Indonesian Journal of Environmental Management and Sustainability e-ISSN:2598-6279 p-ISSN:2598-6260 Research Paper The Effectiveness and Cost Optimization of Coagulant Aluminum Chlorohydrate (ACH), Aluminum Sulfate (AS), and Poly Aluminium Chloride (PAC) in Coagulation Process at The PT. Pupuk Sriwijaya (PT. Pusri) Utility Unit Dedi Teguh 1 , Tuty Emilia Agustina 2 *, M. Hafiz Ridho 2 , Nurdiana Febriyanti 2 , Dewi Ermaya 1 1 Industrial Chemical Engineering Technology Study Program, Department of Agricultural Technology, Politeknik Negeri Lampung, Lampung, 35144, Indonesia 2 Chemical Engineering Department, Faculty of Engineering, Sriwijaya University, Palembang, 30662, Indonesia *Corresponding author e-mail: tuty agustina@unsri.ac.id Abstract PT. Pusri utilizes Musi River water as a source of process water. Colloidal particles suspended in Musi River water can cause blockage and build-up of scale on pipes and process equipment. Therefore, a good coagulation process is needed to reduce the content of colloidal solids suspended in water by using a coagulant. Coagulants that are often used for water treatment include ACH, AS, and PAC. The objectives of the study are to assess the effectiveness and to optimize the usage of the coagulant ACH, AS, and PAC on decreasing the turbidity of Musi River water sample as a raw water in utility unit of PT. Pusri. The coagulation process was carried out by varying the concentration of each coagulant and adding 0.1 ppm of coagulant aid for all samples. Fast and slow stirring was carried out each at a speed of 150 rpm 30 rpm for 10 minutes. From the experiments conducted, it was found that the most effective coagulants to be used were ACH and PAC with the addition of a smaller coagulant dose of 12 ppm to achieve the standard water quality used at PT. Pusri. Meanwhile, the use of AS has higher efficiency when compared to ACH and PAC because it is more cost effective. Keywords Coagulation, Coagulants, ACH, AS, PAC Received: 3 December 2021, Accepted: 18 March 2022 https://doi.org/10.26554/ijems.2022.6.1.189-195 1. INTRODUCTION Water is needed in the industry to run industrial processes and activities. The use of water in the industry such as for process water, heating media, cooling media, raw ma- terials production, drinking water, and daily necessities. Most of the water comes from various sources such as dug wells, drilled wells, springs, rivers, and the sea. Water used in industry has minimum specifications. Decreased water quality can affect the productivity, function, yield, carrying capacity, and capacity of water resources (Rosyidah, 2018). Turbid water such as river water must be treated first to meet the requirements for use as raw water. To meet the water needs in the factory PT. Pusri as one of the largest fertilizer factories in Indonesia, where Musi River water as a source of raw water. The water treatment unit at PT. Pusri uses coagulation and filtration processes to obtain filtered water. Coagulation and flocculation are one of the chemical processes used to remove suspended or colloidal contaminants where these colloidal particles cannot settle by itself and are difficult to handle by physical treatment (Ghernaout, 2020). The coagulation process can be carried out through the stages of stirring between the coagulant and raw water and neutralizing the charge. The principle of coagulation is that in raw water there are solid particles that are mostly nega- tively charged (Prakash et al., 2014). These particles tend to repel each other so that they remain stable in suspended or colloidal forms in water. Neutralization of the negative charge of solid particles is carried out by adding a positively charged coagulant to the water followed by rapid stirring (Romadhon, 2016). Flocculation is the process of collecting particles with unstable charges which then collide with each other to form a collection of particles of larger size known as flocculants or flocs (Rusydi et al., 2017). In water treatment, coagulation and flocculation are still essential components of the overall suite of treatment processes(Rui et al., 2012). These processes are two interconnected processes using the addition of coagulant to form large flocs so that they are easy to precipitate (Khalid and Hind, 2016). Coagulant has