The objectives of this research aimed to study the appropriate ratio for making light weight brick which composed of the sawdust and water hyacinth and to study the efficiency of light weight brick. The research method was done by study the mechanical properties the compressive strengths and the physical properties with water absorption. The main materials were as follows: type 1-normal Portland cement lime gypsum aluminum powder ratio 30:9:9:2 and researchers determined 5 levels including of sand sawdust and water hyacinth according to the following proportions 40:5:5 30:10:10 20:15:15 10:20:20 and 0:25:25. The results revealed that the most appropriated ratio of the light weight brick was 40:5:5. The maximum compressive strength was 1.63 N/mm2. It is close to 2 N/mm2 from class 2 light weight brick standards value. The lowest value of water absorption was 514.29 kg/m3. It is close to 500 kg/m3 from water absorption of light weight brick standard value. Therefore these results supported the environmental conservation objective by increasing the economics values of sawdust and water hyacinth.

The objective of this research was to compare the effectiveness of water hyacinth and cootail for wastewater treatment by taking water sample from Klong Bangkhen-mai near King Mongkut’s University of Technology North Bangkok. The results showed that there was no diifference on water temperature changes in tanks between two plants. pH of water in coontail tanks was between pH 8.69 to pH 8.91 and pH of water in water hyacinth tanks was slightly increasing between pH 7.71 to pH 8.26. The more amount of coontail added the higher DO would be between 9.18 mg/L to 10.02 mg/L. Moreover COD of water was decreasing according to the amount of cootail addition and more effective than that in water hyacinth tank especially in 150 grams coontail tanks but TS in water hyacinth tanks was much more decreasing than that in coontail tanks. TS was between 21.73 mg/L to 25.91 mg/L. COD was between 45.30 mg/L to 48.34 mg/L.