Effect of fertilizer and biopolymers on hydrocarbon biodegradation in sediments

Abstract

Bioremediation of marine foreshore environments contaminated with petroleum hydrocarbons is an environmentally safe and economical clean-up technology. In this study, the effect of two biopolymers, chitin and chitosan, as well as a slow release fertilizer, Osmocote™ (Osmocote), on the bioremediation of oil-spiked beach sediments was investigated using an open irrigation system. Nutrient concentrations (i.e. NH3-N, NO3 --N and PO4 3--P) were measured in sediment leachate, while the microbial activity in the petroleum-contaminated sediments was determined by measurement of dehydrogenase activity of the indigenous microbial biomass. Biodegradation was tracked by GCMS analysis of selected aliphatic hydrocarbons (n-C12 to n-C32, pristane and phytane) and PAHs (2- to 6-ring). In summary, Osmocote was effective in sustaining high levels of nutrient concentration in sediments. At the end of 49-day experiment, total loss of aliphatics was significantly greater in oil-spiked sediments treated with Osmocote (i.e., more than 97%) compared to without (i.e., 40.4-54.1%). Chitin released nitrogen gradually during the experiment, and increased the alkane biodegradation in oil-spiked sediments by approximately 13% compare to the control. The loss of total target PAHs in the sediments treated with the combination of Osmocote and chitosan (i.e., 86.5%) was the highest among all the sediments.