|M.Sc Thesis||Department of Civil and Environmental Engineering|
|Supervisor:||Prof. Emeritus Narkis Nava|
The conventional biological sewage treatment neither achieves the water quality needed for reuse purposes, nor environmental pollution protection. In order to remove contaminants from biological treatment, the tertiary treatment is applied, based on physico-chemical processes, such as flocculation, settling, filtration and adsorption on granular activated carbon.
In this research, an investigation was carried out on an advanced tertiary treatment of municipal sewage treatment plant effluent, utilizing a simultaneous combination of adsorption on powdered activated carbon, PAC, and flocculation with alum, or ferric chloride, performed at the same reactor.
Flocculation removes the colloidal and suspended solids, some of the soluble organics and the phosphorus compounds. However, the effluents following flocculation and settling still contain residues of soluble organics.
Adding powdered activated carbon to the secondary effluents, 5 minutes prior to adding the flocculant, considerably improves the efficiency of removing various organic polluting parameters. Powdered activated carbon removes particularly the soluble organic substances and acts as coagulant aid to improve the flocculation and clarification processes. As a result of PAC addition, there was a reduction in the optimal flocculant doses required for good clarification.
The advanced treatment by simultaneous PAC adsorption and flocculation generates high quality water, suitable for reuse.
The combined process, performed simultaneously in the same reactor, saves constructing new treatment facilities, such as adsorption on granular activated carbon column, and may improve water quality in case of over loading, or unexpected inflow of hazardous organics at the Municipal Sewage Treatment Plant.
The combined treatment might be useful as a pre-treatment before membrane processes, in order to reduce membrane fouling, enhance membrane flux and prolong the life of the membranes.