Microbe assisted phytoremediation of oil sludge and role of amendments: a mesocosm study

A mesocosm study was evaluated to elucidate the influence of amendments such as microbial consortium, plant (Vetiveria zizanioides), bulking agent (wheat husk) and nutrients on remediation of oil sludge over a period of 90 days. The experiment was conducted in a 15 m(2) plot which was divided into eight units comprising of soil sludge mixture (1:1) at CSIR-NEERI premises. During the experiment, oil degradation was estimated gravimetrically and polyaromatic hydrocarbons (PAHs) were quantified on GC-MS. Additionally, dehydrogenase activity was also monitored. The treatment integrated with bulking agent, nutrients, consortium and plant resulted in 28-fold increased dehydrogenase activity and complete mineralization of higher PAHs. Furthermore, 72.8 % total petroleum hydrocarbons (TPH) degradation was observed in bulked treatment with plant, nutrients and consortium followed by 69.6 and 65.4 % in bioaugmented treatments with and without nutrients, respectively, as compared to control (33.4 %). A lysimeter study was also conducted simultaneously using Vetiver and consortium to monitor groundwater contamination by heavy metals in oil sludge which showed a marked decrease in the concentrations of metals such as lead and cadmium in leachates. This study validates a holistic approach for remediation of oil sludge contaminated soils/sites which is a burning issue since decades by the use of microbe assisted phytoremediation technology which not only solves the problem of oil contamination but also takes care of heavy metal contamination.