PowerPoint Presentation

MANHOLES

INTRODUCTIONTop opening to an undergroundutility vault.

Used to house an access point for making connections or performing maintenance on underground and buried public utilityand other services includingsewers,telephone,electricity,storm drainsandgas.

Protected by a manhole cover (biscuit).

Should be so situated as to allow every length of drain to be accessible for maintenance inspection and removal of debris.

sewermanhole exposed during construction

PURPOSEInspection and maintenance of drains or sewersVentilation of drains or sewersFlow conditions change of a medium (change of direction, change of pressure, change of water flow rate)Cleaning and flushing of drains or sewersMaintenance of water meters and fittingsHousing of pumping stationsInlet drain pits

TYPES Precast concrete manholes :

Minimum manhole diameter is 48-inch and maximum manhole diameter is 96-inch

Concrete strengthens with time, while other materials can deteriorate.

Advantages of precast concreteWatertight structures easily achieved Resists buoyant forces Superior strengthReadily available modular flexible design May be designed to accommodate existing utilitiesProduced in a quality controlled plant environment.Internal and external corrosion resistanceOne-piece wall structureRestricts infiltrationAvoids exfiltration

2. Brick manholes

The brick are corbelled inward toward the top to form a clear opening of at least 20 inches.

Empirical design requires an 8-inch-thick wall for depths of 12 feet or less.

If thinner walls are desirable,the structure must be designed as reinforced brick masonry.

SEPTIC TANKSA tank, typically underground, in which sewage is collected and allowed to decompose through bacterial activity before draining by means.

The term SEPTIC refers to the ANAEROBICAL BACTERIAL environment that develops in the tank which decomposes or mineralizes the waste discharged into the tank.

Periodic preventive maintenance is required to remove the irreducible solids that settle and gradually fill the tank, reducing its efficiency.

It should generally be pumped every 3-5 years.

Generally its size varies between 4000 to 7500 liters.

The tank normally consists of two chambers : first chamber allows heavier solids to settle while second chamber allows finer solids to settle to the bottom.

A layer of Scum present consists of Oils, Grease, Fats and Soaps.

A Septic tank is always full upto a certain level (just below the outlet pipe) and it should remain constant.

Every time water enters the tank, the same amount will exit it.

Organic materials which are in the tank will be broken down by Anaerobic bacteria.

WORKING

TYPES OF SEPTIC TANKSConcrete Septic Tanks

Steel Septic Tanks

Fibreglass/Plastic Septic Tanks

Aerobic Septic Tanks

Concrete Septic Tanks

Concrete septic tanks are susceptible to cracking or even separation. Cracks may allow waste to seep out or ground water to seep in.Usually quite durable for several decades.Blockage can cause the system to backup.Any problem may not be detected unless it is manually inspected until serious problems have arisen.

Steel Septic Tanks

Steel Septic tanks are least durable and least popular tank option.Last not more than 20-25 years.They can be susceptible to rust even before that. Steel top covers can rust through and cause an unsuspecting person to fall into the tank.These covers can be replaced without replacing the entire tank.

Fibreglass/Plastic Septic Tanks

Plastic septic tanks are largely impervious to the rusting and cracking of Steel and Concrete septic tanks.More resistant to the natural chemical processes of a septic system.More susceptible to structural damage due to their light weight.Careful installation is needed to ensure the tank isnt damaged.Driving over the tank must be avoided as it can result in shifting during periods of wet soil.

Aerobic Septic Tanks

Aerobic septic tanks use the aid of oxygen to increase the decomposition of the effluent. They also require electricity.They typically cost two or three times as much but their high efficiency can save money from a prolonged life.They require more frequent and more extensive maintenance.It has a more complex system of decomposition .But if the system is maintained its efficiency will keep effluent in check indefinitely.

Group MemberSamiullah ChandSamiya MahwishYusra YasmeenZahra ZabeenTazeem Ahmad