This study aims to compare the quality of water (DO, pH, turbidity) that is treated by the
different age range of water hyacinth. A hypothesis of this study is “I age range of water
hyacinth affects to quality of water after treating then, the oldest water hyacinth is the best
increasing quality of water”. These procedures of the study are as follows: (1) The experiment is divided to 3 sets. Water hyacinth is added into the wastewater then, it is left for 7 days. (2)Dissolve oxygen, pH and turbidity of water are measured by using DO meter, universal indicator and turbidity meter after treating for 10 days. (3) The quality of water is measured again every 10 days and the experiment is tested for 30 days then, Data from the experiment are shown in the Table. (4) The quality of wastewater after treating with each age group of water hyacinth is compared by using data from Tables such as DO values, pH rates and turbidity values. The results are found that the water hyacinth can increase the DO and pH of water and decrease the turbidity values. The water quality of water that is tread by 7 days and 14 days water hyacinth are less than the quality of the water that is treated by 21 days water hyacinth.