Standard No.:	GB 50014-2021
English Name:	Standard for design of outdoor wastewater engineering
Chinese Name:	室外排水设计标准
Professional Classification:	GB    National Standard
Issued by:	MOHURD
Issued on:	2021-04-09
Implemented on:	2021-10-1
Status:	valid
Superseding:	GB 50014-2006 Code for Design of Outdoor Wastewater GB 50014-2006(2011) Code for Design of Outdoor Wastewater GB 50014-2006(2014) Code for Design of Outdoor Wastewater Engineering GB 50014-2006(2016) Code for Design of Outdoor Wastewater Engineering
Language:	English
File Format:	PDF
Word Count:	47000 words
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Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative. In accordance with the requirements of Notice on Printing the Plan of Development, Revision and Relevant Works of National Engineering Construction Standards and Codes in 2017 (JIANBIAO [2016] No. 248) issued by the Ministry of Housing and Urban-Rural Development, this standard was revised by the drafting group through extensive investigation, careful summarization of practical experience, reference to relevant standards of foreign developed countries and on the basis of widely soliciting for opinions. The main technical contents of this standard include: general provisions, terms, wastewater engineering, design flowrate and waste loads, sewer and ancillary structures, pump station, wastewater and reclaimed water treatment, sludge treatment and disposal, monitoring and control, etc. The main technical contents of the revision of this standard are: 1. Some terms are supplemented and modified; 2. Clause 3 “Wastewater engineering” is added, which systematically specifies the composition and interrelationship of outdoor wastewater engineering; 3. The contents of pipeline access to utility tunnel, green rainwater detention and retention facilities, inverted siphon foundation, drainage on elevated road and underpass interchange are supplemented; 4. The contents of the wet well of the pump station of the underpass interchange road are supplemented; 5. The tower biological filters and land treatment processes are deleted, and the widely used and reliable processes such as membrane bioreactor (MBR), moving bed biofilm reactor (MBBR) and constructed wetland are supplemented; 6. The contents of anaerobic digestion with high solid concentration, oxic fermentation, lime stabilization, deep dehydration, sludge drying, incineration, deodorization, etc. are supplemented; 7. The design standards for wastewater treatment and sludge treatment and disposal are supplemented and improved; 8. The contents of smart drainage system such as informatization and intellectualization are added. The provisions printed in bold type in this standard are compulsory and must be enforced strictly. Standard for design of outdoor wastewater engineering 1 General provisions 1.0.1 This standard is developed for the propose of ensuring urban safety, scientifically designing outdoor wastewater engineering, implementing the concept of sponge city construction, preventing and controlling urban flooding disasters and water pollution, improving and protecting the environment, promoting resource utilization and improving people's health. 1.0.2 This standard is applicable to the design of permanent outdoor wastewater engineering in newly built, extended and renovated towns, industrial areas and residential areas. 1.0.3 The design of wastewater engineering shall be based on the approved urban master plan, sponge city special plan, urban drainage and wastewater treatment plan and special plan for urban flooding prevention and control, proceeding from the overall situation, considering the planning period, project scale, economic benefits, social benefits and environmental benefits comprehensively, correctly handling the relationship between short-term and long-term, concentration and dispersion, emission and utilization, and through comprehensive demonstration, achieving safety, reliability, environmental protection, land saving, economic rationality, advanced technology and suitability for local actual conditions. 1.0.4 The design of wastewater engineering shall be coordinated with the special planning and design of water resources, urban water supply, water pollution prevention and control, ecological environment protection, environmental sanitation, urban flood control, transportation, green space system, river and lake water system, etc. Natural water storage and drainage facilities shall be fully utilized according to the requirements of urban planning blue line and water surface ratio, and the elevation layout of different areas shall be specified according to the nature of land to meet the drainage requirements of different areas. 