OPEN JOURNAL OF WATER POLLUTION AND TREATMENT In Press OPEN JOURNAL OF WATER POLLUTION AND TREATMENT Does ISO 14001 accreditation reduces environmental impact of industries: A case study in Addis Ababa, Ethiopia Alebel Abebe* School of environmental health science and technology, Jimma University, P.O. Box 1528. Jimma, Ethiopia. *Corresponding author: alebelab@yahoo.com Abstract: This study was designed to assess the performance of effluent treatment plants of ISO 14001 accredited industries in Ethiopia. Physico-chemical parameters were analysed from influent and effluent to determine pollutant removal efficiency. Same parameters were also measured on receiving water bodies. In total 224 tests were done by following scientific procedures. The result of the study showed that Biochemical oxygen demand (BOD5) removal efficiency for the accredited tannery was 29.6% and found within the recommended limit (25-35%) but quality of effluent released to the river didn’t fulfil the national discharge limit. Regarding Chromium, accredited and non-accredited tanneries were managed to remove relatively in a better efficiency (81.5% and 77% respectively) due to the installation of chromium recovery plant. There was no significant association (Mann-Whitney U Test, p-vale, > 0.05) on treatment efficiency due to accreditation. Therefore, monitoring is mandatory after accreditation is awarded in regular basis to ensure that they are complying with the principles of environmental management system. Keywords: Accreditation; ISO 14001; Effluent Treatment; Performance; Tanneries and Breweries 1. INTRODUCTION Every sectors of our society generate waste: industry, agriculture, mining, energy, transportation, construction and consumers. The environment can only absorb a limited amount of pollutants and if they are found above this critical limit, pollution is inevitable. Industrial wastes are generated from different processes and the amount and toxicity varies with its specific industrial processes [1]. Literatures pointed out that, numerous compounds generated from industrial processes are usually difficult and costly to be treated by merely conventional effluent treatment plants. So, pre-treatment of industrial wastes before discharging in to the municipal sewer or water bodies becomes an essential part of an overall water quality management programme [2]. ISO 14001 standards are developed as a system to provide evidence and confirmation that an orga- nization is committed to an effective EMS for environmental protection. This gives a proof that an EMS system is established, fully implemented, and documented. In fact, an organization would be in compliance with ISO 14001 when all the required requirements of the standards are met. The primary 1