Total Petroleum Hydrocarbon Degradation and BTEX Leaching in Soils after Application of Oil-Base Drilling Mud: Impact of Application Rate, Rainfall Regime, and Time by Chad J Penn in MAOPS- Lupine Publishers
Increases in oil and gas drilling have resulted in large quantities of
oil base “mud” (OBM) to be disposed of. Land application
of OBM to agricultural land is a common disposal technique that presents
agronomic and environmental challenges since the
material is rich in total petroleum hydrocarbons (TPH). Leaching of
lower molecular weight hydrocarbons, mainly benzene, toluene,
ethylbenzene, and xylene (BTEX), is a concern due to their relatively
low octanol: water partition coefficients. The objective of
this study was to determine the effect of rainfall regime and TPH
loading rate on TPH degradation and BTEX leaching after OBM
application. An OBM was characterized for TPH, BTEX, and trace metals. A
soil column study was conducted where OBM was applied
at five loading rates (0, 22,000, 45,000, 67,000, and 90,000 kg TPH
ha-1) and was subjected to four moisture regimes. OBM samples
were taken at day 0, 7, 30, 60, and 91 to monitor TPH degradation.
Leachate samples were taken at day 0, 14, 28, 35, 49, 56, 63, 77,
and 84 to monitor electrical conductivity (EC), pH, metal
concentrations, and BTEX concentrations. After 60 days, a maximum TPH
degradation of 35% was measured. Leachate BTEX concentrations increased
as TPH application rate increased and was mostly
undetectable by day 28. Leachate EC increased over time and with
increasing TPH rates. TPH rate had no effect on leachate pH. OBM
loading rates had the greatest effect on TPH degradation and BTEX
leaching. Under our experimental conditions, little risk of BTEX
leaching from land applied OBM was observed.
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