Synchronized urban wastewater treatment and biomass production using duckweed Lemna gibba L.

This work compiles results of utilizing duckweed Lemna gibba L. in sewage wastewater treatment and converting wastewater nutrients into protein and carbohydrate rich weed biomass. A total of four different strengths of wastewater (100, 75, 50 and 25%) were used to build experimental setups and changes in chemical properties of wastewater were measured at the end. L. gibba L. caused a decrease in pH (9–13%), EC (13–26%), NO3−N (42–64%), SO4−2 (35–82%), total phosphorus (37–54%), totNa (44–75%), totK (45–76%) and totCa (51–72%). The biomass yield in L. gibba L. ranged between 132.62 and 200.95 g/m2 day (fresh weight) or 23.87 and 36.17 g/m2 day (dry weight); about 24.6–36.17% higher than initial level in all experimental setups. The weed biomass was 24.6–52.8% higher than initial level in all set-ups. The yield rate of protein and carbohydrate ranged 1.19–1.95 g/m2 day (dry weight) and 22.72–35.58 g/m2 day (dry weight), respectively in duckweed systems. The high carbohydrate and protein yield in L. gibba advocates the utility of the weed in animal feed and bioethanol production. Results suggested that L. gibba can be utilized effectively for designing of a synchronized wastewater treatment and biomass harvesting system.