Water and Waste Water Engineering - Sanitation

Essentials of Wastewater Engineering

• Wastewater engineering is a critical field focusing on the collection, treatment, and disposal of wastewater to protect public health and the environment.

Sources of Wastewater

• Domestic Wastewater: From households, including sewage and greywater.
• Industrial Wastewater: From manufacturing, processing, and industrial facilities.
• Stormwater Runoff: Rainwater that carries pollutants from roads, rooftops, and landscapes.
• Agricultural Wastewater: Runoff from irrigation, livestock operations, and pesticide use.

Aims and Objectives of Wastewater Disposal

Aims of Wastewater Disposal

• Public Health Protection: Prevents the spread of waterborne diseases by safely disposing of contaminants.
• Environmental Protection: Minimizes pollution in water bodies, preserving aquatic ecosystems.
• Sustainable Water Management: Supports water recycling and reuse to reduce water scarcity.
• Regulatory Compliance: Meets legal standards for wastewater discharge and treatment.
• Odor and Aesthetic Control: Reduces unpleasant odors and visual pollution in urban areas.
• Efficient Resource Recovery: Extracts valuable resources such as energy, nutrients, and reusable water.
• Preventing Groundwater Contamination: Protects groundwater from infiltration of harmful substances.

Objectives of Wastewater Disposal

• Safe Collection and Transport: Ensure efficient conveyance of wastewater from sources to treatment facilities.
• Effective Treatment: Remove physical, chemical, and biological contaminants before discharge or reuse.
• Proper Sludge Management: Safely treat and dispose of sludge generated during treatment.
• Discharge at Suitable Locations: Release treated wastewater into water bodies or land without harming the environment.
• Promoting Wastewater Reuse: Encourage the use of treated wastewater for agriculture, industry, and replenishing water bodies.
• Mitigating Climate Impact: Reduce greenhouse gas emissions and energy use in wastewater treatment.
• Public Awareness & Education: Promote responsible wastewater management practices among communities.

Sanitary Engineering

• Definition: The branch of public health engineering which consists of scientific and methodological collection, conveyance, treatment, and disposal of waste matter so that public health is protected from offensive and injurious substances.

Necessity of Wastewater Engineering

• To Maintain the Public Health
• To Stop the Spreading of Disease
• To Maintain the Aesthetical View

Important Terms Definition

• Refuse: A general term used to indicate what is rejected or left out as worthless. It may be liquid, Semi-Solid, or solid form. It may be divided into 6 Sub Categories
  • Garbage
  • Rubbish
  • Sullage
  • Sewage
  • Stormwater
  • Subsoil water
• Garbage: Word indicating only the dry refuse. Eg: Glass pieces, Paper Waste, Decayed fruits & vegetables, Street waste etc…
• Rubbish: Word indicating sun dry solid wastes. It is dry and Combustible in nature Eg: Waste building materials, broke furniture, paper, Rags etc…
• Sullage: Word indicates the wastewater from bathrooms Kitchens, Wash basins etc.. But it doesn't create bad smell
• Night Soil: It is a term used to indicate the human or animal Excreta
• Sewage: It indicates the liquid waste from the community it includes Sullage, Discharge from the Urinals, Industrial waste and agricultural waste.
• Strom Water: It indicates the rain water of the locality.
• Sub Soil Water: It is the Ground water. It is the ground water that finds its entry into the sewer through leaks.
• Sewer: It is the underground Conduit or drain through which sewage is carried to a point of disposal.
• Sewerage: It is the structure or device which is used for transportation or collection of sewage.

System of Sanitation

• There are 2 system of sanitation
  1. Conservancy system:
     • It is the old system in which various types of wastes such as night soil, garbage waste are collected separately in vessels and deposited in pits. This system is also know as dry system
  2. Water Carriage system:
     • Collection, Conveyance and disposal of waste carried through water

Difference Between Conservancy system and Water Carriage system

Composition of wastewater

• Paper and paperboard 27%
• Food 15%
• Yard trimmings 14%
• Plastics 13%
• Total metals 9%
• Wood 6%
• Textiles 6%
• Glass 5%
• Rubber and Leather 3%
• Other 2%

Wastewater Characteristics

Physical Characteristics

• Temperature
• Color
• Turbidity
• Odour
• Total Solids

Chemical Characteristics

• pH
• COD
• BOD
• Nitrogen
• Chlorides
• Sulphate
• Alkalinity

Biological Characteristics

• Microbial population
  • Bacteria
  • Virus
  • Fungi
  • Protozoa
• Oxygen required for nitrification

PHYSICAL CHARACTERISTICS

• Color: It is normally detected by a naked eye and it indicates the freshness of sewage.
• Odour: Fresh sewage is practically odorless but however in 3-4 hours it becomes state with all oxygen present in the sewage
• Temperature: It has an effect on biological activity on bacteria present in the sewage and it also effects the solubility of gases in sewage.
• Turbidity: Turbidity of wastewater depends on the quantity of solid mater present in the suspension state.