1.0.5 The design of wastewater engineering shall comply with the following requirements: 1 include stormwater safe drainage, resource utilization and pollution control, wastewater and reclaimed water treatment, sludge treatment and disposal; 2 coordinate with the stormwater system and wastewater system in the adjacent area; 3 may properly transform the original wastewater engineering facilities and give full play to its engineering efficiency. 1.0.6 The design of wastewater engineering shall actively adopt new technologies, processes, materials and equipment on the basis of continuously summing up scientific research and production practice experience. 1.0.7 The equipment of wastewater engineering shall be mechanized and automated, and the intellectualization shall be achieved gradually. 1.0.8 In addition to this standard, the design of wastewater engineering shall also comply with the requirements of the current relevant standards of China. 2 Terms 2.0.1 wastewater engineering engineering for the collection, transportation, treatment and reclaim of wastewater and stormwater 2.0.2 stormwater system assembly of facilities for percolation, storage, collection, transportation, treatment and utilization of stormwater combined in a certain way, covering the whole process management, early warning and emergency measures from the generation of stormwater runoff to terminal drainage 2.0.3 wastewater system assembly of facilities for collection, transportation, treatment, reclaim and disposal of municipal wastewater combined in a certain way 2.0.4 wastewater facilities general term for pipelines, structures and equipment in wastewater engineering 2.0.5 combined sewer overflow (CSO) combined sewage discharged into water body when rainfall exceeds the interception capacity of combined sewer system   2.0.6 runoff pollution phenomenon that the pollutants in the atmosphere and surface are brought into the receiving water body through rainfall and surface runoff scouring, so that the receiving water body is polluted, which is the main source of urban non-point source pollution 2.0.7 volume capture ratio of annual rainfall ratio of the controlled annual rainfall to the total annual rainfall by controlling the rainfall runoff on the underlying surface of urban construction through natural and artificial enhanced percolation, storage and purification 2.0.8 low impact development (LID) it is emphasized that the impact on the environment shall be reduced for urban development, the core of which is based on the concept of source control and impact load reduction, constructing drainage system adapted to nature, rationally utilizing space and taking corresponding measures to reduce the peak value and total amount of rainstorm runoff, delaying the occurrence time of peak flow and reducing urban non-point source pollution 2.0.9 dry weather flow (DWF) urban wastewater in sunny days, including overall wastewater, industrial wastewater and infiltrated water. 2.0.10 maximum dry weather flowrate maximum daily and maximum hourly urban wastewater volume in sunny days 2.0.11 wet weather flowrate sum of the maximum dry weather flowrate and the intercepted stormwater for separate sewer system; combined sewage volume after interception for combined sewer system 2.0.12 intercepted stormwater intercepted stormwater in drainage system, which is sent to urban wastewater treatment plant through wastewater pipeline to control urban surface runoff pollution 2.0.13 overall peaking factor ratio of the maximum daily and maximum hourly wastewater volume to the average daily and average hourly wastewater volume 2.0.14 runoff general term for the flowrate of excess water from the ground to the underdrain to the receiving water body after the stormwater falling to the ground exceeds the ground percolation and stagnation capacity in a certain area 2.0.15 recurrence interval for storm sewer design rainstorm recurrence interval used for storm sewer design 2.0.16 recurrence interval for urban flooding design rainstorm recurrence interval used for the design of urban flooding prevention and control system, which makes the accumulated water depth and water receding time on the ground, roads and other areas not exceed a certain standard 2.0.17 urban flooding, local flooding phenomenon that heavy rainfall or continuous rainfall volume exceeds the urban drainage capacity, resulting in ponding disaster on the urban ground 2.0.18 urban flooding prevention and control system assembly of engineering facilities and non engineering measures used to prevent and deal with urban flooding combined in a certain way, including natural and artificial facilities and management measures for rainwater collection, transportation, detention and retention, drainage, treatment and utilization 2.0.19 percolation underdrain underdrain for stormwater percolation, transfer or temporary storage 2.0.20 bar screen machine machine which removes the slag intercepted by the bar by mechanical method 2.0.21 radial flow settling tank tank in which wastewater flows slowly in the radial