I am very lucky that I chose Environmental Engineering as my major because I feel so
great that I can use professional knowledge to reduce pollutants from our beloved living earth.
Ever since I first realized what this major concerns, I have set my goal as to equip myself with
the most advanced knowledge in Environmental Engineering, and that’s the reason for my
pursuing a Ph.D. degree in the U.S now.
For undergraduate study, I feel proud that I didn’t need to sacrifice sleeping time to be No.1.
I knew fundamentals are essential for advanced study and paid special attention to knowledge
accumulation. I deduced every equation in Advanced Mathematics and read a reference book
recommended by the teacher thoroughly for three times. Eventually, my average score for
Advanced Mathematics was 99. With this attitude, I also got the highest scores in Principles of
Environmental Engineering, Water Pollutions Control Engineering, Environmental Toxicology,
Noise Control Engineering and other major courses.
Meanwhile, I tried to deepen my understanding of the abstract theories in textbooks by
reading reference books and doing relative researches. I read Adsorption Science written by
Seiichi Kondo etc. thoroughly and studied the adsorption behavior of PCBs in soil, during
which I found single models in the textbook is insufficient to describe the whole process of
PCBs adsorption, so I verified a composite model based on Henry, Langmuir and Freundlich
equation whose least-squares fit was better than the other three models. I also mastered the
Soxhlet extraction procedure to measure PCBs concentrations in soil and method to investigate influence factors on thermodynamic adsorption by orthogonal test.
Besides, I like to trace phenomena to the mechanisms behind them. In my undergraduate
thesis project, I studied the coagulation mechanisms of wastewater produced from polymer
flooding in oilfield which had been insufficiently investigated due to the complex interrelationships between crude oil, hydrolyzed polyacrylamide (HPAM) and salt coexistent in the
wastewater. I determined the crosslinking action between Al3+ and HPAM is the primary coagulation mechanism, because Al2(SO4)3 had higher efficiency of removing oil and HPAM from
actual wastewater than PAC, however, in two other simulated water systems, PAC had higher
efficiency in water containing solely oil, while Al2(SO4)3 performed better in water containing
solely HPAM. I verified my conclusion with the aid of Zeta Potential analysis and ruled out
electrical neutralization as the main mechanism. Finally, my thesis was graded as the best
undergraduate thesis in my major for its integrity and depth.
As study advanced, my interest became specific and falls on water quality engineering. I
read many papers on existing problems and I am deeply attracted by disinfection and DBPs
formation, transformation and fate of micropollutants and effective control methods.
Then I chose to examine DBPs formation during aquaria seawater ozonation as my graduate research. Ozone is commonly applied in closed artificial seawater systems such as
aquaria and mariculture facilities as an alternative disinfectant to free chlorine. During seawater ozonation, chloride and bromide ions can be readily oxidized to free chlorine and bromine which would further produce other DBPs. Thus, I first developed a novel method for
simultaneous determination of free chlorine and free bromine in high-salinity water by GC-MS.
The established method, about which a paper has been submitted, was based on the derivatization of free chlorine and free bromine to corresponding 4-halo-2,6-dimethylphenol by use of
2,6-dimethylphenol, and it showed good calibration linearity, recovery, precision, and a low
limit of detection (LOD) for both free chlorine and bromine. Besides, considerable amounts of
free chlorine and free bromine were detected in real aquarium water samples, and I supposed
THMs, HAAs and other halogenated DBPs, especially bromine-containing ones, can also be
largely produced during ozonation, so my current work is investigating these DBPs and their
relationships with DOM, free chlorine and free bromine during seawater ozonation, and I will
propose possible solutions (e.g. post-treatment by BAC) in the future work.
Through this research, I also directly realized how quickly free chlorine could react with
electron-rich phenolic compounds through electrophilic substitution, and I associated this with
the DBPs formation by reaction of chlorine with electron-rich phenolic synthetic chemicals (e.g.,
pharmaceuticals and PPCPs) which are commonly found in surface and ground waters. As
ring-chlorinated compounds formed may further undergo cleavage reactions or photochemical
transformation, DBPs such as THMs and chlorinated dioxins may be readily produced, so it is
essential to remove these electron-rich phenolic DBPs precursors before chlorination.
In the future Ph.D. program, besides regulated DBPs, I strongly intend to explore the formation and control of non-regulated DBPs in water, e.g., nitrogenous disinfection by-products
(N-DBPs), which are more cytotoxic and genotoxic than regulated DBP species. Firstly, there
is incomplete information available on the correlations between DON, disinfectants and
N-DBPs formation. So I intend to investigate the precursors and formation pathways of various
N-DBPs (i.e., nitrosamines, cyanogen halides, haloacetonitriles, haloacetamides and halonitromethanes) by determination of formation potential (FP) with representative nitrogenous
organic compounds and disinfectants (free chlorine, chloramine and chlorine dioxide). Besides,
I am also interested in researching the effect of water quality parameters, such as pH, temperature, bromide and iodide concentrations on N-DBPs formation. Finally, pre-oxidation and
treatment processes could have great impact on N-DBPs formation, so I may investigate the
effects of ozonation, UV irradiation, membranes, BAC or other treatment processes on specific
N-DBPs formation, the overall objective of which is to determine the mechanisms and find
effective control methods.