LAKSHMI NARAIN COLLEGE OF TECHNOLOGY BHOPAL CIVIL ENGNEERING

LAKSHMI NARAIN COLLEGE OF TECHNOLOGY BHOPAL (CIVIL ENGNEERING DEPARTMENT) Environmental Engineering ( CE-602) Unit : IV Topic : Collection and Conveyance of Sewage ( L-2) Prepare By : Dr. Anil K. Saxena

Collection of sewage The disposal of waste products , two works are required 1. Collection works 2. Disposal works disposal works consist of treatment works and dispose it safely Depending upon the type of waste two system may be employed for collection , conveyance and disposal 1. Conservancy syatem 2. Water Carriage system

Conservancy syatem • This is an old system in which various types of wastes, such as night soil, garbage etc are collected separetely in vessels or disposed in pits and then removed periodically at least once in 24 hours • This system is also called dry system in which various types of refuges and storm water are collected, conveyed and disposed of separately

Types of wastes • Night soil- Night soils or human excreta in cesspools is collected separately in pans or pails and carried on heads of sweepers to a central place from where it is transported from where it is tranported in bullock carts or motor vans to a place away from the town for its final disposal, in trenches, to give excellent manure in one or two years.

Garbage • Garbage is collected separately , in dust bins and conveyed on hand carts or motor van once or twice in a day • It may consist of waste matter of both non combustible as well as combustible type. • Then it is dumped by suitable method Sullage and storm water are collected and conveyed separately in closed or open gutters

Advantages of conservancy system • It is cheaper in initial cost • The quantity of sewage reaching at the treatment plant is low • the storm water goes in open drains, the sewer section will be small and will run full for the major portion of the year, due to which there will be no silting • In floods if the water level of river rises at the out -fall, it will not be costly to pump the sewage for disposal.

Disadvantages • This system is highly unhygienic and cause insanitary conditions since the excreta starts decomposing within few hours of its prodution • Transportation of night soil takes place in open carts through streets and other crowded localities. This is highly undesirable • Insanitation may be there due to carriage of sullage partially separate system through open drains laid in the streets. • Due to improper or careless disposal of night soli, there are more chance of outbreak of epidemic.

Disadvantages ( Contd. ) • The lavatories or premises are to be located outside the house and slightly away from the main building the compact design is therefore not possible. • The liquid wastes from lavatories etc. , during their washing, may soak in the ground, thus contaminating the soil and it may also be polluted due to percolation of waste water. • The system requires considerable land for the disposal of sewage.

Water Carriage System • In this system , the collection , conveyance and disposal of various type of wastes are carried out with the help of water • Water is used as medium to convey the waste from its point of production to the point of its treatment o • Sufficient quantity of water is required to be mixed with the wastes so that dilution ratio is great the mixture may just like water

Contd… • The sewers lead the sewerage so collected to a suitable site where suitability and then disposed off by dilution • The garbage is collected separately and conveyed in the same manner as is done in the case of conservancy system. • The wastes form kitchens, baths, wash basins etc. are also led to the sewers. The sewers are the underground closed pipes which are laid on suitable longitudinal gradient

Advantages • The system is very hygienic since the night soil and other waste water is conveyed through closed conduits which are not directly exposed to the atmosphere. There is no bad smell because of continuous flow • The liquid wastes etc. are directly conveyed through the sewers, and therefore there are no changes of the waste water being soaked in the ground. • . The waste water does not percolate down to join the ground water. There are no chances of pollution of water of wells in individual houses if any.

Advantages • The labour required for the operation and maintenance is extremely small. In fact, the functioning of the system is practically automatic, problem. • The system permits the use of modern methods of treatment of the sewerage collected through the sewers. The treated waste water and sewage can be safely disposed off without any risk. • The land required for the disposal of the treated wastewater is very much smaller than that required for the conservancy system.

Disadvantages • This system is very costly in initial cost. one set of underground sewer is laid • The maintenance of this system is also costly. • During monsoon large volume of sewage is to be treated whereas very small volume is to be treated in the remaining of the year.