direction, causing solids in wastewater to settle   2.0.22 inclined tube (plate) settling tank tank in which inclined tubes (plates) are added to make the solids in wastewater settle efficiently 2.0.23 high efficiency settling tank tank in which the size of suspended solids is increased by mixing and flocculation of wastewater and return sludge, or the density of flocs is increased by adding heavy media such as sand and magnetic powder, so as to accelerate sedimentation 2.0.24 anaerobic/anoxic/oxic process biological treatment of wastewater by alternating anaerobic, anoxic and oxic treatment to improve the removal rate of total nitrogen and total phosphorus, also known as AAO or A2O process 2.0.25 fill ratio ratio of the amount of wastewater entering the reaction tank to the effective volume of the reaction tank in one cycle of sequencing batch activated sludge process 2.0.26 membrane bioreactor (MBR) wastewater treatment system which combines biological reaction with membrane filtration and uses membrane as separation medium to replace conventional gravity precipitation for solid-liquid separation to obtain effluent 2.0.27 surface nitrification loading rate kilograms of ammonia nitrogen per unit area and per unit time of biological reaction tank, which is generally expressed as NH3-N/(m2·d) 2.0.28 moving bed biofilm reactor (MBBR) wastewater treatment structure that relies on the biofilm on the surface of a fluidized carrier under the action of water flow and air flow to adsorb, oxidize and decompose pollutants, so as to purify wastewater 2.0.29 filling ratio ratio of the volume of the filler in the biofilm reactor to the tank capacity of the reaction zone where the filler is located 2.0.30 effective specific surface area surface area that can be used for biofilm attachment and growth on the suspended carrier filler per unit volume in the moving bed biofilm reactor (MBBR), ensure good mass transfer and protect the biofilm from scouring 2.0.31 disc filter utility model relates to a device for wastewater filtration by stringing a number of parallel, filter cloth-wrapped and hollow filter turntables with a horizontal axis 2.0.32 free surface flow constructed wetland utility model relates to a constructed wetland in which wastewater flows from the head-end to the end of the wetland in a horizontal flow mode, and no filler is arranged inside 2.0.33 horizontal subsurface flow constructed wetland utility model relates to a constructed wetland in which wastewater flows from the head-end to the end of the wetland in a horizontal flow mode, and fillers are arranged inside 2.0.34 vertical subsurface flow constructed wetland utility model relates to a constructed wetland in which wastewater flows from the top to the bottom or from the bottom to the top of the wetland in a vertical flow mode, and fillers are arranged inside 2.0.35 effective ultraviolet dose ultraviolet radiation dose (i.e., ultraviolet bioassay dose) exposed to organisms obtained by bioassay test 2.0.36 sludge drying process of removing water from dewatered sludge by percolation or evaporation 2.0.37 sludge compost process in which sludge generates high temperature under the action of oxic microorganisms under the condition of sufficient oxygen supply, so as to biodegrade and harmless organic matter, and finally produce humic products with stable properties   2.0.38 sludge integrated application method of using the treated sludge as the useful raw material for various purposes 2.0.39 odor control system facilities for collecting and treating odor from the source to discharging at the end, including capping odor source, collecting odor, treating odor and discharging after treatment, etc. 3 Wastewater engineering 3.1 General requirements 3.1.1 Wastewater engineering, including stormwater system and wastewater system, shall follow the whole process management and control from source to end. The stormwater system and wastewater system shall cooperate and connect with each other effectively. 3.1.2 The selection of wastewater system (separate sewer system or combined sewer system) shall be determined according to local conditions, such as local climate characteristics, topographic characteristics, hydrological conditions, water body conditions, original wastewater facilities, wastewater treatment degree and recycling after treatment, and shall meet the following requirements: 1 Different wastewater systems may be adopted in different areas of the same urban region. 2 Except for arid areas with little rainfall, separate sewer system shall be adopted for the wastewater system in newly built areas. 3 Wastewater is prohibited from being discharged to stormwater pipelines in separate sewer system, and measures such as interception, detention and retention and treatment shall be taken to control runoff pollution. 