VEGETATED SUBMERGED BEDS WITH ARTIFICIAL SUBSTRATES .1. BOD REMOVAL

Settled wastewater was batch fed into 22-L microcosms containing monocultures of the emergent aquatic plants Sagittaria latifolia, Scirpus pungens, Phragmites australis, and Typha latifolia. Plants were cultured in 1.25-cm gravel, and 2.5- and 5.0-cm plastic trickling filter media, with specific surface areas of 394, 279, and 138 m2/m3, respectively. Microcosm performance was evaluated in terms of the percent of influent biochemical oxygen demand (BOD) load removed. BOD removals were evaluated at loads ranging between 2 and 24 g BOD5/(m2 day). Nonvegetated microcosms performed equivalently to vegetated microcosms over the range of BOD loads tested. Plastic was equivalent to gravel at low loads, but was inferior at higher loads. This was attributed to the higher specific surface area of the gravel and poorer plant growth in plastic. None of the plant species was consistently superior to the others in terms of BOD removal. First-order BOD-removal rate coefficients for these batch-loaded systems were higher than those reported for continuous-flow systems.