Liming Chen

Degradation of polycyclic aromatic hydrocarbons by microbial consortia enriched from three soils using two different culture media

A consortium composed of many different bacterial species is required to efficiently degrade polycyclic aromatic hydrocarbons (PAH) in oil-contaminated soil. We obtained six PAH-degrading microbial consortia from three oil-contaminated soils using two different isolation culture media. Denaturing gradient gel electrophoresis (DGGE) and sequence analyses of amplified 16s rRNA genes confirmed the bacterial community was greatly affected by both the culture medium and the soil from which the consortia were enriched. Three bacterial consortia enriched using malt yeast extract (MYE) medium showed higher degradation rates of PAHs than consortia enriched using Luria broth (LB) medium. Consortia obtained from a soil and then added back to that same soil was more effective in degrading PAHs than adding, to the same soil, consortia isolated from other, unrelated soils. This suggests that inoculum used for bioremediation should be from the same, or very similar nearby soils, as the soil that is actually being bioremediated.

Bioremediation of hydrocarbon degradation in a petroleum-contaminated soil and microbial population and activity determination.

Bioremediation of hydrocarbon degradation in petroleum-polluted soil is carried out by various microorganisms. However, little information is available for the relationships between hydrocarbon degradation rates in petroleum-contaminated soil and microbial population and activity in laboratory assay. In a microcosm study, degradation rate and efficiency of total petroleum hydrocarbons (TPH), alkanes, and polycyclic aromatic hydrocarbons (PAH) in a petroleum-contaminated soil were determined using an infrared photometer oil content analyzer and a gas chromatography mass spectrometry (GC-MS). Also, the populations of TPH, alkane, and PAH degraders were enumerated by a modified most probable number (MPN) procedure, and the hydrocarbon degrading activities of these degraders were determined by the Biolog (MT2) MicroPlates assay. Results showed linear correlations between the TPH and alkane degradation rates and the population and activity increases of TPH and alkane degraders, but no correlation was observed between the PAH degradation rates and the PAH population and activity increases. Petroleum hydrocarbon degrading microbial population measured by MPN was significantly correlated with metabolic activity in the Biolog assay. The results suggest that the MPN procedure and the Biolog assay are efficient methods for assessing the rates of TPH and alkane, but not PAH, bioremediation in oil-contaminated soil in laboratory.

Remediation of saline-sodic soil with flue gas desulfurization gypsum in a reclaimed tidal flat of southeast China.

Salinization and sodicity are obstacles for vegetation reconstruction of coastal tidal flat soils. A study was conducted with flue gas desulfurization (FGD)-gypsum applied at rates of 0, 15, 30, 45 and 60Mg/ha to remediate tidal flat soils of the Yangtze River estuary. Exchangeable sodium percentage (ESP), exchangeable sodium (ExNa), pH, soluble salt concentration, and composition of soluble salts were measured in 10cm increments from the surface to 30cm depth after 6 and 18months. The results indicated that the effect of FGD-gypsum is greatest in the 0-10cm mixing soil layer and 60Mg/ha was the optimal rate that can reduce the ESP to below 6% and decrease soil pH to neutral (7.0). The improvement effect was reached after 6months, and remained after 18months. The composition of soluble salts was transformed from sodic salt ions mainly containing Na(+), HCO3(-)+CO3(2-) and Cl(-) to neutral salt ions mainly containing Ca(2+) and SO4(2-). Non-halophyte plants were survived at 90%. The study demonstrates that the use of FGD-gypsum for remediating tidal flat soils is promising.

Effects of flue gas desulfurization and mined gypsums on soil properties and on hay and corn growth in eastern ohio.

