Wastewater Treatment Package Plant

I am in the process of building a new MHP. Since my property is not able to connect to a public sewer system, I am forced to install an on-site system.

The park will have an estimated 122 lots and will be located in the Houston, TX area. Can anyone recommend a good, low-cost system to use for a park this size? Also, what could one reasonably expect to pay for such a system?

I have spoken to a rep from a company named Orenco. I have also submitted a request to be contacted by a company named Pollution Control Systems. Does anyone have information or comments about either one of these companies or their systems? Other companies I should be calling?

Thanks for any and all comments!!!