Assessment Of Effects For Composting Treatment And Phytoremediation Of Oily Sludge

The effects of composting treatment on oily sludge with straw and organic fertilizers were studied during a 115d experiment. Total petroleum hydrocarbon (TPH) content, temperature, C/N/P ratios and the amount of functional microorganisms were monitored during the composting process and petroleum components and biotoxicity before and after compost were also analyzed. The results showed that TPH contents decreased from 123±1.3g·kg^-1 to 71.7±0.7 g·kg^-1, giving a degradation rate of 42%, which was 2.5 times higher than the treatment without composting. In the compost treatment the highest temperature reached 50℃on day 21th. The counts of hydrocarbon degraders, aromatic hydrocarbon degraders and heterotrophic bacteria in the composted sludge increased by about 2 orders of magnitudes compared with those in the initial sludge. Moreover, EC50 in the oily sludge increased from 1.77±0.28 mg·ml^-1 before compost to 2.76±0.38 mg·ml^-1 after compost indicating a decrease in biotoxicity of the composted sludge.Effects of phytotreatment on oily sludge with 5 plant species (Sorghum, corn, Glycine max Festuca arudinace, Alfalfa sp.,) were also studied during a 120d experiment. TPH content and components, the functional diversity and biotoxicity after phytoremediation were analyzed. The results showed that the TPH content from 57.7±2.90g·kg^-1 to 37.7±1.16⁴5.7±2.50g·kg^-1 after phytoremediation . Among them , the removal rate of Glycine max, Alfalfa sp. and Festuca arudinace were significantly high, giving a degradation rate of 34.2%, 28.5%, and 26.7% respectively.And the TPH removal rate of Soybean was 3 times high than the treatment without plants. Moreover, the EC50 of all phyto- treatment increased from 4.36±0.09 mg ml^-1 before phytoremediation to 10.5±1.17¹7.9±3.74 mg ml^-1 after phytoremediation, among them the EC50 of alfalfa treatment reached the highest (17.9±3.74 mg·ml^-1) after phytoremediation indicating a decrease in biotoxicity of the sludge. Furthermore, the functional diversity of all phytotreatments raised compared with control.