Characterization and Removal of Tributyltin (TBT) From Shipyard Washwasters Laboratory and Full-Scale Studies

Date of Award

Fall 2003

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Civil & Environmental Engineering

Program/Concentration

Environmental Engineering

Committee Director

Gary Schafran

Committee Member

William Drewry

Committee Member

Jaewan Yoon

Call Number for Print

Special Collections LD4331.E553 P73 2003

Abstract

Tributyltin has long been used as a biocide in many consumer products to prevent biological growth and fouling. One of the persistent uses of tributyltin is as an antifouling agent in marine paints where its use prevents biological growths on hulls and greatly improves the fuel efficiency of ships. Due to observed adverse effects (tributyltin is an endocrine disrupter) on non-target organisms like shellfish, oysters and snails, the use of tributyltin in marine paints has been banned in many nations and its point source discharge is now regulated through the Virginia Permit Discharge Elimination System (VPDES) program (first state to control its discharge). During this research, the limit was set at 50 ng/l.

Characterization and treatment studies were conducted in an effort to evaluate treatment options capable of removing TBT from shipyard washwaters above 1,000,000 ng/L to below 50 ng/l. Laboratory studies and operation of a full-scale treatment plant were used to examine treatment options for TBT removal. Conventional physicochemical treatment processes including coagulation, filtration, and activated carbon adsorption were used.

Significant variability was observed in the influent waters in their color, TBT and DOC concentrations and conductivity. Laboratory efforts showed that on average, 90% of TBT (particulate matter) could be removed by coagulation. Both aluminum sulfate and ferric sulfate were used as coagulants and optimal pH and dose conditions were examined for each coagulant. Results from the research showed that, irrespective of the type of coagulant, at lower pH ( ~ 7) TBT removal was greater compared to higher pH (8-10). There was no statistically significant difference found in removal capacities between the two metal salts. Removal of the dissolved fraction of TBT was achieved by granular activated carbon adsorption. TBT demonstrated its great affinity to GAC surface in both laboratory and full-scale efforts; but it was not consistently removed to levels that would meet the regulatory requirements. TBT persisted in effluents of the full-scale treatment plant and was observed to occur primarily in the particulate fraction. Influence of surface chemistry, pore size and competition rendered by DOC for empty sites on GAC was explored, speculating the complexation of TBT with DOC and its competition with TBT as significant. This study outlines an integrated assessment of research efforts carried out with both a full-scale treatment plant and laboratory scale treatment evaluations.

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DOI

10.25777/j6c2-rc22

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