Fungal Bioremediation of Creosote-Contaminated Soil: A Laboratory Scale Bioremediation Study Using Indigenous Soil Fungi

The aim of the study is to determine the efficacy of indigenous soil fungi in removing (PAHs) from creosote-contaminated soil with a view to developing a bioremediation strategy for creosote-contaminated soil. Five fungal isolates, Cladosporium, Fusarium, Penicillium, Aspergillus and Pleurotus, were separatelyinoculated onto sterile barley grains and incubated in the dark. Thecolonized barley was inoculated onto creosote-contaminated (250 000 mg kg^?1) soil in 18 duplicate treatments and incubated at 25 °C forseventy days. The soil was amended with nutrient supplements to give a C:N:Pratio of 25:5:1 and tilled weekly. Creosote removal was higher (between 78and 94%) in nutrient supplemented treatments than in the un-supplementedones (between 65 and 88%). A mixed population of fungi was more effective(94.1% in the nutrient amended treatment) in creosote removal than singlepopulations wit a maximum of 88%. Barley supported better fungal growthand PAH removal. Pleurotus sp. removed the creosote more than the other isolates. Two andthree-ring PAHs were more susceptible to removal than the 4- and 5-ringPAHs, which continued to remain in small amounts to the end of thetreatment. Reduction of creosote in the present study was higher than wasobserved in an earlier experiment using a consortium of microorganisms, mainly bacteria, on the same contaminated soil (Atagana, 2003).     

Bioremediation of Co-contamination of Crude Oil and Heavy Metals in Soil by Phytoremediation Using Chromolaena odorata (L) King & H.E. Robinson

The capability of Chromolaena odorata (L) to grow in the presence of different concentrations of three heavy metals in crude oil-contaminated soil and its capability to remediate the contaminated soil was investigated using pot experiments. C. odorata plants were transplanted into contaminated soil containing 50,000 mg kg^?1 crude oil and between 100 and 2,000 mg kg^?1 of cadmium, nickel, and zinc and watered weekly with water containing 5% NPK fertilizer for 180 days. C. odorata did not show any growth inhibition in 50,000 mg kg^?1 crude oil. Plants in experiments containing 2,000 mg kg^?1 Cd showed little adverse effect compared to those in Zn-treated soil. Plants in 1,000 and 2,000 mg kg^?1 Ni experiments showed more adverse effects. After 180 days, reduction in heavy metals were: 100 mg kg^?1 experiments, Zn (35%), Cd (33%), and Ni (23%); 500 mg kg^?1, Zn (37%), Cd (41%), and Ni (25%); 1,000 mg kg^?1, Zn (65%), Cd (55%), and Ni (44%); and 2,000 mg kg^?1, Zn (63%), Cd (62%), and Ni (47%). The results showed that the plants accumulated more of the Zn than Cd and Ni. Accumulation of Zn and Cd was highest in the 2,000 mg kg^?1 experiments and Ni in the 500 mg kg^?1 experiments. Crude oil was reduced by 82% in the experiments that did not contain heavy metals and by up to 80% in the heavy metal-treated soil. The control experiments showed a reduction of up to 47% in crude oil concentration, which was attributed to microbial action and natural attenuation. These results show that C. odorata (L) has the capability of thriving and phytoaccumulating heavy metals in contaminated soils while facilitating the removal of the contaminant crude oil. It also shows that the plant??s capability to mediate the removal of crude oil in contaminated soil is not significantly affected by the concentrations of metals in the soil.     

The Use of Surfactants as Possible Enhancers in Bioremediation of Creosote Contaminated Soil

A study on five nonionic surfactants (Arkopal-N-060, Arkopal-N-080, Arkopal-N-100, Hosaf-541-KS and Tween-80)commercially available in South Africa was carried out todetermine their effect on the desorption and degradation ofcreosote in a soil contaminated with 250 000 mg kg^-1creosote with a view to developing a cost effective methodologyfor treating creosote contaminated soils. The surfactants werestudied in concentrations of 0.01, 0.1, 0.35, 0.5 and 1.0% (v/v) in liquid cultures. Results from the studies showedthat all the surfactants studied were able to enhance thedesorption and degradation of creosote to different extents. Theenhancement ranged from as little as <10% in 0.1% surfactant toas high as 45% in 0.5% surfactant. The effect on degradation ofcreosote was more obvious (30–65%) in the different surfactantsat different concentrations. Arkopal-N-060 was observed to be themost effective in the desorption and degradation of creosote. Theeffect of Hosaf-541-KS on the degradation of creosote was foundto be comparable with those of Arkopal-N-060, however, itsdesorption capabilities were much lower than those of Arkopa-N-060.The concentration of the surfactant was found to play asignificant role in desorption of creosote. It was observed thatsurfactant concentrations of 0.35 and 0.5% were the mosteffective in the desorption of creosote. Above and below theseconcentrations, the effect of the surfactants was observed todecrease. All surfactants studied were not found to inhibitmicrobial growth at the concentrations studied.     

Batch Culture Enrichment of Indiginous Soil Microorganisms Capable of Catabolizing Creosote Components

Batch enrichment cultures for creosote catabolizing microorganisms was carried out using a creosote-contaminated soil as the inoculum. The flasks were separately spiked with phenol, o-cresol, m-cresol, p-cresol, naphthalene, anthracene, phenanthrene, pyrrole, fluorene, pyrene, fluoranthene, chrysene,benzo(a)pyrene and creosote (a complex mixture of about 400 compounds) in concentrations of 50, 100, 500, 1000, 5000, 10 000, 15 000, 20 000, 25 000 and 30 000 mg L^-1. The flasks were incubated on a rotary shaker in the dark at 30 °C. Samples for analysis were taken from the flasks every three days for three weeks. Counts of microorganisms were observed to be highest in most cases in 5000 mg L^-1 cultures. The pH values were observed to fluctuate between 5 and8 but this did not seem to affect the growth of the organisms except at 50 and 100 mg L^-1 in the phenolics and some polycyclic aromatic hydrocarbons (PAHs) were the decreases correlated with decreases in cell counts. The isolates in the first week were mainly of one morphological type in most cultures. In subsequent weeks, the populations became mixed. The higher molecular mass PAHs at higher concentration continued to support only a few types of organisms. Isolates included bacteria, actinomycetes and fungi. The phenolics and naphthalene were more readily removed (up to 100%) from the cultures. Other hydrocarbons removal were between 45 and 83% with the higher molecular mass compounds being most recalcitrant. The decreases in creosote concentration was similar to those in the phenolic compounds and the lower molecular mass compounds up to a concentration of 10 000mg L^-1. Decreases in creosote concentration started to decrease from a concentration of 15 000 mg L^-1 upward. Subsequent subculturing was observed to enhance the degradative capabilities of the isolates and the further removal of the higher molecular mass compounds. However, this enhanced degradation was much lower in creosote cultures than in the other cultures.