The Capacity of Duckweed to Treat Wastewater

Abstract

Duckweed species are promising macrophytes for use in sustainable wastewater treatment due to their rapid growth, ease of harvest, and feed potential as a protein source. This paper reviews growth rates of different duckweed species on wastewater and ammonia toxicity to duckweed and summarizes insights into the mechanism of organic matter and nutrient removal. Results were gained from laboratory experiments in small, shallow, duckweed-covered semicontinuous batch systems. Growth rates on different types of wastewater vary considerably among different species. Ammonia is toxic for duckweed in both the ionized and un-ionized forms. Duckweed, however, can be used to treat wastewater containing very high total ammonia concentrations as long as certain pH levels are not exceeded. The degradation of organic material is enhanced by duckweed through both additional oxygen supply and additional surface for bacterial growth. The duckweed mat with attached bacteria and algae is, independent of the loading rates, responsible for three-quarters of the total nitrogen (N) and phosphorus (P) loss in very shallow systems. Based on our results we suggest that full-scale pilot plants with duckweed should be shallower than the range encountered in the literature. A harvesting schedule that allows doubling times of 2 to 3.5 d, maintenance of a full coverage, and plug flow conditions are recommended.

Effects of NH4+and K+enrichments on carbon and nitrogen metabolism, life history and asexual reproduction ofVallisneria natansL. in aquarium experiments

“…The NH 4 C or K C enrichments enhanced ramet production of V. natans separately at the MS stage; however, their combination decreased the ramet production as compared with the NH 4 C enrichment alone. A plausible mechanism for the lower ramet production induced by the K C and NH 4 C enrichments was that massive influx of NH 4 C and K C into the plant cell might have caused H C to efflux from the cell (Taylor & Bloom 1998;Hoopen et al 2010;Marschner & Marschner 2012), inducing deionization of NH 4 C and accumulation of NH 3 in the cell (Hoopen et al 2010), which is about two orders of magnitude more toxic to plants than NH 4 C ion (K€ orner et al 2003;Nimptsch & Pflugmacher 2007).…”

Application of Artificial Neural Network in Horizontal Subsurface Flow Constructed Wetland for Nutrient Removal Prediction

“…Nutrients generally (N, P) accumulate in the plant biomass and are removed through harvesting (Gregory, 1999). Nitrogen and P losses can be attributed to uptake by weeds that become attached to biofilm, which is attached to the walls of the systems, and sedimentation of particular forms of N and P (Körner et al, 2003).…”

Adjuvants Affect Duckweed (Lemna minor) Control with Pelargonic Acid

“…One method of obtaining large quantities of nutrient rich duckweed biomass are commercial sustainable production systems based on waste water, either animal or human (Körner et al, 2003). Duckweed is ideally suited to clean waste water (Alaerts et al, 1996;Hammouda et al, 1995;Körner et al, 1998Körner et al, , 2003Mandi, 1994;Skillicorn et al, 1993), because of its efficient nutrient absorption (Ice & Couch, 1987), its rapid growth rate (Skillicorn et al, 1993), and its ease of harvest (Körner et al, 2003), while providing not only a nutrient rich duckweed biomass for animal feeds, but an alternative feed stock source for biofuels (Cheng & Stomp, 2009).…”

“…Duckweed is ideally suited to clean waste water (Alaerts et al, 1996;Hammouda et al, 1995;Körner et al, 1998Körner et al, , 2003Mandi, 1994;Skillicorn et al, 1993), because of its efficient nutrient absorption (Ice & Couch, 1987), its rapid growth rate (Skillicorn et al, 1993), and its ease of harvest (Körner et al, 2003), while providing not only a nutrient rich duckweed biomass for animal feeds, but an alternative feed stock source for biofuels (Cheng & Stomp, 2009). Use of duckweed biomass for biofuel production also avoids safety concerns about the direct human consumption of animals raised on waste water grown duckweed (Cheng & Stomp, 2009).…”