Restoration of treated domestic wastewater quality at a bottled water factory in North Sumatra, Indonesia using DMAIC framework

Sewage treatment plants (STP) were known to play an essential role in removing organic matter from domestic wastewater, aligning with Sustainable Development Goal (SDG) 6 regarding clean water and sanitation. Despite their importance, STP performance could decline, leading to failure in fulfilling the established standards. This study addresses the decline in treated domestic wastewater quality observed in a bottled water factory in North Sumatra, Indonesia, where the system experienced setbacks leading to poor COD degradation performance, and the pH parameter declined to a low of 4.78 at the outlet tank. Not only does this study aim to fix the quality decline that occurred, but it also describes the application of the DMAIC framework in addressing this matter, which makes this study distinct from the others. Utilizing a root cause analysis within the DMAIC framework, we identified unhealthy activated sludge conditions as the primary cause. Corrective actions, including re-seeding and aeration adjustments, were conducted to enhance and stabilize the pH and COD parameters. Additionally, the disinfection process in the effluent tank was found to be essential for maintaining compliance with quality standards. This research contributes to a better understanding of STP management and the benefits of DMAIC implementation in addressing the problem while underscoring the importance of STP management in achieving SDG 6.