ESTIMATED COST

tant to drain the meltwater as soon as possible. This

meltwater would be returned back to the head of the

plant for treatment because it still contains pollutants

The estimated capital cost of the freezing bed alter-

native is 1,191 (Table 2). This estimate was devel-

such as dissolved organic matter. The impact of this

oped using the unit costs shown in the CTE (1999)

meltwater on the treatment process should not be sig-

report. Not included is the cost of a sludge storage tank.

nificant because it is a relatively small volume in com-

In comparison, the estimated cost of the 1.0-m belt

parison to the raw wastewater flow. There should only

press alternative is 6,000.

be a few centimeters of dewatered sludge left in the

The estimated annual operation and maintenance

bed when draining is complete. For example, only 13

cost of the freezing bed alternative is 06 (Table 3).

cm remained after freezing and thawing 1.0 m of aero-

According to the CTE report, the estimated annual op-

bically digested sludge in a pilot scale freezing bed

eration and maintenance cost of the proposed 1.0-m

(Martel and Diener 1991).

belt press is ,102. This is a significant difference

The final operation would be to remove the dewa-

that is attributable to the freezing bed requiring very

tered sludge and pack it into tri-wall containers. Ac-

little labor and energy to operate. Natural freezethaw

cording to the proposed schedule, this would be done

is used as the dewatering process rather than mechani-

in February. Normally, the ship departs McMurdo for

the U.S. on or about 10 February. This means that all

cal energy and chemicals.

the sludge must be removed from the bed and loaded

into tri-wall containers within 10 days. This should not

CONCLUSION

be a problem if the operator uses a front-end loader. At

Fort McCoy, Wisconsin, this took about 1 hour. Also,

the loader operator was able to remove the sludge layer

A preliminary design analysis indicates that all

of the sludge produced by the proposed extended

without taking much of the sand with it. Thus, only a

aeration wastewater treatment plant at McMurdo could

small amount of new sand was needed to replenish the

be dewatered in a 10- by 16-m by 2-m-deep freezing