الفهرس 
Wastewater characteristics and strategy for treatmentOnly 14 pages are availabe for public view
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Abstract
Chemically enhanced primary treatment (CEPT) or chemical preprecipitation is a wastewater treatment method that serves as an attractive alternative to the conventional primary treatment. In the present study,alum, sea-salt, and homogenous mixtures of alum and sea-salt were evaluated as coagulants using the analytical hierarchy process (AHP) to btain the best coagulant (type-dosage) according to multi-criteria.Consequently, CEPT was processed via the optimum model of swirl flow hydraulic clari-flocculator, which was developed after the steady state analysis versus the simulation using the computational fluid dynamics(CFD) software. Moreover, the design equations for the investigated hydraulic clari-flocculators were derived. The obtained results revealed that a homogenous mixture of 67% alum and 33% sea-salt by weight can be used with dose of 40 mg/L as a suitable coagulant in addition to a range between 60-90 m/d of surface overflow rate of the chemically enhanced primary sedimentation tank (CEPST) were the optimum conditions for CEPT of sewage. These conditions result removal efficiencies in the range between 52-70% of BOD5, 54-68% of COD and 76-88% of TSS. These results enable the primary sedimentation tank (PST) to accommodate double of its design capacity with very simple modifications in the raw sewage inlet to be CEPST according to the present study. In addition,CEPT maintains the operational conditions of the activated sludge system in the recommended limits. Finally, CEPT for upgrading a selected wastewater treatment plant as a case study is definitely advantageous in reducing of the capital costs by 30% and the treatment costs by 28%.