帮我分析下，这个是宾补，还是定语？（H.L.P.E）

应该是

He found {that it came from the river （polluted by the dirty water）} from London
{}部分是宾从
that it came from the river polluted by the dirty water
中it 做dirty water形式主语

HE found that it came from the river (which was) polluted by the dirty water from london.
还原后是这样。应该是定语吧。

定从 polluted by the dirty water from london
the river which was polluted by the dirty water from london

我认为是宾补。

过去分词作后置定语