$$ \mathrm CAPEX =\mathrm First \ \mathrm financial commitment +\sum \mathrm RI _ \mathrm biofilter +\sum \mathrm RI _ \mathrm PSA +\sum \mathrm RI _ \mathrm comp +\sum \mathrm RI _ \mathrm v \_\mathrm pump $$ while in the biotrickling filter, aerobic micro organism decompose H2S, and to help keep these microbes inside the reactor, an enlarged sur