bids are invited for chemicals, sand - sandthe sand shall be of the high quantity quartz of clean single hard and durable grains, completely free from mica, clay, dirt, loam, organic or foreign substances of anykind and shall contain no iron or manganese in form or quantity that shall adversely affect the filtered water quality, specification of sand is given below:i. size (mm) : 0.4 to 0.6 > 95%ii. uniformity coefficient : 1.1 to 1.2iii. % of sio2 : > 99.8iv. bulk density (g/cc) : 1.42-2.0 , chemicals, gravel - gravelthe gravel supplied shell be high quantity quartz, non-calcareous, clean, hard and durable with the following specifications. i. size (mm) : 3/30 (top/bottom)ii. uniformity coefficient : 1.4 to 1.6iii. % of sio2 : >= 90iv. bulk density (g/cc) : 1.6 , chemicals, anthracite - anthracitespecification of anthracite is given below: i. size (in mm) : 0.8 to 2.0 > 90%ii. uniformity coefficient : 1.2-1.3iii. dust content : < 1%iv. bulk density (g/cc) : 0.9 , chemicals, activated carbon - activated carboni. activated carbon base material : lignite / coconut shellii. particle size : 12 x 40 meshiii. effective size (mm) : 0.8 – 0.9iv. uniformity coefficient : 1.5 – 1.6v. bulk density, kg / cum (min) : 400vi. pore volume, cc / g (min) : 0.8vii. active surface area, sq. m/g (min) : 800viii. iodine adsorption capacity, mg / mg (min) : 900ix. ash content, wt % : less than 10%x. carbon content, wt % : more than 90% total quantity : 1