每小时两毫米的降雨都可能引发污水外泄。向伦敦供水的公用设施公司Thames Water表示，每年未经处理注入河水中的污泥达3900万吨。

Two millimetres of rain in an hour can trigger a discharge; 39m tonnes of untreated sludge flushes into the river every year, says Thames Water, the utility firm that supplies London.

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未经消化的二级生活污水处理厂脱水污泥含氮4.12%，其中有机态氮占93%。

Undigested dewatered domestic sewage sludge from secondary treatment plant contained N 4.12%, of which organic form of N accounted for 93%.

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