Key Design and Implementation Points of the Separate Sewage and Wastewater System
The separate sewage and wastewater system requires that domestic sewage (fecal sewage) and domestic wastewater (from washing, bathing, and lavatory use) be collected in independent drainage systems. According to the mandatory provisions of Article 4.1.3 of GB 50015-2019, the following buildings must adopt a separate sewage and wastewater system: buildings equipped with reclaimed water reuse systems; super high-rise buildings with a height exceeding 100 m; and public buildings such as hotels and hospitals with special requirements for drainage treatment. The key design points of the separate sewage and wastewater system include: (1) Sewage risers and wastewater risers shall be provided separately and must not be combined; (2) Discharge pipes shall be led separately to outdoor inspection chambers, with the spacing between inspection chambers preferably not exceeding 40 m; (3) The connection between the bottom of the sewage riser and the discharge pipe shall use two 45-degree elbows or a large-radius 90-degree elbow; (4) The diameter of the wastewater riser may be appropriately reduced, but shall not be less than DN75; (5) In the pipe transfer floor or equipment floor, a dedicated vent system shall be provided to ensure airflow balance. The separate sewage and wastewater system not only facilitates reclaimed water reuse but also reduces the treatment load of sewage treatment plants, in line with the national policy orientation of water conservation and emission reduction.
Grease Interception Technology for Oily Wastewater from Kitchens
Hotel kitchen drainage contains large amounts of grease and residues; direct discharge into the municipal network will cause pipe blockage and environmental pollution. According to Article 4.8.1 of the Standard for Design of Building Water Supply and Drainage GB 50015-2019, oily wastewater from catering kitchens must undergo grease interception treatment before discharge. Grease interception facilities may adopt grease interceptors or oil-water separators, and the following requirements shall be followed in design: (1) The effective volume of the grease interceptor shall be calculated as 6-8 times the maximum hourly drainage volume of the kitchen, with a retention time of not less than 30 min; (2) The interceptor shall be provided with 2-3 compartments, with the flow velocity controlled at 0.005-0.01 m/s; (3) A heating device shall be provided to prevent grease solidification (the water temperature should preferably be maintained at 15-20 degrees); (4) A vent pipe shall be provided and led to a safe outdoor location; (5) The treatment capacity of the oil-water separator shall be calculated based on the number of diners and the water use quota, with the oil content in the effluent not exceeding 100 mg/L. Modern hotel kitchens mostly adopt integrated oil-water separation equipment with automatic grease scraping and air flotation separation, which can achieve a grease removal efficiency of over 95% and is equipped with automatic slag discharge and alarm functions.
Vent System Design and Water Seal Protection
The core objective of vent design for drainage systems is to maintain the air pressure balance within the pipes and prevent water seal destruction that leads to odor backflow. According to Article 4.6.1 of GB 50015-2019, the drainage system of hotel buildings shall be provided with dedicated vent risers, the diameter of which should preferably not be less than 1/2 of the drainage riser diameter. For star-rated hotels, fixture vents or circuit vents are recommended for bathroom drainage to ensure the effectiveness of the water seal of each sanitary fixture. The connection between the vent riser and the drainage riser shall use H-type fittings or oblique tees, connected once every 2-3 floors. The stack vent shall extend not less than 0.3 m above the roof (not less than 2.0 m for accessible roofs), and the pipe opening shall be provided with a stainless steel mesh cover to prevent insects. The water seal depth shall not be less than 50 mm, and the water seal depth of floor drains should preferably be 50-80 mm. Particular attention should be paid to the fact that special drainage such as hotel swimming pool drainage and kitchen drainage shall not share a vent system with the domestic drainage system.
Key Drainage Design Points for Special Areas of Hotels
The hotel drainage system involves a variety of special functional areas and requires targeted specialized design: (1) Swimming pool drainage: an independent drainage system shall be provided, discharging to the outdoor stormwater network or reused after treatment; discharge into domestic sewage pipes is strictly prohibited; (2) Laundry drainage: contains large amounts of detergents and fiber impurities, requiring hair collectors and sedimentation tanks; the water temperature is relatively high (can exceed 60 degrees), so pipes shall use high-temperature-resistant materials; (3) Basement drainage: areas below the elevation of the municipal drainage network shall be provided with sumps and sewage lift pumps, using a dual-pump alternating duty-standby configuration; (4) Boiler room and air-conditioning plant room drainage: acid-alkali wastewater requires neutralization treatment before discharge. The drainage system of each special area shall be provided with an independent vent pipe and shall not be connected in series with the domestic drainage system.