Treatment of domestic wastewater using the nutrient film technique (NFT) to produce horticultural roses

Removal of organic matter, nitrogen and phosphorus was investigated in a pilot based on the nutrient film technique system used for horticultural production. Rosebushes producing commercial roses were set on an inclined impermeable surface over which a thin film of domestic wastewater flowed directly through the root matrix. The roses produced with wastewater as nutrient solution were qualitatively and quantitatively similar to those produced traditionally and can be marketable. In the presence of the rosebushes, the lowering of chemical oxygen demand (COD), biological oxygen demand (BOD5) and suspended solids (SS) increased with their influent strengths in a linear fashion correlation. Whatever the pollutant load of the influent, within the range studied, the level of organic pollution required to allow the discharge of the effluent into water courses was reached after 24 h of treatment. At this time, the COD reached 39±13 mg L−1, the BOD5 7±4 mg L−1 and the SS 8±6 mg L−1. The removal percentages were 89, 95 and 94, respectively, whereas without plants they were 55, 33 and 53, respectively. The rosebushes had a beneficial effect on the removal of phosphorus from 20% to 23% greater in their presence than without. In presence of plants, the nitrate was the principal form of nitrogen from 48 h of treatment whereas without rosebushes, nitrite represent more than 20% of initial nitrogen whatever the treatment duration. The root matrix served not only as a filter for the organic matter, but also provided a microhabitat suitable for nitrifying bacteria and heterotrophic micro-organisms, which responded rapidly to the pollutant load.