Statistical analysis and optimization of nitrogen, phosphorus, and inoculum concentrations for the biodegradation of petroleum hydrocarbons by response surface methodology

Abstract

In order to optimize and evaluate the influence of nitrogen, phosphorus, and inoculum concentrations on the biodegradation of hydrocarbon contaminated effluents, experiments based on central composite design (CCD) method were carried out for 3 days, employing C1 mixed culture and intermittent aeration. The independent variables were nitrogen concentration (X 1 ), phosphorus concentration (X 2 ), and inoculum concentration (X 3 ) and the removal of total petroleum hydrocarbons (TPH) was the dependent variable. The optimized nutrients ratio (C:N:P = 100:20:2.7) and inoculum concentration (1.32 g/ l) provided TPH removal of 71.8% after processing for three days. Analysis using gas chromatography identified five hydrocarbons classes: paraffins, isoparaffins, olefins, naphthenics, and aromatics. The naphthenic compounds did not degrade as readily as the other hydrocarbons that were identified. The following degradation percentages were obtained: 87.1% for the paraffins, 77.7% for the isoparaffins, 78.6% for the olefins, 38.4% for the naphthenics, and 71.7% for the aromatics.

The sedimentation of mixed cultures used in the treatment of effluents generated from terrestrial fuel distribution terminals

“…After an adaptation period, the culture was inoculated into effluent contaminated with diesel and gasoline, as described by Vieira et al [14,16].…”

“…The conditions optimised by Vieira et al [14,16] were adopted in this study and included the following: 0.509 g/L of nitrogen, 0.068 g/L of phosphorous, 1.32 g/L of inoculum, and 2 g/L of autolysed residual brewery yeast (ARBY). Intermittent aeration consisted of air injections at a flow rate of 150 L/h for 5 min every 33 h agitation at 110 rpm.…”

“…Vieira et al [14][15][16] studied the biodegradation of an effluent contaminated with diesel oil and gasoline using intermittent aeration as an alternative to continuous aeration. Results revealed that intermittent aeration is an interesting and economic option for hydrocarbon removal.…”

Biodegradation of diesel oil and gasoline contaminated effluent employing intermittent aeration

“…Most of the literature is concerned with aerobic biodegradation processes [4,16,17], and anaerobic processes [9,18] comprise most of the remainder. However, processes based on intermittent aeration have recently gained attention as an alternative [3,19].…”

“…4). This highlights the importance of optimizing process conditions, such as nutrient and inoculum concentrations [19], aeration interval, and agitation speed.…”