Chemical Characteristics

• pH Valve: It is the negative logarithm of $H^+$ ions to $OH^-$ ions.
• Chloride content: Are the mineral salt. Chlorides in natural water results from the leaching of chloride containing rocks and soils with which the water comes in contact
• Nitrogen Content: The presence of nitrogen in the sewage indicates the presence of organic matter and may occur in one or more of the following forms Organic Nitrogen, Nitrites, Nitrates
• DO: is the amount of oxygen in the wastewater only very fresh sewage contains some DO which is soon depleted by aerobic decomposition
• Surfactants: It comes primarily from synthetic detergents these are discharged from bathrooms kitchen washing machines etc..

Biological Characteristics

• BOD is the amount of DO needed by aerobic biological organisms in a body of water to break down organic material present in a given water sample at certain temp over a specific time period.
• The term also refers to a chemical procedure for determining this amount this is not a precise Quantitative test although it is widely used as an indication of the organic quality of water

Types of Sewerage System

1. Separate system
2. Combined system
3. Partially Separate System

• Separate System: It Provides 2 Separate set of sewers. One intended for Conveyance of sewage and other for rain water
• Combined System: It Provides one set of sewer to carry both sewage and rain Water
• Partially Combined System: It consists of only one set of underground sewer and it will carry foul sewage When the Quantity of Strom water, Wash water exceeds certain limit this will be taken by next set of open drains

Laying Of Sewer

The various steps involved in the laying and testing of sewers are:

1. Setting out Sewer Centre Line
2. Alignment and Gradient of Sewers
3. Excavation of Trenches, Timbering and Dewatering
4. Laying and Jointing of Pipe Sewers
5. Testing of Pipe Sewers
6. Backfilling of Trenches.

Shapes of Sewer

• Sewers are generally circular in shape. The advantages of circular sewers are:
  • The perimeter of circular sewer is the least with respect to the sewer of other shape.
  • The inner surface is smooth hence the flow of sewage is uniform and there is no chance of deposition of suspended particles.
• However non-circular shaped sewers are also adopted for the following reasons:
  • They can be construct in such a convenient shape and size so that a man can enter the sewer for cleaning, maintenance, etc.
  • The process of construction is easy.
  • The structural strength is more.
  • Cost of construction is low.

Standard Egg-shaped sewer

• These types of sewers are generally used in combined sewers. These sewers can generate self cleansing velocity during dry weather flow.

Horse shoe shaped sewer

• This type of sewer is constructed for carrying heavy discharge. This is like a tunnel and resembles a horse-shoe. The size is so large that the maintenance works within the sewer are very easy.

Parabolic shaped sewer

• The upper surface of the sewer is of the shape of a parabola and the invert is in the form of an ellipse. This type of sewer is suitable for carrying small discharges.

Rectangular shape section

• This type of sewer can be easily constructed. These are suitable for large sewers to carry heavy discharge of sewage. The maintenance works are easy in this section

U-shaped section

• The shape of sewer resembles the letter ‘U’. The sewer is suitable for carrying heavy discharges. Maintenance works are very easy in this type of sewers.

SEWER JOINTS

• Following are the 5 common types of sewer joints:
  1. Bell and Spigot Joints.
  2. Collar Joints.
  3. Flexible Joint.
  4. Expansion Joint.
  5. Flanged Joint.

1) Bell and Spigot Joints.

• This joint is also known as socket and spigot joint.
• This type of joint is mainly used for cast iron pipes of all sizes and concrete pipes below 60 cm in diameter.
• The pipes which are to be joined by this joint are made in such a way so that one end is enlarged arid the other end is normal.
• The enlarged end is called socket or bell and the normal end is called spigot.
• The spigot end is inserted into the bell end and the gap of the joint is filled up with molten lead or bitumen or cement mortar.

2) Collar Joints.

• In this type of joint, the ends of sewer are plain.
• Before joining, the pipes are brought face to face at the same level and a collar of slightly bigger diameter is placed over the joint.
• Then the annular space between the pipes and the collar is filled up with cement mortar.
• The collar joints are used for sewers of large diameter.

3) Flexible Joint.

• This joint is used at such places where settlement is likely to occur after laying of the pipe.
• For this joint, one pipe has spigot end and other pipe has socket end.
• The spigot is fitted into the socket and bitumen is filled in the annular space formed between socket and spigot.

4) Expansion Joint.

• This joint is adopted at places where pipes expands or contracts due to variation in atmospheric temperature.
• Here the socket end is cast flanged and the spigot end is plain.
• A flanged ring and a rubber gasket are placed in position on the spigot end.
• Then the spigot end is inserted into the socket end nut and bolts are tightened.

