Adaptation of vegetation in high-rate constructed wetland using artificial carriers for bacterial growth: Assessment using phytopathological indicators

Abstract

A variant of constructed wetland using artificial carriers for bacterial growth as support medium (High Rate Constructed Wetlands (HRCW)) has been developed to depurate high organic loads (45 g BOD5 m−2 d-1). The metabolic state of vegetation in this phytodepuration system affects the treatment processes; therefore, its optimum adaptation is necessary. A comparative study, in mesocosms scale, was undertaken to test the capacity of adaptation of three plant species (Cyperus alternifolius, Heliconia burleana, and Zantedeschia aethiopica) in HRCW. 25 units of each species were planted in three lines of HRCW (one species per line), named for ease of understanding as L1, L2, L3 respectively, and monitored during the start-up phase of the system under climatic conditions of intersection between dry tropical forest and premontane sub-humid. Quantitative epidemiology was used to determine incidence, infection rate, and the relative area under the disease progress curve for each type of plant. The relationship between these epidemiology variables and the environmental conditions was determined. Vegetative stress was observed in all species, followed by a phase of high phytopathology, with infection rates of 0.0049-0.0183; 0.1085-0.1821; 0.0911-0.1158 (units/day) for L1, L2, and L3, respectively. The combination between the high organic load, water volume (94% v/v), and weather conditions favoured this behaviour. This study indicated that Cyperus alternifolius is a type of plant suitable for HRCW; highlighted the importance of studies on plant adaptation in CW with particular conditions; and showed epidemiological analysis as a tool for performing this selection in a low cost and user-friendly way.