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Research Article
Modelling Nitrogen Removal in the Kibendera Wastewater Stabilization Ponds in Ruiru, Kenya
George Kirumba*,
George Thumbi,
John Mwangi,
John Mbugua
Issue:
Volume 8, Issue 1, June 2024
Pages:
1-13
Received:
19 February 2024
Accepted:
8 March 2024
Published:
19 March 2024
DOI:
10.11648/j.ae.20240801.11
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Abstract: Application of waste stabilization ponds (WSP) in wastewater treatment in the tropical regions is primarily due to their affordability and relatively high treatment performance. Monitoring of 2-year nitrogen removal behavior in Kibendera WSP in Ruiru, Kenya, was undertaken between January 2021 and December 2022. The experimental work determined the concentrations and removal efficiencies of Ammonia, Nitrate, Nitrite, Organic Nitrogen and Total Nitrogen. Standard Methods for the examination of water and wastewater determined Nitrogen and Dissolved Oxygen (DO) concentrations. Based on the experimental data obtained, mass balance reaction rate models characterized the nitrogen transformation and removal behavior in the WSP. Whereas model calibration was achieved using observed data from January to December 2021, model validation was achieved using observed data from January to December 2022. Ammonia volatilization, sedimentation, mineralization, nitrification, denitrification and microbial ammonia uptake were the possible transformation and removal pathways. Whereas ammonia volatilization contributed the least to the overall nitrogen removal (0.01-0.02 mg/L.d), denitrification contributed the most (2.12-14.67 mg/L.d). Low DO levels and high ammonia concentrations were responsible for low nitrification rates and high microbial ammonia uptake respectively. Comparison between experimental and modelled effluent concentrations yielded correlation coefficients (r) of 0.77 and 0.69 for ammonia and organic nitrogen respectively during the calibration period. The corresponding model validation r values were 0.74 and 0.93 respectively. The good agreement between the model output and observed effluent concentrations implies that nitrogen removal prediction and optimization is possible. External aeration to spike DO concentration levels is necessary to enhance the long-term nitrification rates.
Abstract: Application of waste stabilization ponds (WSP) in wastewater treatment in the tropical regions is primarily due to their affordability and relatively high treatment performance. Monitoring of 2-year nitrogen removal behavior in Kibendera WSP in Ruiru, Kenya, was undertaken between January 2021 and December 2022. The experimental work determined the...
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Research Article
Evaluations of Crypto-System AES Using Multiple Bloc Ciphering Mode
Rakotondramanana Radiarisainana Sitraka
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Ramafiarisona Hajasoa Malalatiana
Issue:
Volume 8, Issue 1, June 2024
Pages:
14-30
Received:
9 March 2024
Accepted:
21 March 2024
Published:
2 April 2024
DOI:
10.11648/j.ae.20240801.12
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Abstract: Cryptography, a scientific field that has existed even before the beginning of computer science. This article looks at the development symmetric crypto-system, which falls within the framework of image security, by Advanced Encryption Standard (AES- Advanced Encryption Standard) algorithms. AES algorithm is not integrity protected. Cryptanalysis could use modified encrypted image of each ciphered bloc for generating oracle and getting the key. A new crypto-system uses hash function named AES-GCM (Advanced Encryption Standard-) for solving this problem. Using Galois Counter Mode (GCM) combined with Secure Hash Algorithm 256 bits (SHA-256) or BLAKE2s hash function, the old mode of ciphering like: Cipher FeedBack (CFB), Output FeedBack (OFB), Cipher Block Chaining (CBC), Electronic Codebook Block (ECB) and CounTeR (CTR) mode encryption, will increase the security level at confidentiality and integrity. In this article, robustness of the crypto-system will be evaluated by multiple criteria, indeed the statistical analysis, sensitivity measurement and performance measurement. For the statistical analysis, the histogram is flat and the correlation between adjacent pixel is not linear for the encrypted image. The relation between clear image and encrypted image doesn’t exist. For the sensitivity analysis, Number of Pixel Changing Rate (NPCR) and Unified Averaged Changed Intensity (UACI) permit to avoid differential attack of the crypto-system. The two values are respectively near 99% and 30%. For performance measurement, the similarity of the decrypted image and original image will be tested. The Peak Signal to Noise Ratio (PSNR) and Mean Square Error (MSE) are equals of infinity and zero. The decrypted image and original image are the same. The integrity of the image on the crypto-system will be evaluated by modifying one bit of the encrypted image. The decryption process doesn’t give decrypted image and show that the tag value is incorrect.
