The characteristics and performance of solid-liquid separation of raw sewage using floating media and multiple inlets were studied using pilot-scale equipment. Particles over 7 µm, representing approximately 80% of SS and 50% of BOD in raw sewage were efficiently removed. Smaller particles and soluble components, comprising a large part of total BOD, were difficult to remove by filtration. The maximum SS removal ratio (SSRR) and SS quantity removed per unit filter surface (SSR) was achieved using a medium size of 5.5 mm and a filtration rate of 150 µm/d. Inlet switching to a lower position significantly extended the filter run lengths and increased the total SS removed by filtration. Using 5.5 mm filter particles and a 150 m/d filtration rate, 80-89% of SS was removed, 38-42 kg of SS was removed per unit filter sectional area, and filter runs were 55-65 hours. The backwash-filtrate ratio was around 2%. The space requirement of this system will be significantly smaller than the ordinary primary treatment system judging from the trial design of a prototype plant.
Pilot Plant Studies on Filtration of Raw Sewage Using Floating Filter Media and Multiple Filter Column Inlets
Mitsuo Mouri, Chiaki Niwa; Pilot Plant Studies on Filtration of Raw Sewage Using Floating Filter Media and Multiple Filter Column Inlets. Water Sci Technol 1 October 1993; 28 (7): 143–151. doi: https://doi.org/10.2166/wst.1993.0155
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