2.2. Nutrient budgeting
As in the recirculation systems the complete
water volume passed over the trickling filter
once every 20min, concentration differences
between in- and outflow were within detection
limits. Thus, samples were taken in the main
water reservoir only (fish tank or water reservoir).
Input and removal rates were calculated through
mass balance, calculated over a specified time
interval, by the addition of nutrient input in the
form of fish fodder, nutrient removal in the form
of fruit and plant biomass harvest, change in the
nutrient reservoir in the water, and nutrient losses
by water exchange.