The arrival and discharge of conjugated estrogens from a range of different sewage treatment plants in the UK

The occurrence of free and conjugated estrogens were examined in a survey of eleven sewage treatment plants (STPs) and their discharge water in the United Kingdom using grab sampling. The STPs included trickling filter with and without tertiary treatment, and activated sludge with tertiary treatment. For three activated sludge plants both influent and effluent samples were compared. For a further 8 STPs only the effluent was examined. The estrone-3-sulphate, estradiol-3-sulphate and estriol-3-sulphate concentrations (up to 20 ng/L) were typically fivefold that of their respective free estrogen concentrations in the effluents. This represents a substantial additional ‘potential’ estrogen load arriving in the receiving waters. Estrone-3-glucuronide was found at 9.3 ng/L, estradiol-3-glucuronide at 7.0 ng/L, and estriol-3-glucuronide at 32.2 ng/L in sewage influent. Except on one occasion, no glucuronide conjugates could be found in the effluent.. The results suggest in most cases glucuronide conjugates will be completely transformed in sewage treatment whilst sulphate conjugates will only be partially removed.