Thesis - faculty.ait.ac.th - Asian Institute of Technology

% Inhibition .
100
80
60
40
20
0
0.0 0.5 1.0 1.5 2.0 2.5
Concentration of Soluble Lead (mg/L)
Figure 4.11 Inhibition Effect of Lead in Yeast Sludge
In the bacterial system, 50% inhibition occurred at a concentration approximately 3
mg/L. The toxicity effects to both marine and freshwater invertebrates have been recorded
at the concentrations range between 0.5 and 5.0 mg/L (Oladimeji and Offem, 1989),
whereas it was between 2 and 6 mg/L for the activated sludge process (Madoni, et al.,
1996). Madoni, et al. (1999) also found that the microbial activity in an activated sludge
plant treating wastewater containing 3.5 to 9.2 mg/L of soluble lead could be adversely
affected. The higher concentrations of soluble lead applied in the experiments point out the
higher resilience of bacteria in the presence of lead.
4.3 Application of Yeast and Bacteria Based Membrane Bioreactors in Leachate
Treatment
Landfill leachate treatment is a complex task due to the highly variable waste
landfilled, the type and design of the landfill, landfill age and climatic and seasonal
variations in different regions. Hence, rather than recommending treatment options based
on specific factors, it would be necessary to consider landfill age as a unique case.
Medium-aged landfill leachate is characterized by a high COD and ammonia content with
a relatively lower BOD. Leachate treatment systems in recent years are sophisticated,
reliable and are able to consistently treat leachate to keep up the specific discharge
standards (Robinson, 1999). One such treatment technique is the membrane bioreactors.
Membrane reactor in recent years has been proved to be effective and economically
feasible for treatment of various kinds of toxic wastewaters. Moreover, industrial
utilization of the MBR has worked successfully for treating complex wastes like landfill
leachates and cosmetic wastewaters (Manem, 1993; Mandra, et al., 1995). In the present
study, initially performance of the membrane bioreactors have been evaluated without any
pre-treatment based on various factors such as removal efficiency of TKN and COD,
membrane fouling, etc.
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