19

COST AND DESIGN FOR APPLICATION OF COMPOSTING AND BIOSLURRY TREATMENT OF EXPLOSIVES-CONTAMINATED SOILS

The U.S. Army Environmental Center (USAEC) has dedicated years of effort to developing and fielding biotreatment alternatives to the conventional technology, high temperature incineration.

In 1992, USAEC demonstrated the effectiveness of windrow composting of explosives-contaminated soils. Based on its capacity to reduce explosives concentrations by over 99% and toxicity by 90-98%, composting was selected in a 1992 Record of Decision as the remediation process for a Superfund site at Umatilla Depot Activity, OR (UMDA).

Contracting for cleanup with an innovative technology presented unique challenges in providing sufficient design and technical information to generate reliable bids.

Follow-up on studies charted the success of the first full-scale application of windrow composting at UMDA. A new report documents the remedial design and determines a unit cost of $250-299 per ton.

Slurry phase biotreatment was successfully demonstrated at Joliet Army Ammunition Plant, IL, in 1995. Bioslurry consistently achieved removal rates above 99%, with a high rate of mineralization. 1996 studies performed in support of Feasibility Studies at Joliet and Iowa Army Ammunition Plants developed comprehensive concept designs and cost estimates for full-scale application of aerobic and anaerobic bioslurry processes.

The studies found that bioslurry systems have higher construction and facility costs, but lower operation and maintenance costs when compared to composting. An estimated unit cost of $290-310 per ton is surprisingly close to that of windrow composting .

Bioslurry costs are dominated by two factors: process time and the ultimate disposal of the soil. If dewatering and subsequent water treatment is required, the cost can increase at a minimum of $25-65 per ton. Disposition of the treated soil must be carefully considered within risk-based goals and future land use.

This presentation will review the full-scale design and process costs for these biotreatments, and offer lessons learned in contracting for innovative technologies.

Key words: explosives contamination, windrow composting, bioslurry