Foreword

TCVN 4038:2012 replaces TCVN 4038:1985.

TCVN 4038:2012 was converted from TCVN 4038:1985 according to the provisions of Clause 1, Article 69 of the Law on Standards and Technical Regulations and Point b), Clause 1, Article 6 of Decree 127/2007/ND-CP detailing the implementation of some articles of the Law on Standards and Technical Regulations.

TCVN 4038:2012 was compiled by the Institute of Architecture, Urban and Rural Planning – Ministry of Construction, proposed by the Ministry of Construction, appraised by the Directorate for Standards, Metrology and Quality, and announced by the Ministry of Science and Technology.

1. Scope of application

This standard provides terminology and definitions, applied in the field of drainage.

2. Terminology and definitions

2.1. General concepts

2.1.1. Wastewater

Water that has changed characteristics and properties due to human use or human activities and production and business activities.

2.1.2. Domestic wastewater

Wastewater from human daily activities such as eating, drinking, bathing, washing, and personal hygiene.

2.1.3. Industrial wastewater

Wastewater from industrial production activities, craft villages, business activities or other production activities.

2.1.4. Stormwater

Rainwater that, after falling, flows on the surface of streets, squares, residential areas and industrial enterprises and becomes polluted.

2.1.5. Wastewater receiving source

Surface water or coastal waters, with a defined purpose of use, where wastewater is discharged into.

2.1.6. Water source

A place where natural water is concentrated regularly or temporarily on the ground surface or in rock layers with a flow regime.

2.2. Drainage and wastewater flow

2.2.1. Wastewater flow

The amount of wastewater flowing through the wet cross-section of the stream in a unit of time.

2.2.2. Wastewater flow non-equalization coefficient

The ratio between the maximum or minimum wastewater flow and the average wastewater flow in a unit of time.

2.2.3. Drainage standard

The amount of wastewater per water user or per product unit in a unit of time.

2.2.4. Drainage area

An area drained by a drainage network.

2.2.5. Design rainfall duration

The duration of rainfall with a certain intensity and frequency used to calculate the drainage network.

2.2.6. Cycle of exceeding the design rainfall intensity

A number representing the number of rainfall events that may occur in a year with an intensity exceeding the design intensity.

2.2.7. Surface wastewater concentration area

An area where surface wastewater is concentrated to be led to a location on the drainage network.

2.2.8. Flow module

The amount of water flowing through a unit area of wastewater area in a unit of time.

2.2.9. Batch wastewater discharge

The discharge of wastewater in short batches, causing a significant increase in flow or pollutant concentration, or both simultaneously.

2.2.10. Fullness of the drainage network

The ratio between the height of the water layer in the gravity pipe or drainage channel and the diameter of the pipe or the height of the drainage channel at the calculation point of the drainage network.

2.3. Drainage networks and structures

2.3.1. Drainage network

A system of pipelines, sewers or drainage channels and structures to collect and drain wastewater in a certain area.

The drainage network includes: domestic wastewater drainage network, industrial wastewater drainage network and stormwater drainage network.

2.3.2. Drainage lateral

An external drainage network pipeline for collecting and draining wastewater in a drainage area.

2.3.3. Stormwater discharge sewer

A pipeline for directing stormwater from an overflow well to the wastewater receiving source.

2.3.4. Steep flow trough on a drainage lateral

A straight section on a drainage lateral installed with a slope creating turbulent flow and aerating the wastewater.

2.3.5. Drainage management well

A well arranged on the drainage network to manage the drainage network.

2.3.6. Stepped drainage well

A well used to reduce the burial depth of the pipe between the starting and ending points of the pipeline, or to avoid abrupt changes in flow velocity, usually applied to areas with steep terrain (slope greater than the design slope).

2.3.7. Drainage inspection well

A well placed at points with a change in flow direction, transitioning from inside the yard, residential area, from the street pipeline, the basin lateral sewer… to the final discharge pipe.

2.3.8. Overflow well

A structure on the drainage network to discharge excess stormwater into the wastewater receiving source.

2.3.9. Wastewater discharge pipe

A pipe section that directs wastewater from buildings and structures to the external drainage system.

2.3.10. Wastewater discharge sewer

A pipeline section that directs treated wastewater to the water body.

