This study describes a laboratory scale development of an in-situ bioremediation method, which uses a water table management system to supply nutrients to subsoil microorganisms, for biostimulation and subsequent biodegradation of pollutants such as fertilizer-nitrate and hydrocarbons (e.g., diesel oils), in the unsaturated zone of the soil. The study, which was divided into two parts: first nitrate bioremediation and secondly diesel biodegradation, was carried out on packed soil columns. / For the nitrate study, different levels of glucose were introduced into packed soil columns, 1,000 mm long x 200 mm, diameter, via subirrigation in order to supplement the organic carbon levels in the soil. Two sandy soils were used, with 1.6% and 3.4% organic matter content, respectively; and the water table in the soil columns was maintained at a depth of 350 mm below the surface. Fertilizer-nitrate was applied to the soil surface at a rate of 180 kg/ha nitrate-N. Simulated rainfall was used to leach nitrates to lower depths. The efficacy of using the subirrigation system, as a method for nutrient delivery in the bioremediation of leached nitrate, was monitored with time and with reference to the nitrate residue, redox potential of the soil solution, and solubilized Fe and Mn. / Leached nitrate was denitrified to less than 10 mg/L nitrate-N, which is the limit permitted in drinking water. The ideal organic carbon range was considered to be the glucose level (20 mg/L glucose-C) that reduced mom nitrate and gave redox potential and soluble Fe and Mn levels, similar to the control soil solution, when subjected to 96 days of subirrigation. Successful delivery of nutrient for the bioremediation of nitrate, within the farm boundaries, will be considered a "break through" toward nitrate residue control if this novel approach to nitrate control is demonstrated in the field. The delivery method will offer a technical solution to on-farm nitrate pollution. It is inexpensive, easy to adopt, and does not require major changes in the current farm practices. / In the second part of the study, a diesel contaminated sandy soil was packed in columns, 2,000 nun long x 200 nun diameter. The subirrigation method was used to supply two different combinations of treatments to the microorganisms in the soil for the biodegradation of the diesel namely: air, water and nutrients (N, P etc.), and air and water. The success of using subirrigation, to deliver nutrients to the soil in the columns, was monitored by measuring the trend in the reduction of soil diesel-TPH (diesel-total petroleum hydrocarbon) residue with time. Results obtained from the treated columns were compared with each other, and with the control columns undergoing passive biodegradation. / The study showed that subirrigation can be used as a method of nutrient delivery in the -bioremediaton of diesel contaminated soil. The TPH in the contaminated soil decreased, from an initial 670 mg diesel TPH/kg soil to an acceptable level of 40 mg diesel TPH/kg soil, in 82 days in the columns subjected to a combination of nutrient, air and water treatments. If this method of delivering biostimulants to the subsoil microbial population is demonstrated in the field, it will be invaluable to in-situ bioremediation of contaminated soils.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.34691 |
| Date | January 1996 |
| Creators | Ugwuegbu, Benjamin U. |
| Contributors | Prasher, S. O. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Agricultural and Biosystems Engineering.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001642421, proquestno: NQ37038, Theses scanned by UMI/ProQuest. |
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