Application of Water/Wastewater Treatment in Trace Organic Compounds Removal and Other Industry Sectors

• Main Author: Dong, Bingfeng
• Other Authors: Arnold, Robert. G.
• Language: en_US
• Published: The University of Arizona. 2014
• Subjects: Effluent dependent stream; Megasonic cleaning; Trace organic compounds; Wastewater treatment; Environmental Engineering; Biodiesel
• Online Access: http://hdl.handle.net/10150/333205

Wastewater reuse is fast becoming an imperative issue based on the developments in water/wastewater engineering coupled with increasing pressures on water resources. Trace organic compounds (TOrCs) that exist in water/wastewater, are a serious threat once they were released in the environment. During the past decade, there has been much progress toward understanding the occurrence, fate and toxicology of trace organic pollutants that enter the environment in treated wastewater. The objective of the first part of this research was to evaluate the combined effects of sequential anaerobic/aerobic digestion on residual TOrCs, concentrating on chemicals that are responsible for observed estrogenic/androgenic activities in biosolids. Full-scale digestion was simulated using bench-scale bioreactors in which the primary independent variables were retention time, temperature, and oxygen loading during aerobic digestion. Treatment-dependent changes in estrogenic/androgenic activity and concentrations of specific Endocrine disrupting compounds (EDCs) were measured. Results suggest that standard mesophilic anaerobic digestion increases the total estrogenic/androgenic activity of sludge while aerobic digestion was effective in the reduction of estrogenic/androgenic activity as a supplementary treatment stage. The second part of the study was focused on the fate of TOrCs and estrogenic activity in water and sediment of the Santa Cruz River, which is effluent dependent except during infrequent periods of rainfall/runoff in Tucson area. Several sampling campaigns were carried out from 2011 to 2013. Results suggest that some organic TOrCs, including those that contribute to estrogenic activity, were rapidly attenuated with distance and time of travel in the Santa Cruz River. Indirect photolysis of estrogenic compounds through the river might play an important role for the observation of estrogenic activity changes in the SCR. Hydrophobic TOrCs may accumulate in river sediments during dry weather periods. Riverbed sediment quality is periodically improved through storm-related scouring during periods of heavy rainfall and runoff. Wastewater effluent can be applied to the algal biodiesel industry based on regional water stress across the world. In the third part of the research, reclaimed wastewater was explored for this purpose, simultaneously satisfying the needs for water, macronutrients such as nitrogen and phosphorus, and micronutrients necessary for growth of microalgae. At the same time, algal growth in conventionally treated wastewater will improve water quality through the same nutrient removal processes and perhaps by lowering residual levels of trace organics that are an impediment to potable reuse. Results showed that metals levels in most municipal wastewaters are unlikely to disrupt growth, at least by metals tolerant microalgae like Nannochloropsis salina. Cells can grow without inhibition on nutrients from treated municipal wastewater or a centrate stream derived from wastewater treatment. The results also suggest while wastewater provides a suitable nutrient source for algal growth, there is simply not enough municipal wastewater available to support a meaningful biofuels industry without water recycling and nutrient recovery/reuse from spent algae. The last part of the dissertation was the application of water/wastewater treatment techniques, specifically advanced oxidation processes (AOPs) in other industrial sectors. In the integrated circuit production industry, chemical formulations used for megasonic cleaning typically contain hydroxides, peroxides and carbonates, which can affect particle removal efficiency and feature damage. The role of carbonates and ammonia in modulating the oxidation power of megasonic irradiated alkaline solutions through the scavenging of hydroxyl radicals by varying levels of carbonates, bicarbonates, ammonia and solution temperatures on net generation of hydroxyl radicals for applications in semiconductor industry was investigated in this study. The simulation of actual megasonic cleaning process was carried out at acoustic frequency of ~ 1 MHz and different power densities. Carbonate ions were better scavengers of hydroxyl radicals than bicarbonate ions. The effect of bulk solution temperature revealed that the rate of generation of hydroxyl radicals at a power density of 8 W/cm² increased with temperature from 10-30°C, which suggests an increase of transient cavitation with temperature.