2.3.11. Wastewater discharge sewer cover

A structure placed on the wastewater discharge sewer to protect the sewer from damage.

2.3.12. Stormwater collection well

A structure on the network to drain stormwater.

2.4. Wastewater treatment

2.4.1. Biochemical oxygen demand in wastewater (BOD)

The amount of oxygen used to biochemically oxidize pollutants in wastewater over a certain period of time.

2.4.2. Wastewater treatment process under aerobic conditions

The process of decomposing organic pollutants in wastewater under the action of microorganisms in the presence of atmospheric oxygen.

2.4.3. Wastewater treatment process under anaerobic conditions

The process of decomposing organic substances in wastewater under the action of microorganisms in the absence of atmospheric oxygen.

2.4.4. Mineralization of pollutants in wastewater

The process of converting organic compounds in wastewater into inorganic substances.

2.4.5. Equivalent population

The conventional number of people determined by the mass or concentration of pollutants in wastewater.

2.4.6. Hydraulic load of wastewater

The amount of wastewater corresponding to a unit area or a volume of the structure in a certain period of time.

2.4.7. Pollutant load of wastewater

The mass of pollutants in wastewater corresponding to a unit area or a volume of the structure in a certain period of time.

2.4.8. Wastewater recirculation

Directing treated wastewater back to the structures at the treatment plant for dilution or to ensure the wastewater flow through those structures or for other purposes.

2.4.9. Wastewater treatment

The entire technological processes of wastewater treatment aimed at decomposing, detoxifying and reducing the concentration of pollutants.

2.4.10. Wastewater treatment by mechanical methods

The technological process of wastewater treatment by mechanical and physical methods.

2.4.11. Wastewater treatment by biological methods

The technological process of wastewater treatment based on the ability of pollutant-decomposing microorganisms to decompose pollutants.

2.4.12. Wastewater treatment by chemical methods

The technological process of wastewater treatment using chemicals.

2.4.13. Advanced treatment

Continued treatment of treated wastewater to further reduce some remaining substances in the wastewater.

2.4.14. Disinfection of wastewater and sludge

Treatment of wastewater and sludge to kill pathogenic microorganisms.

2.4.15. Residual pollutants in wastewater

The mass of pollutants remaining in wastewater after treatment.

2.4.16. Wastewater treatment plant

The entire facility, structures and equipment for wastewater treatment and sludge processing.

2.5. Wastewater treatment by mechanical methods

2.5.1. Screens

Equipment for mechanical wastewater treatment to retain large suspended solids and floating objects.

2.5.2. Wastewater equalization tank

A structure to equalize the fluctuations in flow, concentration of pollutants or temperature of wastewater.

2.5.3. Grit chamber

A structure to remove insoluble inorganic impurities such as sand, gravel, slag and other solid materials with high settling velocity or specific gravity. Grit chambers are arranged at wastewater treatment works with a capacity of ≥ 100 m³/day.

2.5.4. Grease trap

A structure placed on the final drainage pipe discharging into the common drainage system to collect oil, grease or other impurities in the wastewater. Grease traps must be arranged when the concentration of oil and grease is greater than 100 mg/l.

2.5.5. Wastewater sedimentation tank

A structure for settling suspended pollutants including sludge in wastewater.

2.5.6. Sludge scraper equipment

Equipment used to scrape and remove settled sludge from the bottom of the sedimentation tank.

2.5.7. Fresh wastewater sludge

The settled sludge from the primary sedimentation tank.

2.5.8. Filter tank for wastewater treatment

A structure for filtering suspended pollutants in wastewater by passing wastewater through a filter material.

2.5.9. Filter material for wastewater treatment

Material placed in the filter tank.

2.6. Wastewater treatment by biological methods

2.6.1. Biological filter (Biofilter)

A wastewater treatment structure operating on the principle of passing wastewater through a layer of filter material with a biofilm.

2.6.2. Trickling filter (Trickling biofilter)

A wastewater treatment structure operating on the principle that wastewater is evenly distributed over the surface of the filter material in the form of trickling or spray jets and has an unsaturated filter material layer.

2.6.3. High-rate biological filter (High-rate biofilter)

A wastewater treatment structure operating on the principle that wastewater flows through a filter material layer many times larger than a trickling filter.

