Using stabilization ponds and constructed wetlands to treat Laguna de Bay wastewater
Continuous depletion of the country's water resources stresses the need for wastewater treatment facilities. However, current technologies used consume large amounts of energy and chemicals that are found harmful to the environment. Thus, stabilization ponds and constructed wetlands can be better alternatives in treating wastewater.
Water hyacinth (Eichhornia crassipes)
This is according to Dr. Zenaida Andrade, head of the Chemical Engineering Department, Eastern Visayas State University, during the SEARCA Agriculture and Development Seminar Series (ADSS) held 16 June 2010.
Her dissertation aimed to design a technically suitable natural wastewater treatment facility by assessing the physico-chemical and microbiological characteristics of wastewater in Paete, Laguna. The area is one of the 32 municipalities covering the entire Laguna de Bay basin. It was chosen as the pilot site because it is said to be the "receptacle" of various pollutants coming from domestic and agricultural wastes within the Bay.
As part of her study, she characterized wastewater sampled in five sites and computed specifications for the proposed treatment system design based on the area's topography, climate, and soil type. She pointed out that like natural wetlands, which filter water and trap sediments before entering a body of water, the constructed wetland also employs ecological processes found in natural wetland ecosystems. It is an engineered system using natural treatment processes to reduce pollution levels in wastewater.
On the other hand, a stabilization pond is a large shallow excavation that receives sewage from a sewer system. She explained that the combination of soil, plants, and microorganisms efficiently remove organic pollutants, nutrients, and toxic contaminants in water using a variety of physical, biological, and chemical processes.
She enumerated some floating aquatic plants that could serve as phytoremediators – vegetative species used for in situ treatment of areas polluted by various hazardous substances. These include water lily (Nymphaea odorata), water hyacinth (Eichhornia crassipes), and swamp cabbage (Ipomoea aquatica).
Constructed wetlands have been effectively applied in Western countries for decades and the Philippines has also joined the bandwagon in recent years, she further explained. She also noted that aside from treating wastewater, there are additional benefits derived from the system. They provide an opportunity to create or restore wetlands for environmental enhancement such as wildlife habitat, greenbelts, and other forms of recreation associated with ponds. However, constructing the said system requires the acquisition of a large land.
Results of this study can help enhance the implementation of the Philippine Clean Water Act of 2004 (Republic Act 9275) as well as the rehabilitation of an aquatic ecosystem (i.e., Laguna de Bay). Likewise, it could serve as a vehicle of change toward developing more positive environmental values for citizens residing near the lake.