Pumping cassettes are disclosed. Each cassette includes a housing, at least one fluid inlet and at least one fluid outlet as well as at least one reciprocating pressure displacement membrane pomp in fluid relation to the cassette. The balancing cassette includes at least one balancing pod in fluid connection. The mixing cassette includes at least one mixing chamber in fluid connection. The system includes a mixing cassette, a balancing cassette, and an outer or middle cassette fluid! y connected to the mixing cassette and the balancing cassette and at least one pod. The mixing cassette is flaidly connected to the middle cassette by at least one fluid line and the middle cassette is fluidiy connected to the balancing cassette by at least one fluid line. The at least one pod is connected to at least two of the cassettes wherein the pod is located in an area between the cassettes.
