To increase tourism in Bali Island, in the year 1971 Government assisted by United Nations Development Programme conducted a study about Bali tourism. That study suggested that more international hotels should be built in Bali Island to accommodate the increment of foreign and domestic tourists. Statistic data issued by Central Statistics Agency of Indonesia showed that the number of tourists in the year 2016 has increased 23.14% compared to the previous year. The Nusa Dua Project is a part of the Bali tourism development master plan. Domestic waste water from hotels in Nusa Dua region needs to be treated, so Bali Tourism Development Corporation Waste Water Treatment Plant was built in 1976 which later changed its name to the WWTP Indonesia Tourism Development Corporation (ITDC). However, the final processed product at WWTP ITDC Bali is still affected by algae bloom which reducing water quality. The existing practice to harvest microalgae is based on flocculation method using alum & polyelectrolyte chemicals causing the harvested microalgae contaminated by chemicals. The purpose of this study is to compare two different methods of microalgae harvesting namely filtration and flocculation methods, to know the effective filtration method based on slope and pressure variations, and to recommend the utilization of the dominant type of microalgae. The microalgae harvesting by using filtration was made in various variations, namely variations in water pressure and slope. In the variation of water pressure, three stages are carried out, namely the pressure of 1.5 bar, 2.5 bar, and 3.5 bar which each pressure was done for 10 minutes, 20 minutes, and 30 minutes. In the slope variation, there were 3 stages, namely pressure 10°, 20°, and 30° which each pressure was carried out for 10 minutes, 20 minutes, and 30 minutes. From the results of the harvesting water quality test microalgae that is effective and in accordance with the WWTP ITDC Bali vision and mission, that is go green or green company, the parameter concluded that has the highest lowest value is using the method of harvesting microalgae filtration with a pressure variation of 1.5 bar. Because harvesting microalgae by filtration method does not use any chemical mixture. Effective slope variation filtration method is at 10° in 30 minutes with a weight of 203 grams, while the effective pressure variation filtration is at 1.5 bar in 30 minutes weighing 212 grams. This is because the weight of microalgae is filtered the most. The dominant in the whole sample is microalgae Gramatophora angulosa which belongs to the class of algae brown (Phaephyceae) and Sphaerocystis schroeteri which belongs to the class of green algae (Chlorophyceae). Benefits of algae brown Gramatophora angulosa as an ingredient in organic fertilizer and animal feed. Benefits of green algae Sphaerocystis schroeteri as freshwater fish feed ingredients.

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