Performance Effectiveness of Communal Wastewater Treatment Plant as an Effort to Control Pollution of the Gajah Wong River, Yogyakarta

The Gajah Wong River receives wastewater from the high population of Sleman Regency, including agricultural activities and home industries that contain organic pollutants. High organic pollutants cause dissolved oxygen depletion in waters that can threaten the lives of various aquatic biota. The construction of a communal wastewater treatment plant (WWTP) for handling domestic wastewater is an effort to control river pollution. The effectiveness of WWTP performance based on key parameters is continuously monitored, which is the purpose of this research. Surveys on 4 (four) communal WWTPs (Ngudi Mulyo, Wahana Bina Lingkungan, Tirto Mili, and Karya Asri Ambarukmo) were conducted in February – April 2021 with the key parameters observed were pH, BOD5, COD, and NH3. Sampling wastewater by grab sampling at each inlet and outlet of the WWTP using ABR (Anaerobic Baffled Reactor) and RBC (Rotating Biological Contactor) technology 6 times. The results provide an overview of the quality characteristics of wastewater that has been treated (outlet) at the Ngundi Mulyo WWTP (NH3 16.55 mg/L, BOD5 32.53 mg/L, COD 213.52 mg/L, pH 5) Wahana Bina Lingkungan (NH3 29.85 mg/L, BOD5 262.36 mg/L, pH 6-7), Tirto Mulyo (NH3 20.42 mg/L, BOD5 66.67 mg/L, COD 248.7 mg/L, pH 6-7) and Karya Asri Ambarukmo (NH3 21.60 mg/L, BOD5 252.64 mg/L, pH 6-7). These results reveal that the performance of the four WWTPs is still low and has not been effective in reducing COD and NH3 parameters, except that BOD5 reaches the required quality standard, and the processed wastewater still has the potential to reduce the water quality of the Gajah Wong River. This result is also a signal for WWTP managers to improve the processing process in each of these WWTPs.