Efficiency and social acceptability of the constructed wetland of Bayawan City, Negros Oriental [Philippines]

In principle, the constructed wetland as a wastewater treatment facility cleans dirty or contaminated water by filtering it through the soil and the root zone of the reeds. These reeds are filled with aerobic and anaerobic bacteria known to decompose organic and inorganic materials. The treated waste water is then directed into a collecting sump-a reservoir or tank as a drain or receptacle for liquid to be salvaged or further disposed of - which will then be pumped into the header tank for storage or reusing in construction works, irrigation, fire fighting, and home gardening. The physical and chemical parameters of the treated wastewater showed significant improvement when compared with the untreated wastewater. Specifically, the constructed wetland was able to improve total dissolved solids by 54%, dissolved oxygen from 0 mg/L to 6.25 mg/L, phosphate by 62%, biological oxygen demand (BOD) after 5 days by 99% and total coliform by 71%. The color and odor of wastewater greatly improved from dark gray and noxious into colorless and odorless, respectively. The average phosphate content of the untreated wastewater was 40.90 mg PO4-P/L while treated wastewater showed an average of 15.52 mg PO4-P/L. This represented a significant reduction from the original P content of the untreated wastewater. However, this value was still high when compared to the DENR [Department of Environment and Natural Resources, Quezon City, Philippines] standard of 0.1 mg PO4-P/L of water. But this phosphate level was comparable with treated wastewater of constructed wetlands in several countries suggesting that the case of Bayawan City was within the norm of similar facility elsewhere (Vymazal 2005). The average total coliform count of the untreated wastewater was 33,566 CFU/mL while the treated wastewater showed a significant decrease of 9,733 CFU/mL. However, the E. coli level in the treated water was still high as compared to the DENR standard of 1,000 mpn/100 mL. The social acceptability level of the constructed wetland by GK [Gawad Kalinga] village residents was seemingly high as compared with those residing outside the resettlement site but near the facility. This favorable sentiment was expressed on the agreement with the GK residents on the following issues: reasons for its establishment, effectiveness in its functioning benefits to the community, worthiness of the investment, and establishment of more engineered wetlands.