However, in sewage, these chemicals become diluted and bacteria have evolved resistance to them.

然而，在下水道里，这些化学药品被稀释，细菌对它们产生了抗药性。

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Last year 32m cubic metres of diluted sewage were dumped into the river, at a rate of roughly one discharge a week.

ECONOMIST: The capital's overflowing drains are due for a big upgrade

The council said the sewage system and the River Clwyd have high levels of water from the recent heavy rains, and the sewage has therefore been heavily diluted.

BBC: Clwyd Estuary: Rhyl sewage spill warning