Optimization of Aeration Conditions for Enhanced Nitrogen Removal in Wastewater Treatment
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Wastewater treatment, aeration conditions, nitrogen removal, sludge recirculation, nitrification, denitrification, filamentous growth, optimal aeration time range
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Abstract
This document presents a study on the optimization of aeration conditions for nitrogen removal in wastewater treatment, focusing on the Grange David wastewater treatment plant of Tours Métropole Val de Loire. The study aims to improve the management of nitrogen discharged and reduce costs related to aeration. The document includes an analysis of the influence of aeration conditions on global nitrogen concentration and sludge index, as well as the optimization of daily aeration duration for aerator operation. The study also examines the recirculation rate of sludge and its impact on nitrification and denitrification. The results of the study provide insights into the optimal aeration time range for nitrogen removal and control of filamentous growth in a single basin.
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[...] Decantation tests are carried out daily except on weekends according to the protocol described below. Decantation Test Protocol 1. In the clarifier, take a sample of sludge at the outlet 15 minutes after the blower is lit. 2. Take a sample of clarified water without floaters in order to resuspend the sludge. 3. Dilute the sample by and introduce it into a 1L graduated cylinder. 4. Shake the graduated cylinder from bottom to top, taking care not to lose the mixture. [...]
[...] (Alternation of phases of aeration and anoxia The alternation of phases of operation and shutdown of aerators and the total aeration and anoxia times per day must be optimized to achieve a high level of nitrification and denitrification. To allow for sufficient anoxia time in a completely mixed basin, aerators must be shut down simultaneously if there are multiple ones. The required aeration and aerator shutdown times can be determined from the knowledge of nitrification and denitrification rates and the loads to be removed. [...]
[...] The raw water arrives in lamellar decanters. These decanters remove the majority of the pollution. The suspended solids settle at the bottom of the basin. In order to confine this work, the decantation process is facilitated by the presence of honeycomb-shaped lamellas. In fact, in order to treat a minimum of contaminated air, this work has been designed in a minimum volume. This process separates the solid from the liquid. The particles denser than water descend to the bottom of the basin. [...]
[...] Figure 21 : Concentration in BOD5 and removal rate of the Grange David wastewater treatment plant of Tours Métropole Val de Loire from January to June 2019 4. Aeration duration and nitrogen removal performance How to optimally share the 24-hour daily period between aeration and anoxia to achieve these nitrogen removal objectives? What is the sensitivity of the system to under-aeration and over-aeration compared to the optimal setting? The experimental part of the study was conducted on the wastewater treatment plant. The optimal aeration duration was determined by observing the effects on nitrogen removal, from a progressive, step-by-step decrease in daily aeration duration. [...]
[...] In the first stage, in contact with microorganisms, the sludge is transformed into fatty acids, metabolized by a second type of bacteria producing PHA. During this study, we were mainly interested in the water treatment device within the water sector. During this process, a large quantity of sludge is produced, which will be treated to meet regulatory requirements and be revalued, in particular in agriculture. It could be interesting to work on other systems of valorization. For example, industrialists in the field have worked on the production of recycled plastic from wastewater sludge. [...]
