Production and Application of Agar-based Slow-release Fertilizers, in the Bioremediation of Petroleum Hydrocarbon-impacted Soil

Aims: The study was carried out to determine the potentials of novel slow-release fertilizers (SRF) in the bioremediation of petroleum hydrocarbon-impacted soil, in order to determine their potentials in the bioremediation of petroleum-impacted sites and as well evaluate the effect of nutrient concentration on the rate of bioremediation.

Study Design: A marine biopolymer (agar agar) was used as a coating for soluble NPK fertilizer in slow-release formulations (capsular and granular form).

Place and Duration of Study: This study was carried out in the Environmental Microbiology Laboratory, University of Port Harcourt, Nigeria, between January and June 2015.

Methodology: The contaminated soil sample was recreated in four clean plastic containers and labeled A - D, as follows: Sample A = 300 g Soil + 20 g NPK Capsular SRF; Sample B = 300 g Soil + 20 g NPK Granular SRF; Sample C = 300 g Soil + 20 g Direct NPK; Sample D = 300 g Soil (without fertilizer - control). The determination of the effect of SRF on the population dynamics of total aerobic heterotrophic bacteria (THB) and hydrocarbon utilizing bacteria (HUB) was achieved through the use of nutrient agar (spread plate technique) and mineral salts agar (vapour phase transfer technique) in the enumeration of THB and HUB respectively.

Results: After a 42-day period, there was a significant difference, (p <0 .05) in the percentage loss of total petroleum hydrocarbon between the various treatment options. Sample D had the least percentage loss (33.6%) of total petroleum hydrocarbon, Sample A (50.5%), Sample B (73.1%) and Sample C had the highest percentage loss of 74.83%. The various bacterial counts (THB and HUB) increased progressively with increase in nutrient concentration.

Conclusion: The results revealed the applicability and effectiveness of slow release fertilizers in the bioremediation of hydrocarbon impacted soil. These novel SRFs are also recommended for their applicability in the bioremediation of water and sediments.