Treatment of wastewater from cafeteria by Multi-Soil-Layering system

Preliminary experiment on wastewater treatment of Kasetsart University's cafeteria was conducted to compare the effectiveness of various organic materials as carbon source for nitrate removal. Sand and Pakchong soil series were each mixed with 20 percent of iron scrap and with 0 and 20 percent of organic material (rice straw, kenaf, sawdust and corncob). The mixture was filled into the open end tube and leached with nitrate solution. The results revealed that Pakchong soil was more effective in removing nitrate than sand. Rice straw, kenaf and corncob at the rate of 20 percent were more effective in removing nitrate than sawdust at the same rate. Comparative study of iron scrap and iron wire for phosphate fixation was also investigated. Sand and Pakchong soil were separately mixed with 20 percent of rice straw and with 0 and 20 percent of iron scrap and iron wire. The mixture was filled into the open end tube and leached with phosphate solution. Pakchong soil was more effective in phosphate fixation when compared to sand. Iron scrap at the rate of 20 percent was more effective in removing phosphate when compared to iron wire. Third experiment was conducted to study the effectiveness of various materials in purifying the wastewater. The wastewater was discharged continuously through each material that filled up to 85 cm of the 7.6 cm diameter PVC pipe. The results revealed that each material had different capacity in removing the pollutants. The study on wastewater treatment by Multi-Soil-Layering system was also conducted. The system consisted of Pakchong soil mixed with iron scrap and organic material (pelletized jute, corncob or kenaf) at the ratio of 75:12.5:12.5. Each layer of the mixture was a brick-like filled into the 15*50*100 cm acrylic model using zoelite, sand, limestone separately as an interlayer to prevent clogging and charcoal as the top layer of each mixture layer. The wastewater was then gravitationally and continuously discharged from the top of the acrylic model through the system. Wastewater and treated water were collected every two week for chemical analysis. The results revealed that the combination of sand+corncob was effective in removing 75, 83, 77 and 100 percent of suspended solids, BOD, total N and dissolved P, respectively, with the loading rate of 128 l/square m/d. The combination of sand+kenaf could remove 46, 83, 67 and 100 percent of those respective pollutants with the loading rate of 128 l/square m/d. These two treatments had the highest effects on water purification although clogging was observed. The combination of zeolite+pelletized jute, zeolite+corncob and zeolite+kenaf were more or less similar in effectiveness for purifying the wastewater. When the wastewater was diluted 4 times with tap water, the effectiveness of the system did not increased appreciably because of the high loading rate.