Biological treatment of domestic wastewater by selected aquatic plants

Around 30 percent of the operating costs of conventional centralized wastewater treatment is required for energy to operate the machines for pump and aeration. Comparatively, constructed wetlands involving photosynthetic plants and other organisms have a lower energy requirement. The aim of the present work is to select aquatic plants which have high efficiency of removing infection in wastewater. Four plants were chosen from locally available plants growing in wastewater. They were put in raw wastewater from toilets for 24 h and were tested for their survival and growth measured by chlorophyll content. Brahmi (Bacopa monnieri) and Duckweed were found to be best compared to Azolla and Hydrilla. The efficiency of removal of enteric infections was done by culturing the treated wastewater on Eosin Methylene Blue (EMB) agar media, a selective and differential medium for enteric gram negative bacteria. The best performing plants were Brahmi and Hydrilla which reduced the load by 67-70%. But Hydrilla did not grow as well compared to Brahmi as evident from the chlorophyll content. Hence Brahmi and Duckweed can be considered as most effective for removal of infection in wastewater among the four tested plants and potentially may save energy and synthetic chemicals otherwise required for conventional treatment systems. Brahmi, famous for its high value medicinal compounds against neuronal problems, may be used for extraction of the compounds. The remaining biomass can be used as feedstock in anaerobic digester for methane/ethanol generation to be used as biofuel.