NOVEL APPLICATION OF SULFUR METABOLISM IN DOMESTIC WASTE-WATER TREATMENT

The feasibility of utilizing the symbiotic relationship of bacteria re lated to sulphur metabolism was investigated for organic matter remova l in a sludge blanket type reactor. The microaerophilic upflow sludge bed reactor (MUSE) relies on the interaction between sulphate reducing bacteria (SRB) and microaerophilic sulphide oxidizing bacteria (SOB), Beggiatoa, for organic matter removal. A five-stage MUSE reactor with a volume of 173 L was operated for 120 days at three hydraulic loadin gs. The efficiency of the process to remove total-GOD (T-COD), filtere d-GOD (F-COD), and suspended solids (SS) depended on the hydraulic loa ding. Maximum removals of T-COD, F-COD, and SS were 92%, 94%, and 87% respectively at hydraulic retention time (HRT) of 4.5 h. At a low HRT of 2.5 h, a F-COD removal efficiency of 89% could still be achieved. A lthough no granulation was observed, a dense flocculated biomass devel oped which exhibited very good settleability (SVI = 16 mL/g). While th e effluent SS increased at the lower HRTs of 3.5 and 2.5 h, the system still operated effectively without a secondary sedimentation tank. Su lphate balance, batch studies, and microscopic examinations indicated the proliferation of SRB and SOB, Beggiatoa, in the biological vessels . Although some COD removal took place by aerobic metabolism in the ae ration vessels, sulphur metabolism appears to be the principal mechani sm responsible for organic matter removal in the MUSE process.