GAS HOLD-UP, MASS-TRANSFER, AND TREATMENT EFFICIENCY OF AN UPFLOW SLUDGE BLANKET SEQUENCING BATCH AIRLIFT REACTOR FOR THE TREATMENT OF HIGH-STRENGTH DOMESTIC WASTEWATERS

A sequencing batch wastewater treatment process was developed in a 200 litre air-lift reactor using a synthetic wastewater feed solution wit h a chemical oxygen demand (COD) of approximately 1050 mg/l. The purpo se of these experiments was to conduct a preliminary investigation int o the potential of the air-lift reactor as part of a wastewater treatm ent process. The static Fill stage of the sequencing batch reactor (SB R) operational mode had an upflow feed of wastewater through a sludge blanket, which remained in the reactor from the previous cycle. This w as followed by Aerated React, Settle and Draw stages. All stages were confined to the single reactor. The mixed liquor suspended solids conc entration (MLSS) was maintained at approximately 2500 mg/l. Reactor pe rformance was found to be excellent with a mean COD removal rate of 99 .6%, mean final effluent suspended solids of 4.9 mg/l, and sludge volu me index (SVI) of 67.2 ml/g MLSS. These preliminary results indicate t he potential of the sequencing batch air-lift reactor wastewater treat ment process. Gas hold-up and mass transfer coefficient studies were a lso conducted over a range of MLSS values which were representative of activated sludge treatment processes, as well as solids concentration s found in aerobic digesters. The gas hold-up and mass transfer coeffi cients, K(L)a, were not significantly affected by the varying concentr ation of MLSS, over the range of values examined. The air-lift reactor was found to meet the oxygen demand needed for both the activated slu dge and aerobic digestion processes.