Bin-Le Lin* and Masaaki Hosomi**

* Institute of Industrial Science, University of Tokyo
** Department of Chemical Engineering, Tokyo University of Agriculture and Technology

+ Correspondence should be addressed to Masaaki Hosomi:
(2-24-16 Nakamachi, Koganei, Tokyo 184-8588, Japan)

Abstract

The use of sulfur-oxidizing bacteria (SOB) in corporation with granular activated carbon (GAC) to treat photo-processing waste (PW) has been established as one of the most effective options. Breakthrough behavior of GAC during the continuous treatment using an SOB/GAC system was studied in this paper, in which a hypothesis has been proved that GAC effects as biological activated carbon in adsorbing the toxic/refractory compounds contained in PW therefore simultaneously enhancing the activity of SOB sludge. Long term continuous treatment (about 400d) was performed during a range of thiosulfate (S2O32-) load and the hydraulic retention time (HRT) fixed as 0.8-3.7kg-S2O32-/l/d and 7.7-1.9d, respectively. The results demonstrated that the treatment effectiveness trends to worsen every period of 3 or 4 months, i.e., reactor pH, the dissolved organic carbon (DOC) and S2O32- in the effluent increased gradually, while formation rates of sulfate (SO42-) decreased to about 50%. During the 400 days treatment, three cases of worse trends were observed, and were then recovered by just renewing the GAC in the reactor. This suggests that absorption of GAC progressed in parallel with its regeneration, and then reached its saturation point while its further regeneration ability lost. Thus, to further clarify the adsorption capacity of the spent GAC, its equilibrium and comparison experiments with new GAC were examined, which confirmed that the spent GAC has been reaching breakthrough situation with no further adsorption capacity.

Key words: biological activated carbon, breakthrough, sulfur-oxidizing bacteria, photo-processing waste, continuous treatment.