aquatic plants for domestic wastewater treatment: lotus (nelumbo nucifera) and hydrilla (hydrilla verticillata) systems

A pilot scale aquatic pond, with dimensions of 1.8 m in length, 0.6 m in width and 1.2 m in depth, was constructed at the Hat Yai Municipality Central Wastewater Treatment Plant, Thailand. The experiment was carried out to investigate the enhanced removal efficiency of unconventional plants for aquatic treatment system as post treatment. Wastewater from the selected pond of the Hat Yai Municipality Central Wastewater Treatment Plant was introduced to the systems using peristaltic pumps to maintain a fixed flow rate at HRT of 5.4 and 10.5 days, respectively. Lotus (Nelumbo nucifera) and hydrilla (Hydrilla verticillata) were planted along with one control unit. Influent and effluent were analyzed for pH, SS, BOD5, TKN, NH3-N, NO2 --N, NO3 --N, TP and Coliform bacteria twice a week. The results showed that ponds with aquatic plants were superior to those without plants. The system with lotus showed the best removal efficiency for wastewater treatment. For the system with hydrilla, it was found that pH and SS of the effluent were high. It might not be suitable to use hydrilla for effluent polishing. This study could emphasize that lotus and hydrilla could provide an alternative aquatic plant system for wastewater treatment.