Anaerobic digestibility of estrogens in wastewater sludge: effect of ultrasonic pretreatment.

BACKGROUND: Estrogenic compounds have been detected in the secondary effluents and in the biosolids from conventional wastewater treatment plants, which are not designed for their removal. Furthermore, existing limited studies on anaerobic digestibility of estrogens report conflicting results. The objective of the present work was to determine the fate and anaerobic digestibility of estrogenic compounds in various types of sludge including primary sludge (PS), waste activated sludge (WAS), and anaerobically digested sludge (seed). METHODS: Estrone (E1) and 17-ß estradiol (E2) were chosen as the model estrogenic compounds. Initially batch adsorption was conducted to determine the extent of adsorption and isotherm of E1 on various sludge. Thereafter, batch anaerobic digestion of E1 and E2 was conducted in various sludge using So/X ratio of 4 gCOD/gVSS in 250 ml bottles. The effect of earlier optimized ultrasonication dosage on the anaerobic digestion of E1 and E2 was also characterized. Estrogenicity of the digested samples was determined by the YES assay. RESULTS: Most of E1 and E2 was adsorbed on the biosolids and the Freundlich isotherm fitted the experimental data well. No anaerobic digestion of E1 and E2 was found in any of the sludge tested, and the estrogenicity of the sludge measured by YES assay increased during digestion due to the formation of E2 from E1 in a reduced environment. Ultrasonication decreased the initial mass of E1 and E2 by 20% in the sonicated digester as compared to control digester, however, there was no further decrease in E1 and E2 during digestion. CONCLUSIONS: Most of the estrogenic compounds partitioned onto the solids and remained there during digestion. Ultrasonication pretreatment reduced the estrogen burden for the digester due to advance oxidation, but no further removal of the estrogens occurred in the digester.

Degradation of estrone in water and wastewater by various advanced oxidation processes.

A comprehensive study was conducted to determine the relative efficacy of various advanced oxidation processes such as O3, H2O2, UV, and combinations of UV/O3, UV/H2O2 for the removal of estrone (E1) from pure water and secondary effluent. In addition to the parent compound (E1) removal, performance of the advanced oxidation processes was characterized using removal of total organic carbon (TOC), and estrogenicity of the effluent. Although E1 removal was high for all the AOPs, intermediates formed were more difficult to degrade leading to slow TOC removal. Energy calculations and cost analysis indicated that, although UV processes have low electricity cost, ozonation is the least cost option ($ 0.34/1000 gallons) when both capital and operating costs were taken into account. Ozonation also is superior to the other tested AOPs due to higher removal of TOC and estrogenicity. The rate of E1 removal decreased linearly with the background TOC in water, however, E1 degradation in the secondary effluent from a local wastewater treatment plant was not affected significantly due to the low COD values in the effluent.