)/L) of MMC inoculation treatment was 0.89 ± 0.04 on day 44, which was significantly lower than that of the control group (1.14 ± 0.02). At the end of the landfill process, the reductive organic matter, ammonia nitrogen, and volatile fatty acids in the leachate of the MMC group decreased to 9400.00 ± 288.68, 332.78 ± 5.77, and 79.33 ± 6.44 mg L-1, respectively, significantly lower than those of the control group (24,167.00 ± 208.17, 551.14 ± 5.60, and 156.33 ± 8.22 mg L-1). Meanwhile, MMC inoculation increased the methane production to 118.12 ± 5.42 L kg-1 of dry matter, significantly higher than the output of the control group (60.60 ± 2.24 L kg-1). MMC inoculation optimized the microbial community structure in ABL and increased lignocellulose-degrading microorganisms (Brevundimonas, Cellvibrio, Leifsonia, and Devosia) and methanogen (Methanosaeta and Methanoculleus) abundance in the middle stage of landfill. Moreover, MMC introduction improved the abundance of carbon metabolism enzymes and increased saprophytic fungal abundance by 30.09% in the middle stage of landfill. Overall, these findings may help in developing an effective method to increase the lifespan of landfills and enhance their post-closure management.

A pilot-scale comparative study of bioreactor landfills for leachate decontamination and municipal solid waste stabilization

Many studies have sought to optimize operation parameters and enhance the treatment capacity of bioreactor landfills (BL) under ideal laboratory conditions. At pilot scale, conclusions drawn from laboratory-scale experiments will be different due to variations in actual landfill composition and changes in environmental conditions. However, comparative pilot-scale studies of traditional anaerobic landfills (AnL) and BLs are rare. In this study, three pilot-scale landfills, including an AnL, anaerobic BL (AnBL) and semi-aerobic BL (SABL), were monitored to examine the difference in performance at different scales and among types of landfills. Settlement amount followed the order SABL (25.45 cm) > AnBL (18.67 cm) > AnL (14.38 cm). Decomposition of organic matter (i.e., volatile fatty acids) was more rapid in SABL than in the other landfills and no hydrolytic acidification period was observed. Therefore, among the three landfills, SABL entered the methanogenic stage in a much shorter time and MSW stabilization was accelerated due to this landfill's unique combination of aerobic-anoxic-anaerobic ambient. In addition, NH₄⁺-N concentration in leachate from the SABL (~19.96 mg/L) was substantially lower than from AnL (338.28 mg/L) and AnBL (233.22 mg/L), and SABL leachate exhibited the least chloride pollution risk. This study provides theoretical support and strong evidence for using SABLs to treat MSW in practical applications.

Anammox and partial denitrification coupling: a review

As a new wastewater biological nitrogen removal process, anammox and partial denitrification coupling not only plays a significant role in the nitrogen cycle, but also holds high engineering application value. Because anammox and some denitrifying bacteria are coupled under harsh living conditions, certain operating conditions and mechanisms of the coupling process are not clear; thus, it is more difficult to control the process, which is why the process has not been widely applied. This paper analyzes the research focusing on the coupling process in recent years, including anammox and partial denitrification coupling process inhibitors such as nitrogen (NH₄⁺, NO₂⁻), organics (toxic and non-toxic organics), and salts. The mechanism of substrate removal in anammox and partial denitrification coupling nitrogen removal is described in detail. Due to the differences in process methods, experimental conditions, and sludge choices between the rapid start-up and stable operation stages of the reactor, there are significant differences in substrate inhibition. Multiple process parameters (such as pH, temperature, dissolved oxygen, redox potential, carbon-to-nitrogen ratio, and sludge) can be adjusted to improve the coupling of anammox and partial denitrification to modify nitrogen removal performance.

As a new wastewater biological nitrogen removal process, anammox and partial denitrification coupling not only plays a significant role in the nitrogen cycle, but also holds high engineering application value.

Editorial: Technically-based use of by-products as a tool to control pollution

This Virtual Special Issue of Journal of Environmental Management dealt with the recycling of waste and by-products, focusing on their use in controlling environmental pollution. The field of research was previously considered as promising, in view of its relevance and the increasing number of papers published in last years. And this Special Issue allows going a step ahead in the matter, with 90 submissions and a number of 48 high quality papers finally accepted and published. We think that it will be useful at a global level, especially for researchers, social partners, and social actors involved in environmental and public health issues related to environmental pollution.