Page 201 - Environmental Control in Petroleum Engineering

Waste Treatment Methods 18?

lower disposal costs (Groves and Bartman, 199la and 1991b; Mayer
and Cregar, 1991; Steward, 1991).
The effectiveness of mechanical methods to dewater solids from a
reserves pit and a production pit varies ( Wojtanowicz et al., 1987).
The dewatering of most oilfield wastes can be improved by precon-
ditioning before mechanical separation with nonionic or low-charge
anionic polymers with high molecular weights. Belt presses and
centrifuges show similar performance, but belt presses are difficult to
clean. Vacuum filtration and screw presses are not as effective because
of their low volume reduction of the solid waste stream. Comparison
of the effectiveness of several mechanical separations methods for
reserves and production pits are provided in Tables 6-3 and 6-4,
respectively. For these tables, initial solids contents of 10 wt% and
30.5 wt% were used, respectively.

Table 6-3
Effectiveness of Solids Separation Methods for Reserve Pits
Belt Press Centrifuge Vacuum Filter

Volume Reduction (vol%) 70 71 45
Solids Recovery (wt%) 99.91 99.85 99.84
Cake Dryness (wt% solids) 45 44 23
Effluent Solids (mg/1) 150 180 130

Source: after Wojtanowicz et al., 1987.
Copyright SPE, with permission.

Table 6-4
Effectiveness of Solids Separation Methods for Production Pits

Belt Press Centrifuge Screw Press
Volume Reduction (vol%) 50 38 26
Solids Recovery (wt%) 99.83 99.99 99.98
Cake Dryness (wt% solids) 55 59 45
Effluent Solids (mg/1) 300 30 95

Source: after Wojtanowicz et al., J987.
Copyright SPE, with permission