Concrete Corrosion - Sewage & H2S

[sewerratt]

Historically, we've used coal-tar epoxy to coat new concrete manholes in the collection system where we expect to get lots of H2S production. I hear this material is listed as a carcinogen and the industry is moving away from it. Regardless, I am less than happy with its performance and am not interested in continuing to do the same thing and paying on the back end to rehab the structures. Is there a reliable product available to 1) coat these manholes prior to installation or 2) add to the concrete mixture that will extend the base concrete's life in a corrosive environment? There are lining products that we use in larger diameter, higher cost installations that work fine, but they are expensive. I'd like to look at less expensive alteratives before requiring lining for regular installations.

Any suggestions toward a solution are very welcome.