Optimizing the Coagulation Dose Considering Multi Factors: A Design of Experiment Approach
DOI:
https://doi.org/10.33736/jaspe.11048.2025Keywords:
COD, Design of Experiments, Optimization, Residual Coagulant, TurbidityAbstract
Optimizing coagulant dosage for drinking water treatment is essential for enhancing water quality. It also improves operational efficiency and cost-effectiveness. Traditionally, treatment plants focus on removing turbidity, often neglecting other critical factors such as co-pollutant removal, residual coagulant levels, and sludge production. This study addresses these limitations by optimizing coagulant dosage to simultaneously maximize turbidity and chemical oxygen demand (COD) removal, minimize residual Al concentrations, and reduce sludge generation. It employs a multi–parameter approach to improve the water treatment process, targeting low (10 NTU), medium (50 NTU), and high (400 NTU) turbidity synthetic water samples, representative of Mahaweli River water quality. The methodology includes preparing synthetic water, conducting jar tests to evaluate coagulation performance, and using design of experiments with Response Surface Methodology to identify optimal coagulant dosages and mixing speeds. Poly-aluminum chloride (PAC) was found to be the most effective coagulant for low- and medium-turbidity waters, with optimal dosages of 7 mg/l and 7.8 mg/l, and mixing speeds of 220 rpm and 216 rpm. Under these conditions, the final turbidity of water was 0.1648 NTU and 0.6890 NTU, with sludge weights of 0.0047 g and 0.0382 g, respectively. For high turbidity water, alum was optimal at 27 mg/l, with a mixing speed of 226 rpm, resulting in a turbidity of 2.3904 NTU and a sludge weight of 0.2203 g. COD removal percentages for low, medium, and high turbidity samples were 49.12%, 53.45%, and 49.57%. Residual aluminum levels remained below 10 ppm across all samples, measured via titration and Atomic Absorption Spectroscopy (AAS). These findings show that optimized coagulant dosage improves water quality, reduces sludge, and minimizes chemical residuals, providing cost-effective and sustainable improvements in water treatment. The study recommends multi–parameter optimization strategies and mechanical mixing methods in conventional water treatment plants to enhance efficiency and ensure high-quality drinking water.
References
Ji, X., Li, Z., Wang, M., Yuan, Z., & Jin, L. (2024). Response Surface Methodology Approach to Optimize Parameters for Coagulation Process Using Polyaluminum Chloride (PAC). Water (Switzerland), 16(11). https://doi.org/10.3390/w16111470
Ciobanu, R., Asachi, G., Mihai, M., & Teodosiu, C. (2023). An Overview of Natural Organic Matter Removal by Coagulation in Drinking Water Treatment, Buletinul Institutului Politehnic Din Iaşi, 68(4), 69-92. https://doi.org/10.5281/zenodo.7539887
Mustereț, C. P., Morosanu, I., Ciobanu, R., Plavan, O., Gherghel, A., Al-Refai, M., Roman, I., & Teodosiu, C. (2021). Assessment of coagulation–flocculation process efficiency for the natural organic matter removal in drinking water treatment. Water (Switzerland), 13(21), 3073. https://doi.org/10.3390/w13213073
Sillanpää, M., Ncibi, M. C., Matilainen, A., & Vepsäläinen, M. (2018). Removal of natural organic matter in drinking water treatment by coagulation: A comprehensive review. In Chemosphere (Vol. 190, pp. 54–71). Elsevier Ltd. https://doi.org/10.1016/j.chemosphere.2017.09.113
Sajath, S. H. M., Nihmiya, A. R., & Arachchige, U. S. P. R. (2022). Handling the sludge when using polyaluminum chloride as a coagulant in the potable water treatment process. Nature Environment and Pollution Technology, 21(2), 617–624. https://doi.org/10.46488/NEPT.2022.v21i02.020
Balik, Ö. Y., & Aydin, S. (2016). Coagulation/flocculation optimization and sludge production for pre-treatment of paint industry wastewater. Desalination and Water Treatment, 57(27), 12692–12699. https://doi.org/10.1080/19443994.2015.1051125
