The differential proliferation of AOB and NOB during natural nitrifier cultivation and acclimation with raw sewage as seed sludge

Development and Characterization of Ammonia Removal Moving Bed Biofilms for Landfill Leachate Treatment

Urbanization growth has intensified the challenge of managing and treating increasing amounts of municipal solid waste (MSW). Landfills are commonly utilized for MSW disposal because of their low construction and operation costs. However, this practice produces huge volumes of landfill leachate, a highly polluting liquid rich in ammoniacal nitrogen (NH3-N), organic compounds, and various heavy metals, making it difficult to treat in conventional municipal wastewater treatment plants (WWTPs). In recent years, research has shown that microbial biofilms, developed on carriers of different materials and called "moving bed biofilm reactors" (MBBRs), may offer promising solutions for bioremediation. This study explored the biofilm development and the nitrification process of moving bed biofilms (MBBs) obtained from high ammonia-selected microbial communities. Using crystal violet staining and confocal laser-scanning microscopy, we followed the biofilm formation stages correlating nitrogen removal to metagenomic analyses. Our results indicate that MBBs unveiled a 10-fold more enhanced nitrification rate than the dispersed microbial community present in the native sludge of the Porto Sant'Elpidio (Italy) WWTP. Four bacterial families, Chitinophagaceae, Comamonadaceae, Sphingomonadaceae, and Nitrosomonadaceae, accumulate in structured biofilms and significantly contribute to the high ammonium removal rate of 80% in 24 h as estimated in leachate-containing wastewaters.

Enhancing swine manure treatment: A full-scale techno-economic assessment of nitrogen recovery, pure oxygen aeration and effluent polishing

In regions with intensive livestock production, managing the environmental impact of manure is a critical challenge. This study, set in Flanders (Belgium), evaluates the effectiveness of integrating process intensification measures into the treatment of piggery manure to mitigate nitrogen (N) surplus issues. The research investigates the techno-economic benefits of implementing three key interventions: pure oxygen (PO) aeration, ammonia (NH3) stripping-scrubbing (SS) pretreatment, and tertiary treatment using constructed wetlands (CW), within the conventional nitrification-denitrification (NDN) process. Conducted at a full-scale pig manure treatment facility, our analysis employs steady-state mass balances for N and phosphorus (P) to assess the impact of these process intensification strategies. Findings indicate that the incorporation of advanced treatment steps significantly enhances the efficiency and cost-effectiveness of the manure management system. Specifically, the application of PO aeration is shown to reduce overall treatment costs by nearly 4%, while the addition of an NH3 SS unit further decreases expenses by 1-2%, depending on the counter acid utilized. Moreover, the implementation of a CW contributes an additional 4% in cost savings. Collectively, these measures offer substantial improvements in processing capacity, reduction of by-product disposal costs, and generation of additional revenue from high-quality fertilising products. The study highlights the potential of advanced treatment technologies to provide economically viable and environmentally sustainable solutions for manure management in livestock-dense regions, emphasizing the cumulative economic benefit of a holistic approach to process intensification (10%).

Recurrent multi-stressor floc treatments with sulphide and free ammonia enabled mainstream partial nitritation/anammox

Selective suppression of nitrite-oxidising bacteria (NOB) over aerobic and anoxic ammonium-oxidising bacteria (AerAOB and AnAOB) remains a major challenge for mainstream partial nitritation/anammox implementation, a resource-efficient nitrogen removal pathway. A unique multi-stressor floc treatment was therefore designed and validated for the first time under lab-scale conditions while staying true to full-scale design principles. Two hybrid (suspended + biofilm growth) reactors were operated continuously at 20.2 ± 0.6 °C. Recurrent multi-stressor floc treatments were applied, consisting of a sulphide-spiked deoxygenated starvation followed by a free ammonia shock. A good microbial activity balance with high AnAOB (71 ± 21 mg N L-1 d-1) and low NOB (4 ± 17 % of AerAOB) activity was achieved by combining multiple operational strategies: recurrent multi-stressor floc treatments, hybrid sludge (flocs & biofilm), short floc age control, intermittent aeration, and residual ammonium control. The multi-stressor treatment was shown to be the most important control tool and should be continuously applied to maintain this balance. Excessive NOB growth on the biofilm was avoided despite only treating the flocs to safeguard the AnAOB activity on the biofilm. Additionally, no signs of NOB adaptation were observed over 142 days. Elevated effluent ammonium concentrations (25 ± 6 mg N L-1) limited the TN removal efficiency to 39 ± 9 %, complicating a future full-scale implementation. Operating at higher sludge concentrations or reducing the volumetric loading rate could overcome this issue. The obtained results ease the implementation of mainstream PN/A by providing and additional control tool to steer the microbial activity with the multi-stressor treatment, thus advancing the concept of energy neutrality in sewage treatment plants.

A review of ammonia removal using a biofilm-based reactor and its challenges

Extensive growth of industries leads to uncontrolled ammonia releases to environment. This can result in significant degradation of the aquatic ecology as well as significant health concerns for humans. Knowing the mechanism of ammonia elimination is the simplest approach to comprehending it. Ammonia has been commonly converted to less hazardous substances either in the form of nitrate or nitrogen gas. Ammonia has been converted into nitrite by ammonia-oxidizing bacteria and further reduced to nitrate by nitrite-oxidizing bacteria in aerobic conditions. Denitrification takes place in an anoxic phase and nitrate is converted into nitrogen gas. It is challenging to remove ammonia by employing technologies that do not incur particularly high costs. Thus, this review paper is focused on biofilm reactors that utilize the nitrification process. Many research publications and patents on biofilm wastewater treatment have been published. However, only a tiny percentage of these projects are for full-scale applications, and the majority of the work was completed within the last few decades. The physicochemical approaches such as ammonia adsorption, coagulation-flocculation, and membrane separation, as well as conventional biological treatments including activated sludge, microalgae, and bacteria biofilm, are briefly addressed in this review paper. The effectiveness of biofilm reactors in removing ammonia was compared, and the microbes that effectively remove ammonia were thoroughly discussed. Overall, biofilm reactors can remove up to 99.7% ammonia from streams with a concentration in range of 16-900 mg/L. As many challenges were identified for ammonia removal using biofilm at a commercial scale, this study offers future perspectives on how to address the most pressing biofilm issues. This review may also improve our understanding of biofilm technologies for the removal of ammonia as well as polishing unit in wastewater treatment plants for the water reuse and recycling, supporting the circular economy concept.