Figure 2. PVA membrane breakthrough experiment in which 1,2,4-trichlorobenzene was added upstream of membranes containing no powdered activated carbon (PAC) (u or n) or 2.5 weight percent PAC (ò or p). Upstream trichlorobenzene concentrations were 15 _M (no PAC) or 150 _M (2.5% PAC). All membranes were approximately 280 _m thick.