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Accueil du site → Doctorat → Royaume-Uni → 1997 → Guidelines for design of an integrated instream water reclamation system supported by a high-performance aeration weir

University of Southampton (1997)

Guidelines for design of an integrated instream water reclamation system supported by a high-performance aeration weir

Bayoumi, Mohamed Nabil

Titre : Guidelines for design of an integrated instream water reclamation system supported by a high-performance aeration weir

Auteur : Bayoumi, Mohamed Nabil

Université de soutenance : University of Southampton

Grade : Doctor of Philosophy (PhD) 1997

In arid and semi arid regions, reuse of drainage water for irrigation can dramatically increase the overall water use efficiency. In Egypt, introduction of raw sewage in agricultural drains increase the health risks associated with the reuse of drainage water. The essential treatment in this case can readily be achieved by waste stabilization ponds but in Egypt where fertile land is very expensive, an instream water reclamation system is suggested as an alternative to the pond system. This thesis investigates the possibility of establishing a two reach system in open drains supported by a drop structure that can improve the self-purification process in streams to achieve reduced risk in the reuse of drainage water. The US-EPA water quality model Qual2EU has been used to study the influence of the physical dimensions of the drain on the water quality and to determine the modified design of the drain that can achieve the required level of treatment. The simulation results indicate that for a given discharge of 0.5 m$\sp3$/s and initial BOD concentration of 40 mg/l, increasing the cross-sectional area of the first reach to 24 m$\sp2$ for a length of 0.6 km succeeded in providing sufficient retention time to lower the BOD concentration to around 10 mg/l. However, the major drawback of the proposed reclamation system was identified as the lack of oxygen supply in the first reach which resulted in the initiation of undesired anaerobic biological processes and consequently aeration weirs were suggested to assist in the oxygenation of the water. Experimental results for two physical models of an innovative design of a lateral outflow drop structure achieved a three fold increase in aeration efficiency over that of linear weirs, especially at low heads and flow rates. The aeration efficiency of the lateral outflow was found to be 55-60% for a one metre drop operating under flow rates that ranged between 10 and 100 ls/m which corresponds to 24-46% for linear conventional weirs. Eventually, a mathematical expression for the prediction of aeration efficiency over the studied structure was developed using multiple regression techniques. The construction of a one metre high, lateral outflow drop structure, was found to be sufficient to raise dissolved oxygen concentration from zero to above the standard level of 5 mg/l. This means that in lands of mild slope, an aeration weir can be used at the end of the first reach in order to maintain high dissolved oxygen content in the second reach. If more head is available undesired anaerobic processes can be converted into facultative conditions of better water quality in the first reach with a total drop height of 2.5 and 1.5 m, for initial BOD concentrations of 40 and 30 mg/l respectively.

Mots clés : Egypt, wastewater treatment, Applied sciences, Environmental science, Health and environmental sciences, Environmental engineering

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Page publiée le 2 mars 2015, mise à jour le 23 mars 2017