Effect of Rotation Speed on Phosphate and Nitrate Removal from Domestic Wastewater in The Oxidation Ditch

Abstract

Oxidation Ditch (OD) has been widely used for domestic wastewater treatment technology, especially in Indonesia. In its operation, an OD uses a rotor to increase oxygen concentration. This rotational speed of the rotor will be valuable in OD performance for decreasing contaminants, especially nutrients. Remaining high concentration of nutrients at the end of the processing unit might generate environmental issues. This study analyses the effect of rotational speed on pilot scale OD. Rotation speed conducted were 45 rpm and 60 rpm. The study was conducted for five days by measuring nitrate, phosphate, dissolved oxygen, temperature and pH. The difference between 45 and 60 rpm on nitrate reduction was not significant. The decrease in total P at 45 and 60 rpm tended to increase steadily until the fourth day but experienced a slight decrease on day 5. The complexity of N and P processes in OD pilot scale units were much noticable. Efficient removal of nitrate concentrations was influenced by the lack of anoxic conditions to enable the denitrification process. Supplementary wastewater treatment unit was needed to reduce nutrient levels.