2.6.4. Aeration tank

A wastewater treatment structure operating by the aerobic biological method on the principle of supplying oxygen and mixing wastewater with activated sludge.

2.6.5. Biofilm

A film formed by bacteria and other organisms on the surface of the filter material, capable of oxidizing and mineralizing pollutants.

2.6.6. Grid device of biological filter

A device used to evenly distribute wastewater on the surface of the filter material in the biological filter.

2.6.7. Wastewater aeration

The introduction of air into wastewater to increase the oxygen content in wastewater.

2.6.8. Wastewater aeration intensity

The air flow per unit area or unit volume of the structure in a certain period of time.

2.6.9. Preliminary aeration tank

2.6.10. Activated sludge

Sludge containing microorganisms capable of absorbing and decomposing pollutants in wastewater.

2.6.11. Activated sludge age

The period of time for the complete recovery process of activated sludge in wastewater treatment structures.

2.6.12. Growth of activated sludge

The increase in the mass of activated sludge due to the activity of microorganisms in the aeration tank (2.6.21).

2.6.13. Activated sludge dose

The concentration of activated sludge in the aeration tank (2.6.21).

2.6.14. Activated sludge index

The volume of activated sludge in 1 g of dry residue after 30 min settling.

2.6.15. Activated sludge loading

The mass of pollutants per 1 kg of dry residue of activated sludge in one day.

2.6.16. Activated sludge recirculation

The recirculation of activated sludge from the secondary sedimentation tank to the aeration tank (2.6.21).

2.6.17. Activated sludge recirculation coefficient

The ratio between the volume of recirculated activated sludge and the average wastewater flow in the aeration tank (2.6.21).

2.6.18. Regeneration of activated sludge

The process of restoring the absorption and oxidation capacity of recirculated activated sludge by aeration.

2.6.19. Bulking of activated sludge

The phenomenon of activated sludge floating on the surface of wastewater due to the fermentation process.

2.6.20. Activated sludge mixture

A mixture of wastewater and activated sludge.

2.6.21. Aeration tank

A structure for wastewater treatment by the biological method with aeration.

Aeration tanks include: settling aeration tank, high-rate aeration tank, extended aeration tank, oxidation ditch, complete mix aeration tank…

2.6.22. Oxygenation tank

A structure for wastewater treatment by the biological method with the supply of pure oxygen or oxygen-rich air.

2.6.23. Oxidation ditch

An oxidation ditch operating on the activated sludge principle, used for secondary or tertiary treatment of wastewater.

2.6.24. Activated sludge regeneration tank

A part of the aeration tank (2.6.21) or an independent structure for the regeneration of activated sludge.

2.6.25. Biological pond

A pond for wastewater treatment by the biological method under natural conditions.

2.7. Sludge treatment

2.7.1. Sludge treatment system

The entire structures and equipment for collecting, treating, disinfecting, transporting and utilizing sludge formed during the wastewater treatment process.

2.7.2. Aerobic sludge stabilization

The mineralization of activated sludge by the oxidation method.

2.7.3. Sludge dewatering

The technological process of reducing the water content in sludge to increase its density.

2.7.4. Sludge digestion

The technological process of decomposing organic substances in sludge under anaerobic conditions.

2.7.5. Methane tank (Methane digester)

A structure for digesting sludge and high-strength wastewater under anaerobic conditions at high temperature.

2.7.6. Sludge water

Dirty water separated during the process of digestion, dewatering, drying of sludge and residue.

2.7.7. Wastewater sludge treatment

Aimed at treating sludge (sludge generated during the wastewater treatment process):

• Reducing the volume and moisture content of sludge;
• Stabilizing sludge;
• Disinfecting and reusing sludge for various purposes.

2.7.8. Sludge treatment by thermal methods

A method of treating sludge at high temperatures for disinfection and drying of sludge.

2.7.9. Sludge drying beds

A structure for drying digested sludge from methane tanks and contact tanks to the necessary level.

2.7.10. Septic tank

A structure for wastewater treatment by mechanical methods, sedimentation combined with digestion under anaerobic conditions.

A structure for preliminary aeration of wastewater to improve the settling efficiency of wastewater.