Enhancement of streams water quality using in-situ filters

The conventional water resources in Egypt are limited to mainly the NileIRiver and groundwater. Egypt is optimizing the use of freshwater andexploring the use of new non-conventional sources of water, such asagricultural drains. Bilbeas and El-Qalyoubia drains are two of the mostpolluted water streams in Egypt. One of the proposed methods to enhance thedrain self-purification capacity is the use of submerged biofilter (SB).Four streams pilot were installed at KP 35.0 of Bilbeas drain, and two streamswere installed at KP 12.0 of El-Qalyoubia drain. The experimental work wasdivided into two stages. Stage ”1” was carried out in Bilbeas drain during theperiod (December 2005- July 2006). It included four runs, each two runspreceded by start up period. whereas stage ”2” was done during the period(June 2007- July 2007), and included one run preceded by start up period.At Bilbeas drain three of the streams were equipped with three differenttypes of media (pall rings, star shape and gravel) working as SBs while thefourth remained without any media to provide a corresponding reference forthe natural purification. The three biofilters had the same total surface area ofmedia -for biofilm growth, the same width, and depth, but differed in lengthin the flow direction. The four streams were operated at the same time underthe same flow rate.Results of the hydraulic study showed that, Pall rings medium has thehighest hydraulic conductivity (Kc) value of about 5.55 m/s, compared to 2.40and 1.51 m/s for Star shape medium and Gravel medium respectively.Pall rings biofilter achieved the highest percentage of flow passing throughthe clean media to the total applied flow rates (8.7 - 19.0%), followed by Starshape biofilter (8.6 - 18.0%) of the total applied flow rates, and finally gravel(2.6 - 5.1 %).11