Evaluation of Settling Pond Management at PT Borneo Indobara to Maintain the Total Suspended Solid (TSS) Outflow Within Standard Threshold

Abstract

Effective wastewater management in coal mining is critical for minimizing environmental impact and ensuring regulatory compliance. This study evaluates the performance of Settling Pond SP 02 GH at PT Borneo Indobara (PT BIB), a major coal producer in South Kalimantan, Indonesia. Despite existing controls, TSS outflow from SP 02 GH has periodically exceeded this threshold, resulting in environmental complaints, operational costs, and reputational risks. The primary research objectives are to identify the root causes of excessive TSS discharge and to develop data-driven, economically viable solutions. A Lean Six Sigma DMAIC (Define, Measure, Analyze, Improve, Control) framework was employed. Data collection involved semi-structured interviews, field observations, water sampling, and the use of historical TSS and rainfall records. Analytical methods included descriptive statistics, linear regression, and root cause analysis using Fishbone Diagrams. The analysis revealed a strong correlation (R² = 0.9997) between TSS levels at the inlet and TSS pump discharge, identifying the pump system as the dominant contributor to excessive TSS. In contrast, rainfall intensity showed no significant effect (R² = 0.027). Key interventions include the establishment of a maximum TSS pump limit of 25,000 mg/L, installation of real-time TSS sensors at both pump and outlet points, and the development of standard operating procedures (SOP) for monitoring and maintenance of the settling pond. Economic feasibility was assessed using a Benefit-Cost Ratio (BCR) analysis, indicating a highly favorable outcome: projected annual benefits of IDR 51.94 billion versus implementation costs of IDR 1.6 billion, resulting in a BCR of 32.57.