Evaluasi Kualitas dan Kuantitas Lumpur Alum dari Instalasi Pengolahan Air Minum Citayam

Water treatment plants (WTPs) produces residues in the form of alum sludge during the treatment process. In Indonesia, due to various techno-economic constraints, some WTPs are not equipped by sludge treatment systems, so the generated alum sludge is discharged directly into water bodies without appropriate treatment. This condition may pollute water bodies because alum sludge contains various contaminants such as solid particles, organic compounds, inorganic metals, aluminum, and pathogenic microorganisms. This study aims to evaluate the characteristics of alum sludge from aspects of quality and quantity, which is indispensable for the design of sludge treatment facilities. Citayam WTP (capacity of 120 L/s) in Depok City was chosen as a case study. The study was conducted in several stages as follows: (i) survey and sampling; (ii) quality analysis of alum sludge; (iii) estimation of sludge generation; and (iv) mass and volume balance analysis. Results of comparative analysis of alum sludge quality against the Regulation of Minister of Environment of Indonesia 5/2014 shows alum sludge from flocculation units meets quality standards. In contrast, alum sludge from sedimentation and filter units were exceeded for TSS, COD, and Total Coliform parameters. Quantity-wise, the estimation of sludge generation by theoretical and empirical methods was found to be 1,898 kg/day and 4,854 kg/day. Analysis of mass and volume balance using STAN software indicates that the theoretical approach is quite representative, while the empirical method tends to be over-estimated.