Waste water recycling by duckweed for protein production and effluent renovation

Waste water treatment and recycling facilities are becoming increasingly necessary in arid zones, especially in the light of the shortage of conventional water sources. The simultaneous treatment of waste water and the production of duckweed in a pond system, as an alternative protein source, is an attractive proposition for solving the feed and water shortage problem. Outdoor experiments conducted in mini-ponds showed that duckweed ponds may be highly competitive with existing secondary treatment methods. The duckweed biomass, with a crude protein content of above 30% (dry weight), may be used as an alternative source for animal feed. The ease of the duckweed harvesting makes the system even more economically attractive. The work describes the basic outdoor biotechnology aimed at eliminating the superior organic loading in the pond as given by the ratio of COD and NH₄⁺ in the raw domestic sewage. This ratio was examined in respect to the retention time of the wastes in the ponds and protein production by the floating vascular plant biomass.