  We consider a system of random walks in a random environment interacting via
exclusion. The model is reversible with respect to a family of disordered
Bernoulli measures. Assuming some weak mixing conditions, it is shown that,
under diffusive scaling, the system has a deterministic hydrodynamic limit
which holds for almost every realization of the environment. The limit is a
nonlinear diffusion equation with diffusion coefficient given by a variational
formula. The model is nongradient and the method used is the ``long jump''
variation of the standard nongradient method, which is a type of
renormalization. The proof is valid in all dimensions.