5) Flanged Joint.

• This joint is mostly used for temporary work.
• The pipe used in this type of joint has flanges on both ends.
• While joining the pipes, a rubber gasket is inserted between the flanges and nut bolts are tightened

Testing Of Sewer

The sewers after being laid and jointed are tested for watertight joints and also for correct straight alignment as described below:

i. Test for Leakage

ii. Test for Straightness of Alignment and Obstruction

Sewer Testing for Leakage (Water Test)

• The sewer testing is ensure no leakage through the joints after giving sufficient time to these joints to set in.
• For this purpose sewer pipe sections are tested from manhole to manhole under a test pressure of 1.5m of water head i.e. depth of water in the manhole is maintained at about 1.5m.
• The lower end of the sewer is first of all plugged.
• The water is then filled in the manhole at the upper end and is allowed to flow through the sewer line.
• The sewer line is watched by moving along the trench and the joints which leak or sweat are repaired.
• The leakage pipe if any will also be replaced.

Sewer Testing for Straightness of Alignment and Obstruction

• The straightness of the sewer pipe can be tested by placing a mirror at one end of the sewer line and a lamp at the other end.
• If the pipe line is straight, the full circle of light will be observed. However, if the pipe line is non-straight, this would be apparent and the mirror will also indicate any obstruction in the pipe barrel.
• Any obstruction present in the pipe can also be tested by inserting at the upper end of the sewer a smooth inserting at the upper end of the sewer a smooth ball of diameter 13mm less than internal diameter of the sewer pipe.
• In the absence of any obstruction, such as yarn or mortar projecting through the joints etc. the ball shall roll down the invert of the sewer pipe and emerge at the lower end.

SEWER APPURTENANCES

• Catch basin
• Manhole
• Flushing tanks
• Oil and grease Traps
• Drainage Traps
• Clean-outs
• Definition: The structures, which are constructed at suitable intervals along the sewerage system to help its efficient operation and maintenance, are called as sewer appurtenances. These include:

CATCH BASIN

• Catch basins are the primary part of many landscape drainage systems.
• A catch basin has a grate on top and a drainage pipe that slopes away from the basin.
• This box is set into the ground at a low point on the property.
• Catch basins help maintain proper drainage and catch debris, which helps prevent pipes downstream from becoming clogged.
• Water and solids enter the box through the grate. Solids settle to the bottom while water drains out of the pipe.
• This pipe typically connects to the larger local plumbing system and directs the water to a sewage plant or stream.

MANHOLE

• The manhole is masonry or R.C.C. chamber constructed at suitable intervals along the sewer lines, for providing access into them. Thus, the manhole helps in inspection, cleaning and maintenance of sewer.

PURPOSE OF MAN HOLE:

• They are used to carry out inspection, cleaning and removing obstruction in the sewer line.
• Manhole allows joining of sewers or changing the direction of sewer or alignment of sewer or both.
• They allow the escape of considerable gases through perforated cover and thus help in ventilation of sewage.
• They facilitate the laying of sewer line in convenient lengths.

LOCATION OF MANHOLE:

• Manhole is provided when
  • There is change in grade of sewer
  • There is change in alignment
  • There is change in size of sewer
  • At junction of two or more sewers
• Manhole is also provided in straight alignment of sewers at regular intervals depending upon the diameters of sewers. It ranges from 90m to 150m

Classification of manhole:

• Depending upon the depth the manholes can be classified as:
  • (a) Shallow Manholes,
  • (b) Normal Manholes, and
  • (c) Deep Manholes

Shallow Manhole:

• These are 0.7 to 0.9 m depth, constructed at the start of the branch sewer or at a place not subjected to heavy traffic conditions.
• These are provided with light cover at top and called inspection chamber.

Normal Manhole:

• These manholes are 1.5 m deep with dimensions 1.0 m x 1.0 m square or rectangular 1.2 m x 0.9 m. These are provided with heavy cover at its top to support the anticipated traffic load.

Deep Manhole:

• The depth of these manholes is more than 1.5 m. The section of such manhole is uniform throughout. The size in upper portion is reduced by providing offset. Steps are provided in such manholes for descending into the manhole. They are provided with heavy cover at its top to support the traffic load.

FLUSHING TANK

• In manually operated flushing arrangement water or sewage is held up in the sewer by plugging the inlet and outlet ends of the sewer. When the flushing tank is filled up with water by tap the outlet plug is removed, all the water rushes towards outlets and flushes the sewer.
• Automatic Flushing tank is as shown in fig It consists of the masonry structure fitted with the tap for filling the tank with the water.
• A U-Tube with the bell cap as its one end connects the chamber with sewer. When the water level increases in the chamber it also increases in the bell cap.
• As soon as it reaches a certain level, siphonic action takes place and the whole water of the chamber rushes to the sewer pipe and flushes it.
• The capacity of these tanks is usually 900-1400 litres and it is adjusted in such a way as to work twice or thrice a day depending on the quantity of deposits in the sewer and size of sewer.

