Study on De-Nitrification of Improved Step-Feed Progress

Modeling of simultaneous denitrification – Anaerobic digestion – Organic matter aerobic oxidation and nitrification in an anoxic–anaerobic–aerobic compact filter reactor

A pilot-scale primary maturation pond was spiked with (15)N-labelled ammonia ((15)NH(4)Cl) and (15)N-labelled nitrite (Na(15)NO(2)), in order to improve current understanding of the dynamics of inorganic nitrogen transformations and removal in WSP systems. Stable isotope analysis of delta(15)N showed that nitrification could be considered as an intermediate step in WSP, which is masked by simultaneous denitrification, under conditions of low algal activity. Molecular microbiology analysis showed that denitrification can be considered a feasible mechanism for permanent nitrogen removal in WSP, which may be supported either by ammonia-oxidising bacteria (AOB) or by methanotrophs, in addition to nitrite-oxidising bacteria (NOB). However, the relative supremacy of the denitrification process over other nitrogen removal mechanisms (e.g., biological uptake) depends upon phytoplanktonic activity.

Simultaneous denitrification and denitrifying phosphorus removal in a full-scale anoxic–oxic process without internal recycle treating low strength wastewater

This study evaluated the roles of two common sources of Fe(III)-minerals-volcanic rock (VR) and synthetic banded iron formations from waste iron tailings (BIF-W)-in vertical flow-constructed wetlands (VFCWs). The evaluation was conducted in the absence of critical environmental factors, including Fe(II), Fe(III), and soil organic matter (SOM), using metagenomic analysis and integrated correlation networks to predict nitrogen removal pathways. Our findings revealed that Fe(III)-minerals enhanced metabolic activities and cellular processes related to carbohydrate decomposition, thereby increasing the average COD removal rates by 10.7% for VR and 5.90% for BIF-W. Notably, VR improved nitrogen removal by 1.70% and 5.40% compared to BIF-W and the control, respectively. Fe(III)-mineral amendment in bioreactors also improved the retention of denitrification and nitrification bacteria (phylum Proteobacteria) and anammox bacteria (phylum Planctomycetes), with increases of 3.60% and 3.20% using VR compared to BIF-W. Metagenomic functional predictionindicated that the nitrogen removal mechanisms in VFCWs with low C/N ratios involve simultaneous partial nitrification, ANAMMOX, and denitrification (SNAD). Network-based analyses and correlation pathways further suggest that the advantages of Fe(III)-minerals are manifested in the enhancement of denitrification microorganisms. Microbial communities may be activated by the functional dissolution of Fe(III)-minerals, which improves the stability of SOM or the conversion of Fe(III)/Fe(II). This study provides new insights into the functional roles of Fe(III)-minerals in VFCWs at the microbial community level, and provides a foundation for developing Fe-based SNAD enhancement technologies.

Aerobic granules are the potential tools to develop modern wastewater treatment technologies with improved nutrient removal efficiency. These granules have several promising advantages over conventional activated sludge-based wastewater treatment processes. This technology has the potential of reducing the infrastructure and operation costs of wastewater treatment by 25%, energy requirement by 30%, and space requirement by 75%. The nutrient removal mechanisms of aerobic granules are slightly different from that of the activated sludge. For instance, unlike activated sludge process, according to some reports, as high as 70% of the total phosphorus removed by aerobic granules were attributed to precipitation within the granules. Similarly, aerobic granule-based technology reduces the total amount of sludge produced during wastewater treatment. However, the reason behind this observation is unknown and it needs further explanations based on carbon and nitrogen removal mechanisms. Thus, as a part of the present review, a set of new hypotheses have been proposed to explain the peculiar nutrient removal mechanisms of the aerobic granules.

Lumen air pressure regulated multifunctional microbiotas in membrane-aerated biofilm reactors for simultaneous nitrogen removal and antibiotic elimination from aquaculture wastewater

