Role of Macrophyte Typha latifolia in a Constructed Wetland for Wastewater Treatment and Assessment of Its Potential as a Biomass Fuel

Abstract

In the last decade, constructed wetlands have been gaining in popularity as a reduced cost and low maintenance technology for treating wastewater from small urbanised areas. In these wetlands at the same time that pollutant removal from wastewater occurs, great quantities of biomass are produced. As according to some authors, plants must be harvested for the most effective removal of pollutants, large amount of biomass would be available for different uses. Although different solutions have been proposed (to transform it into compost or feed supplements for animals), the biomass potential for fuel production has been neglected. Therefore, the objectives of this work were focused to the study of the suitability of the macrophyte Typha latifolia produced in a wetland as a fuel. Main goals were: (1) to assess the role of the macrophyte, in the removal of biological oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), nitrogen, phosphorous and pathogens from raw municipal wastewater; and (2) to determine the thermochemical characterisation of the biomass produced in order to examine the suitability of the biomass as a fuel. The constructed wetland consisted of two beds, of 40 m2 each with gravel as the supporting medium. The hydraulic application rate was 50 mm day−1. One of the beds was planted with cattail (Typha latifolia) and the other one was used as an unplanted control bed. With regard to wastewater treatment efficacy, the results obtained agree with the important role of macrophytes for maintaining the wetlands treatment capability, particularly for systems with high organic matter and ammonia-N content. Due to the high biomass yields obtained in the planted bed, and to the thermal behaviour of both cattail biomass and their ash, the utilisation of cattail biomass as fuel in thermochemical processes could be recommended.