in the figure which are functionally the same as in prior figures two extra ports 68 and 69 are shown the first connecting to the tank 52 interior above plate 31 and the second to plenum 27 below plate 31 these ports can be used with instrumentation or the like for measuring desired parameters in the spaces with which the ports communicate fig7 is a schematic longitudinal cross section showing a two stage mercury removal filtering system 55 in which the first stage is an oleophilic prefilter system 50 as in fig6 and the second stage is an mc filter system 45 as in fig2 for removing and collecting finely aerosolized mercury corresponding elements of the filter systems 50 and 45 are identified here by corresponding reference numerals of fig6 and 2 the output flow 66 from outlet 64 of prefilter system 50 is schematically shown entering mc filter system 45 as stream 40 the physical duct between outlet 64 and inlet 41 is not shown but can take any convenient form such as a pipe or the like the oleophilic filter is thus disposed upstream of the mc filter so that the former acts as a prefilter for the latter as has been discussed in the u201c background of invention u201d section herein the present invention is inter alia applicable to remediation of various flue and exhaust gases such as those produced in coal fired power generation in such instances as well as in other environments in which exhaust gases result from combustion of high energy.