Gypsum (CaSO·2HO) is a quality source of Ca and S and has various beneficial uses that can improve agricultural production. This study was conducted to compare rates of flue gas desulfurization (FGD) gypsum and commercially available agricultural (i.e., mined) gypsum as soil amendments on soils typical of eastern Ohio or western Pennsylvania. Two field experiments were conducted, one involving a mixed grass hay field and the other corn ( L.). Gypsum was applied once at rates of 0.2, 2.0, and 20 Mg ha and a seventh treatment was a zero rate control. Corn grain yields response to gypsum was mixed with significant differences between low and high gypsum rates in 2010 but not between gypsum and no gypsum treatments. In the hay study, the low and intermediate gypsum rates generally did not result in any significant changes compared with the control treatment. At the high rate of 20 Mg ha, the following results were observed for the hay study: (i) both gypsums generally increased Ca, S, and soluble salts (electrical conductivity) in the topsoil and subsoil, when compared with the control; (ii) the FGD gypsum decreased Mg in soil when compared with all other treatments, and mined gypsum decreased Mg when compared with the control; and (iii) there were few effects on soil concentrations of trace elements, including Hg. Also at the high application rate, hay yield for the first cutting (May) in 2009 and 2010 was significantly less for mined and FGD gypsum compared with the control, but increased yields in subsequent cutting resulted in no significant treatment differences in total annual hay yield for 2008, 2009, or 2010 or cumulative yield for 2008 to 2010. Overall, for the hay study, the absence of significant soil chemical effects for the intermediate gypsum rate and the decrease in soil Mg concentrations for the high gypsum rate indicate that an application rate of approximately 2.0 Mg ha would be optimal for this soil.

Composting of waste paint sludge containing melamine resin as affected by nutrients and gypsum addition and microbial inoculation

Melamine formaldehyde resins have hard and durable properties and are found in many products, including automobile paints. These resins contain high concentrations of nitrogen and, if properly composted, can yield valuable products. We evaluated the effects of starter compost, nutrients, gypsum and microbial inoculation on composting of paint sludge containing melamine resin. A bench-scale composting experiment was conducted at 55 °C for 91 days and then at 30 °C for an additional 56 days. After 91 days, the composts were inoculated with a mixed population of melamine-degrading microorganisms. Melamine resin degradation after the entire 147 days of composting varied between 73 and 95% for the treatments with inoculation of microorganisms compared to 55-74% for the treatments without inoculation. Degradation was also enhanced by nutrients and gypsum additions. Our results infer that large scale composting of melamine resins in paint sludge is possible.

EFFECTS OF GYPSUM ENHANCED COMPOSTS ON YIELDS AND MINERAL COMPOSITIONS OF BROCCOLI AND TALL FESCUE

Gypsum (CaSO4·2H2O) addition during composting of manure or biosolids can reduce ammonia nitrogen losses and represents a new method for controlling odors. Additional work is needed, however, to test the ability of the gypsum-containing composts to support plant growth and affect uptake of nutrients and heavy metals. A field study using broccoli (Brassica oleracea L. var. italica) and a growth chamber study using tall fescue (Festuca arundinacea) were conducted by application of composts at 10 Mg ha−1 for broccoli and 10 and 25 Mg ha−1 for tall fescue. Compared to composts without gypsum, at 10 Mg ha−1, gypsum composts significantly increased or had a strong trend to increase yields of broccoli and tall fescue. Gypsum composts affected concentrations of nutrient elements but did not increase concentrations of environmental concern elements in broccoli flowers and tall fescue tissue. Thus gypsum composts can be safely applied to soils to enhance crop growth.

Surface coal mine land reclamation using a dry flue gas desulfurization product: Short-term and long-term water responses

