Efficiency of water hyacinth and water lettuce in stimulated hydroponic system for domestic wastewater treatment

Abstract

The objective of this research was to investigate the efficiency of water hyacinth and water lettuce, which were floating plants, in stimulated hydroponic system for domestic wastewater treatment. The results showed that both plants could treat domestic wastewater efficiently. Total solid (TS), total dissolved solid (TDS) total suspended solid (TSS), fat/oil/grease (FOG), total bacteria, nutrients; ammonia nitrogen and phosphate phosphorus; water hardness and biochemical oxygen demand (BOD) significantly decreased (p<0.05), while dissolved oxygen (DO) increased. The process of rhizofiltration of these plants played an important role in the reduction of solids. Water hyacinth and water lettuce have the fibrous roots which filter the wastewater through a mass of roots and trapped much of solids. Moreover, groups of fibrous roots also absorb ammonia nitrogen, phosphate phosphorus, and calcium and magnesium through their root system. Plants also transport the atmospheric and photosynthetic oxygen to the roots and release oxygen to water, thus dissolved oxygen was increased and BOD was decreased. However, water hyacinth and water lettuce did not affect to temperature and pH, because the experimental models were established in greenhouse. Temperature depended only on the weather of each day. The pH of wastewater was not significant difference (p>0.05). The pH of treated water was between 6.8-7.0, which were not exceed the standard value. In conclusion, Water hyacinth and water lettuce were useful for domestic wastewater treatment and appropriate to local operation.