1997 Volume 33 Issue 4 Pages 223-232
Improvement of eutrophicated lake water by biological treatment processes equipped with fixed bed, fluidized bed and their hybridized bed reactors packed with non-adsorbing or adsorbing contact materials was examined at bench scale level in situ. In the fixed reactor with nonadsorbing media, such as string, honeycomb-like tube and ceramics, particles like chlorophyll a (chl.a) as well as suspended solid (SS) were reduced with the removal of 30-50%, however removal efficiency of dissolved organics was very low. Removal capacity of chl.a and SS was as follows. String>Ceramics>Honeycomb-like tube. In the fluidized bed reactors with adsorbing granular activated carbon (GAC), total organics carbon (TOC), and dissolved organic carbon (DOC) as well as chl.a and SS were efficiently removed in comparison with the fixed reactors with non-adsorbing media. The removal was in the following order. Coal GAC (F-400) >Palm GAC>Coal GAC (Kureha) and Porous ceramic pellet. Removal efficiency of chl.a, SS and TOC were over 50%, and that of DOC reached about 60%. When GAC was granulated, chl.a and SS were reduced twice, comparing with the non-granulated GAC. There was a good correlation between the removal of chl.a and the number of microanimals appeared on the carriers in all of the bioreactors. In the survey of the attached microanimals on the biofilm, protozoan of Vorticella, Trochilia and sarcodina such as Euglypha and Centropyxis, and metazoan Philodina were found to contribute to the reduction of chl.a and SS on the non-adsorbing media. The efficient removal of dissolved organics from algae by the reactors with GAC was considered to be due to the activated bacteria and/or the attachment of suitable bacteria for utilization of the organics, not depending on the amount of bacteria.
