Bioreactor-based bioremediation of hydrocarbon-polluted Niger Delta marine sediment, Nigeria

Abstract

Crude oil-polluted marine sediment from Bonny River loading jetty PortHarcourt,Nigeriawas treated in seven 2.5 l stirred-tank bioreactors designated BNPK, BNK5, BPD, BNO3, BUNa, BAUT, and BUK over a 56-day period. Five bioreactors were biostimulated with either K2HPO4, NH4NO3, (NH4)2SO4, NPK, urea or poultry droppings while unamended (BUNa) and heat-killed (BAUT) treatments were controls. For each bioreactor, 1 kg (wet weight) sediment amendedwith 1 l seawaterwere spikedwith 20 ml and 20 mg of crude oil and anthracene which gave a total petroleum hydrocarbons (TPH) range of 106.4-116 ppm on day 0. Polycyclic aromatic hydrocarbons (PAH) in all spiked sediment slurry ranged from 96.6 to 104.4 ppm. TPH in each treatment was ≤14.9 ppm while PAH was ≤6.8 ppm by day 56. Treatment BNO3 recorded highest heterotrophic bacterial count (9.8 × 108 cfu/g) and hydrocarbon utilizers (1.15 × 108 cfu/g). By day 56, the percentages of biodegradation of PAHs, as measured with GC-FID were BNK5 (97.93%), BNPK (98.38%), BUK (98.82%), BUNa (98.13%), BAUT (93.08%),BPD(98.92%), and BNO3 (98.02%).BPDgave the highest degradation rate for PAH. TPHdegradation rates were as follows: BNK5 (94.50%), BNPK (94.77%), BUK (94.10%), BUNa (94.77%), BAUT (75.04%), BPD(95.35%), BNO3 (95.54%). Fifty-six hydrocarbon utilizing bacterial isolates obtained were Micrococcus spp. 5 (9.62%), Staphylococcus spp. 3 (5.78%), Pseudomonas spp. 7 (13.46%), Citrobacter sp. 1 (1.92%),Klebsiella sp. 1 (1.92%), Corynebacterium spp. 5 (9.62%), Bacillus spp. 5 (9.62%), Rhodococcus spp. 7 (13.46%), Alcanivorax spp. 7 (13.46%), Alcaligenes sp. 1 (1.92%), Serratia spp. 2 (3.85%), Arthrobacter spp. 7 (13.46%), Nocardia spp. 2 (3.85%), Flavobacterium sp. 1 (1.92%), Escherichia sp. 1 (1.92%), Acinetobacter sp. 1 (1.92%), Proteus sp. 1 (1.92%) and unidentified bacteria 10 (17%). These results indicate that the marine sediment investigated is amenable to bioreactor-based bioremediation and that abiotic factors also could contribute to hydrocarbon attenuation as recorded in the heat-killed (BAUT) control. © The Author(s) 2011.