Related Experiment Videos
Effect of microbial activity on trace element release from sewage sludge.
Shabnam Qureshi1, Brian K Richards, Anthony G Hay
1Department of Biological and Environmental Engineering, Cornell University, Ithaca, New York 14853, USA.
Environmental Science & Technology
|September 12, 2003
Summary
Microbial activity in wastewater sludge significantly mobilizes trace elements like zinc, nickel, and copper through acidification. Inhibiting microbial action reduces this leaching, crucial for understanding environmental impacts of land application.
Area of Science:
- Environmental microbiology
- Geochemistry
- Soil science
Background:
- The role of microbial activity in trace element mobilization from wastewater sludge is not well understood.
- Land application of sludge can introduce trace elements into the environment.
Purpose of the Study:
- To investigate the leachability of trace elements (Cd, Cr, Cu, Mo, Ni, P, Pb, S, Zn) from dewatered sludge.
- To determine how altered microbial activity affects trace element mobilization.
Main Methods:
- Sludge columns were incubated at various temperatures (4, 16, 28, 37°C) with and without a biocide (AgNO3).
- Six incubation-leaching cycles using synthetic acid rain were performed.
- Microbial activity was assessed using glucose mineralization tests.
- Sulfur-oxidizing bacteria were characterized.
Main Results:
- Trace element leaching and sludge acidification were significant at 16 and 28°C, favoring microbial activity.
- Zinc (99%), nickel (67%), and copper (57%) showed the highest mobilization.
- Mobilization was reduced at 4°C and significantly inhibited at 37°C or with biocide addition.
- Sulfur-oxidizing bacteria were identified in the sludge.
Conclusions:
- Microbial acidification, primarily via sulfur oxidation, is a key mechanism for mobilizing trace elements from wastewater sludge.
- Environmental factors like soil buffering and adsorption capacity influence actual field mobility.