This paper describes a bioreactor set-up used to simulate degradation of petroleum hydrocarbons in a static biopile. The largescale test was performed in a 28 m 3 custom-designed reactor. Oily sludge (40% by weight, having 7% dry matter [DM], and hydrocarbons C 10 -C 40 160,000 mg kg -1 DM) was mixed with organic-rich amendments -mature oil-compost (40%) and garden waste compost (20%). Within the reactor, the temperature and soil gases were monitored continuously during 370 days via 24 measurement points. Also, moisture content was continuously recorded and airflow through compost mix occasionally measured. Three-dimensional ordinary kriging spatial models were created to describe the dynamic variations of temperature, air distribution, and hydrocarbon concentration. There were large temperature differences in horizontal and vertical sections during initial months of composting only. Water content of the mixture was uneven by layers, referring on relocation of moisture due to aeration and condensation. The air distribution through the whole reactor varied largely despite of continuous aeration, while the concentration of O 2 was never reduced less than 1-2% on average. The results showed that composting of sludge using force-aerated static biopile technology was justified during the first 3-4 months, after which the masses could be re-mixed and heaped for further maturation in low-tech compost windrows. After 370 days of treatment, the content of hydrocarbons (C 10 -C 40 ) in the compost mixture was reduced by 68.7%.
In order to assess the effectiveness of aerobic degradation with emphasis on the 16 U.S. EPA priority polycyclic aromatic hydrocarbons (PAH), oily sludge generated by a dissolved air flotation flocculation unit of a wastewater treatment plant in a petroleum refinery was amended with remediated oil-contaminated soil and non-mature garden waste compost 40:40:20 (wet weight) respectively. About 21 t of the mixture with a top-layer formed by 30 cm of remediated soil was treated in a 28 m3 air-forced reactor. The PAH concentration was monitored for 370 days. In the top-layer, a reduction of 88 % of the total extractable PAH was measured at day 62 and a final reduction of 93% at day 370. In the mixture, a reduction of 72% in total PAH was measured at day 62, followed by fluctuation in concentration with a final measured reduction of 53% at day 370. The analysis of individual PAH in the mixture suggested that volatilization and biodegradation are the main mechanisms responsible for the reduction of 2 ring PAH and 3-4 ring PAH, respectively. Fluctuation of 5-6 ring PAH concentrations with increase observed at the end of the period might result from a combination of the following: (i) sequestration of large PAH in the organic matrix (reducing bioavailability, biodegradability and eventually, extractability) and desorption as composting progresses; (ii) heterogeneous distribution of the stable large PAH in the mixture, thus affecting sampling. It was concluded that one-time composting in static-aerated biopiles with organic amendments as the sole strategy to treat oily sludge is very effective in reducing the content of 2-4 ring PAH, but it is not effective in reducing the content of 5-6 ring PAHs, even after a relatively long time span (370 d). The concentrations measured in the remediated soil that formed the top layer after 62 days of composting suggests that further relevant reduction of residual PAH (89% of total PAH and 69% of 5-6 ring PAH) can be obtained if the contaminated masses are exposed to a second thermophilic phase. This could be achieved by adding new easily biodegradable organic amendments to the contaminated masses after some months of composting, remixing and composting again for a minimum additional period of 2 months.
This paper focuses on the volatile organic compound emissions from baled municipal solid waste (MSW). The analytical methodology was based on sampling with adsorbent tubes once a month during seven occasions within a time period of 1 year. Automated analyses were carried out on-line work-up with thermal desorption directly connected to a gas chromatograph-mass spectrometer. The effect of different baling techniques, cylindrical and rectangular baling was compared. It was found that cylindrically baled MSW emitted larger concentration of esters than their rectangular counter parts. Conversely, aromatic compounds emissions dominated in rectangularly baled MSW. This indicates that different degradation mechanisms operate in the waste bales. Cylindrical and rectangular bales are generally wrapped with six layers of 250 microm thick low density polyethylene (LDPE). It was observed that by wrapping an extra six layers of LDPE film onto the bales, the emissions from cylindrical bales increased while emissions from the rectangular counterpart decreased. Over time, the volatile organic compound emissions from cylindrical bales decreased two orders of magnitudes from 96.2 +/- 20.8 microg m(-3) in September 2003 to 0.80 +/- 0.07 microg m(-3) in July 2004. The rectangular bales exhibited an almost identical relative emission reduction from 54.4 +/- 4.3 microg m(-3) in September 2003 to 0.46 +/- 0.02 microg m(-3) in July 2004. Future work will concentrate on full-scale storages, taking into account waste type, storage size, temperature development and the different baling techniques among other variables.
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