Coagulation is a well-known technology applied in water and wastewater treatment. Inorganic salts, such as alum, ferrous sulfate, and polyaluminum chloride, are usually used. It is widely known that utilization of these inorganic coagulants poses several disadvantages, such as high coagulant cost and high sludge volume that increase water treatment expenses. The use of alum also poses health risk to human as it may cause degenerative diseases. In order to minimize these disadvantages, the use of various coagulants from natural resources has been recently proposed. In this research, study was performed on the extraction and use of a potential natural coagulant (Leucaena leucocephala) seed kernel as natural coagulant. Leucaena seed kernel was extracted at various NaCl concentrations (0-5 mol L −1). Extract with highest protein content obtained at NaCl concentration of 3 mol L −1 was further used to treat a synthetic wastewater model substance (Congo red solution) at various pH (2-10) and dosage (2-40 mL L −1). This natural coagulant successfully removed 99.9% of the color at pH 3 and dosage 10 mL L −1 , with only half sludge volume discharged when compared to alum. The result suggests that leucaena is a promising natural coagulant for water and wastewater treatment.

PT ABC is a subsidiary of PT PXZ (state owned companies under SKK Migas and PT Pertamina supervision) which is engaged un upstream sector in Indonesia. Seeing the continuing decline in oil and gas reserves in Indonesia and increasing demand, the government request all upstream company to find more source. PT ABC is trying to continue to increase production of oil and gas by opening a new potential project. Revenue sharing will use the gross split method. The purpose of writing this final project is to help PT ABC analyze new projects that will be undertaken. The analysis is carried out by looking at the business situation externally and internally and will be followed by economic analysis and risk analysis to identify the factor that has impact of the project. External analysis shows that the oil and gas industry is still an attractive industry for the government to run and support. However, in its implementation the company have to follow the applicable regulations since oil and gas industry are one of the strategic industries. In addition to funding activities, PT PXZ as the holding company is in a healthy financial condition. The results of economic analysis on the PT ABC project show that this project can be implemented and will generate profits for the company. The NPV to be obtained is USD 46.701.182, the IRR obtained is 17.15%, PBP will last for 5.52 years, and the PI has a value of 1,98. From the risk analysis, there are several factors that affect the economic results of the project, namely the price of oil and gas, the percentage of oil and gas sales, capital expenditure, and the percentage of oil and gas split.