4 The existing combined sewer system shall control the overflow pollution through measures such as interception, detention and retention and treatment, and shall also implement the transformation of rain and wastewater after comparing schemes according to the requirements of urban drainage planning. 3.2 Stormwater system 3.2.1 The stormwater system shall include engineering measures such as source emission reduction, sewer, drainage and danger elimination, and non-engineering measures of emergency management, and shall be connected with flood control facilities. 3.2.2 Source emission reduction facilities shall be conducive to percolation, detention and retention or collection and utilization of stormwater nearby, reduce the total amount and peak flowrate of stormwater runoff, and control runoff pollution. 3.2.3 Sewer facilities shall ensure the transfer, detention, retention and discharge of stormwater during the recurrence interval for storm sewer design, and shall consider the influence of water level of receiving water body. 3.2.4 Source emission reduction facilities, sewer facilities and drainage and danger elimination facilities shall be checked as a whole system to meet the design requirements of recurrence interval for urban flooding design. 3.2.5 In the design of stormwater system, engineering and non-engineering measures shall be taken to strengthen the resilience of urban to cope with rainfall beyond the recurrence interval for urban flooding design, and emergency measures shall be taken to avoid casualties. After the disaster, the normal order of urban shall be restored quickly. 3.2.6 Stormwater runoff from sites polluted by hazardous substances shall be collected and treated separately, and shall not be discharged into sewer until it meets the current relevant national standards. 3.2.7 Measures shall be taken to prevent flood from affecting urban wastewater engineering in stormwater system design. 3.3 Wastewater system 3.3.1 The wastewater system shall include collection pipeline, wastewater treatment, advanced and reclaimed treatment and sludge treatment and disposal facilities. 3.3.2 Wastewater and polluted stormwater runoff from all water use processes in urban areas shall be included in the wastewater system. Supporting pipeline shall be constructed and put into operation synchronously to realize the integrated construction and operation of plant and pipeline. 3.3.3 The quality of wastewater discharged into urban wastewater pipeline must conform to the current national standards, and shall not affect the normal operation of urban sewer and wastewater treatment plants; it shall not cause harm to maintenance and management personnel; it shall not affect the recycling and safe discharge of treated effluent; it shall not affect the treatment and disposal of sludge. 3.3.4 Sewage and wastewater from industrial parks shall be collected and treated separately, and shall be discharged after reaching the standard. 3.3.5 The wastewater system shall be designed with measures to prevent the entry of external water. 3.3.6 When wastewater collection and centralized treatment facilities have been built in urban, septic tanks shall not be installed in the separate sewer system. 3.3.7 For wastewater treatment, the degree of wastewater treatment shall be scientifically determined and the treatment process shall be reasonably selected according to the current relevant national discharge standards, wastewater quality characteristics and the purpose of treated effluent. 3.3.8 The wastewater, sludge, odor and noise discharged from wastewater treatment shall conform to the current national standards. 3.3.9 The target of reclaimed water treatment shall be determined according to the current national standards and reclaimed water planning. 3.3.10 Urban wastewater treatment plants shall simultaneously build sludge treatment and disposal facilities, and shall carry out reduction, stabilization and harmless treatment, so as to realize the utilization of sludge energy and resources on the premise of ensuring safety, environmental protection and economy. 3.3.11 The design of wastewater engineering shall properly treat the solid waste generated in the process of wastewater, reclaimed water treatment and sludge treatment, and prevent the secondary pollution to the environment. 4 Design flow and waste loads 4.1 Design flow I Stormwater volume 4.1.1 The design water volume of source emission reduction facilities shall be determined according to the volume capture ratio of annual rainfall, and the corresponding design rainfall shall be specified, which can be calculated according to Annex A of this standard. 4.1.2 When the rainfall is less than the rainfall corresponding to the volume capture ratio of annual rainfall determined by the plan, the source emission reduction facilities shall be able to ensure that uncontrolled stormwater is not directly discharged to the municipal storm sewer. 