A study of a horizontal flow vertical fixed phase biochemical wastewater treatment reactor

A bench-scale horizontal-flow, vertical fixed-phase aerobic biological process was studied with reference to support media, biological growth and film characteristics, oxygen requirements, and organic carbon removal for retention times of 0.1-12 day. 1° Butyl alcohol, 2° butyl alcohol, and methyl ethyl ketone were the components in the waste stream. Butyl alcohol, both normal and secondary, were consumed more rapidly, by the biological film than methyl ethyl ketone, although total removal was equal. This was demonstrated by direct aqueous injection gas chromatography. Biological treatment was found to be impractical below an organic waste concentration of 50-100 mg/1 Biochemical Oxygen Demand (BOD). Exchange of soluble biological intermediate and end products for organic wastewater components maintained approximately the same organic concentration in the process effluent. Oxygen requirements were found to be 400 m3 /kg-BOD loading for the diffuser at a depth of 4 inches. This corresponds well with a calculated value of 425 m3/kg-BOD, using the relationship that oxygen transfer rate is proportional to 0.7 exponent of the diffuser depth. The aerobic zone of the biological film was shown to have a maximum thickness of 2-3 mm. Polypropylene plastic mesh was shown to be a more satisfactory support media than cotton or nylon netting because it was relatively impervious to biological attack and was structurally superior.