Abstract: Cryptography, a scientific field that has existed even before the beginning of computer science. This article looks at the development symmetric crypto-system, which falls within the framework of image security, by Advanced Encryption Standard (AES- Advanced Encryption Standard) algorithms. AES algorithm is not integrity protected. Cryptanalysis co...
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Review Article
Numerical Study of Heat Transfer in a Partitioned Cavity Containing a Porous Medium
Souleye Faye*,
Sory Diarra,
Sidy Mactar Sokhna,
Vincent Sambou
Issue:
Volume 8, Issue 1, June 2024
Pages:
31-40
Received:
25 January 2024
Accepted:
26 March 2024
Published:
17 April 2024
DOI:
10.11648/j.ae.20240801.13
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Abstract: Cavities separated by multiple vertical partitions and filled with a porous medium present a remarkable thermal insulation quality, offering potential solutions in various engineering fields. The aim of this study is to analyze the impact of the presence of a porous medium on heat transfer through a partitioned cavity. We have developed a numerical model based on the Navier-Stokes and heat transfer equations, solved using Ansys Fluent software. We examine the evolution of the Nusselt number (convection and radiation) as a function of the position of the porous medium inside the cavity, as well as physical properties such as emissivity, wall conductivity and Rayleigh number. Current lines and isotherms are obtained from this numerical model. Nusselt numbers for both convection and radiation are calculated, taking into account the position of the porous medium in the system, as well as the effect of varying physical parameters on heat transfer. It has been observed that the presence of the porous medium leads to a reduction in the rate of heat transfer within the cavity. The further the porous medium is from the hot wall, the more pronounced this reduction. In addition, radiative transfer has a downward influence on convective transfer. Furthermore, the convective transfer rate decreases with increasing emissivity. As far as conductivity is concerned, transfer rates (convective and radiative) initially increase until a maximum Nusselt number is reached, after which they gradually decrease with a further increase in conductivity. Nusselt numbers (convection and radiation) increase as the Rayleigh number increases.
Abstract: Cavities separated by multiple vertical partitions and filled with a porous medium present a remarkable thermal insulation quality, offering potential solutions in various engineering fields. The aim of this study is to analyze the impact of the presence of a porous medium on heat transfer through a partitioned cavity. We have developed a numerical...
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Research Article
Application of Free Ball Check Valve Mixed Grouting Device
Yifang Liu*
Issue:
Volume 8, Issue 1, June 2024
Pages:
41-46
Received:
21 March 2024
Accepted:
7 April 2024
Published:
17 April 2024
DOI:
10.11648/j.ae.20240801.14
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Abstract: In recent years, due to the uneven water abundance of the aquifer and the complexity of the underground seepage field, the grouting reconstruction project of coal mining enterprises is more difficult. The previous method is to install a high-pressure ball valve before the grouting pipe connected to the grouting pump is connected to the mixing device, which can be manually adjusted when the number of grouting pumps needs to be changed. However, under certain pressure, the ordinary high-pressure ball valve often fails due to the influence of high-pressure mixed slurry, cement solidification and wear, and the number of grouting pumps cannot be increased or decreased in real time. In order to solve the problem that the mixing device of traditional grouting system is easy to fail by using ordinary high-pressure ball valve, the mixing device of free ball check valve was developed and applied in the process of treating the Ordovician limestone aquifer area on the floor of No.9 coal seam in Xipang Well. The practical results show that the pipeline can be automatically closed when a single grouting pump stops grouting, and there is no need to flush the grouting pipeline with a large amount of water, which can improve the grouting efficiency and quality, and the influence time of single hole section is reduced from 8.25h to 0.34h. The process performance can meet the requirements of efficient grouting.
Abstract: In recent years, due to the uneven water abundance of the aquifer and the complexity of the underground seepage field, the grouting reconstruction project of coal mining enterprises is more difficult. The previous method is to install a high-pressure ball valve before the grouting pipe connected to the grouting pump is connected to the mixing devic...
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