4.1.3 The design flowrate of storm sewer shall be determined according to the recurrence interval for storm sewer design. The recurrence interval for storm sewer design shall take into account the factors such as the characteristics of catchment areas, urban types, topographic characteristics and climatic characteristics, etc., and shall be taken as specified in Table 4.1.3 after technical and economic comparison, the corresponding design rainfall intensity shall be specified, and the following requirements shall be met: Table 4.1.3 Recurrence interval for storm sewer design (years) Urban type City type Central city Non-central city Important areas in the central city Underground passages and sunken plaza in the central city Super- and hyper-cities 3–5 2–3 5–10 30–50 Mega-cities 2–5 2–3 5–10 20–30 Medium and small cities 2–3 2–3 3–5 10–20 Notes: 1 The design recurrence interval listed in the table is applicable to the rainstorm intensity equations determined by the annual maximum method. 2 Storm sewers shall be calculated according to gravity flow and full pipe flow. 3 Super-cities refer to cities with a permanent resident population of more than 10 million; hyper-cities refer to cities with a permanent resident population of more than 5 million and less than 10 million; mega-cities refer to cities with a permanent resident population of more than 1 million and less than 5 million; medium-sized cities refer to cities with a permanent resident population of more than 500,000 but less than 1 million; small cities refer to cities with a permanent resident population of less than 500,000 (the "more than" mentioned herein includes such figure and "less than" excludes such figure). 1 Urban areas with dense population, easy local flooding and good economic conditions shall adopt the prescribed upper limit of design recurrence interval; 2 For newly-built areas, the specified design recurrence interval shall be implemented. For existing areas, the stormwater system shall be checked and updated in combination with sponge city construction, regional reconstruction and road construction, and the specified design recurrence interval shall be implemented; 3 Different design recurrence interval can be adopted for the same stormwater system; 4 The recurrence interval for storm sewer design of underpass interchange in central city shall be implemented according to the requirements of "underground passages and sunken plaza in the central city" in Table 4.1.3, while the recurrence interval for storm sewer design of underpass interchange in non-central city shall not be less than 10 years, and the recurrence interval for storm sewer design on elevated roads shall not be less than 5 years.   4.1.4 The design flowrate of drainage and danger elimination facilities shall be determined according to the recurrence interval for urban flooding design and the corresponding maximum allowable water receding time. The recurrence interval for urban flooding design shall take into account factors such as the urban type, the influence degree of ponding and the change of inland river water level, and shall be taken as specified in Table 4.1.4 after technical and economic comparison, the corresponding design rainfall shall be determined, and the following requirements shall be met: 1 Cities with dense population, easy local flooding and good economic conditions shall adopt the prescribed upper limit of design recurrence interval; 2 Areas that do not have the conditions at present can meet the standards by stages; 3 When the accumulated water on the ground does not meet the requirements of Table 4.1.4, measures such as percolation, detention and retention, setting discharge channel and inland river regulation shall be taken; 4 Emergency measures shall be taken for rainstorm exceeding the recurrence interval for urban flooding design. Table 4.1.4 Recurrence interval for urban flooding design (years) Urban type Recurrence interval Design standard for ground water accumulation Super-cities 100 1 There is no water on the ground floor of residential buildings and industrial and commercial buildings; 2 The depth of accumulated water in one lane of the road does not exceed 15 cm. Hyper-cities 50–100 Mega-cities 30–50 Medium and small cities 20–30 Note: See Note 3 in Table 4.1.3 for details. 4.1.5 The maximum allowable water receding time under the recurrence interval for urban flooding design shall meet those specified in Table 4.1.5. For cities with dense population, prone to cause flooding, especially important and good economic conditions, the specified lower limit shall be adopted for the maximum allowable water receding time, and 0.5h shall be adopted for transportation hub. Maximum allowable water receding time under the recurrence interval for urban flooding design City type Central city Non-central city Important areas in the central city Maximum allowable water receding time 1.0–3.0 1.5–4.0 0.5–2.0 Note: The maximum allowable water receding time specified in this standard is the maximum allowable drainage time of ground accumulated water after the rain stops. 