STANDARDS FOR POTABLE WATER and drinking water treatment

STANDARDS FOR POTABLE WATER :

Suspended Solids < 500 ppm

Turbidity < 10 ppm

B-Coli—NIL

M.P.N. – one number in 100 ml

Hardness <100 ppm="">

Chloride<250 ppm="<!--250--">

Iron and Manganese < 0.3 ppm

PH= 6.5 to 8

Lead< 0.1 ppm

Arsenic< 0.05 ppm

Sulphate < 250 ppm

Carbonate Alkalinity < 120 ppm

Dissolved Oxygen = 5 to 6 ppm

B.O.D—NIL

Any parameter above the limits as mentioned above will require treatment .

           TABLE OF WATER PROBLEMS AND SOLUTIONS :

Problem	Process	How it Works	Equipment Used
Turbidity - cloudy water that will clear if left to set for a few minutes	Filtration	Mechanically traps particles between pores of media	Filter tank and media with automatic backwashing head. Media will vary depending on application
Turbidity - cloudy water that will not clear if left to set for a few minutes.	Flocculation	Chemicals are added that will grow large particles that will settle out and then can be mechanically removed by filtration	solution feed pumps, static mixers, and filters
Low pH - Blue-green staining-pin hole leaks in pipes caused by corrosive water	Acid Neutralisation	There are two ways to do this: 1. Dissolves sacrificial media (limestone) to raise pH and at the same time increases the hardness. 2. A pump injects a solution that raises the pH. The solution is usually made by dissolving soda ash (baking soda) or potash (baking soda with potassium instead of sodium)	Filter with AN (acid neutralizer) for technique #1 and solution feed pump for technique #2.
Gas and VOC removal. Not for hydrogen sulfide removal. Radon at less than 5000pCi/L	Adsorption	Gases attach themselves to the surface of the activated carbon. The carbon must eventually be replaced	Filter with GAC (granular activated carbon)
Iron, manganese and hydrogen sulfide- Staining and Odor problems. hydrogen sulfide has an odor that is usually egg like. The staining can be any color from orange to brown to black	Oxidation Filtration	The material being removed is first oxidized . The oxidation causes a precipitate to be formed. The precipitated material is filtered. For instance, to remove iron the oxidation causes the dissolved iron to turn to rust and make the water cloudy red. Once the iron has rusted, it is a particle that can be mechanically filtered.	Air injection systems use air for the oxidation process and chlorine systems use chlorine for the oxidation process. Air is introduced by a venturi and chlorine maybe introduce by either a solution feed pump or a dry pellet down the well chlorinator. The filter maybe any of the mechanical filters mentioned above.
Hardness, iron, manganese, tannins - Hardness causes scaling. Iron and manganese stains will have colors ranging from orange to black. Tannins will make the water tea colored.	Ion Exchange	The system simply replaces the material that is to be removed with one that is more desirable. The total amount of material in the water does not change, only the kind of material. The materials that are usually introduced into the water are either sodium or potassium. Chloride ions will be added only when an anion resin is used.	Water Conditioner (softener) with either cation or anion resin. The anion will only be used when there is a tannin problem. See our Technetic water softener
TDS, salt, nitrates, gross alpha	Reverse Osmosis (RO)	RO uses pressure to force water through a plastic membrane leaving the minerals behind where they are flushed down the drain. Although this is not filtration, many people visualize this as filtration on the atomic level because molecules are being separated from one another. RO is usually done at the point of use (POU) and only for the water that will be used to drink or cook with.	Reverse osmosis system at either the point of use (POU) or point of entry (POE).
Radon	AERATION	Aeration drives the radon gas off by bubbling air through the water. The agitation caused by the air removes the gas in a similar fashion to shaking a soda to make it fizz.	Shallow tray aeration from NEEP .