MIWW modul 1

Q. explain sedimentation filtration and Disinfectio ?

Sedimentation is a physical water treatment process using gravity to remove suspended solids from water.^[1] Solid particles entrained by the turbulence of moving water may be removed naturally by sedimentation in the still water of lakes and oceans. Settling basins are ponds constructed for the purpose of removing entrained solids by sedimentation.^[2] Clarifiers are tanks built with mechanical means for continuous removal of solids being deposited by sedimentation

  Suspended solids (or SS), is the mass of dry solids retained by a filter of a given porosity related to the volume of the water sample.

The limit sedimentation velocity of a particle is its theoretical descending speed in clear and still water. In settling process theory, a particle will settle only if :-

1. In a vertical ascending flow, the ascending water velocity is lower than the limit sedimentation velocity.
2. In a longitudinal flow, the ratio of the length of the tank to the height of the tank is higher than the ratio of the water velocity to the limit sedimentation velocity.

Removal of suspended particles by sedimentation depends upon the size, zeta potential and specific gravity of those particles.

Water disinfection means the removal, deactivation or killing of pathogenic microorganisms. Microorganisms are destroyed or deactivated, resulting in termination of growth and reproduction. When microorganisms are not removed from drinking water, drinking water usage will cause people to fall ill.

Disinfection can be attained by means of physical or chemical disinfectants.

For chemical disinfection of water the following disinfectants can be used:
- Chlorine (Cl₂)
- Chlorine dioxide (ClO₂)
- Hypo chlorite (OCl^-)
- Ozone (O₃)
- Halogens: bromine (Br₂), iodene (I)
- Bromine chloride (BrCl)
- Metals: copper (Cu²⁺), silver (Ag⁺)
- Kaliumpermanganate (KMnO₄)
- Fenols
- Alcohols
- Soaps and detergents
- Kwartair ammonium salts
- Hydrogen peroxide
- Several acids and bases
For physical disinfection of water the following disinfectants can be used:
- Ultraviolet light (UV)
- Electronic radiation
- Gamma rays
- Sounds
- Heat

2.Rainwater harvesting (RWH) is the collection and storage of rain, rather than allowing it to run off. Rainwater is collected from a roof-like surface and redirected to a tank, cistern, deep pit (well, shaft, or borehole), aquifer, or a reservoir with percolation.

A rainwater harvesting system has three main stages

1) Collecting & transporting rainwater

This is done through catchment areas & conduits. The catchment of a water harvesting system is the surface which receives rainfall directly.

It can be a paved area like the terrace or courtyard of a building. Conduits are the pipelines that carry rainwater from the catchment or rooftop to the harvesting system.

Filtration

A filter unit is a chamber filled with filtering media to remove debris and dirt from water before it enters the storage tank or recharge structure.

3) Storage in tanks for reuse / Recharging the groundwater levels

The harvested water can now be stored in storage tanks for immediate usage, which are designed according to the water requirements of the society.

Existing non-potable water storage tanks in the society can also be used to store the harvested rainwater.