Abstract
An investigation on the seasonal change and removal of estrogen in a swine wastewater treatment plant was carried out from July 2004 to September 2005. Natural estrogens (estrone, estradiol and estriol) in raw wastewater showed similar seasonal changes and their peak values reached 162, 872, 4,480 ng · l-1, respectively, whereas equol showed a different trend in which the maximum concentration was markedly high at 43,300 ng · l-1. The results showed that approximately 93% of the total estrogenicity in raw wastewater was attributed to equol. The sequencing batch reactor (SBR) process of the swine wastewater treatment plant was efficient to remove selected estrogens for quantitative analysis as well as nitrogen and phosphate. Moer than 99% removal efficiencies for all selected estrogens and total estrogenicity were attained by the SBR process. The total estrogenicity that remained after the SBR process was, however, still higher than the predicted noneffective concentration level for fish (PNEC). It was found that a baffle channel located at the final stage of the treatment flow contributed to decreasing the estrogenicity to the PNEC level. Experimental results in the laboratory showed that filamentous algae inhabiting the bottom of the channel were responsible for the estrogenicity decrease observed in the baffle channel.
