Within the process of biological wastewater treatment aerobic and anaerobic bacteria degrade organic compounds und pick up nutrients for their growth. As a result sewage sludge occurs as a by-product of the wastewater treatment process. Depending on the characteristics of the raw wastewater, pollutants and toxic substances such as heavy metals accumulate in the sludges. Therefore sewage sludges need to be treated adequately and disposed of safely in order not to harm the environment. In Ethiopia many industries, especially the textile and garment sector are organized in huge industrial parks.
The facilities are equipped with a centralized common effluent treatment plant (CETP). Currently there is no overall strategy for characterization and disposal of sewage sludge in place. Within the framework of a GIZ project, Henning Zeich conducted a 10-days field visit to Addis Ababa in February 2018. The main objective was to understand the current situation and practice of sludge management as well as the institutional framework conditions. At the End of the stay a half-day workshop on best practice and sludge treatment approaches from Germany was carried out.