|
|
|
|
| NIRE Annual Report | 
| 1998 |
Effect of Addition of Easily Degradable Organic Substances on Acclimation of 2,4-Dichlorophenoxyacetic Acid (2,4-D) Degradation Capability of Activated Sludges, and Their 2,4-D Degrading Population.Ecological Chemistry and Microbiology DivisionHydrospheric Environmental Protection Department |
|---|
Objectives
Acclimation of microbial community in activated sludge is a first important step in starting-up a wastewater treatment system for treating (hazardous) chemical compounds. Acclimation to chemical compound is, in other words, microbiologically, predominating process of microbes capable of degrading chemicals. It is supposed that this predominating process of chemical degraders would be affected by several factors, such as properties of a chemical itself, its concentration, environmental factors (e.g. pH, temperature, and salinity) and coexisting substances. In many studies on microbial degradation, hazardous chemicals have rather been used as sole source of carbon and energy. On one hand, positive effect of non-recalcitrant on degradation of chemicals has been known as cometabolism. In reality, besides hazardous contaminants, coexistence of easily degradable carbon substances, i.e. BOD, would be quite likely. This study has been focused on effect of addition of peptone, as an easily degradable carbon substance, on acclimation of microbial community from a sewage activate sludge against a herbicide, 2,4-Dichlorophenoxyacetic Acid (2,4-D). We also preliminary have analyzed differences in their 2,4-D degrading population.
Results
Activated sludge (MLSS, 1,500 mg/L) obtained from a sewage treatment plant was incubated in basal salt solution with 100 mg/L 2,4-D with (sludge A) and without (sludge B) 800 mg/L peptone. All of medium was replaced after separation of activated sludge biomass by centrifugation once in 2 - 3 days. In 10 days of operation, 2,4-D was completely degraded by sludge A, and its treatablity of 2,4-D was very stable for over 200 days. On the other hand, completely degradation of 2,4-D by sludge B was not attained for over 200 days, and its treatability was extremely unstable; percentage of 2,4-D degradation kept fluctuating from 0 - 100. This indicates presence of peptone disturbed full-acclimation of 2,4-D degradation capability. After MPN enumeration, 2,4-D degraders were isolated from sludges A and B to compare diversity of 2,4-D degraders developed in each laboratory activated sludge and their 2,4-D degrading characteristics. Bacteriological studies are currently being conducted.
