Biodegradation of Bisphenol-A and 17β-Estradiol Under Alternating Aerobic/Anoxic Conditions

Abstract

Certain methods for reusing treated municipal wastewater, such as soil-aquifer treatment (SAT), are characterized by alternating cycles of aerobic and anoxic conditions. It is not yet known how these alternating redox conditions affect biodegradation of potentially harmful endocrine-disrupting compounds (EDCs) from treated effluents. To address this question, batch mesocosms were constructed and redox conditions in mesocosms were controlled by switching the atmosphere between air (to induce aerobic conditions) and nitrogen (to induce anoxic or anaerobic conditions). The length of anoxic cycles was varied to determine how this affects biodegradation of two target EDCs, bisphenol-A (BPA) and 17β-estradiol (E2). Important findings include: (1) BPA was biodegraded only during aerobic cycles, but E2 was biodegraded during both aerobic and anoxic cycles; (2) when redox conditions were switched from anoxic to aerobic, biodegradation of target EDCs commenced after a lag period during which no biodegradation was observed; and (3) lag time for biodegradation in the aerobic cycle was longer when anoxic cycles were longer in duration. As expected, more rapid biodegradation of both BPA and E2 was observed under aerobic conditions than under anoxic conditions, though the effect was not statistically significant for E2. Results suggested that, in actual SAT systems, length of flooding and drainage cycles may have an important effect on the degree of biodegradation achieved and, hence, on the ability of the system to provide water of acceptable quality.