FILTRATION

Introduction 

Filtration is an operations that separate solids from fluids  by adding a medium through which only the fluid can pass. The fluid that passes through is called the filtrate. In physical filters oversize solids in the fluid are retained. However, the separation is not complete; solids will be contaminated with some fluid and filtrate will contain fine particles (depending on the pore size, filter thickness).

Type of Filters :
  1. MGF (Multi-grade Sand Filter)
  2. ACF (Activated Carbon filter)
  3. IRF (Iron removal Filter)
  4. Softener

 

1) MGF (Multi-grade Filter)

MGF works on the principle of retention and removal of physical impurities(suspended solids, dirt, dust, etc.) through the voids of the filtering media in a graded manner.

It is a depth filter that makes use of fine and coarse bubble diffuser which are mixed in a fixed proportion. This arrangement produces a filter bed with adequate pore dimensions for retaining both large and small suspended particles.

It has higher specific flow rate as compared  to conventional filters.

Working

Raw water is passed through the Multi grade media filter, containing  anthracite at a top layer of media followed by fine & Coarse Garnet and quartz sand supported by pebbles and gravels. Multi grades of media and layers provide extra ordinary dirt holding capacity at various level of total media depth and produce unparalleled filter water quality.

During the filtration cycle the largest particles are strained out by the anthracite, coarse and fine sand.  Since the particles in the water are filtered out at various depths in a multimedia filter, the filter does not clog as quickly as if all of the particles were all caught by the top layer.

 

Features:
  • Higher specific velocity ·
  • Raw water can be used for back washing the filter

 

Applications:
  • Side-stream filtration for cooling tower.
  • Potable water treatment.
  • Sea water filtration
  • Filtration of chemical solutions.

 

2) ACF(Activated carbon filter)

Activated carbon filters are generally employed in the process of removing organic compounds and/or extracting free chlorine from water, thereby making the water suitable for discharge or use in manufacturing processes.

Activated carbon is usually derived from charcoal and is sometimes utilized as biochar. Those derived from coal and coke are referred as activated coal and activated coke respectively

Working Principles:

Activated carbon filtration is an adsorptive process in which the contaminant is attracted to and adsorbed onto the surface of the carbon particles. The efficiency of the adsorption process is influenced by carbon characteristics (particle and pore size, surface area, density and hardness) and the contaminant characteristics.

Features:
  • Single layer of activated Carbon
  • Adsorption efficiency up to 85 to 90 %
  • Low Pressure drop across the vessel
  • Pre-assembled construction minimizes start-up time and installation costs
  • Proven design of internal distribution and collection system.
  • Simple design maximizes reliability and efficiency.

 

Advantages:
  • Efficient – Chlorine, color, organic matter and odor removal.
  • High surface area.
  • Adsorption efficiency up to 90%
  • Easy operation & maintenance
  • Wide range in material of construction
  • Economical way of production & design.

 

Applications:

 

Drinking Water Treatment
  • Organic matter, colour and odour removal
  • Pre-treatment to Reverse Osmosis Plant
  • Pre treatment to Desalination Plant
River Water Treatment
  • Organic matter removal
Ground Water Treatment
  • Organic matter, colour and odour removal
  • Pre-treatment to reverse Osmosis Plant
  • Pre-treatment to Desalination Plant
Waste Water Treatment Plant
  • Organic matter, colour and odour removal.

 

3) IRF(Iron Removal Filtration)

The iron removal filter (IRF) is a cylinder built using ferrocement construction techniques. Inside, from top to bottom order, is a plastic basin full of charcoal, a layer of gravel, and an empty space for sedimentation. The water to be treated first passes through the charcoal, aerating it, flows to the empty space at the bottom via a pipe where sedimentation of the precipitated iron takes place, then wells up through the gravel for filtration purposes. The finished water accumulates above the gravel filter, and this elevation enables users to draw it.

                                                                                        OR

The process through which iron is removed from water is known as Oxidation Filtration that involves the oxidation of the soluble forms of iron (Fe) to their soluble forms and then removal by filtration. The oxidant chemically oxidizes the iron (forming a particle), and kills iron bacteria and any other disease-causing bacteria that may be present after that the filter removes the iron and particles.

 

Features:
  • Increased solid removal
  • Ensures processing stability
  • Better drainage reduces blockage cleaning
  • Less tube blockages increase effective settlement rates
  • In-tube contact flocculation

 

Applications:
  • Hospitals & others medical institutes
  • Municipality water supply
  • Chemical plant
  • Community purpose in rural areas
  • Residence
  • Office building
  • Hotels
  • Pharmaceutical industry
4)  Softener

Water softening is the removal of calcium, magnesium, and certain other metal cations in hard water. The resulting soft water is more compatible with soap and extends the lifetime of plumbing.

Water Softening process:

 The unit contains several cubic feet of porous plastic resin covered with molecules that attract and bind to positive ions dissolved in the water. Normally, sodium positive ions coat the resin, but as water flows over the resin on its way to your sink or washer, the naturally occurring calcium and magnesium positive ions that exist in hard water stick to the resin. This releases sodium ions into the water in order to maintain a balance of electrical charge on the resin. Gradually, most of the sodium ions are released into the household water, and the resin becomes saturated with calcium and magnesium ions. Every few days, the unit must renew the resin by rinsing it with a concentrated solution of saltwater (sodium chloride). The high concentration of sodium ions in the salty water displaces the calcium and magnesium ions the resin, and the resin becomes once again covered with sodium ions. The salty rinse water, calcium and magnesium ions are flushed down the drain, and the system resumes normal operation. (Every so often it is necessary to add a bag of sodium chloride salt to the softener unit to prepare this salty rinse water.)

Advantages:
  • It protects appliances and saves cleaning time.
  • Equipment is reliable and effective.
  • Less consumption of soaps and detergents.