The Need
The City of Tlacolula, with about 20,000 residents, is served by a highly insufficient pond wastewater treatment system. Currently, the plant discharges the equivalent of raw wastewater to the Oaxaca Valley watershed. The City is working with Engineers Without Borders (EWB) and the Autonomous University of Benito Juarez in Oaxaca (UAJBO) to use wastewater as a resource for agriculture and to create a community park focused on recreation, education, and tourism through a beneficial use plan. The project goals provide the municipality with an upgraded design incorporating natural wastewater treatment systems to reclaim wastewater for agriculture. The project increases public awareness on the importance of wastewater treatment, demonstrates natural treatment system technology, diversifies wildlife habitat and boosts the microeconomy.
The EWB-NCP Response
The EWB California North Coast Professionals (NCP) Chapter conducted their official project assessment in February 2008. Details were gathered through a community health survey, and surveys of the existing system and surrounding lands. In addition, UABJO was sampling the system to characterize performance through their ongoing outreach program. The determination is that the existing treatment system is severely overloaded and may be contributing health risks in the area.
What Was Done
The NCP team toured the existing facility and met with the Municipal President, City Engineer, and Director of Ecology to discuss project needs and goals. The team met with UABJO to review water quality data and to conduct evaluation of process performance. Initial surveys of the site were performed along with discussions with the community to identify the reasons behind the unusually high organic loading entering the system. The team developed initial estimates to achieve community goals with a low-energy, low-cost system and coordinated with UABJO to have the necessary areas for the treatment system expansion topographically surveyed.
Following up
In March 2008, the team provided Tlacolula and the Oaxaca State Engineer with preliminary system upgrade plans, a project description, and a materials estimate. The upgrade plans utilize the existing pond system, provide a redundant pond system, and add enhancement wetlands to improve water quality. The system accommodates thirty years of growth.
Moving Forward
The NCP team and UABJO continue to collect water quality and flow data, topographic survey, and geotechnical report to refine the design. The team will return in July 2008, finalize the design in subsequent months, provide engineering assistance during construction, and support the beneficial use plan.