The list of the types of oil raw sludge includes off-grade oily or hydrocarbon-bearing mixtures. The main sources of oil raw sludge are:
- Oil polluted priming coats of sectional and other industrial slots.
- Priming coats soaked with oil after oil pipeline accidents.
- Ground precipitation in oil-collecting reservoirs.
- Hard or liquid wastes from oil-processing oil-chemical industries.
Harmful Environmental Impacts of Oil Raw Sludge
Usually oil raw sludge is taken to raw sludge storage, where it is burnt or buried. At the process of burning large amounts of raw sludge (dozens and hundreds of tons of raw sludge) the atmosphere is polluted by the products of incomplete hydrocarbon oxidizing. It is also added by a mass outburst of carbon monoxide and smoke black.
Smoke contains a number of carcinogenic substances, such as benzopyrones and dioxins, that are also produced when raw sludge is burnt. Moreover, it is not possible to achieve complete burn-up of hydrocarbons in the oil raw sludge group that contain extraneous matters of mineral components: soil, sand, etc.
Partially burnt-out oil raw sludge is burnt in special storehouses. Sludge that didn’t undergo burning is stored there as well.
Such sludge storehouses are very dangerous due to their high fire danger and the possibility of the spreading out of hydrocarbons by groundwater and precipitation.
Construction and guarding of these storehouses require significant resources. Ground where the storehouse is constructed cannot be utilized for several dozens of years, which also requires additional resources. Sludge burning requires air pollution payments.
However, oil raw sludge can be recycled and transformed into environmentally-friendly substances using bioremediation techniques. This operation allows decrease hydrocarbon concentration to the admissible level in 1-2 years thus ensuring significant savings that are needed for construction and management of storehouses and penalties.
Biological Treatment of Oil Sludge
One of such operations is microbiological reprocessing with the usage of harmless microflora representatives that can decompose oil with excretion of environment friendly substances. Since structure and physical characteristics of sludge vary, the process of its biological decomposition requires a number of measures that lead to inactivation of toxic sludge components.
The list of oil sludge components includes:
- Hydrocarbons (oil, oil products)
- Water
- Mineral salts from reservoir waters
- Mechanical extraneous matters of natural or technological origin
- Heavy metals.
Biological decomposition of oil sludge have been used for sludge-containing groundwater that can be used on the spot without violation of production process. These methods were tested in 25 oil extraction and processing slots 1997.
The developed methods allow decomposition of sludge that differs according to the following characteristics: viscosity, salinity, nature of mechanical extraneous matter, and heavy metals presence.
In sum, the methods aims at the usage of adapted indigenous microorganisms cultures. The culture is selected in chemostasis in order to have it adapted to the negative factors: salinity, low temperatures and others. This process allows to extract a group capable of active hydrocarbon decomposition with the presence of negative factors.
In summer time (50-70 days) it is possible to reduce hydrocarbon concentration from 200-300 grams per kilogram to 5-10 grams per kilogram, which meets admissible norms of environment-friendly level of residual pollution. Recultivation becomes possible without the exportation of soil from industrial slots and without the stopping of industrial process.
If there is a need for sludge exportation, the recultivation takes place on special polygons. Thus, in summer time it is possible to purify up to 1000-1500 tons of sludge on 1 hectare of plantation. These polygons can work in continuous regime with the constant exportation of the purified soil and its replacement with polluted groundwater.
In order to support biological activity it is possible to ensure heating of the purified sludge. In winter time the process of biological degradation stops. During this period germs experience the negative temperature period and in spring restore their activity. The cleaned soil saturated with oil assimilating microorganisms can be used for the treating of oil overflows.
Salman is a prolific environmental writer, and has authored more than 500 articles in reputed journals, magazines and websites. He is proactively engaged in creating mass awareness on renewable energy, waste management, sustainability and conservation all over the world.
Salman can be reached on salman@cleantechloops.com
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