Wastewater of municipal toilets contains higher nitrogen to carbon ratio than other types of wastewater. The removal of nitrogen from municipal toilet wastewater has become a major concern due to problems caused by discharge of insufficiently treated wastewater, such as eutrophication and toxicity. Moving Bed Biofilm Reactor (MBBR) has been developed in order to facilitate nitrogen removal. Treatment of nitrogen is commonly achieved in separate aerobic and anoxic tanks in typical MBBR systems. However the treatment process using a single MBBR tank as an advantageous method because of the low cost and low complexity, has not been thoroughly studied. This research is focused on the performance of MBBR in nitrogen removal based on simultaneous nitrification and de-nitrification in single aerobic MBBR with continuous operation. A moving-bed biofilm reactor system with an anoxic–aerobic arrangement was set up and the wastewater extracted from the wastewater treatment plant at temple of Tooth Relic, Kandy, was kept in the prepared laboratory set up for the accumulation of microorganisms. The operation was carried out in 3 steps. In the first step, the DO concentration in the reactor was maintained at 5 mg/l and the synthetic wastewater was introduced initially to the reactor at low nitrogen concentration. Then, the nitrogen concentration was increased varying the BOD/N. In the second step BOD/N ratio was maintained at 4.2, which is the BOD/N value of public toilet wastewater and the DO concentration was varied. Volatile Suspended Solids (VSS) of the reactor was kept at around 2200 mg/l. In the third step the DO concentration was maintained at 1.5 mg/l since it was the optimum DO concentration for highest de-nitrification in the 2nd step. Then the VSS of the reactor was maintained at 2200 mg/l and the BOD/N ratio was varied. Under the operating conditions, 67% of BOD and COD removal and 60% of TN removal could be achieved from the prepared laboratory set up. Further it was observed that the removal of nitrogen increased when the BOD/N ratio was increased.

Deciphering the internal mechanism of nitrogen removal from sludge and biofilm under low temperature from the perspective of microbial function metabolism.

Simultaneous nitrification and denitrification (SND) via the nitrite pathway and anaerobic-anoxic-enhanced biological phosphorus removal (EBPR) are two processes that can significantly reduce the energy and COD demand for nitrogen and phosphorus removal. The combination of these two processes has the potential of achieving simultaneous nitrogen and phosphorus removal with a minimal requirement for COD. A lab-scale sequencing batch reactor (SBR) was operated in alternating anaerobic-aerobic mode with a low dissolved oxygen (DO) concentration (0.5 mg/L) during the aerobic period, and was demonstrated to accomplish nitrification, denitrification, and phosphorus removal. Under anaerobic conditions, COD was taken up and converted to polyhydroxyalkanoates (PHAs), accompanied by phosphorus release. In the subsequent aerobic stage, PHA was oxidized and phosphorus was taken up to <0.5 mg/L by the end of the cycle. Ammonia was also oxidized during the aerobic period, but without accumulation of nitrite or nitrate in the system, indicating the occurrence of simultaneous nitrification and denitrification. However, off-gas analysis showed that the final denitrification product was mainly nitrous oxide (N(2)O), not N(2). Further experimental results demonstrated that nitrogen removal was via nitrite, not nitrate. These experiments also showed that denitrifying glycogen-accumulating organisms (DGAOs), rather than denitrifying polyphosphate-accumulating organisms (DPAOs), were responsible for the denitrification activity.

Can membrane aerated biofilm reactor (MABR) realize more efficient simultaneous partial nitrification and denitrification than conventional biofilm under low COD/N?

Research on enhanced effects and mechanisms of nitrogen removal with plant carbons sources in constructed wetlands

Excessive accumulation of nitrogen is a major cause of water eutrophication. Developing an inexpensive and efficient nitrogen removal technology is therefore essential for wastewater purification. The microbial technology for nitrogen removal has been widely used for its low cost, high efficiency, and strong environmental adaptability. Most recently, with the advances in synthetic biotechnology, artificial multicellular systems have been sufficiently developed and exhibited unique definability and controllability. Compared with those in the natural microbial consortia, the nitrogen removal pathways and environmental response mechanisms are easy to be clarified in the artificial multicellular systems, which allow for efficient nitrogen removal under low cellular metabolic loading. Therefore, artificial multicellular systems demonstrate great application potential in the purification of wastewater, including landfill leachate, industrial wastewater, seawater aquaculture wastewater, and domestic sewage. We focused on the design, building, and application of artificial multicellular systems for nitrogen removal from wastewater. Specifically, we summarized the functional microorganisms and their nitrogen removal mechanisms, introduced the design principles and building methods of artificial multicellular systems, illustrated the application of artificial multicellular systems with examples, and prospected the future research trend in nitrogen removal from wastewater. The conclusion is expected to provide new insights and efficient strategies for optimizing the microbial nitrogen removal from wastewater.

Synthesis and performance of iron oxide-based porous ceramsite in a biological aerated filter for the simultaneous removal of nitrogen and phosphorus from domestic wastewater

Nitrous oxide emission and microbial community of full-scale anoxic/aerobic membrane bioreactors at low dissolved oxygen setpoints

Comparison and Optimization of Intermittent Aeration/Interval Aeration for Enhancing Nitrogen Removal in Continuous Flow Anaerobic/Oxic/Anoxic Processes.