Kilómetro 71, Villanueva
Sanitation, Treatment Plant
Although there is no direct data or evidence that the stabilization pond at Kilómetro 71 is experimenting loading-related loss of performance, it is believed that expanded capacity is necessary, primarily as a result of population growth in the area.
Expansion is necessary because the stabilization pond was designed to serve approximately 10,000 people and the tributary community is now significantly larger. No effluent sampling is performed and none is planned. These lagoon systems, this one being anaerobic due to site constraints and resulting depth, are very robust in meeting their primary purpose, which is helminth egg removal.
Helminth eggs originate from parasitic worms such as ringworms, roundworms, and tapeworms. They cause a variety of digestive health issues that can be fatal to the young, sick, or elderly. Research by Dr. Stewart Oakley, University of California State at Chico, suggests that regardless of loading, these lagoons are extremely effective in helminth egg removal.
Settlement is the primary egg removal mechanism, and the typical egg concentration in the lagoon sludges is indicative of this. Of more concern than the reported overloaded operational condition is the current depth of sediment in the lagoon.
The sludge depth is reported to be at 80% of the total lagoon depth, so sediment removal is the most immediate need for the Km 71 lagoon. It is expected that the helminth eggs will be washed out if the sludge depth gets close to the surface. The result is complete loss of performance at which point the lagoon will become a public health threat to the community as eggs are discharged to the nearby Chamelecón River.
The municipality of Villanueva prioritized the following additional needs related to the Kilómetro 71 sewer system and treatment plan. Expansion of the stabilization pond was the top priority, followed by adding a collection system for the Nuevo Chamelecón community and tying it into the same network.
The municipality believes that approximately one kilometer of sewer trunk line needs to be installed to carry the increased capacity. The sewer collection system at Kilómetro 71 also needs to be cleaned out of debris to reduce odors and improve performance. Finally, the community of Vista Hermosa needs repairs to the sewer collection system, and possibly additional sewer lines.