Reliability of solid phase microextraction in estimating bioavailability of pyrene in soil.

Solid phase microextraction (SPME) coupled with gas chromatography was employed to estimate bioavailability of pyrene in soils with different properties of textures, organic matter contents (SOM) and aging periods. Experimental results indicated that biodegradation rates increased from 0.10 (sandy loam) to 0.15 (silty loam) μg g-1 hr-1. By contrast, biodegradation rate decreased from 0.10 (1.3% SOM) to 0.04 (7.6% SOM) μg g-1 hr-1. The amounts of pyrene biodegraded decreased 27% when SOM was modified from 1.3 to 7.6%, indicating that distributions of pyrene in soils at biodegradation end points were affected by the SOM. Sequestration as measured by sonication extraction had evidently occurred in aged soil samples. SPME measurements slightly overestimated the amount of pyrene degraded by indigenous and seeded microorganisms, in soils with the different properties (correlation coefficient, R2 = 0.74). The present study demonstrates that the SPME method can not replace biodegradation tests commonly used for predicting bioremediation efficacy.

Bioavailability evaluation of naphthalene in soil using persulfate oxidation and ultrasonic extraction method.

Bioavailability is defined as the fraction of a soil contaminant readily available for microbial degradation and for naphthalene it could be estimated by conventional exhaustive extraction methods. In this study, a novel method that employed persulfate oxidation in combination with ultrasonic extraction (POUSE) was developed. Three parameters, temperature, duration of persulfate oxidation, and the ratio of persulfate to soil organic matter (S2O8 2- /SOM; g g-1), were investigated to obtain an optimum operating conditions. Under the condition, naphthalene bioavailability estimated by the POUSE method was verified and compared with other three exhaustive methods i.e. sonicator, supercritical fluid extraction (SFE), and soxhlet extraction (SE). When the S2O8 2-/SOM ratio was controlled at 11.6 g g-1, the optimum operating conditions of the POUSE method were 70oC and 3 hr, for the temperature and duration. Under these conditions, the residual naphthalene concentrations were correlated well with the residual naphthalene concentrations for both the cases of freshly spiked and aged soils. By contrast, the sonicator, SFE, and the SE overestimated the naphthalene bioavailability since these three methods extracted naphthalene much more than that of biodegradation test. These results demonstrated that the POUSE could estimate more precisely the naphthalene bioavailability.

Effect of applying biosolids on the biodegradation of toluene and naphthalene contaminated soils.

Biosolids contain nutrients, organic matters and micro-organisms that can provide soil benefits. In this study, toluene and naphthalene-contaminated soils were used to investigate the effect of applying biosolids on the enhancement of the biodegradation rate. The oxygen uptake rate (OUR) was determined with a respirometer and was used to calculate the oxygen uptake percentage of substrate in biosolids (a value) using a two-phase respirogram. Experimental result showed that the application of biosolids had positive effect on the enhancement of the biodegradation rate of toluene and naphthalene in the contaminated soils. The biodegradation rates of toluene and naphthalene were 15% and 20% in soils without applying biosolids, respectively. With the biosolids, its biodegradation rate for the two contaminants was about 4-fold higher in relative to control and the maximum value occurred in a soil to biosolids ratio as 1: 0.5. The a value for toluene and naphthalene was in the levels of 10-20% which revealed that the biosolids used in this study was mainly composed by micro-organism.

Biological heat potential and temperature effect of an autothermal thermophilic aerobic treatment (ATAT) system.

This study focused on the evaluation of the specific biological heat potential (hb) of a food-processing artificial wastewater in the autothermal thermophilic aerobic treatment (ATAT) system. A novel experimental method was developed to evaluate the hb value by using the heat balance model under the steady state. This system was daily fed with oily and artificial wastewater at 21460 mg l-1 COD. The sludge retention time (SRT) was controlled at 15 days. The results showed that the average values of hb were 3.25 to 3.63 kcal g-1-COD-removed for the artificial wastewater. The values of true growth yield (Y0) were 0.08 to 0.19 mg-MLSS mg-1-COD for the food-processing wastewater at different temperatures. The COD removal efficiency was 77 to 91%, and it was decreased as temperature increased. But, the oil and grease (O and G) removal efficiency was 50 to 69%, and increased as temperature increased. These results might indicate that oil and grease become more soluble and accessible to microorganisms at high temperatures. The study indicated the temperature effect constant (Æ) of van’t Hoff- Arrhenius law was 0.958, which explained and showed typical characteristics in the low sludge yield of an ATAT process.

Evaluation of specific biological heat potential of oily wastewater in an autothermal thermophilic aerobic treatment system.

This study focuses on the specific biological heat potential (h(b)) of oil and grease wastewaterin an autothermal thermophilic aerobic treatment (ATAT) system. A novel experimental device was applied to evaluate h(b) by using heat balance model under steady state. In the study the treatment system was daily fed with realistic and artificial wastewater at 11250 and 17420 mg COD l(-1), respectively. The wastewater was rich in oil and grease at 1220 and 600 mg l(-1), respectively. The sludge retention time (SRT) was controlled at 5 days. The results showed that the average values of h(b) were 3.7 and 3.1 kcal g(-1) COD removed and the true growth yield (Y0) were 0.10 and 0.13 mg MLSS mg(-1) COD for realistic and artificial wastewater respectively. These two systems could maintain reactoroperating temperatures at 43 degrees C and 48 degrees C, respectively. The COD removal efficiency was as high as 90 to 97%. The oil and grease reduction was 68 to 72%. The high organic matter removal capacity and low sludge yield of ATAT process have been demonstrated.

Using respirometer in biodegradation phenomenon of natural organic matters.

This study conducted in monitoring respirometer oxygen consumption of aerobic microorganism during biodegradation processes of ozonated organic matters, which can estimate both biodegraded efficiency and coefficient of natural organic matters (NOMs) in water source. It can be proposed that different ozone dosage might change biodegradation characteristics of organic matters. The result reveals that higher ozone dosage may cause higher biomass yield coefficient of microorganism, and cultured microorganism may easily utilize biodegradation organic matters (BOMs) produced by ozonation, finally increasing overall removal efficiency. Therefore, using respirometer to evaluate the production of BOMs by ozonation before the biological treatment is effective for controling ozone dosage and enhancement of NOMs removal by biological processes.