Carbon and nutrient-limiting conditions stimulate biodegradation of low concentration of phenol

Biological removal of phenol in wastewater is kinetically constrained if its initial concentration is low (<5 mg/L) making compliance of environmental norms (<= 0.35 mg/L) difficult. Taking a cue from the soil matrix where bio-remediation of very low concentrations phenol is possible under nitrogen (N), phosphorus (P) and carbon (C) limiting conditions, the present study was carried out to stimulate phenol biodegradation in a low-phenolic (<5 mg/L) refinery wastewater. Experiments with nutrient limiting conditions showed that N-limited and P-supplemented conditions were necessary to stimulate phenol uptake if the initial concentration of phenol is <1 mg/Loris between 2.5-5.8 mg/L. Further studies revealed that instead of manipulating nutrients, enforcing the C-limited condition on the microorganisms through a two-staged reactor process, not only did the phenol removal efficiency improve but also eliminated the need to externally manipulate N and P concentrations in the system. The high abundance of hydrocarbon degrading gram-negative bacteria and Pseudomonas species in the second stage of the two-staged process, further confirmed that C-limitation was a better option than the nutrient manipulation. The study thus illustrates methods of acclimatizing microorganisms to remove very low concentration of target substrate (here phenol) in low strength wastewater. (C) 2017 Elsevier B.V. All rights reserved.