Interactions between Residual Ionizable Micropollutants in Treated Wastewater and Metal Oxides in Soil

Abstract

It is becoming increasingly essential to use treated sewage effluent (TSE) due to water scarcity in arid regions such as the UAE. However, the use of TSE is not without its risks. Human pharmaceuticals, many of which are ionizable organics, tend to persist in TSE because of inadequate removal in conventional wastewater treatment plants (WWTPs) and can bio-magnify in crops or lead to problems such as antibiotic resistance in bacteria. It is important to consider methods that can remove micropollutants from TSE so that it can be used in applications such as aquifer storage and recovery (ASR). Two naturally occurring processes, biodegradation and sorption can attenuate the migration of micropollutants to groundwater, of which the latter was the focus of this study. This research studied the interactions of four soil metal oxides (titanium (IV) oxide, iron (III) oxide, aluminum (III) oxide, and magnesium oxide) with four ionizable pharmaceutical micropollutants present commonly in TSE. The effect of pH and sorbent dosage on the sorption of three common non-steroidal antiinflammatory drugs (NSAID), ibuprofen, naproxen and diclofenac, and one antidepressant, fluoxetine, was investigated. The sorbents i.e. metal oxides were characterized by measuring the zeta potential at the studied pH levels (3, 7 and 11). Batch experiments were conducted at the studied pH levels and sorbent dosages (200, 600 and 1000 mg/L). Results indicated that ibuprofen, naproxen and diclofenac have higher adsorption at lower pH values whereas fluoxetine has higher adsorption at higher pH values. Flow through column experiments were also conducted at pH 7 to demonstrate removal of the studied pharmaceuticals via their sorption onto (i) sand (ii) sand and a mixture of the studied metal oxides. Results from the column experiments indicated that there is some retardation for ibuprofen and naproxen. Conclusively, this study revealed that the studied NSAIDs and fluoxetine can be appreciably attenuated by metal oxides via adsorption.

Date of Award	May 2017
Original language	American English
Supervisor	Farrukh Ahmad (Supervisor)