Bioremediation Process for Sediments Contaminated by Heavy Metals:  Feasibility Study on a Pilot Scale

Abstract

The core stages of a sediment remediation process--the conditioning of dredged sludge by plants and the solid-bed leaching of heavy metals using microbially produced sulfuric acid--were tested on a pilot scale using a highly polluted river sediment. Conditioning was performed in 50 m3 basins at sludge depths of 1.8 m. During one vegetation period the anoxic sludge turned into a soil-like oxic material and became very permeable to water. Reed canary grass (Phalaris arundinacea) was found to be best suited for conditioning. Bioleaching was carried out in an aerated solid-bed reactor of 2000 L working volume using oxic soil-like sediment supplemented with 2% sulfur. When applying conditioned sediment, the oxidation of easily degradable organic matter by heterotrophic microbes increased the temperature up to 50 degrees C in the early leaching phase, which in turn temporarily inhibited the sulfur-oxidizing bacteria. Nevertheless, most of the metal contaminants were leached within 21 days. Zn, Cd, Mn, Co, and Ni were removed by 61-81%, Cu was reduced by 21%, while Cr and Pb were nearly immobile. A cost-effectiveness assessment of the remediation process indicates it to be a suitable treatment for restoring polluted sediments for beneficial use.

Developments in Bioremediation of Soils and Sediments Polluted with Metals and Radionuclides – 1. Microbial Processes and Mechanisms Affecting Bioremediation of Metal Contamination and Influencing Metal Toxicity and Transport

“…Operational conditions studied include soil sediment characteristics (Loser et al 2004), initial pH (Chen & Lin 2001a), percentage of inoculum, retention time, initial solid content (Chen & Lin 2000) and nutrition (Chen & Lin 2001b). When insoluble elemental sulfur is used as substrate in the bioleaching process, the microbial oxidation of the sulfur by Thiobacilli is believed to take place by the adsorption and growth of bacteria on the surface of the sulfur particles (Boseker 1997).…”

“…Some influences on process operation under practical conditions, such as the effects of solid inhomogeneity, channeling, or pH and temperature gradients can only be studied reliably on a pilot scale. To be applicable in a commercial plant, the process must be scaled up without loss of efficiency (Seidel et al 2004). …”

Developments in Bioremediation of Soils and Sediments Polluted with Metals and Radionuclides: 2. Field Research on Bioremediation of Metals and Radionuclides

“…Bioleaching has been used in Germany for removal of metals from dredged sediments (SEIDEL et al 2004). About 62% of the Zn, Cd, Ni, Co, and Mn were removed from the sediment in 120 days if the sediment was oxic and of good permeability.…”

Chromium removal from polluted water and its influence on biochemical and physiological parameters in algal cells used for phytoremediation

“…Use of metal-accumulating plants for removal of metals from contaminated waters may generate recyclable metal-rich plant residues, causes only minimal environmental disturbance and has a general public acceptance, so optimization of bioremediation technologies represents a priority for applied environmental sciences [13,25,27,33].…”