The system and method for processing flowback fluid include a plurality of wellheads producing flowback fluid flows, a plurality of first stage separators corresponding to at least one wellhead of an installation with multiple wellheads and multiple flowback fluid flows, a plurality of metering devices corresponding to each first stage separator, and a second stage separator in fluid connection with the metering devices and the first stage separators. The second stage separator includes a solids separator to further control the storage volumes of the first and second stage separators and retention time in the second stage separator by removing solids.