In standard setups, water chemistry data is output as milli-equivalents in addition to the standard outputs (such as mg/L). The milli-equivalents output is typically named "LChem3_milliequivalents" and appears under the "Water Chemistry" button (in Landfill versions, where water chemistry is output as "Leachate", "SW","GW", it will be under the "All Queries" button).
Conversions to milli-equivalents from the standard Liquid Output Unit for that compound are given under the "Equivalent Weight" field in the Chemistry Lookup table (zRef_Chemistry_Lookup). Only those compounds for which conversions are relevant (ie certain inorganics and metals) have a value entered. Values can be entered by the user, and only those compounds for which a value is entered will be output in the milli-equivalents query.