Abstract:
ABSTRACT
Clean drinking water initiative project (2005-06) of Ministry of Environment, offered five types of filtration systems to treat waters which could be polluted with one or more of pollutants such as Ca2+ Mg2+ NOG, F etc other than turbidity. Institute of Environmental Science and Engineering, at National University of Sciences and Technology, designed and fabricated a standard filtration unit capable of treating any or all of the pollutants in the single system. Major aim of this study was to test the performance of IESE designed filtration unit for turbidity and ionic pollutants e.g. Ca+2, Mg*2 , F, N03 - etc removal at pre-selected flow rates. After construction and hydraulic testing of the system with and without filtering media, the system was subjected to (i) IESE stored tap water (ii) IESE Low turbidity tap water (iii) Dry weather raw water from Khoker Zer reservoir Chakwaal, and (iv) Ground water from H-12 Campus of NUST. At hydraulic loading rate of
8.5gpm/ft2 i.e. 0.55BV/min, the system showed 40% and 6.67% turbidity removal efficiency for untreated waters (i) and (ii) per cycle respectively. Keeping in view the high turbidity of Khoker Zer reservoir Chakwaal water and H-12 ground water, pre-sedimentation and batch/in-line coagulation was applied, which helped improving the filter efficiency. Using batch coagulation process, plant exhibited
32.3% and 70% removal efficiency against treated waters (iii) and (iv) per cycle respectively under the filtration rate of 5.7gpm/ft2 while using in-line coagulation process, for the same waters and operating conditions, plant showed removal efficiency of 80% and 90% per cycle without any settling time. Non-availability of enough quantity of water did not allow reaching the break-through period in any
case. The system was therefore, subjected to effluent recycling which improved quality after each cycle. In order to overcome the water shortage problem, a mini filter system was devised based upon the scale-down approach. This system was operated at 2.2 gpm/ft2 i.e.0.52BV/min. This system comprised silica sand column, cation and anion exchange media column. This new system over all using three filter media, removed turbidity up to 98.7%, total hardness 93.7%, Calcium 94.3%, Magnesium 93.2%, Nitrate 97.9%, Fluoride 98.2%, Chlorides 98.5% Sulfate
89.2%, TDS 94.1% and pH changed from 8.11 to 5.28. It was concluded that IESE designed filter could remove these pollutants effectively if operated at lower HLR
(8.5 gpm/ft2 or below) with enough quantity of feed water.
