Journal of Petroleum & Environmental Biotechnology

Challenges Faced by Petroleum Industry due to Bio-Sludge and their Solutions

Alexander Hopkins^* Department of Petroleum Engineering, University of Wyoming, Wyoming, United States
^*Correspondence: Alexander Hopkins, Department of Petroleum Engineering, University of Wyoming, Wyoming, United States, Email:

Received: 02-May-2022, Manuscript No. JPEB-22-16760; Editor assigned: 06-May-2022, Pre QC No. JPEB-22-16760(PQ); Reviewed: 20-May-2022, QC No. JPEB-22-16760; Revised: 27-May-2022, Manuscript No. JPEB-22-16760(R); Published: 06-Jun-2022, DOI: 10.35248/2157-7463.22.13.462

Description

Through a combination of physical, chemical and biological processes, the petroleum industry generates a large amount of sludge from wastewater or Effluent Treatment Plants (ETP), resulting in oily, chemical and bio sludge, respectively. PRS is a complex mixture of hydrocarbons, water-oil emulsions, heavy metals and refractory components found in petroleum refineries. An oily sludge's total petroleum hydrocarbon (aliphatic and aromatic) concentration is typically 15%-50%, with 30%-85% water and 5%-50% solids. Alkanes, cycloalkanes, aromatics, asphaltenes and resins are among the hydrocarbons found in PRS. The storage and disposal of such large volumes of sludge, which create substantial environmental contamination and toxicity and which persist in the environment for longer periods of time and cannot be removed without treatment, is a major challenge for petroleum industry.

Incineration, pyrolysis, centrifugation, oxidation, froth-floatation, plasma gasification and other methods are used to treat PRS all over the world. Because oily sludge has calorific values ranging from 17,000 to 19,000 kJ/kg², incineration or pyrolysis at high temperatures of 500°C to 1100°C are interesting choices for treatment. However, other types of PRS, such as bio sludge, have significant moisture content, ranging from 70% to 85% and thus cannot be burned. Other methods, such as centrifugation, consume a lot of energy and oxidation necessitates chemical additions (Fenton's reagent, permanganate, ozone), which are costly. Overall, the prevalence of these treatments is unsustainable economically or environmentally, particularly in developing nations like India.

Treatments for reduction of sludge

Anaerobic Digestion (AD), for example, is a green solution to the treatment and utilization of PRS since it produces methane rich biogas (for fuel and energy generation), improves sludge dewater ability and stability and reduces overall toxicity. Hydrocarbons have been discovered to be a source of electron donors and carbon for bacteria during anaerobic biodegradation under redox conditions. However, AD of PRS is difficult since it is dependent on the concentration of toxicants that inhibit methaneproducing bacteria as well as the existence of recalcitrant chemicals.

Hydrocarbons' recalcitrance is due to unfavorable environmental circumstances and a lower prevalence of bacteria that use hydrocarbons in anaerobic environments. As a result, establishing a favorable microbial inoculation for PRS AD is critical, as it will boost microbial diversity while also improving biodegradation efficiency and solubilization. Microbial inoculums should be homogeneous, sieved and pre-incubated, with a diverse microbial population to ensure optimal hydrolytic and methanogenic activity.

There are few studies that indicate AD of petrochemical waste employing a microbial source from a continuously operating anaerobic digester or wastewater treatment sludge. However, there are no studies comparing the utilization of non-acclimated and well-acclimated methanogenic inoculum containing appropriate microbial communities for PRS AD. Furthermore, because the hydrolysis rates of complex substrates are low, pretreatment is required for simple access by anaerobic bacteria.

Various studies have looked into using thermal pretreatments to improve the breakdown of refractory organic compounds in sewage sludge and waste activated sludge from various industries. However, the heat application mechanism chosen can be effective up to a specific temperature, after which inhibitory chemicals occur, lowering the biogas yield.

There are few studies that look at how different forms of heat application affect PRS biodegradability, solubilization and fatty acid buildup under optimal working conditions. During the digestion period, AD of any organic substrate produces nutrientrich digestive, but for hydrocarbon-rich substrates, microorganisms should use these hydrocarbons for their survival by synthesizing enzymes that catalyze anaerobic reactions, thereby degrading the complex substrates into less toxic and simpler compounds. There is a scarcity of relevant literature testing the toxicity of such substrates following anaerobic digestion.

The effectiveness of anaerobic biodegradation and methane production from PRS in the presence of two distinct inoculations (undigested and anaerobically acclimated or digested) at various mixing ratios is compared. Different heat modes are applied to PRS to determine the best heat mode for pretreatment with the most effective inoculum. To determine the economic viability of the pretreatment utilized, a morphological examination of the substrate and an energy assessment of recovered energy after pretreatment are conducted. In addition, PRS phytotoxicity (before and after methane production) is tested on mung bean (Vigna radiata L.) for environmental safety.