Oil and grease Trap

• Grease and oil traps are those trap chambers which are constructed in a sewerage system to remove oil and grease from the sewage before it enters into the sewer line. Such traps are located near the sources contributing grease and oil to the sewage. They are, therefore, generally located at places, such as, automobile repair work- shops, garages, kitchens of hotels, oil and grease industries, etc.
• The grease and oil, of allowed to enter the sewer, will stick to the sewer sides, and thus reducing the sewer capacity.
• The suspended matter which would have, otherwise, flown along with the sewage, also sticks to the sides of the sewer, due to sticky nature of oil and grease ; thus further reducing sewer capacity.
• The presence of oil and grease in the sewage adds to the possibilities of explosion in the sewers.
• The presence of oil and grease traps work is simple: the grease and oil being lighter in weight float on the top surface of the sewage. Hence, if an outlet draws the sewage from lower level, grease and oil will get excluded. Based on this principle, the grease and oil trap chambers are designed in such a way that the outlet level is located near the bottom of the chamber, and the inlet level is kept near the top of the chamber.

Clean-outs

• It is a pipe which is connected to the underground sewer. The other end of the clean- out pipe is brought up to ground level and a cover is placed at ground level
• A clean-out is generally provided at the upper end of lateral sewers in place of manholes.
• During blockage of pipe, the cover is taken out and water is forced through the clean- out pipe to lateral sewers to remove obstacles in the sewer line.
• For large obstacles, flexible rod may be inserted through the clean-out pipe and moved forward and backward to remove such obstacle.

system of plumbing in high raise buildings

ONE PIPE SYSTEM

• A Separate vent pipe is provided in this system.
• This system is costly and difficult to construct
• Ventilation is provided to sullage pipe and soil pipe too.
• Arrangement of pipe work is difficult.
• In this system of plumbing, the waste connections from sinks, baths, washbasins, and the soil pipe(water closets) which is connected directly to the drainage system.

TWO PIPE SYSTEM

• Water closets, bath traps, kitchen traps and wash basin traps all are connected to vent pipes.
• Separate soil pipe and waste pipes are provided.
• Two vent pipes are provided.
• There are four stakes in this system
• It is efficient system but costlier than other systems.
• In this plumbing system, two pipes are installed. W.Cs and urinals are connected to vertical soil pipe baths, kitchens, basins, etc are connected to another separate vertical waste pipe. Soil pipes and waste pipes are provided with separate vent pipes.

Single stack system

• In this system, only one vertical soil pipe is used. The wastes from all the sanitary and soil appliances are discharged in the same pipe. The traps of WCs, sink basins, etc are directly connected to the single stack pipe. In this system, there is no separate pipe for ventilation purposes.

One-pipe Partially Ventilated System

• This system is via media between the first and second one. There is only one soil pipe into which all W.Cs, baths, sinks, and washbasins discharge. In addition, there is a relief vent pipe that ventilates only the traps of W.Cs and urinals.

software used in design of sewerage system

• SWMM (Storm Water Management Model) – Used for dynamic rainfall-runoff modeling, developed by the EPA.
• HEC-RAS – Hydraulic modeling for open channel flow and stormwater management.
• SewerGEMS (Bentley Systems) – Advanced sewer modeling with GIS integration.
• InfoWorks ICM (Innovyze) – Integrated modeling of stormwater and wastewater systems.
• MIKE URBAN (DHI) – Hydrodynamic modeling of urban drainage systems.
• StormCAD (Bentley Systems) – Stormwater drainage analysis and design.
• CivilStorm (Bentley Systems) – Comprehensive stormwater modeling.
• AutoCAD Civil 3D (Autodesk) – Used for designing and drafting sewer networks, profiles, and terrain modeling.
• MicroStation (Bentley Systems) – For infrastructure design and drafting.
• Revit (Autodesk) – BIM-based sewer infrastructure modeling.
• InfraWorks (Autodesk) – Conceptual design and visualization of sewer networks.
• ArcGIS (Esri) – Spatial analysis and mapping of sewer networks.
• QGIS (Open Source) – Free GIS tool for sewerage planning and mapping.
• Global Mapper – Geospatial data processing for sewer network planning.
• SAP2000 (CSI) – Structural analysis of sewer pipes and culverts.
• STAAD.Pro (Bentley Systems) – Structural design for sewerage infrastructure.
• EPANET – Water distribution and pressure analysis, useful for combined sewer systems.