Proceedings of the 13 th International Conference of Environmental Science and Technology Athens, Greece, 5-7 September 2013 TREATMENT OF TROPICAL DOMESTIC WASTEWATER BY UASB REACTOR INOCULATED WITH EFFECTIVE MICROORGANISMS CONSORTIUM - COD AND SUSPENDED SOLIDS REMOVAL MAALIM, M.K 1 , MGANA, S.M 2 , MBULIGWE, S.E 2 , KASSENGA, G.R 2 AND MOHAMED, S.M 1 1 Institute of Marine Sciences, University of Dar es Salaam, P.O. Box 668, Zanzibar Tanzania, 1 School of Environmental Science and Technology, Ardhi University, P.O. Box 35176, Dar es Salaam, Tanzania, E-mail: maalim@ims.udsm.ac.tz EXTENDED ABSTRACT The effluent from UASB reactor often contains residual COD and TSS that must be further reduced through post treatment so as to meet effluent disposal standards. In this study, Effective Microorganisms (EM) consortium was inoculated at the ratio of 1:500 in the UASB reactors to ascertain its impact on improving removal efficiency of both COD and TSS. Laboratory scale UASB reactors with effective volume of 4L made of PVC pipe with internal diameter of 100mm were used. Three experimental set-ups were organized and operated for 60 days to investigate not only performance of the reactor but also to investigate the best configuration for EM consortium inoculation. Set-up A comprised of two individual reactors without and with EM (R1 and R2 respectively); Set-up B (R2*) and Set-up C (R3) both comprised of two sequential reactors where EM consortium was injected at the inlet of the second reactor and first reactor. The findings of the experiment showed a significant contribution of EM consortium to the removal efficiency in R2, R2* and R3 reactors compared to conventional UASB reactor (R1) whereby the COD removal were 85±10%, 84±14%, 85±15% and 76±13% respectively. Similarly TSS removal was 90±9%, 91±9%, 91±9% and 82±13% correspondingly. However, reactors inoculated with EM showed insignificant impact in performance regardless of reactor configuration. Similar results were generally obtained for all forms of COD fractions. The COD mass balance depicted that EM consortium was not consumed as a substrate but rather enhanced bioconversion anaerobic processes in the UASB reactor. This study shows that EM consortium can be applied in the UASB reactor to improve removal efficiency of COD and TSS so as to produce better effluent quality of the wastewater, which has less pollution load for consequent post treatment. However, more research is needed to study the optimum percentage removal of these pollutants to the extent that the post-treatment might not be necessary. KEYWORDS: UASB, COD, TSS, EM, wastewater 1. INTRODUCTION There has been a growing interest in anaerobic treatment of wastewaters (Azimi and Zamanzadeh, 2004) and they have already been applied for the number of waste streams (Foresti, 2001). A better understanding of the microbiological and hydraulic mechanisms that regulate the anaerobic systems has contributed to the development of more compact and modern high-rate reactors, such as the Upflow Anaerobic Sludge Blanket (UASB), which combines operational simplicity and efficiency (Miranda et al., 2005). The UASB reactor offers great promise (Van Haandel and Lettinga, 1994; Gnanadipathy and Polprasert, 1993) and thus appears popular for both high and low