A wastewater sampling system including: an inlet tube; an outlet port; a high-flow circuit fluidly coupling the inlet tube to the outlet port; a first pump, along the high-flow circuit, configured to pump wastewater through the high flow circuit; a sampling circuit, fluidly coupled to the high-flow circuit via a junction, comprising a solid waste filter fluidly coupled to the junction and a solid-phase extraction cartridge fluidly coupled to an outlet of the solid waste filter; a second pump along the sampling circuit; a controller configured to, during a sampling cycle at a first time, activate the first pump; at a second time, activate the second pump; and at a third time succeeding the second time by a sampling duration, deactivate the second pump.