Modeling Phytoremediation of Heavy Metal Contaminated Mine Spoil

Modeling Phytoremediation of Heavy Metal Contaminated Mine Spoil Dumps Parikshit Verma EIA and Sustainability Assessment – Asian EIA and Effective Tool Development Seol, Korea, June 5, 2007 National Environmental Engineering Research Institute (NEERI), Nagpur

Barren Manganese Mine Spoil Dump

After 10 years - Revegetated Manganese Mine Spoil Dump

Definitions / Terminology Phytoremediation Use of plants / vegetation for in situ treatment of wastewater, contaminated soils or sediments. Some plants shows the capability to withstand relatively high concentration of chemicals without toxic effects (Hyperaccumulators). It is applied at sites with contamination of Organic Chemicals – BTEX, TNT, RDX, PCBs − Nutrient – Ammonia, Phosphate, Nitrate − Metal pollutants – Lead, Cadmium, Zinc, Arsenic, Chromium −

Chemical uptake and translocation in the plant body

Unsaturated / Vadose zone

Processes that takes place in the root zone

Soil Water Partitioning

Metal Uptake by Plant Root Michaelis and Menton Type of Reaction

Plant Root Growth

Saturated and Unsaturated Zone –Soil –Water –Soil –Air –Thin film of Water around soil particle

Saturated and Unsaturated Zone – Residual Moisture – Saturation Moisture

Moisture Retention Characteristics Curve

Moisture flux in Unsaturated Zone Relationship between Soil Moisture and Suction Head is called Soil Moisture Retention Characteristics (MRC)

Mathematical models used in the Metal Uptake model • • • Richards Equation Water uptake by plant root Metal uptake by plant root Root growth with time Plant root properties Moisture Retention Characteristics (MRC) Soil properties – Bulk Density, Clay content, Carbon content etc. Pedotransfer Function Soil Water Partition of pollutants Hydrodynamic Dispersion Moisture flux joining groundwater Chemical species flux joining groundwater

Pedotransfer Functions Expensive and time consuming MRC Parameters θs, θr, n, m, α • f • • • Bulk density Clay content Carbon content Particle size distribution

Space – Time Domain of One Dimensional Transient Metal Uptake Model

Computational Scheme Richard’s Equation descritized using Implicit scheme

Applicability – – – Other treatments are not cost effective Very large sites Low concentration of contaminants Only polishing treatment is required Where vegetation is used as final cap / site closure Limitations – Limited regulatory acceptance – Long duration of time for cleanup – Potential contamination of fodder crop and food chain Techniques of Phytoremediation – Phyto-transformation – – Rhizosphere Bioremediation Phyto-stabilization Phyto-extraction Rhizo-filtration

Why Phytoremediation Model Software ? • Design of experiments to determine the parameters of subsurface phenomenon. • Preparation of irrigation schedule for plantation on mine spoil dump. • Decision on harvesting time of plants. • Estimation of amount of heavy metal present in the plant.

NEERI PHYTOREM Model Software Demonstration