filtering muddy and or dirty water

Question
I own a small hand car wash and use six 55 gal. plastic barrels cut in half for the wash water but after so many the water starts to get dirty and having to dump them and refill them 5 to 6 times a day is costly. I would like to know is there anyway to filter the water or do I just have to live with the cost of dumping and refilling all day? And scene I have only been open 18 months every penny counts. I would like to thank you for any information on this and even if you can't help I still am grateful for your time, Thanks again,DON

Answer
Well this a great green idea provided.
What all filter have is a sand. you filter water by passing it through sand.
And after that it has to be backwashed that is  water has to be pumped from bottom to top.
For that you will have to use pump or replace the sand.
This would again add the cost.
or
Buy a smallest sand filter install it.
Collect the water in a pit and pump it through the filter and Residual water head can be used for washing the cars.
Once the pressure of water coming from filter has reduced backwash it.
This is the best option available use it.