4.1.6 When the area is renovated, the runoff of the same design recurrence interval after renovation shall not exceed the original runoff. 4.1.7 When the reasoning equation method is adopted, the stormwater design flowrate of sewer shall be calculated using the following equation. When the catchment area is larger than 2 km2, the mathematical model method shall be used to determine the design flowrate of stormwater, in consideration of the spatial and temporal heterogeneity of regional rainfall and ground permeability and the confluence process of pipeline. Qs = qΨF (4.1.7) where, Qs——the design flowrate of stormwater, L/s; q——the design rainstorm intensity, L/(hm2·s); Ψ——the comprehensive runoff coefficient; F——the catchment area, hm2. 4.1.8 The comprehensive runoff coefficient shall be strictly controlled according to the plan and shall meet the following requirements: 1 Measures such as percolation, detention and retention shall be adopted in areas with comprehensive runoff coefficient higher than 0.7. 2 The comprehensive runoff coefficient can be calculated by weighted average of surface types according to the runoff coefficient specified in Table 4.1.8-1, and can also be taken according to the value specified in Table 4.1.8-2, and the composition and proportion of ground types shall be verified. 3 The runoff coefficient specified in Table 4.1.8-1 should be increased when the inference equation method is used to check the urban flooding design. When the design recurrence interval is 20 to 30 years, the runoff coefficient should be increased by 10% to 15%; when the design recurrence interval is 30 to 50 years, the runoff coefficient should be increased by 20% to 25%; when the design recurrence interval is 50 to 100 years, the runoff coefficient should be increased by 30% to 50%; when the calculated runoff coefficient is greater than 1, it shall be taken as 1.   Table 4.1.8-1 Runoff coefficient Ground type Runoff coefficient Various roofing, concrete or asphalt pavement 0.85–0.95 Pavement paved with large stones or various gravel pavements with asphalt surface 0.55–0.65 Pavement paved with graded crushed stone 0.40–0.50 Dry brickwork or gravel pavement 0.35–0.40 Unpaved soil pavement 0.25–0.35 Park or green space 0.10–0.20 Table 4.1.8-2 Comprehensive runoff coefficient Regional situation Comprehensive runoff coefficient Dense urban building area 0.60–0.70 Relatively dense urban building area 0.45–0.60 Sparse urban building area 0.20–0.45 4.1.9 The design rainstorm intensity shall be calculated using the following equation: (4.1.9) where, q——the design rainstorm intensity, L/(hm2·s); P——the design recurrence interval; t——the duration of rainfall, min; A1, C, b, n——the parameter, which is calculated and determined according to statistical methods. In areas with self-recorded rainfall records for more than 20 years, the design rainstorm intensity equation of stormwater system shall adopt the annual maximum value method, and shall be compiled according to the requirements of Annex B of this standard. 4.1.10 The rainstorm intensity equation shall be revised according to climate change. 4.1.11 The rainfall duration of storm sewer shall be calculated using the following equation:   t = t1 + t2 (4.1.11) where, t——the duration of rainfall, min; t1——the ground water collection time, in minutes, which shall be determined by calculation according to catchment distance, topographic slope and ground type, preferably 5min to 15min; t2——the time of flow for stormwater in underdrain, min. II Wastewater flow 4.1.12 The design flowrate in dry weather and rainy weather shall be determined in the design of wastewater system. 4.1.13 The design flowrate of the separate sewer system in dry weather shall be calculated using the following equation: Qdr = KQd + K′Qm + Qu (4.1.13) where, Qdr——the maximum dry weather flowrate, L/s; K——the overall peaking factor; Qd——the design overall wastewater quantity, L/s; K′——the industrial wastewater factor; Qm——the design industrial wastewater quantity, L/s; Qu——the infiltrated water quantity, in L/s, which shall be considered in areas with high groundwater level. 4.1.14 The overall wastewater quantity quota shall be determined according to the local water quota and the level of water supply and wastewater facilities inside the building, and can be adopted according to 90% of the relevant local water quota. 