一篇英语游记的作文，请大家帮修改

Last Monday,I went to Beijing Gaobeidian Wastewater Treatment Plant,as the biggest and most important wastewater
treatment plant in Beijing ,is a major factory which for improving the environment to benefit the society.

First of all, when I arrived the factory , I smelt the smelly odor.Then I saw a film of treating with the wastewater,and I learn a lot of tings about water,including saving water and using reuse water.In addition ,I visited the factory,and saw many workers work in it.Although the air is very dirty, they work here every day for Beijing's environment.
This experience makes me understand that the water is very important for us.Please not waste water ,for our environment
and for 2008 Olympic game.

应该有很多错误~
大家看看有没有什么写的语法错误或者可以修改更好的地方说下~谢谢~

我快~ ~ 是高中生吧？那我就稍微说下我的看法吧

Last Monday,I went to Beijing Gaobeidian Wastewater Treatment Plant,the biggest and most important wastewater
treatment plant in Beijing ,which dedicates in improving enviroment and benefit the society as well.
(原句is a major factory which for improving the environment to benefit the society.主句 与前面有两个谓语，重复，并且which 后面的从句中缺乏谓语，其实，我建议你这句话不要，因为前面已经说了the biggest /most important，这后面的话不就是多余的吗）

First of all, when I arrived the factory 差介词at，

I saw a film of treating with 介词有误，saw a film on treating whith....

I learn a lot of tings about water 动词时态有误，用过去时

using reuse water 修饰语 应为 reused water

saw many workers work in it.我认为应该为 saw many workers working in it.你看见这个动作时候，发生的

This experience makes me understand that the water is very important for us.Please not waste water ,for our environment
and for 2008 Olympic game.

时态，made me....
please do not ..