Comparison of Two Pleurotus Species and Their Consortium to Evaluate Their Potential for Biodegradation of Spent Drilling Mud

Abstract

Biodegradation potentials of two white rot fungi (Pleurotus ostreatus and Pleurotus pulmonarius) in soil contaminated with spent oil based drilling mud were investigated. The study was conducted over 63 days, with periodic monitoring after every 21 days. Four treatment options were used for the experimental set-up: Treatment A had P. ostreatus, B had P. pulmonarius, AB had both P. ostreatus and P. pulmonarius and the Control (without fungal spawn). The parameters monitored were pH, conductivity, total organic carbon (TOC), total nitrogen, available phosphorus, chloride, total heterotrophic bacterial (THB) count, total fungal (TF) count, heavy metals (Zinc, lead, Copper, Cadmium and Barium), and Total Petroleum Hydrocarbon (TPH). Furthermore, a phytotoxicity test was carried out to determine the effect of the treatments on maize (Zea mays var. indentata) plant growth. The results showed an increase in microbial population. Treatment A recorded the highest THB count of 2.65x107 (cfu/g) and Treatment C the highest TF count of 1.07x105 (cfu/g). The percentage loss of TPH was in the order of: AB (98.08%)>A (94.79%)>B (87.02)>Control (6.12%) at the end of 63 days. The values for pH for the treatments ranged from 6.05-8.08; conductivity (µS/cm) ranged from 6580-14540; TOC (%) ranged from 2.15-5.19; total nitrogen (mg/kg) ranged from 696.36-742.77; available phosphorus (mg/kg) ranged from 402.71-642.38; chloride (mg/kg) ranged from 3200-5980; zinc (mg/kg) ranged from 43.66-128.47 respectively, the copper (mg/kg) ranged from 20.09-89.29; barium (mg/kg) 53.92-237.98; cadmium (mg/kg) 5.38-24.98 and lead (mg/kg) ranged from 4.41-22.27. The results revealed that treatment option (consortium) AB was more efficient in remediating the contaminated soil. The phytotoxicity results showed that the vegetative growth attributes of the maize plant were more prolific in the treated and uncontaminated soil than in untreated soil after 28 days of cultivation. Although, the study indicates that P. ostreatus and P. pulmonarius showed good levels of biodegradation potential, the consortium proved to be a better alternative in biodegradation compared to the individual species.