**5. Performance of the bioreactor**

The performance of the bioreactor in terms of sulphate reduction efficiency of the system starting from an initial concentration of 2000 ppm was measured after 24 hours of incubation according to the method of Nasipuri et al. [1] for a period of 361 days (**Figure 4**). The quarterly data revealed 36.29 ± 16.55, 63.46 ± 15.24, 57.44 ± 17.32 and 91.81 ± 7.97 sulphate reduction, respectively, indicating stabilization of the bioreactor. The data generated from the bioreactor were used for carrying out the time series analysis after detrending (**Figure 5**) the series using Matlab 7.4.0 (R2007a) to study the bioreactor performance in terms of sulphate reduction. The time series plot (**Figure 5**) clearly reflects the inherent oscillatory nature of the system as has been reported earlier by other investigators [25]. This oscillatory nature is an inherent property of the biofilm-based system. Taherzadeh reported such oscillatory property in case of contin‐ uous mode operations of reactors due to shearing force, but in this case, the same property is observed even in case of batch mode operation as an outcome of biofilm property, where there exists only minimum of shearing force [27]. However, the impact of seasonal variation may also be important. The effect of seasonal variation on the performance of the system was analysed (**Figure 6**). Its performance appears to be independent of the seasonal variation. This is a positive finding in terms of application of this system on site. Hence, the correlation between ambient temperature and age of the biofilm with that of the performance of the system was determined using Pearson's correlation coefficient. The correlation coefficient among sulphate reduction and biofilm formation, biofilm formation and ambient temperature, sulphate reduction and ambient temperature was observed to be 0.738, 0.538 and 0.284, respectively. It was observed that there was no statistical trend in performance of the system with either ambient temperature or age of the biofilm. It was revealed that the two variables were not related (**Figure 6b**).

**Figure 4.** Performance of the SRB consortia in 78-litre packed bed bioreactor for 361 days. The 78-litre bioreactor is con‐ structed of acrylic body and stainless steel for the bottom portion with three nozels for sample collection (distance be‐ tween first and second nozels is 18 cm, whereas the distance between second and third nozels is 40 cm. The anaerobicity was mentioned by purging nitrogen gas (60 lm/cm2 ) into the bioreactor from outside.

Developing Tailor-Made Microbial Consortium for Effluent Remediation http://dx.doi.org/10.5772/62594 25

**Figure 5.** Time series of geometric mean of sulphate dataset after removing trend.

**5. Performance of the bioreactor**

24 Nuclear Material Performance

were not related (**Figure 6b**).

anaerobicity was mentioned by purging nitrogen gas (60 lm/cm2

The performance of the bioreactor in terms of sulphate reduction efficiency of the system starting from an initial concentration of 2000 ppm was measured after 24 hours of incubation according to the method of Nasipuri et al. [1] for a period of 361 days (**Figure 4**). The quarterly data revealed 36.29 ± 16.55, 63.46 ± 15.24, 57.44 ± 17.32 and 91.81 ± 7.97 sulphate reduction, respectively, indicating stabilization of the bioreactor. The data generated from the bioreactor were used for carrying out the time series analysis after detrending (**Figure 5**) the series using Matlab 7.4.0 (R2007a) to study the bioreactor performance in terms of sulphate reduction. The time series plot (**Figure 5**) clearly reflects the inherent oscillatory nature of the system as has been reported earlier by other investigators [25]. This oscillatory nature is an inherent property of the biofilm-based system. Taherzadeh reported such oscillatory property in case of contin‐ uous mode operations of reactors due to shearing force, but in this case, the same property is observed even in case of batch mode operation as an outcome of biofilm property, where there exists only minimum of shearing force [27]. However, the impact of seasonal variation may also be important. The effect of seasonal variation on the performance of the system was analysed (**Figure 6**). Its performance appears to be independent of the seasonal variation. This is a positive finding in terms of application of this system on site. Hence, the correlation between ambient temperature and age of the biofilm with that of the performance of the system was determined using Pearson's correlation coefficient. The correlation coefficient among sulphate reduction and biofilm formation, biofilm formation and ambient temperature, sulphate reduction and ambient temperature was observed to be 0.738, 0.538 and 0.284, respectively. It was observed that there was no statistical trend in performance of the system with either ambient temperature or age of the biofilm. It was revealed that the two variables

**Figure 4.** Performance of the SRB consortia in 78-litre packed bed bioreactor for 361 days. The 78-litre bioreactor is con‐ structed of acrylic body and stainless steel for the bottom portion with three nozels for sample collection (distance be‐ tween first and second nozels is 18 cm, whereas the distance between second and third nozels is 40 cm. The

) into the bioreactor from outside.

**Figure 6.** (a) Graph representing biofilm performance in term of sulphate reduction and temperature variation with days. Sulphate reduction indirectly indicates the active biofilm at any point of time. *X* axis represents days that the reactor was functioning, whereas *Y* axis represents performance of the system in terms of sulphate reduction in orange colour and ambient temperature in blue. (b) Surface plot among *X*, *Y* and *Z* variables, where *Z* variable is the percent sulphate reduction, *Y* variable is the age of the biofilm in days and *X* variable is the ambient temperature in degree centigrade.
