Advanced Water Management Centre

AWMC Seminar Program: Glen De Vera & Dr Astals-Garcia

Dynamics of nitrate and ammonium formation during ozonation of dissolved organic nitrogen

Abstract: The presence of dissolved organic nitrogen (DON) like amino acids is an emerging concern in water treatment because DON exerts a certain oxidant demand and forms disinfection byproducts. When ozone is used as the oxidant, DON is transformed into various products that may be beneficial for ozonation characterization. In this study, we investigated the reaction of ozone with DON with a special focus on the formation of nitrate (NO3-) and ammonium (NH4+) ions. Through batch ozonation experiments, the formation of inorganic nitrogen was observed for ozonated surface water, humic acid, and wastewater effluent samples. An apparent increase in NO3- concentration was observed for all water samples when O3 exposure was increased. To determine the main precursor of NO3- during ozonation, synthetic DON solutions composed of tannic acid and amines such as glycine, dimethylamine, and trimethylamine were prepared and treated at varying O3 exposures. The yield of NO3- decreases as follows: glycine > trimethylamine > dimethylamine. Consistent with real water experiments, increasing the O3 dose and exposure during ozonation of glycine resulted in an increase in NO3-. The opposite was observed for NH4+. A mechanistic interpretation was then proposed based on the observed experimental results for NO3- and NH4+, RCt (exposure ratio of hydroxyl radicals (OH) and O3), O3 decay, and OH yield (28%). As confirmed from kinetic simulations, NO3- was produced via a pathway that involves oxygen transfer to nitrogen to form an N-oxide, while NH4+ was formed through electron-transfer reactions yielding N-centered radicals and imine intermediates. From the observed linear relationship of NO3- with O3 exposure, this study also highlighted the potential application of NO3- monitoring as an easy means to evaluate Ct values that are necessary for disinfection.


Title: Batch assays for anaerobic digestion research

Abstract: Batch assays are a key technique for anaerobic digestion research and industry engagement. Batch assays comprise (i) biomethane potential test (BMP), (ii) activity test and (iii) inhibition test; each of them useful to tackle a specific research question.In this seminar, I will explain the fundamentals and the challenges that we need to be aware when performing such tests.



Host: Advanced Water Management Centre
Event Details
Date & Time: 
Friday, 08 April 2016
9am - 10am
Venue: Building 76, Room 228

Event Contact: