Macrophyte biosorption system of Molawin Creek to reduce plant nutrient and heavy metal pollution of Laguna de Bay [Philippines]

A study was done to explore the effects of installing a macrophyte biosorption system (AMBS) cross the Molawin Creek, and use the positive results as bases for carrying out the initial steps towards a sustained community-based restoration, protection and conservation program for this body of water. Initially, the baseline physico-chemical conditions in the creek were established in terms of total kjeldahl nitrogen (TKN), soluble reactive phosphorus (SRP), total phosphorus (TP), BOD, and COD measured in six different parts of the creek. The sampling stations were Sta. 1, UPLB Hortorium; Sta. 2, UPLB Student Union; Sta. 3, above sewage outfall no. 1; Sta. 4, below sewage outfall No. 1; Sta. 5 after the STCJP outfall; and Sta. 6, Sitio Riverside. The water quality effects of the AMBS located in two different parts of the stream about 800 m apart were evaluated based on the results of comparison of the observed levels in the stream water before and after passing through the system. The baseline data indicated two out of six sampling stations as having acceptable water quality based on COD, namely, Sta. 1 and Sta. 2. Impairment of water quality occurred in the rest of the stations, based on the very high levels of COD. Nitrogen and phosphorus levels were indicative of eutrophication. The most polluted was Sta. 6 or Sitio Riverside where people use the stream up to the present for bathing, washing and kitchen water. Fishes were very scanty in the stream and no individuals were spotted within the next 10-m stretch downstream from the outfall. Stream water that passed through the two AMBS was found to have a high but widely varying % reduction in the levels of alkalinity (0.6-24%), COD (33-64%), TKN (4-30%) and TP (2.5-9%). Both set-ups increased the Cd by 2-9%, decreased Pb by ~7%; but had inconsistent results on Fe levels. The most remarkable effect of the AMBS was the proliferation of fingerlings in the creek.