4.1.15 The overall peaking factor can be determined according to the local actual overall wastewater quantity variation data. When the measurement data is unavailable, the value of new projects can be taken according to those specified in Table 4.1.15; the renovated and expanded projects can be determined according to the actual conditions and the actual flow analysis, or can be expanded by stages according to those specified in Table 4.1.15. Table 4.1.15 Overall peaking factor Average daily flow (L/s) 5 15 40 70 100 200 500 ≥1000 Variation factor 2.7 2.4 2.1 2.0 1.9 1.8 1.6 1.5 Note: When the average daily flow of wastewater is an intermediate value, the variation factor can be obtained by interpolation. 4.1.16 The design quantity of industrial wastewater shall be determined according to the process characteristics of industrial enterprises, and the quantity of domestic wastewater of industrial enterprises shall comply with the relevant requirements of the current national standard GB 50015 Standard for design of building water supply and drainage. 4.1.17 The variation factor of industrial wastewater quantity shall be determined according to process characteristics and work shifts. 4.1.18 The quantity of infiltrated water shall be determined after calculation according to the groundwater level and the properties of underdrain. 4.1.19 The wet weather flowrate of the wastewater system shall be based on the maximum dry weather flowrate, and the intercepted rainwater shall be increased according to the investigation data. 4.1.20 The intercepted stormwater of the separate sewer system shall be determined according to factors such as the environmental capacity of the receiving water body, the pollution of stormwater, the scale of source emission reduction facilities and the size of drainage area. 4.1.21 The wastewater pipeline of the separate sewer system shall be designed according to the maximum dry weather flowrate and checked under the wet weather flowrate. 4.1.22 The design flowrate of combined sewer pipeline in front of intercepting well shall be calculated using the following equation: Q = Qd + Qm + Qs (4.1.22) where, Q——the design flowrate, L/s; Qd——the design overall wastewater quantity, L/s; Qm——the design industrial wastewater quantity, L/s; Qs——the design flowrate of stormwater, L/s. 4.1.23 The interception quantity of combined sewage shall be determined by the overflow pollution control target according to the environmental capacity of the receiving water body. Intercepted combined sewage can be transported to wastewater treatment plants or detention and retention facilities. When transported to the wastewater treatment plants, the design flowrate shall be calculated using the following equation: Q′ = (n0 + 1) × (Qd + Qm) (4.1.23) where, Q′——the design flowrate of wastewater pipeline after interception, L/s; n0——the intercepting multiple. 4.1.24 The intercepting multiple shall be calculated and determined according to the water quality and quantity of dry weather flow, the environmental capacity of receiving water body and the size of drainage area, etc., which should be 2 to 5, and measures such as detention and retention should be taken to improve the interception standard and reduce the impact of CSO pollution on the river channel. Different intercepting multiples can be used in the same wastewater system.

Foreword iii 1 General provisions 2 Terms 3 Wastewater engineering 3.1 General requirements 3.2 Stormwater system 3.3 Wastewater system 4 Design flow and waste loads 4.1 Design flow 4.2 Design waste loads 5 Sewer and ancillary structures 5.1 General requirements 5.2 Hydraulic calculation 5.3 Pipelines 5.4 Manholes 5.5 Drop manholes 5.6 Water sealed manholes 5.7 Stormwater inlets 5.8 Intercepting facilities 5.9 Outfalls 5.10 Interchange drainage 5.11 Inverted siphons 5.12 Percolation underdrain 5.13 Channel 5.14 Stormwater detention and retention facilities 5.15 Relation to other utilities 6 Pump station 6.1 General requirements 6.2 Design flowrate and head 6.3 Wet well 6.4 Design of pump house 6.5 Discharge facilities 7 Wastewater and reclaimed water treatment 7.1 General requirements 7.2 Site selection and general layout 7.3 Screenings 7.4 Grit removal chambers 7.5 Settling tanks 7.6 Activated sludge process 7.7 Returned sludge and excess sludge 7.8 Attached growth process 7.9 Oxygen supply facilities 7.10 Chemical phosphrus removal 7.11 Advanced treatment and wastewater relaimation 7.12 Natural treatment 7.13 Disinfection 8 Sludge treatment and disposal 8.1 General requirements 8.2 Sludge thickening 8.3 Sludge digestion 8.4 Sludge compost 8.5 Sludge dewatering 8.6 Lime stabilization of sludge 8.7 Sludge drying 8.8 Sludge incineration 8.9 Sludge disposal and utilization 8.10 Sludge transportation and storage 8.11 Odor control 9 Monitoring and control 9.1 General requirements 9.2 Monitoring 9.3 Automation 9.4 Informatization 9.5 Intellectualization 9.6 Smart drainage system Appendix A Conversion between volume capture ratio of annual rainfall and design rainfall depth Appendix B Statistical methods for obtaining design rainfall intensity Appendix C Minimum clearance between sewers and other utilities Explanation of wording in this standard List of quoted standards