Abandoned coal-mined lands are a worldwide concern due to their potential negative environmental impacts, including erosion and development of acid mine drainage. A field study investigated the use of a dry flue gas desulfurization product for reclamation of abandoned coal mined land in USA. Treatments included flue gas desulfurization product at a rate of 280 Mg ha(-1) (FGD), FGD at the same rate plus 112 Mg ha(-1) yard waste compost (FGD/C), and conventional reclamation that included 20 cm of re-soil material plus 157 Mg ha(-1) of agricultural limestone (SOIL). A grass-legume sward was planted after treatment applications. Chemical properties of surface runoff and tile water (collected from a depth of 1.2m below the ground surface) were measured over both short-term (1-4 yr) and long-term (14-20 yr) periods following reclamation. The pH of surface runoff water was increased from approximately 3, and then sustained at 7 or higher by all treatments for up to 20 yr, and the pH of tile flow water was also increased and sustained above 5 for 20 yr. Compared with SOIL, concentrations of Ca, S and B in surface runoff and tile flow water were generally increased by the treatments with FGD product in both short- and long-term measurements and concentrations of the trace elements were generally not statistically increased in surface runoff and tile flow water over the 20-yr period. However, concentrations of As, Ba, Cr and Hg were occasionally elevated. These results suggest the use of FGD product for remediating acidic surface coal mined sites can provide effective, long-term reclamation.

Enzyme activities in soil treated with sulfite- or sulfate-based flue gas desulfurization products

A study was conducted to examine the impact of synthetic calcium sulfite (CaSO3u2009·u20090.5H2O) and calcium sulfate (CaSO4u2009·u20092H2O, i.e., gypsum) from flue gas desulfurization (FGD) on soil enzyme activities, used as soil quality indicators, following land application. We used application rates of 0, 1.12xa0Mgxa0ha−1 of FGD-CaSO3 (CaS-1.12T), 3.36xa0Mgxa0ha−1 of FGD-CaSO3 (CaS-3.36T), and 1.12xa0Mgxa0ha−1 of FGD-gypsum (Gyp-1.12T). The field experiments were conducted on a silt loam soil with 1.6xa0% total C and a pH of 6.5. No crop was grown during the experiment. The concentration of water soluble SO42−-S and the associated electrical conductivity (EC) significantly increased during the first 2xa0weeks following gypsum application but decreased later on (2–4xa0weeks) due to leaching. There was no significant difference between the Gyp-1.12T and CaS-1.12T treatment after approximately 2xa0weeks indicating all of the sulfite in the CaS-1.12T treatment was completely oxidized to sulfate. In contrast, the sulfite treated with highest application rate (CaS-3.36T) was not completely oxidized within the 12-week experimental period. Application of FGD-CaSO3 and FGD-CaSO4 did not negatively affect C and N mineralization because β-glucosidase and β-d-glucosaminidase activities did not show any negative change compared with the control. Arylsulfatase activity of the CaS-1.12T treatment markedly declined compared with Gyp-1.12T and control, but then increased after 2xa0weeks. The arylsulfatase activity reduction, however, persisted for the duration of the experiment in the CaS-3.36T treatment. These activity changes were similar to the observed oxidation pattern of sulfite to sulfate, which indicated that arylsulfatase activity could be used as an indicator for the extent of sulfite oxidation in soil.

Windrow Composting of Waste Paint Sludge Containing Melamine Resins

ABSTRACT Melamine resins (MR), widely used in various industries, are thermosetting plastics that have hard and durable properties. These resins can be introduced into the environment as components of waste products or via industrial effluents. It is important to seek environmentally friendly means to recycle, remove, or degrade melamine resins before they are released to the environment. Waste paint sludge containing MR has been shown to be efficiently composted under bench-scale conditions. In this study, the impacts of C/N ratios on windrow composting of waste paint sludge containing MR were evaluated. As composting proceeded, temperature, concentrations of MR and melamine degradation products (i.e., ammeline, ammelide, and cyanuric acid) were determined. After 98 days of composting, 87.5, 83.3, 80.9, and 70.1% of the initial MR were degraded under the treatments with C/N ratios of 30, 33, 35, and 37, respectively. Degradation of MR was enhanced by relatively low C/N ratios. Significant amounts of plant nutrients were found in the final composts, while heavy metals were well below values considered to be of concern regarding surface water quality or crop production. We conclude that adjusting C/N ratio to approximately 30 in the initial mixtures with oat and hay straws can increase the degradation of MR and its derivatives during windrow composting of waste paint sludge containing MR and produce a good quality compost product.