2021 : Rainwater Harvesting System as Clean Water Supply (Case Study ITS Dormitory)

Ir. Mas Agus Mardyanto M.E., Ph.D



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The ITS’ dormitory serves more than one thousands students. They consume for about 3700 m3/month of clean water. Therefore, the management must spend much money for clean water expenses. On the other hand, Surabaya is a rain rich area. The rain water can be utilized as an alternative to replace the clean water obtained from the water enterprise (PDAM). This study presents the potential of rain water harvesting to be applied in the dormitory. This rainwater harvesting system is considering the quality and quantity of rainwater in ITS’ Dormitory. Rain water was sampled from the roof. The quality of rainwater was then analyzed. The quantity of rainwater catched by the building’s roof was calculated based on the average rainfall. The rainfall data was obtained from the nearbyKeputih Raingauge Station. The amount of water used by the dormitory was compared to the one catched by the roof. The difference was considered as saving water. The quality of the collected rain water was as follows: pH value is 6.75; 35.71 mg/L of hardness; and total dissolved solid (TDS) is 336 mg/L. According to the Decree of Minister of Health No. 492 2010, the rainwater could be used as clean water. During the rainy season, the catched rain water could replace the water needed for daily use of the tenants. The results of analysis showed that the use of rainwater for alternative of clean water save up to IDR 17,000,000.00 per month during the rainy season.