Abstract:
Hydraulic fracturing (‘fracking’) is a drilling and extraction technique that uses large volumes of
high-pressure, chemically-treated water to free petroleum and natural gas trapped deep in
underground strata. The chemically-enriched water, along with brine and groundwater, are
recovered from the well together with the oil and gas. There is an urgent need for treatment of
this contaminated water prior to possible reuse. The reported research tested two methods for
removal of contaminants from synthetic fracking fluids: (1) physical sorption using activated
charcoal (GAC), peat, synthetic resin, and plastic chips packed in columns; and (2) biological
treatment using a two-stage constructed wetland grown to cattail (Typha latifolia). The resulting
leachates were tested for chemical composition; likewise, the soil and Typha grown in the
constructed wetland were analyzed. GAC and peat were moderately successful as compared with
plastic and resin for both increasing pH of the hydraulic fracturing fluid (from 4.1 to 7.4) and in
removing Na. Results were variable for Cu and Pb removal. In the constructed wetland, pH
increased from 4.1 to 7.0 and electrical conductivity decreased significantly. Transfer factors for
Pb were 0.67 (Stage 1 of wetland) and 1.37 (Stage 2). Typha shoots had bioconcentration factors
for Pb ranging from 2.9 (Stage 1) to 8.0 (Stage 2). These data indicate that Typha may be
effective for Pb removal from hydraulic fracturing fluids. The reported study may be of
significant practical value to oil and gas production industries which generate large quantities of
contaminated oil and gas wastewater.
