A Study on the Feasibility of Integrated-Composting as a Method for the Remediation of Hydrocarbon-Contaminated Soils Under Intense Rainfall Conditions

  • Aliyu Shuaibu

Student thesis: Doctoral Thesis

Abstract

The current growth-surge in global population has led to an increase in the demand for crude oil and its constituent products to support and improve the day-to-day running of our lives. However, this has been accompanied with pollution due to frequent hydrocarbon spills that have become a great cause for concern in the world today. A significant number of these occurrences are a direct consequence of anthropogenic activities. These spilled hydrocarbons have not only caused environmental degradation but also adversely affected human and animal well-being.

This study assesses the suitability and potential use of integrated-composting as a method for remediating hydrocarbon-contaminated soils. Animal manures (cow and chicken) and white-rot fungi (Pleurotus ostreatus) were utilised as the bacteria and fungi dominated inocula during the integrated-composting process. The effectiveness of the remedial method was examined by monitoring the changes in the concentration of hydrocarbon contamination, microbial population, and physicochemical properties. An examination into the application of this method under intense rainfall conditions was also investigated with a view to determining if the leachate released would possess high pollutant levels. In a bid to establish the suitability of the treated soil and leachate generated, contaminant concentrations in both matrixes were measured against existing soil and water quality guideline limits for agricultural purposes. The study consisted of two phases. The first phase involved laboratory-based bench-scale dynamic respirometric tests (DR-4) over a 24-day period, carried out as a screening protocol to establish the most effective amendment combination for the treatment of the contaminated soil. The second phase was a pilot study that used 100 L reactors fitted with external air supply with leachate collection component following the rainfall simulation tests.

The results of the study showed that integrated-composting was successful in the breakdown of hydrocarbon contaminants. Total petroleum hydrocarbons (TPHs) saw reductions of up to 90%. However, it was noted that Low (LMW) and medium (MMW) molecular weight polycyclic aromatic hydrocarbons (PAHs) were considerably degraded compared to high molecular weight (HMW) PAHs over the test period. The treatment with animal manures only and fungi only showed the most potential while the manure-fungi combination treatment showed a comparatively lower rate of contaminant degradation. It was also established that a number of physicochemical parameters influenced the rate of degradation. Finally, the results indicated that the contaminant levels in leachate were within permissible threshold ranges and thus deemed suitable and safe for agrarian uses.
Date of Award8 Sep 2022
Original languageEnglish
SupervisorJohn Williams (Supervisor), Muhammad Ali (Supervisor) & Fay Couceiro (Supervisor)

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