Treatment of small scale gold mining wastewater using pilotscale sedimentation and Cocopeat filter bed system

The use of amalgamation process to recover gold from mined ores by the smallscale gold miners in the Philippines and other developing countries produces and dispose of untreated wastewater to the receiving water bodies. In this study, a fieldscale filter bed system was constructed to treat heavy metal metalladen wastewater collected from smallscale gold mining site in Paracale, Camarines Norte, Philippines. The filter bed system was consists of sedimentation tank and filter bed with Cocopeat, a byproduct of coconut husk, as adsorbent. Physicochemical parameters (temperature, pH, oxidationreduction potential, electrical conductivity, turbidity, dissolved oxygen, total dissolved solids, salinity, total suspended solids, color) and heavy metal (As, Ba, Cd, Hg, Pb) concentrations were monitored during the 50 days experiment at a flow rate of 40 Liter per hour for 3 hours daily wastewater application. Significant reduction was achieved on heavy metals; As (97.11%), Ba (39.75%), Cd (74.24%), Hg (97.02%), Pb (98.82%) from smallscale gold mining (SSGM)wastewater in sedimentation phase and further reductions on As (1.39%), Ba (28.00%), Cd (4.95%), Hg (2.91%), Pb (0.97%) were achieved by adsorption in the Cocopeat filter bed. Measured effluent physicochemical parameters and heavy metal concentrations were within the respective regulatory limits. Other effluent parameters with strong correlation with total suspended solids such as turbidity and color, though not regulated, were reduced significantly. All adsorbed heavy metals accumulated in the upper 25 cm of the Cocopeat column in the filter bed. Measured heavy metal concentrations in Cocopeat suggest that the adsorbent was not saturated and further application of smallscale gold mining wastewater is recommended to determine its useful life.