University of Khartoum

The Influence of Some Parameters on Pond Design

The Influence of Some Parameters on Pond Design

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Title: The Influence of Some Parameters on Pond Design
Author: Ali Mohammed, Zeidan
Abstract: The stabilization of organic matter and the BOD removal is a very complicated process due to the interaction of various parameters and environmental conditions. With this regard, the major role is referred to the microbiological agents, which control the biochemical reactions with the aid of the various parameters. Accordingly, unexpected problems may arise, owing to some conditions developed within the pond. Generally, some of the parameters that affect significantly the BOD removal rate and the overall performance of the pond are reviewed and related in this study. The influential parameters include solar radiation, photosynthesis, dissolved oxygen, nutrierlts, temperature, organic loading depth, toxicity and heavy metals from industrial wastes, sludge accumulation, detention times, thermal stratification, mixing characteristics and hydraulic flow patterns, pH, oxidation reduction potentials, and the removal rate constant. Despite the significance of these parameters and factors on the pond performable, it was rather difficult to combine them in proposed design models. Waste stabilization ponds are, usually, designed according to empirical or rational design equations based on monitoring of laboratory scale or pilot scale ponds, regarding simple design criteria such as detention time organic load and temperature. However, the hydraulic flow regime is, usually, regarded as one of the two extreme conditions, plug flow or complete mixing, despite the fact that ponds exhibit neither or them. The normal conditions at flow, or the realistic mixing conditions occurring in ponds are the non ideal flow, or the partially mixed conditions. Based on the kinetic reactions aspect, and the non ideal flow conditions, the BOD removal rate is regarded as a function of temperature, detention time, organic loading, and the degree of mixing or flow pattern which could be expressed by the dispersion number. The lack of field data related to the various parameters mentioned before, restricted the area of this study on the above three mentioned parameters as the most effective parameters on the pond overall performance. The first-order BOD removal rate constant is regarded as the principal design parameter in the proposed design equations. The Wehner-Wilhelm equation, of the partially mixed conditions is adopted in this research as the most appropriate equation that can depict the actual performance of the pond. Dispersion number, detention time and the removal rate constant are included in this equation. The regression analysis carried out in this work has been done by using computer programmes for the available data collected from literature, in order to study the correlation between the first-order removal rate constant and temperature, detention time, and organic load. The results revealed higher correlation. The correlation coefficient were found to be 0.9262, 0.9048, 0.9582, and 0.9888 corresponding respectively to temperature, organic load at constant, hydraulic load, organic load at varying detention time, and detention time. The verification of the various correction factors suggested by researchers (4,28 ,48,49,74) for the removal rate constant was carried out herein. The result obtained from the analysis of the available data has shown the inadequacy of some factors such as that of the organic load. Although the suggested correction for detention time has shown better results, the combined effect of organic load and detention time on the removal rate constant revealed higher correlations of 0.9927-0.9948. Since the various parameters expected to have a combined effect on the really existed pond performance, a new relationship has been suggested herein to estimate the design value of the removal rate constant as a function of temperature, organic load, detention time, and dispersed flow.
URI: http://khartoumspace.uofk.edu/handle/123456789/14255
Date: 2015-06-23


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