الفهرس | Only 14 pages are availabe for public view |
Abstract Wastewater treatment has always been a major concern in the developed countries. Granular activated carbon (GAC) is a promising technique for removal of organics from water and wastewater. Although the use of GAC can be a rather expensive process, the cost can be greatly reduced by proper design of the treatment units. Over the last decades, activated carbon adsorption has gained importance as an alternative tertiary wastewater treatment. GAC as tertiary treatment to biological effluent was studied at Zenein Wastewater Treatment Plant, Giza. The aim of present study is determine the optimum GAC columns fixed and fluidized flow pattern (down flow & upflow modes), which could be applied for tertiary treatment of biologically treated wastewater. A pilot plant was designed and constructed at Zenien WWTP which consists of three plexiglas columns filled with GAC. The pilot plant was fed from the effluent of the secondary clarifier of Zenien plant, and operated for a period of about fourteen months. The’ experimental work was divided into four main parts namely; fixed carbon column, fluidized carbon column, comparison between fixed and fluidized carbon column and fmally dual sand / carbon columns.Results of experiments showed that triple fixed carbon column can produce a removal ratio of BODs and COD equal to 82 % and 59 %, while fluidized column 78 % and 58 %. BODs, COD, and TSS in the tertiary effluent using fixed GAC columns were 2.7 mg/L, 20.1 mg/L and 3.3 mg/L, which comply with the Egyptian Law No 48 for year 1982. Removal of BODs ill sand and carbon columns was equal to 40 % and 80 %, while COD equals to 45 % and 65 %. Removal of of BODs, COD, and TSS was improved by increasing the empt bed contact time (EBCT). A rate of filtration through GAC columns of 100 m3/m2/day, which is corresponding to an EBCT of 8 minutes was proved to be suitable and economical using GAC columns. Using sand column prior to GAC column tends to increase the life’ of carbon column and also improves the quality of treated wastewater. Sand column also tends to increase the removal of BODs and COD by 14 % and 30 % respectively, compared with single fixed carbon column alone. A mathematical model has been established to predict the values of removal of BODs or COD for single fixed column, knowing the initial concentration of BODs or COD, empty bed contact time (EBCT) and surface area of carbon grams. Economic analysis indicated that GAC columns could be economically competitive with the other alternatives of conventional physiochemical treatment processes. The cost estimates of tertiary treatment of Zenein WWTP effluent using GAC filters including capital and 0 & M costs, amounts to 0.50 LE/m3 of treated effluent based on regeneration interval of two months. This cost estimates could be reduced to 0.37 and 0.34 LE/m3 if the regeneration interval increased to 6 and 12 months respectively |