WATER CONSERVATION MODEL IN HOTEL AND APARTMENT BUILDING IN SEMARANG CITY, INDONESIA

Environmental problems such as land subsidence, seawater intrusion, and groundwater contamination are the impacts of groundwater exploitation in hotel and apartment buildings in the city of Semarang. This research was conducted on ten buildings using a four-model approach to water conservation, which includes rainwater harvesting, water-saving plumbing fixtures, the reuse of recycled water from gray water, and condensate water from air conditioners in buildings. The results showed that rainwater harvesting contributes 13.12-166.77% of the total building water demand, depending on the size of the catchment area of the building. Rainwater harvesting can be combined with infiltration wells, but the research location is relatively shallow; the groundwater depth is less than 1 meter, so infiltration wells cannot be applied. The use of water-saving plumbing fixtures accounts for 6.4% of the total building water demand. Likewise, with gray water, the reuse of recycled water from gray water contributes 59.87- 69.71% of the total building water demand. Gray water is treated at STP, then flows to RWT, then flows to WTP to be treated. Gray water should not be mixed with black water so that the treatment load at the STP and WTP is not too large. Finally, condensate water from air conditioners in buildings is no less important to note; although it contributes only 1.43% of the total building water demand, it plays a role in creating green buildings.