The%20Practical%20Application%20of%20Constructed%20Wetlands%20in%20the%20Philippines

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The Practical Application of Constructed Wetlands
in the Philippines

• R.E. James, N. Callora, R. Inion, G. Tolentino

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I. Review

• Background
• Constructed Wetland Types

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Outline

• Review
• Pilot Testing and Preliminary Results
• Vegetation Propagation
• Pilot Anaerobic Wetland
• Pilot Aerobic Wetland with Open Limestone Channel
  (OLC)

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I. Review
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Acid Mine Drainage

• Acid Mine Drainage (AMD)
• Sulfide minerals exposed to water and oxygen
• 4 FeS2 15 O2 14 H2O ? 4 Fe(OH)3 8 H2SO4
• Pyrite Oxygen Water ? Iron Oxide Sulfuric
  Acid
• Fe oxyhydroxides smother vegetation
• Acidity dissolves and mobilizes toxic metals
• As, Cd, Cr, Cu, Fe, Mn, Ni, Zn
• Contamination of aquatic biota and drinking water

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Constructed Wetlands

• Energy sources
• Photosynthesis
• Topographical gradients
• Microbial metabolism

• Constructed Wetlands (CW) are a proven passive
  wastewater treatment technology
• Immobilization of metals as solid precipitates
• Generation of alkalinity

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Wetland Types

• Anaerobic Wetlands
• Compost wetland

• Aerobic Wetlands
• Surface reed ponds
• Metal removal as Fe precipitation, heavy metal
  coprecipitation, adsortion, physical settling,
  and plant-metal uptake

PROS CONS
Treats acidic water Less clogging of substrate Complicated water distribution, and substrate design
PROS CONS
Simple design and construction Requires alkaline influent water
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CW Modification 1

• Reducing and Alkalinity Producing System (RAPS)

C
B
A
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CW Modification 2

• Limestone Channels
• Open Limestone Channels (OLC)
• ALD/OLC aerobic wetland
• Limestone dissolution
• Pretreatment of pH 3 water

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II. Design Program and Preliminary Results
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Wetland Components

• Vegetation
• Substrate

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Vegetation
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Substrate

• Nursery batch experiments
• Local substrate
• Carabao manure
• Forest litter
• Sawdust from local sawmill
• Rice straw

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Results of Batch Experiments

• Successful growth of plants in pH 3 test water

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Hydrology

• Water Balance
• Mean annual rainfall approximately 3,064 mm
• Mean annual evaporation approximately 1,203 mm
• Highly variable conditions
• Monthly unit base flow ranges from 800
  m3/ha/month to nearly 2,000 m3/ha/month.
• Short-term high intensity storm events show an
  even greater range of flows.

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Erosion Controls

• Slope stabilization
• Abaca mats
• Stabilizing vegetation
• Berms
• Water distribution
• Anaerobic conditions? Constant water supply!
• Trestles
• 3-pond water collection

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Pilot CW Design RAPS and OLC Aerobic Wetland
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Metal Analysis Plant and Water
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Pilot RAPS
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OLC Aerobic Wetland
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Thank You!