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Figure 1.3 The concept of coupling AOP-based pre-treatment with biological post-
treatment Mantzavinos, 2007.
1.2 Problem Statement
In the above context, this work has been undertaken to experimentally investigate the degradability of alkanolamines using Fenton’s reagent for advanced
oxidation. Monoethanolamine MEA and diethanolamine DEA are selected as the model compounds for the study. Effects of different process parameters such as the
initial concentration of the amine, the dosage of Fenton’s reagent, pH and the mode of
addition of the reagent one time or continuous are to be studied. In order to explore the advantage of the hybrid strategy of combined AOP and biological oxidation, the
biodegradability of the partially degraded amines as well as ‘pure’ amines will be investigated following standard procedure and using locally available activated
sludge.
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1.3 Objectives
In the above context, the objectives of the present work are as follows:
1. Fenton’s oxidation of two model alkanolamines MEA and DEA,
2. To investigate the effect of various process parameters on the rate and
extent of degradation of the amines, 3.
To identify the optimum process condition within the range of parameters studied,
4. To identify the degradation intermediates and reaction pathway,
5. To develop a simplified rate equation and to estimate the kinetic constants,
6. To compare the rate and extent of degradation for different modes of
addition of the reagents H
2
O
2
and FeSO
4
;7H
2
O to the reaction medium, 7.
To study the biodegradability of the partially degraded amines and compare with that of the ‘pure’ amines,
8. To fit the data on biological oxidation with a kinetic equation.
1.4 Scope of Work
The waste water generated during cleaning and maintenance of the absorption and stripping towers heat exchangers, and reboilers in a natural gas processing plant
contains a substantially high concentration of amine to the tune of 20,000 ppm or more. In this prospective we have used in the degradation experiments synthetic
wastewater containing similar high concentrations of the amine down to several hundred ppm. This is one the major parameter studied in this work. The variation of
pH was confined to the acidic range only since rapid decomposition of hydrogen peroxide to water and oxygen occurs at a high pH particularly in the presence of
8
suspended iron oxide particles that act as decomposition catalyst. On the lower side, pH up to 2 was used although, as it will be detailed later, vigorous reaction with
foaming and gas liberation occurs at such a low pH. The ratio of H
2
O
2
and Fe
2+
was varied over a wide ranges. Studies were confined to nearly ambient temperature since
a higher temperature promotes H
2
O
2
decomposition and reduce the utilization of the oxidizing capacity of the reagent. The mode of the addition of the reagents was well
within the scope of this study because of its significantly better performance. So far as the biological post-treatment is concerned, we used a diluted solution
of the degraded amines. The COD was around 1000mgL. This was done in consideration of the fact that in the event of pumping in the real partially degraded
wastewater to the conventional biological treatment unit in a plant, its concentration would be greatly lowered after mixing with all other effluents from different units of
the plant. The activated sludge locally available in the wastewater treatment facility of the university, in consideration of avoiding exotic strains, was used.
CHAPTER 2 LITERATURE REVIEW
2.1 Industrial wastewater
Metcalf and Eddy 1991 defined wastewater as a combination of liquid and water which carry the wastes that are removed from residence, institution and
industry, together with such ground water, surface water, and storm water. When untreated wastewater is allowed to accumulate, the decomposition of organic material
lead to the production of malodorous gases. Wastewater also contains numerous pathogenic or disease-causing microorganisms. The nutrient rich wastewater that
enters the aqueous ecosystem leads to eutropication, which still causes oxygen depletion. It is also toxic to the aquatic life and responsible for methemoglobinemia
when it is contaminated to the drinking water.
2.1.1 Wastewater characteristics
Industrial wastewater is characterized in term of physical, chemical and biological constituents. The important physical properties are color, odor and
dissolved substances. While the chemical constituents may include organic compounds such as carbohydrates, phenol, pesticides, etc, gases such as hydrogen
sulfide, methane, and oxygen; and inorganic such alkalinity, heavy metals, nitrogenous substances, pH, etc, the biological constituents may contain various
species, protista, virus, etc Metcalf and Eddy, 1991.
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