Choque-Quispe, Y., Solano-Reynoso, A. M., Choque-Quispe, D., Ligarda-, C. A., Ramos-Pacheco, B. S., Flores-Ccorisapra, Y., Felipe Carhuarupay-, Y., & Arguedas, M. (n.d.). Optimization of the flocculating capacity of a new coagulant extracted by micro-2 atomization of a high Andean algae 3. SSRN 4792929 https://dx.doi.org/10.2139/ssrn.4792929
El-taweel, R. M., Mohamed, N., Alrefaey, K. A., Husien, S., Abdel-Aziz, A. B., Salim, A. I., Mostafa, N. G., Said, L. A., Fahim, I. S., & Radwan, A. G. (2023). A review of coagulation explaining its definition, mechanism, coagulant types, and optimization models; RSM, and ANN. In Current Research in Green and Sustainable Chemistry (Vol. 6). Elsevier B.V. https://doi.org/10.1016/j.crgsc.2023.100358
Rathnayake, R. M. L. D., Wijesinghe, H. P. S. M., Dissanayake, D. M. P. T., & Dias, D. D. (2024). Influence of land use on the water quality of the upper Mahaweli river: a comparative analysis in dry and wet weather conditions. In 30 Sri Lankan Journal of Applied Sciences, 2(2), 30-37. https://www.sljoas.uwu.ac.lk/index.php/sljoas/article/view/85
Thilakarathna, P. A., Fareed, F., Makehelwala, M., Weragoda, S. K., Fernando, R., Premachandra, T., Rajapakse, M., Wei, Y., Yang, M., & Karunaratne, S. H. P. P. (2024). Land-use pattern-based spatial variation of physicochemical parameters and efficacy of safe drinking water supply along the Mahaweli River, Sri Lanka. Water (Switzerland), 16(18), 2644. https://doi.org/10.3390/w16182644
Hewakoon, H. P., Miguntanna, N., Siriwardhana, K. D., & Rathnayake, U. (2024). Impact of COVID-19 lockdown on water quality of major rivers in Sri Lanka. Water Practice and Technology, 19(10), 4163–4177. https://doi.org/10.2166/wpt.2024.256
Kotti, M., Papafilippaki, A., & Stavroulakis, G. (2012). Removal of turbidity and COD from a synthetic water sample by coagulation. Journal of Environmental Science and Engineering. A, 1(11A), 1243. https://www.researchgate.net/publication/243457345
Tahraoui, H., Toumi, S., Boudoukhani, M., Touzout, N., Sid, A. N. E. H., Amrane, A., Belhadj, A. E., Hadjadj, M., Laichi, Y., Aboumustapha, M., Kebir, M., Bouguettoucha, A., Chebli, D., Assadi, A. A., & Zhang, J. (2024). Evaluating the Effectiveness of Coagulation–Flocculation Treatment Using Aluminum Sulfate on a Polluted Surface Water Source: A Year-Long Study. Water (Switzerland), 16(3), 400. https://doi.org/10.3390/w16030400
Zainol, N. A., Al Balqis Khalilullah, P., Ghani, A. A., Rashid, N. A., & Makhtar, S. M. Z. (2022). Turbidity removal from kaolin synthetic wastewater via coagulation process using sludge from water treatment plant. International Journal of Integrated Engineering, 14(9), 222–231. https://doi.org/10.30880/ijie.2022.14.09.028
Khettaf, S., Bouhidel, K. E., Khouni, I., Louhichi, G., Ghrabi, A., Bousselmi, L., & Bouhelassa, M. (2021). Optimization of coagulation-flocculation process in the treatment of surface water for a maximum dissolved organic matter removal using RSM approach. Water Supply, 21(6), 3042–3056. https://doi.org/10.2166/ws.2021.070
Ye, C., Wang, D., Shi, B., Yu, J., Qu, J., Edwards, M., & Tang, H. (2007). Alkalinity effect of coagulation with polyaluminum chlorides: Role of electrostatic patch. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 294(1–3), 163–173. https://doi.org/10.1016/j.colsurfa.2006.08.005
Zouboulis, A. I., & Traskas, G. (2005). Comparable evaluation of various commercially available aluminium-based coagulants for the treatment of surface water and for the post-treatment of urban wastewater. Journal of Chemical Technology and Biotechnology, 80(10), 1136–1147. https://doi.org/10.1002/jctb.1300
Yang, Z. L., Gao, B. Y., Yue, Q. Y., & Wang, Y. (2010). Effect of pH on the coagulation performance of Al-based coagulants and residual aluminum speciation during the treatment of humic acid-kaolin synthetic water. Journal of Hazardous Materials, 178(1–3), 596–603. https://doi.org/10.1016/j.jhazmat.2010.01.127
Miranda, R., Latour, I., & Blanco, A. (2020). Understanding the efficiency of Aluminum coagulants used in dissolved air flotation (DAF). Frontiers in Chemistry, 8, 27. https://doi.org/10.3389/fchem.2020.00027
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