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Food Industry Effluent Treatment Techniques
Published in Mihir Kumar Purkait, Piyal Mondal, Chang-Tang Chang, Treatment of Industrial Effluents, 2019
Mihir Kumar Purkait, Piyal Mondal, Chang-Tang Chang
Conventional biological nitrogen removal occurs in two distinct stages: nitrification (conversion of ammonia to nitrite and nitrate) and denitrification (conversion of nitrate to nitrogen gas). Nitrification occurs in an aerobic environment, while denitrification occurs under anoxic conditions, with the presence of oxygen in nitrite and nitrate molecules, but in the absence of dissolved molecular oxygen. As a result, the denitrification process must occur at a time or medium other than the nitrification process. The denitrification process, besides forming nitrogen, an inert gas, also causes alkalinity, which makes the recycling of the effluent from this process to the nitrification tank, where an alkalinity source is necessary. Due to the high oxygen consumption required in the nitrification process (4.2 g of O2 per mole of ammonia nitrogen nitrified) and the possibility of carrying out denitrification from nitrite, some alternative technologies are being studied to increase the sustainability of the nitrogen removal process, such as simultaneous nitrification denitrification (SND; Pochana and Keller, 1999); anaerobic ammonium oxidation (ANAMOX; Tsushima et al., 2007); single reactor system for high ammonium removal over nitrite (SHARON; Van Dongen et al., 2001); and direct oxidation of ammonia nitrogen to N2 by autotrophic microorganisms (OLAND; Kuai and Verstraete, 1998).
Media Supported Biofilms and the Activated Sludge Process
Published in Dwight Houweling, Glen T. Daigger, Intensifying Activated Sludge Using Media-Supported Biofilms, 2019
Dwight Houweling, Glen T. Daigger
The ability to install MABR media in anoxic bioreactor zones provides a means to enhance both the nitrification and denitrification capacity of the zone. Compared to a conventional BNR process, where the purpose of the anoxic zone is denitrification only, an anoxic zone with MABR media can simultaneously nitrify in the biofilm and denitrify in the mixed liquor. Simultaneous nitrification/denitrification (SND) is highly valued as a means to maximize total nitrogen removal in the available bioreactor zone.
Effect of intermittent induced aeration on nitrogen removal and denitrifying-bacterial community structure in Cork and gravel vertical flow pilot-scale treatment wetlands
Published in Journal of Environmental Science and Health, Part A, 2021
Lorena Aguilar, Ángel Gallegos, Leonardo Martín Pérez, Carlos A. Arias, Raquel Rubio, Leila Haulani, Josep García Raurich, Marc Pallarés, Joan de Pablo, Jordi Morató
On the other hand, nitrogen removal is a microbial-governed process, where a great diversity of microorganisms related to the nitrogen cycle are involved.[5] Simultaneous nitrification-denitrification plays a major role for nitrogen removal, being ammonium-oxidant bacteria (AOB) nitrifiers and denitrifiers the dominant microbial communities associated to such bioprocesses.[22–24] Nitrification is carried out in aerobic conditions, whereas denitrification occurs strictly under anoxic-anaerobic conditions.[21,25] A recent work[26] reported that intermittent aeration in VFCW facilitates the establishment of aerobic and anaerobic conditions at the same treatment improving total nitrogen removal. However, nitrogen removal in TW is still a key problem, especially for treating low C/N ratio wastewaters since the aerobic process removes most of the C/BOD as well as the ammonium resulting in insufficient carbon for the subsequent growth of denitrifying bacteria.[24] In such case, carbon supplementation in the form of organic material may be important for optimizing NO3- removal from waters since carbon source is the key factor that limits the growth of denitrifying bacteria and therefore denitrification.[1,27–29]
Appropriate technologies for upgrading wastewater treatment plants: methods review and case studies in China
Published in Journal of Environmental Science and Health, Part A, 2018
Kai Hu, Qing L. Zhao, Wei Chen, Wei Wang, Feng Han, Xing H. Shen
