Model studies on granular activated carbon adsorption in fixed bed filtration

The removal of natural organic matter (NOM) using a continuous flow fixed bed granular activated carbon (GAC) column was studied and the results were then fitted with the Adams-Bohart, Bed-Depth-Service-Time and Clarks models. The GAC, KI-6070 and KI-8085 used in the study had external surface areas of 277 m2/g and 547 m2/g, respectively. Adsorption of NOM by the GAC was complex and involved more than one rate-limiting step. The critical bed depths for KI-6070 and KI-8085 were 0.24 m and 0.3 m, respectively. The Clark model was more effective in simulating the absorbent breakthrough process as compared to the Adams-Bohart model. The lower empty bed contact time (EBCT) i.e. 15 minutes gave a better fit to the Clark Model as compared to EBCT of 20 and 30 minutes.

Performance of an extended aeration-microfiltration (EAM) reactor in treating high strength industrial wastewater

A laboratory study was conducted on an Extended Aeration-Microfiltration (EAM) reactor in treating a food industry wastewater. The reactor contained horizontally laid hollow fibre microfiltration (MF) units that were fully submerged. The MF units were connected to a peristaltic pump that was used to extract permeate continuously under suction pressure. Continuous aeration from beneath the modules provided the crossflow effect to the MF units. Active activated sludge was used in the start-up where the sludge was mixed together with the feed water at a Food/Microorganisms (F/M) value of about 0.1. Primary effluent with Chemical Oxygen Demand (COD) values ranged between 1,500 and 3,000 mg/l was used as feed water. The EAM reactor was operated for nearly three months without initiating cleaning of the MF units. A suction pressure of 0.9 bar and Mixed Liquor Suspended Solids (MLSS) of over 5,500 mg/l were reached when nearing the end of the three month operation period. Permeate COD and turbidity reduction of over 97% and 99% respectively, were achieved. Prior to this, the MF module arrangements were studied; where vertically arranged modules were found to perform poorly as compared to the horizontally laid modules, in terms of clean water permeate flux.