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PILOT LAND TREATMENT OF PAH-CONTAMINATED SEDIMENTS
Citation:
Sayles*, G D., C M. Acheson*, L J. Fichter*, M. Rahman, AND A. D. Zaffiro. PILOT LAND TREATMENT OF PAH-CONTAMINATED SEDIMENTS. Presented at Platform presentation at Battelle In-Situ and On-Site Bioremediation Symposium, San Diego, CA, 4/19-22/99.
Description:
Hazardous dredged sediments are typically placed in confined disposal facilities (CDFs) which are designed to dewater and contain but not treat sediments. Since navigational dredging in the U.S. is quickly filling many CDFs, these facilities have little available capacity for newly dredged sediments. Thus, inexpensive treatment technologies are needed to minimize the use of CDFs for newly dredged sediments, and to reclaim capacity in CDFs by treating previously placed sediments. The land treatment process may be applied to sediments to destroy aerobically biodegradable contaminants such as polycyclic aromatic hydrocarbons (PAHs) and provide the necessary treatment at relatively low cost.
A pilot scale test of land treatment was conducted using sediments contaminated with PAHs dredged from the East River in New York Harbor. The sediment texture was similar to a clay loam (56% silt+clay) with an average total PAH concentration of 1100 mg/kg and 10% total organic matter. Total PAHs were defined as the sum of 19 specific 2, 3, 4, 5, and 6-ring PAHs. The pilot scale land treatment reactors were 1-ft3 stainless steel pans where 8-inches of sediment-amendment mixture was placed on a gravel underdrain. Water baths maintained the temperature of the 12 pans at 20oC. The wet sediment and the sediment-amendment mixtures were mixed thoroughly before placement in the reactors. Initially, the sediment was tilled daily until it dried to the moisture holding capacity of the sediment-amendment mixture. Subsequently, the sediment was tilled weekly and moisture levels maintained at each treatments= water holding capacity.
A 2x2 randomized block experimental design was established to determine the effects of amendments and reactor location on land treatment performance. Two levels of anaerobic digester biosolids (none and 10%(w/w)) and two bulking types (50% (w/w) sand and 50% (v/v) Perlite) were tested. Sand and Perlite were tested as bulking agents to aid in drying and to increase the tilth of the clay loam sediment. Anaerobic digester solids was tested as a nonspecific amendment that may act as a source of microorganisms, nutrients, and as a bulking agent. Each treatment was operated in triplicate. The process was monitored with time for the 19 PAHs, pH, moisture, and toxicity as measured by the solid phase Microtox assay. The pH of the solids was maintained between 5.3 and 8.2.
Over the 24-week test, the performance of the treatments ranged from 57 to 64 % removal of total PAHs, while Microtox showed a decrease in toxicity of 33 to over 200 times the initial level. The Perlite amended sediment dried much faster than the sand-amended sediment resulting in a faster initial rates of PAH removal in the Perlite treatments. The dynamics of PAH removal will be reported. Results of an Analysis of Variance of the PAH and Microtox data will be shown to distinguish the effectiveness of the treatments.