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Thesis (Ph. D.)--University of Queensland, 2002. / Includes bibliographical references.

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Thesis (M.S. - Soil and Water Science)--University of Arizona. / Includes bibliographical references (leaves 86-91).

Water, flowing through beds of refuse in a sanitary landfill, will leach organic and inorganic substances from the fill. These leached substances may be a source of pollution for receiving surface or ground waters. The leachate, before it is diluted by the receiving water, can usually be classed as a very strong waste water; that is, the levels of the waste water parameters COD, Suspended Solids, low dissolved oxygen and turbidity are many times those found in normal, municipal waste water. Added to these foregoing parameters are possible high levels of toxic chemicals and metals. It is now generally recognized that the leachate from refuse landfills should be controlled, and in some recently designed landfills, leachate collection is incorporated into the overall design. Toxic chemicals and metals are not adequately removed from waste waters by the standard biological sewage treatment processes; thus, the collected landfill leachate often requires pretreatment before it can be discharged to a municipal sewer system. If it is to be discharged to a natural receiving water, it requires more complete treatment. It was the purpose of this research to attempt to develop a physical-chemical treatment system for landfill leachate, such that the effluent might be safely discharged to a biological treatment plant or a natural receiving water. To deal with the extremely large number of possible chemical reagents, and to a lesser extent, physical methods available-, it was first necessary to select a number of primary candidates from prior information and theory available in the literature; secondly, it was advantageous to use a statistically designed experimental programme for screening those candidates chosen. In the screening process, no changes in the physical parameters screened, such as duration and speed of mixing or duration of settling, were found to be significant, if normal minimum times and usual speeds were used. Four chemical reagents, lime, ozone, ferric sulfate, and alum were indicated as having a potentially significant effect on the leachate-contained Total Solids (TS), Total Carbon (TC), Turbidity (Turb), Cadmium (Cd), Copper (Cu), Iron (Fe), Zinc (Zn), Potassium (K), Calcium (Ca), Sodium (Na), Phosphorus and the acid-base relationship as expressed by the term pH. The follow-up experiments determined that only two of the above four reagents were significantly effective in removal of the afore-named pollutants, as well as Manganese (Mn), Lead (Pb), Colour, Chemical Oxygen Demand (COD), the components of Total Carbon (TC) Total Inorganic Carbon (TIC) and Total Organic Carbon (TOC), and the components of Total Solids (TS)—Suspended Solids (SS) and Dissolved Solids (DS). All of the multivalent metals, except Calcium, were significantly removed from this wastewater by pH adjustment with lime, with additional minor removals by oxidation with ozone. Dissolved organic materials were not removed by pH adjustment and only removed in approximate stoichiometric amounts by reaction with ozone. In these experiments, the polymers tested were not effective in the removal of the named pollutants. Ozone is indicated to be an effective disinfectant, but highly sensitive to the COD of the leachate. An ozone-COD ratio, which determines the quantity of applied ozone necessary for the oxidation of some of the dissolved metals and for disinfection, as a function of the contained COD, is proposed for this leachate. The possibility of the application of this ozone-COD ratio is put forth, subject to further investigation. / Applied Science, Faculty of / Civil Engineering, Department of / Unknown

In the biostabilization phase, a BOD₅:N:P loading of 100:3.2:1.1 was found to be "adequate" for treatment, while the standard nutrient loading of 100:5:1 was found to be "excessive". This was evident by the much higher nitrite-nitrate concentration in the effluent of the BOD₅:N:P = 100:5:1 reactor. Organic removal by the first stage units was excellent. BOD₅ and COD removals of at least 99.4 and 96.4 percent, respectively, were achieved under all conditions investigated, except for the two units close to washout conditions (the 5-day sludge age units at 10° and 5°C). Temperature and sludge age also had minimal effects on the removal of metals, except under the two conditions mentioned above; removals were greater than 90 percent, for most of the metals monitored. The reactors only reduced magnesium concentrations by 32.5 to 52.7 percent, mainly because the mixed liquor pH's (about 8.5) were not high enough for magnesium precipitation as magnesium hydroxide. For the lime-magnesium polishing step, samples were dosed with lime to pH levels of 10.0, 10.7, and 11.4. Magnesium doses of 0, 10, 20, 35 and 50 mg/L were then added to the samples at each pH level. In general, removals of impurities were not enhanced significantly by these magnesium additions. This was due, in part, to the initial low concentrations of contaminants; in addition, there already existed greater than 20 mg/L of magnesium in the samples. Aerobic biostabilization, at a sludge age greater than 15 days, at BOD₅:N:P = 100:3.2:1.1, and liquid temperatures of at least 3°C, followed by lime precipitation (to pH greater than or equal to 10.0), is capable of reducing most contaminants of a medium strength leachate (BOD₅ = 8090 mg/L) to levels below local (Province of British Columbia) pollution control objectives. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

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No description available.