1. WATER QUALITY CRITERIA & STANDARDS
1. Acceptability aspects
Microbiological aspects
Chemical aspects
Radiological aspects

2. . ACCEPTABILITY ASPECTS
1.Turbidity
On aesthetic grounds, drinking water should be free from turbidity.
Turbidity in drinking water is caused by inadequate treatment or
Re-suspension of sediment in the distribution system.
Presence of inorganic particulate matter in some ground water. Turbidity interferes with disinfection and microbiological determination.
Water with turbidity of less than 5 nephelometric turbidity units (NTU) is usually acceptable to consumer.

3. (2)Colour 3.Taste and odour:
Drinking water should be free from color which may be due to the presence of colored organic matter metals such as iron and manganese, or highly colored industrial wastes.
sources when their water is coloured to an aesthetically displeasing degree. The guideline value is upto 15 true colour units (TCU) although levels of colour above 15 TCU can be detected in a glass of water.
3.Taste and odour:
Taste and odour originate from natural and biological sources or processes, from contamination by chemicals, or as a by-product of water treatment. Taste and odour may develop during storage and distribution. It is indicative of some from of pollution or malfunction during water treatment or distribution. The cause should be investigated, particularly if there is substantial

4. change. An unusual taste or odour might be an indication of the presence of potentially harmful substances. No health – based guideline value is proposed for taste and odour.
4.Temperature:
Cool water is generally more palatable. however, high water temperature enhances the growth of microorganisms and taste, odour, colour and corrosion problem may increase. No guideline value is recommended since its control is usually impracticable.

5. B-Inorganic constituents
To sum up, we cannot judge the quality of drinking water by physical characteristics.
B-Inorganic constituents
Chlorides
The standard prescribes for chloride is 200/mg/ltr. The maximum permissible level is 600mg/ltr.
Hardness
The taste threshold for the calcium ion is in the range of mg/ltr, depending on the associated anion, and the taste threshold of magnesium is probably less than that for calcium. In some instances. Water hardness is excess of 500 mg/ltr is tolerated by consumers.

6. 3. Ammonia
Ammonia in the environment originated from the metabolic, agricultural and industrial processes and from disinfection with chloramines usually below 02 mg/ltr. Anaerobic ground waters may contain upto 3 mg/ltr. Ammonia contamination can also arise from cement mortar pipe lining.

7. 4. PH
PH levels is less than 7 may cause severe corrosion of metals in the distribution pipes and elevated levels of certain chemical substances, such as lead may result. At PH levels above 8 there is a progressive decrease in the efficiency of the chlorine disinfection process. An acceptable PH drinking water is between 6.5 and 8.5.
5. Hydrogen sulphide
The taste and odour threshold of hydrogen sulphide in water are estimated to be between 0.05 and 0.1 mg/ ltr.

8. 6. Iron
May contain ferrous iron at concentration of up to several mg/ ltr without discoloration or turbidity in water. Iron also promoted the growth of “iron bacteria ”. At level above 0.3 mg/ltr, iron stains laundry and plumbing fixtures.
7. Sodium
The taste threshold concentration of sodium in water depends on the associated anion and the temperature of the solution about 200 mg/ltr

9. 9. Total dissolved solids
8. Sulphate
The presence of sulphate in drinking water can cause noticeable taste. It is generally considered that taste impairment is minimal at level below 250 mg/ltr.
9. Total dissolved solids
Total dissolved solids (TDS can have an important effect on the taste of drinking water. The palatability of water with a TDS level of less than 600 mg/ltr is generally considered to be good. Drinking water becomes increasingly unpalatable at TDS levels greater than 1200 mg/ltr

10. 10. Zinc
Taste indicate a taste threshold concentration of 4 mg/ltr. Zinc at concentration in excess of 5 mg/ ltr may appear opalescent and develop a greasy film on boiling. Zinc at concentration above 0.1 mg/ltr levels in tap water can be considerably higher.
11. Manganese
Below 0.1 mg/ltr are usually acceptable to consumers. At level above 0.1 mg/ltr, manganese in water supplies stains sanitary ware and laundary, and causes an undesirable taste in beverages.

11. 12. Dissolved oxygen
dissolved oxygen content of water is influenced by the raw water temperature composition treatment any any chemical or biological processes taking place in the distribution system. Depletion of dissolved oxygen in water supplies can encourage microbial reduction of nitrate to nitrate and sulphate to sulphide, giving rise to odour problem. It can also cause an increase in the concentration of ferrous iron in solution. No health-based guideline value has been recommended.

12. 13. Copper
It increases the corrosion of galvanized iron and steel fittings. Staining of laundry and sanitary ware occurs at copper concentrations above 1mg/ ltr
14. Aluminium
In excess of 0.2 mg/ ltr often leads to deposition of aluminum hydroxide floc in distribution system and the exacerbation of discoloration of water by iron.

13. MICROBIOLOGICAL ASPECTS
(a) Bacteriological indicators
Coliform group of organisms as a whole supplementary indicators organisms, such as feacal streptococcal and sulhphite - reducing clostridia.
1. Coliform organism
The “coliform” organisms include all aerobic and facultative anaerobic, gram-negative, non-sporing to 37 deg. C is less than 48 hours.E coll and of the non.- faecal group, Klebsiella aerogens.

14. It is estimated that an average person excretes 200 – 400 billion of these organisms per day .
They are easily detected by culture methods – as small as one bacteria in 100ml of water where as the methods for detecting the pathogenic organisms or complicated and time consuming .
They survive longer than which tend to die out more rapidly than coliform bacilli.