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Development of Environmentally Sustainable Methods for Treatment of Domestic Wastewater and Handling of Sewage Sludge on Yap Island
1  University of Guam

Published: 31 October 2014 by MDPI in The 4th World Sustainability Forum session Sustainable Engineering and Science
Abstract: A survey was conducted of the wastewater treatment systems and related sludge handling practices on the island of Yap in the Federated States of Micronesia to assist in identifying areas where further work would be merited to improve on effectiveness and sustainability. A detailed inventory was made of communal septic tanks as found at health centers and schools. The precise location of each unit was determined using global positioning and the general condition and functionality were documented. Though most of these septic tanks appeared to be fully functional, there were concerns due to some units being positioned within the tidal zone, covered over with vegetation, or out of reach of the pump truck. The only centralized wastewater treatment plant on Yap consists of an Imhoff-tank system, which services 300 connections in the town of Colonia. The system provides only primary treatment consisting of a limited removal of suspended solids, thus essentially raw sewage is being discharged to the bay. Excess sludge is drawn from the Imhoff tanks on a quarterly basis, which following drying is supposed to be transferred to the landfill; however, local farmers regularly take it for use as fertilizer without adequate treatment. As an immediate target for further study and pilot testing, exploring the use of an attached-growth process as an inexpensive retrofit to enhance the treatment power of the Imhoff-tank system is presented. In addition, the implementation of a composting program for recycle of waste sludge in a safe manner and the development of a framework for management of septic tanks are proposed.
Keywords: Wastewater treatment; septic tanks; waste sludge; attached growth; composting