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.

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.