Responses of Egeria densa to various influent ammonia concentrations: A microcosm study on plant morphology

An experimental study and a regression analysis were carried out to find out the growing patterns of Egeria densa at three different NH 4+ -N concentrations as low (2 mgL -1 ), medium (4 mgL -1 ), and high (6 mgL -1 ). DO concentration during respiration and photosynthesis was monitored in daily basis while plant morphological characteristics were examined with harvesting at six-day interval. There was no any significant difference in morphological characteristics indicated at low and medium NH 4+ -N concentrations (p>0.05). On contrary, the total plant length at high NH 4+ -N concentration has deviated significantly (p<0.01) from other two concentrations after 15 days since commencement of the experiment. Averaged relative growth rates (RGRs) were recorded as 0.05, 0.04 and -0.01 mgday -1 in terms of dry weight production for low, medium and high NH 4+ -N concentrations, respectively. The results of the non-linear regression analysis explained the effect of low and medium concentrations over high concentration of NH 4+ -N, while the medium concentration provided the best correlation coefficient (r 2 = 0.901) for the modeled equation. These results can be used in optimizing the effects of E.densa at tertiary wastewater treatment.