The inlet COD of the biological reactor is 6000-8000 ppm and the inlet phenol varies from 170-190 ppm. In the first biological reactor the COD reduction is above 50% but the phenol is increasing (Bio out Phenol is 210-240 ppm).
In second bio reactor, COD degradation is 30% and Phenol degradation is 10-20% (as compared with the Bio 1 outlet).
No dosing is done in both the bioreactors.
Why is the phenol increasing in the Bioreactor-1??
In biological treatment, the microorganisms degrade phenol into other non-toxic compounds. Aerobic biodegradation of phenol is most common. The ability of active biomass to degrade pollutants is affected by the presence of naturally occurring carbon sources. Phenol is degraded by diverse microorganisms including yeasts, fungi and bacteria.Biological removal of the phenolic compounds is difficult at either low concentration (lower than 200 mg L−1), or at sufficiently high phenol concentration, as it inhibits growth rate of the microorganisms . The presence of toxic pollutants such as phenol may also result in the deflocculation, which results in settling problems in clarifier. Thus, to achieve satisfactory phenol removal efficiency, phenol concentration needs to be maintained below the threshold limits and acclimatization of the microorganisms to the toxic wastewater is a must. It has been reported that acclimatized activated biomass degrades phenolic compounds more effectively than the pure strains by one or more than two orders of magnitude faster.Activated sludge has been successfully applied for phenol degradation with the help of batch reactor up to 1500 mg L−1 at a pH of 6 . Moving bed bio-film reactor has been used for treating phenol containing wastewater with high TDS.
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