Introduction to Sewage Collection SystemDr Sher Jamal KhanSubject: Wastewater Collection and Treatment (ENE-326)

Course OutlineSewage Collection & Management SystemAnalysis & Selection of Wastewater Flow rates;Waste Stabilization PondsPrinciples of Aerobic BioreactorsPrinciples of Aerobic Biological TreatmentDesign of Aerated LagoonsPrinciples & Design of Aeration Suspended Growth System◦ Conventional Activated Sludge◦ Extended Aeration Attached Growth System◦ Design of Trickling Filter◦ Design of Rotatory Biological ReactorsDesign of Constructed WetlandsDesign of Anaerobic Digester

Recommended Books

Water and Wastewater Engineering, Design Principal and Practices◦ Mackenzie L. Davis

Wastewater Treatment for Pollution Control and Reuse◦ 3rd Edition by ArceivalaTheory and Practice of Water and Wastewater Treatment◦ Ronald L. Droste

Grading Policy - Theory

Quizzes (4-6) 10Assignments (4-6) 10OHT (2) 30Final 50

Grading Policy - Practical

GPS-X Modeling Assignments 70Quiz 30

Difference b/w Water Supply and Sewerage System

Flow by gravity (mostly) in sewerage system;Designed as open channel flow, but with cover;More suspended material;Release of gases i.e. Hydrogen sulfide (H2S);

Components of Wastewater Flows

Domestic (sanitary) wastewater: Discharged from residences, commercial, institutional and similar facilities;Industrial Wastewater: Wastewater in which industrial waste predominate;Inflow/Infiltration: Water that enters the collection system through indirect or direct means: Stormwater: Runoff resulting from rainfall and snowmelt;

Type of Collection System

Sanitary Collection SystemStormwater Collection SystemCombined Collection SystemPartially Combined Collection System

Sanitary Collection SystemThe load on treatment plant becomes light;Small diameter pipes are used as sewers;Natural water does not become polluted unnecessarily;Where pumping of sewage is necessary, this system becomes economical;In this system maintenance cost become high;The cleaning of sewers is difficult as these are small in size;Steeper gradient is permitted to get self-cleaning velocity;Storm sewers don’t flow during the whole year, in dry season these sewers become uneconomical;Sanitary sewer is laid below the storm sewer so that storm water may not become contaminated in this way depth of sanitary sewer may become unnecessarily more;

Combined Collection SystemThe maintenance cost is comparatively low;The storm water reduces the strength of sewage by dilution;Due to single pipe laying this system is economical;It is easy to clean a combined sewer as it is of large size;There are less chance of choking the sewer because the size of sewer used is large;Due to extra quantity of sewage the load on treatment increase unnecessarily;The sewers used in this system are large in diameter;The storm water is unnecessarily polluted;In this system sewer get easily silted if not properly designed;In dry weather discharge become very low and it become foul;This system become uneconomical when pumping is required for the lifting of sewage to the ground level;In case of heavy rains, sewer may become overflow and it may put public health in danger;

Partially Combined Collection System

The size of sewers remains reasonable in the system;Self-cleaning velocity is easily attained in this system;The storm water diluted the sanitary sewage and quantity of combined sewage does not exceed a particular limit;In combined portion of the system it is difficult to attain self-cleaning velocity in dry season;If pumping may require in combined portion, extra quantity is to be pumped;Storm water increases the load on the treatment plant;

Definition and TermsSewer: A pipeline intended to carrying wastewater and storm water;Sewage: Water that is not intended to use or that has been used and is permitted to escape, or which unavoidably escapes;Sewerage: The system of sewers used to collect and carry storm and wastewater away for treatment and disposal;Separate Sewer System: A sewer system carrying sanitary wastewater and other waterborne waste from residences, commercial buildings, industrial plants, and institutions;Combined Sewer: A sewer intended to receive both wastewater and storm or surface water;

Definition and Terms

House Sewer: The extension from the building to the public sewer, also called house sewer;Sanitary Sewer: A sewer intended to carrying sanitary wastewater and other waterborne waste from residences, commercial buildings, and institutions;Storm Sewer: A sewer that carries storm water and surface water, street wash and other wash water, or drainage but excludes domestic wastewater and industrial waste;Lateral Sewer: A sewer that discharges into a branch or other sewer and has no other common sewer tributary to it;Main Sewer: A sewer to which one or more branch sewers are tributary;Trunk Sewer: A sewer that receives many tributary branches and serves a large territory;Outfall Sewer: A sewer that receives wastewater from a collecting system or from a treatment plant and carries it to a point of final discharge;

Definition and TermsForce main: this term is used to describe a pressurized pipe that is used to convey wastewater;Infiltration: the seepage of groundwater into a sewer system, including service connections. Seepage frequently occurs through defective or cracked pipes, pipe joints, connection or manhole wallsInflow: Storm water runoff connection to the sanitary collection system and cause an almost immediate increase in wastewater flow rates;Invert Level: The lowest point of the internal surface of a sewer;

Wastewater Collection System

Wastewater Collection System

Typical Layout of House Connections

1/2" DIA G. I. PIPE

2" ‐ 8"  DIA G.I. PIPEVARIABLE

MAIN SEWER 

WATER SUPPLY LINE

SUB  MAIN SEWER 9" DIAMINIMUM 

LATERAL SEWER 9" DIA

1" DIA G.I. PIPE

HOUSE SEWERCONNECTION 6" DIA

Plots Plots

Typical Layout Of Manhole

LATERAL SEWER HOUSE SEWER

ROAD

WALK WAYHOUSE

GREEN

Wastewater Sources and FlowratesDomestic Wastewater Sources: water consumption record may also be used for estimating flowrates; 90 % or more water becomes wastewater if water use for landscape and irrigation is limited; Averagely 60 – 90 % of the per capita water consumption becomes wastewater; (In Punjab-Pakistan 70-75% in peri-urban area & 80-85% in urban area);◦ Residential areas

◦ Commercial districts

◦ Institutional facilities

◦ Recreational facilities

◦ Infiltration

◦ Inflow