Vitaliano V. Fernandez
This research aimed to determine how much the main source of Cebu water supply was polluted by measuring water quality indicators;BOD, COD, NH3+, NO2-,NO3-,and PO43- at Buhisan river from May to September. The main objectives were to determine the values of water quality indicators and to compare the results among different sites along the river. Three(3) sampling stations; upstream, midstream, and downstream were set up. At each sampling station, samples of riffle and pool were taken separately. The upstream is located in Sitio Taytayan in Barangay Buhisan, the midstream is located north of Barangay Guadalupe and south of Barangay Punta Princesa, and the Downstream is at Barangay Duljo Fatima. Two(2) five hundred(500) mm bottles of samples were collected at each sampling site to measure DO. Initial DO readings were done at the site of sampling right away or done in less than two hours from the collection. The bottles of samples were taken home to incubate for five(5) days before measuring DO for the second time. The differences between the first and second DO reading were the BOD. It can be said that the higher the difference of initial and second readings of DO is, the more polluted the river is. To determine the BOD, the electronic measurement device was used and to measure the rest of the indicators, the colorimetric methods were used respectively.
The upstream of the river belonged to Class C set by DENR. This water is suited for propagation and growth of fish and other aquatic resource. The mid and downstream of the river belonged to Class D set by DENR. This water is suited only for agriculture, irrigation, livestock. Flushing effect of rains contributed to the good result of BOD, and COD compared to the benchmarks. Nitrogen and phosphate were higher than the benchmarks due to the excessive use of detergent for laundry, fecal waste, and run off nutrients by piggery farms and vegetations. Often times at upstream, the residence were doing laundry at the time of sampling. In midstream and downstream, human fecal matters, garbage, cycling gears, and plastic bags were observed all the time.
Based on the findings, the researcher concluded that the water quality indicators in pool and riffle were not different from each other, that phosphate and nitrate were above the benchmarks set by EPA and DENR , and that river is more polluted in dry season than rainy season. During rainy season, the rainfall washed off the accumulated pollution including fecal matter, and garbage. It means that the river is cleaning itself. Further study is recommended at the mouth of river near the sea since accumulated pollution stay in the place in rainy season. It is also recommended to study throughout a year to get a better grasp of seasonal variation
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