Dave's ESL Cafe's Student Discussion Forums

[Yukineko]

Hello teachers, Could you help me?

I really don't understand the Italic part of the following sentence, especially how the bold word "retained" works in it.
What is the subject of the verb "retain(ed)" in this sentence?

"The first stage of the NEWater production process is known as Microfiltration (MF). In this process, the treated used water is passed through membranes to filter out and retained on the membrane surface suspended solids, colloidal particles, disease-causing bacteria, some viruses and protozoan cysts."

Could you please paraphrase this in easier English?

Thanks in advance.

Yukineko

[SimpleEnglishBlogger]

It's a mistake. The sentence doesn't make sense. It appears to be missing some key words. I can't guess exactly what the author is trying to say.
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[Lorikeet]

I believe it should be "retain" and not "retained".

""The first stage of the NEWater production process is known as Microfiltration (MF). In this process, the treated used water is passed through membranes to filter out and retain on the membrane surface suspended solids, colloidal particles, disease-causing bacteria, some viruses and protozoan cysts." "

It could be said in a better way, but it looks like the microfiltration process has the treated used water pass through membranes so that the suspended solids, colloidal particles, disease-causing bacteria, some viruses and protozoan cysts are retained on the membrane surface, and therefore filtered out of the water.

[SimpleEnglishBlogger]

I initially thought the same thing but it's still such an awkward sentence.

You should be able to break it up into these two sentences:

1) The treated used water is passed through membranes to filter out suspended solids, colloidal particles, disease-causing bacteria, some viruses and protozoan cysts.

2) The treated used water is passed through membranes to retain on the membrane surface suspended solids, colloidal particles, disease-causing bacteria, some viruses and protozoan cysts.

But here, (2) still doesn't really work, IMO.

The purpose of passing the water through membranes is to filter out the impurities but I can't say the "purpose" is also to have those impurities stay on the membrane. It's just what ends up happening.

The only way I can see this working is to rewrite the sentence as:

"In this process, the treated used water is passed through membranes to filter out and the suspended solids, colloidal particles, disease-causing bacteria, some viruses and protozoan cysts are retained on the membrane surface."
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