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SANITARY ENGINEERING. Planning, designing and installation of system for the collection, conveyance, treatment and disposal of the waste. Definitions. Refuse: Any waste matter lest as waste or worthless
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SANITARY ENGINEERING • Planning, designing and installation of system for the collection, conveyance, treatment and disposal of the waste
Definitions • Refuse: Any waste matter lest as waste or worthless • Sewage: includes all types of liquid wastes from latrines urinals, storm water, industrial wastes etc… • Sullage: Liquid discharge from bathrooms, kitchens, wash basins etc… • Garbage: Dry refuse including decayed fruits, leaves, paper pieces • Sewer: closed drain through which drainage is conveyed • Chemical oxygen demand: the amount of oxygen required to oxidize (chemically decompose) the given quantity of sewage is called COD • Bio chemical oxygen demand: the amount of oxygen required for biological decomposition of waste matter
SEPTIC TANK • Water tight single storied sedimentation tank where the sewage undergoes anaerobic decomposition BIOLOGICAL ACTION • Sewage is retained for specific period- suspended solids settle down – sludge • Sludge and the liquid undergo anaerobic decomposition – gets digested and reduces itself – sludge formed is removed at frequent intervals – effluent treated properly – either to soak pit or dispersion trenches • Grease and fat rise to the surface of the sewage as scum
DESIGN ASPECTS • For treatment of human excreta and urine • Minimum diameter of pipes – 100 mm • Volume septic tank depends on quantity of flow and the detention period • Detention period – 24 hours ( may vary from 12-72 hours ) • Rectangular in shape – length is usually 2-4times breadth • Grease, detergents, disinfectants- should not be allowed to the tank • Minimum free board is 300mm
Construction details • Two compartments- seperated by baffle walls • Rectangular tank with brick or concrete • Brick walls – 200mm, Concrete walls – 150 mm • Plastering – 12 mm thick ( 1:3) • Flooring – M15 concrete; 1:10 slope towards sludge outlet • RCC or cast iron covers are provided over the tank • Ventilation pipes – 50mm dia., taken to a height of 2m minimum, covered with mosquito nets
SEPTIC DON’TS • Eliminate anti-bacterial cleaners. • Don’t use detergent with bleach. • Don’t do excessive cold water washing. • Septic tank bacteria needs a warm climate. • No water softeners into tank.
SOAK PIT • Effluent from septic tank – fed to soak pit • Soil absorption method • Liquid effluent- soaks the soil • Covered pit • Rectangular in shape • Minimum lateral dimension -atleast 1 m • Filling-brick bats or broken stones • Lining above inlet level is plastered • Pit is covered with RCC slab
DISPERSION TRENCH • Trenches of depth 50 to 100 cm and 30 to 100 cm excavated to a slight gradient • Bottom layer – washed gravel / crushed stone • Rest layers – coarse aggregates • Length of trench - 30 m with a min. spacing of 1.8 m • Covered with ordinary soil and the top surface is turfed ( 15 cm above ground level)
Water is our most precious resource. • We can live without oil or gas • We cannot survive without clean and safe water
