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Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Applied Engineering in Agriculture. Vol. 21(2): 271-274. (doi: 10.13031/2013.18150) @2005
Authors:   J. Xi, K. M. Mancl, O. H. Tuovinen
Keywords:   Biochemical oxygen demand (BOD5), Chemical oxygen demand (COD), Wastewater treatment, Food processing waste, Sand filtration

The purpose of this study was to examine the transformation and accumulation of carbon during gravel/sand filtration of cheese-processing wastewater. Carbon was fractionated using chemical oxygen demand (COD), biochemical oxygen demand (BOD5) and a carbon analyzer. The experimental design was based on 12 columns containing layers of sand and gravel. The 12 columns were divided into duplicates of six groups of experimental treatments. Each group received a different loading rate, dosing frequency, pH, or received supplemental air for seven months. In every case, BOD5 removal from the wastewater exceeded 99% for all treatments, making gravel/sand biofilters a feasible treatment option. Dosing the system 12 times per day rather than only once per day slowed the progression of filter clogging. The differences in clogging could not solely be explained by the accumulation of organic carbon in the filter. The wastewater had an initial pH of 12.7, which decreased to pH 8.5-9.0 during treatment. Adjustment of pH to circumneutral values did not influence BOD5 removal but did enhance the degradation of the slowly degradable organic carbon trapped in the filter matrix over the seven months of the experiment.

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