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< prev - next > Water and sanitation Water quality and treatment KnO 100401_Arsenic and iron removal plant (Printable PDF)
A small-scale arsenic and iron removal plant
Practical Action
Steps for preparing the site
Clean the site (2.0 m x 2.0 m) close to the contaminated water source
Water source (tubewell) should be at the left side (first corner) of the plant
If the soil condition of the bed of the plant has been found loose/slushy, then additional
earth should be excavated and filled with compact sand as per site condition
3 inches thick cement concrete (CC) or Reinforced Cement Concrete (RCC) with proportion
of 1:2:4 (cement:sand:brick chips) over Brick Flat Soling (BFS) platform should be
constructed. Note that the foundation bed of the plant should be constructed considering
the level of nearby drainage network so that wastewater could pass easily from the plant; If
necessary, the bed of the plant may be raised by additional brick work on the periphery
(outer wall) of the plant
Steps for constructing the superstructure
Start the 5 inch (127mm) thick brick masonry work of the outer and inner walls after
completing the CC/RCC bed (at least 24 hours delay is required). The height of the walls
should be up to 600mm.
Each chamber should be equal in size (600mm x 600 mm x 600 mm).
After the brick works, plaster the walls with neat cement finishing (NCF) with 1:4 mortar
(cement:sand) ratio. Water resistant additive (padlu) may be used during plaster works to
keep the chambers impermeable. About 0.5 kg of padlu should be mixed with one bag of
cement (50 kg) for making the plaster mortar.
Side drain should be constructed with proper slope and connected to nearby drainage
Steps for adding fittings and fixtures:
One outlet pipe for each chamber should be placed about 10 mm above the plant bed. The
outlet should have an end cap at the outside and a plastic net placed on the inner side. The
outlet pipe should be put in place during the brickwork stage. These outlets will drain
wastewater while cleaning the chambers.
Better drainage of wastewater and other settings of the plant should be considered while
placing the outlet pipes.
A perforated PVC pipe (100mm diameter) should be placed at chamber C1 as the inlet to
introduce raw water from the contaminated tubewell into the plant. The perforated portion
of the pipe should be fully within chamber C1.
Pipes should be placed for circulating water between chambers as well. Between chambers
C1 and C2, two galvanized iron (GI) pipes (38mm diameter and 150 mm long) covered with
plastic net at both ends should be placed at the top level of the finished plant bed. Between
chambers C2 and C3, two similar pipes should be placed at the middle height from the bed.
Between chambers C3 and C4, two PVC strainers (38mm in diameter and 450 mm in
length) should be placed between chambers C3 and C4 at the top level of the finished plant
bed. The strainers should have end caps at chamber C3 and open ends at chamber C4.
About 300mm length of the strainers should be within chamber C3.
An outlet with a stopcock (tap) should be placed at chamber C4 about 150 mm above the
finished bed of the plant. This will let users collect purified water. The outlet should be
located so that the users could easily collect water by commonly used pots.