In simultaneous nitrification–denitrification processes, such as A/O process, the DO concentration in the tank determines the reaction because nitrification is promoted by a high DO concentration while denitrification requires a low concentration. High DO concentrations are achieved by aeration. The energy consumed by aeration can account for more than 50% of the total energy of a WWTP.[47] Therefore, it is advisable to maintain an adequate DO level for economic reasons and process stability. The optimum DO levels can be achieved by adjusting the duration of each step as a function of the ammonium and nitrate levels, and these can be monitored on-line throughout the process.[48,49] Available DO control strategies for plants operated under a continuous recycling regime include changing the oxygen setpoint according to the ammonium concentration, controlling the DO start/stop sequence as a function of the nitrate and ammonium concentrations, intermittent aeration of the aerobic reactor, altering recirculation according to the nitrate concentration in the aerobic reactor, and using an increased oxygen concentration (biofilm carriers, oxygen addition) in the first step of the nitrification reactor.[50] One on-line control system, called Superior Tuning And Reporting (STAR), has been successfully applied to full-scale WWTPs.[51] This system decreased the TN and NH4+N concentrations by 49% and 64%, respectively.[51] One example of DO setpoint and Oxidation-Reduction Potential (ORP) control in a patented control device is shown in Table 9.[52]
Enhancing biological removal of nitrogen from wastewater in activated sludge process
Published in HBRC Journal, 2021
Taha Sharkawy, Hesham Mo. Abdel Halim, Mahmoud M. Abd Elazeem, Mohamed Abdel Moneim Haikal, Ehab Helmy Rozaik
For more than one hundred years and still, it emphasizes that domestic wastewater is the prominent source in addition to agriculture runoff contribution for eutrophication, so that biological sewage treatment by activated sludge process has been utilized to resolve problems associated with the water pollution, such as organic materials, nitrogen and phosphorous. The most widely applied nitrogen removal method in WWTPs is nitrification–denitrification process, where aerobic autotrophic nitrification of NH4+ to NO2- and NO3- is followed by anoxic heterotrophic denitrification of the oxidized N species to N2. To perform nitrification–denitrification process, the classic bioreactor configuration applied consists of an anoxic tank followed by an aerobic tank (i.e. anoxic/oxic (A/O) process) and a secondary clarifier (Figure 1.A), called the Modified Ludzack-Ettinger (MLE) configuration. Two recirculation flows are used in the MLE configuration: (1) internal recirculation from the aerobic tank to the anoxic tank to supply electron acceptors (NO2- and NO3-) for denitrification and (2) external recirculation from the secondary clarifier to the biological process inflow to maintain a proper sludge concentration and a target biomass retention time. Emerging treatment technologies, such as the anaerobic/anoxic/oxic (A2/O) process and the University of Cape Town (UCT) process, have been proposed and implemented to carry out the conventional nitrification–denitrification process based on modifying the traditional A/O process. Other commonly used nitrification–denitrification-based wastewater treatment technologies include the oxidation ditch (Figure 1.B), which is usually equipped with aerators to provide aeration and circulation and to achieve simultaneous nitrification–denitrification process in the same bioreactor through spatial DO gradient and the sequencing batch reactor (SBR) (Figure 1.C), which creates aerobic and anoxic conditions in the same bioreactor through temporal separation. To design and operate the bioreactors, sludge retention time (SRT) and aeration are the two parameters of key importance. Compared with heterotrophic bacteria, autotrophic nitrifying bacteria (i.e. AOB and NOB) grow slowly; thus, a proper SRT should be considered to maintain those microorganisms in the systems to ensure high nitrification efficiencies and hence better total nitrogen (TN) removal. Aeration is the main treatment in WWTPs performing the conventional nitrification–denitrification process and must be controlled to provide enough oxygen supply for nitrification while avoiding unnecessary energy consumption [4].