A modular series of vertical flow wetland (VFW) systems was established in 1989/90 to treat up to 130,000 litres per day of primary settled sewage on the north coast of New South Wales, Australia as an experimental scale-up of wetland microcosms that had been developed with this hydrological format. Monitoring of inflow and outflow water quality was maintained on a weekly basis from January 1991 to February 1992. Some management parameters (e.g. flow rates) were varied during this period. Dye injection to examine hydraulic behaviour within the gravel bed was carried out on two occasions in one VFW. In general the removal of nutrients was lower than expected, with between 20% and 40% reduction in concentrations and removal of loads over the year. Suspended solids and BOD removals were excellent, with a surprisingly good reduction in faecal coliform counts as well. Reduction in flow rates improved performance markedly in all parameters.