Evaluasi Proses Dalam Kolam Fakultatif Pada Instalasi Pengolahan Air Limbah (Ipal) Kota Yogyakarta Di Desa Pendowoharjo, Bantul

The characteristics of domestic wastewater is the high content of organic matter, including the Yogyakarta domestic wastewater which treated at The Wastewater Processing Plants in Pendowoharjo, Bantul. Although the industrial wastewater does not content the hazardous materials, it does not include the domestic wastewater. Therefore, the treatment does not need chemically precipitation. To optimize the process, it needs a conclusive condition such as a certain temperature, pH and dissolved oxygen. This research is continuing the research before in which emphasized the removing of organics matter in facultative ponds. The previous research has shown that the reducing efficiency of the BOD (Biological Oxygen Demand) is 88%, COD (Chemical Oxygen Demand) is 86.63%, SS (Suspended Solids) is 86.13%, and the efficiency of the DO (Dissolved Oxygen) revised is 33.12%. The main treatment in the facultative ponds is biological process that will reduce the organic matter by microorganism activity. The detention time (0) is employed as the independent parameter in design and control, which functionally related to microbial growth rate and process performance. Therefore it is important to know the change of the reaction in the varied detention time. The research shows that the value of reaction-rate constant in the facultative ponds (K) is 1.6 days-'. This result is less than the value of the criteria of design which is recommended by Thirumurthi that is 2.4 days-'. The detention time is 12.324 days with 88% of the BOD removal. This result is in line with the criteria of design for 3 days to 20 days long with 80% to 90% of the BOD removal