Thailand water quality standards

The Surface Water Quality Standard in Thailand

Parameter	Unit	Statistic	Standard Value for Class***
Parameter	Unit	Statistic	1	2	3	4	5
1. Colour, Odour and Taste	-	-	n	n	n	n	-
2. Temperature	°C	-	n	n’	n’	n’	-
3. pH value	-	-	n	5-9	5-9	5-9	-
4. Dissolved Oxygen	mg/l	P20	n	6	4	2	-
5. BOD (5 days, 20°C)	mg/l	P80	n	1.5	2.0	4.0	-
6. Coliform Bacteria - Total Coliforms	MPN/100 ml	P80	n	5000	20000	-	-
- Faecal Coliforms	MPN/100 ml	P80	n	1000	4000	-	-
7. NO₃ - N	mg/l	Max allowance	n	5.0			-
8. NH₃ -N	mg/l	Max allowance	n	0.5			-
9. Phenols	mg/l	Max allowance	n	0.005			-
10. Cu	mg/l	Max allowance	n	0.1			-
11. Ni	mg/l	Max allowance	n	0.1			-
12. Mn	mg/l	Max allowance	n	1.0			-
13. Zn	mg/l	Max allowance	n	1.0			-
14. Cd	mg/l	Max allowance	n	0.005,0.05*			-
15. Cr (hexavalent)	mg/l	Max allowance	n	0.05			-
16. Pb	mg/l	Max allowance	n	0.05			-
17. Hg (total)	mg/l	Max allowance	n	0.002			-
18. As	mg/l	Max allowance	n	0.01			-
19. Cyanide (CN^-)	mg/l	Max allowance	n	0.005			-
20. Radioactivity - Gross α	Becqurel/l	Max allowance	n	0.1			-
- Gross β	Becqurel/l	Max allowance	n	1.0			-
21. Pesticides(total) - DDT	mg/l µg/l	Max allowance Max allowance	n n	0.05 1.0			- -
- αBHC	µg/l	Max allowance	n	0.02			-
- Dieldrin	µg/l	Max allowance	n	0.1			-
- Aldrin	µg/l	Max allowance	n	0.1			-
- Heptachlor & Heptachlorepoxide	µg/l	Max allowance	n	0.2			-
- Endrin	µg/l	Max allowance	n	none			-

Note: P = Percentile value

n = naturally

n’ = naturally but changing not more than 3 °C

* = when water hardness not more than 100 mg/l as CaCO₃

** = when water hardness more than 100 mg/l as CaCO₃

*** = Water Classification

The surface water quality standards are classified into 5 classes as follows:

Class 1: Extra clean for conservation purposes

Class 2: Very clean used for (1) consumption which requires ordinary water treatment processes (2) aquatic organism conservation (3) fisheries, and (4) recreation

Class 3: Medium clean used for (1) consumption but passing through an ordinary treatment process and (2) agriculture

Class 4: Fairly clean used for (1) consumption, but requires special treatment process and (2) industry Class

Class 5: Waters are not classification in class 1-4 which is no water quality requirement and used for navigation

Source: Notification of the Ministry of Natural Resources and Environment (B.E. 2537 (1994.)) water quality standards in surface water sources, published in the Royal Government Gazette, vol. 111, No.16, dated April 24, B.E. 2539 (1996). Available at: https://www.pcd.go.th/laws/4168/

Drinking Water Quality Standard in Thailand

Properties	Parameter	Units	Standards
Properties	Parameter	Units	Maximum Acceptable Concentration	Maximum Allowable Concentration
Physical	1. Colour	Platinum-Cobalt (Pt-Co)	5	15
	2. Taste	–	Non-Objectionable	Non-Objectionable
	3. Odour	–	Non-Objectionable	Non-Objectionable
	4. Turbidity	Silica scale unit (SSU)	5	20
	5. pH	–	6.5 - 8.5	9.2
Chemical	6. Total Solids	mg/dm³	500	1,500
	7. Iron (Fe)	mg/dm³	0.5	1.0
	8. Manganese (Mn)	mg/dm³	0.3	0.5
	9. Iron & Manganese (Fe & Mn)	mg/dm³	0.5	1.0
	10. Copper (Cu)	mg/dm³	1.0	1.5
	11. Zinc (Zn)	mg/dm³	5.0	15.0
	12. Calcium (Ca)	mg/dm³	75^b	200
	13. Magnesium (Mg)	mg/dm³	50	150
	14. Sulphate (SO₄)	mg/dm³	200	250^c
	15. Chloride (Cl)	mg/dm³	250	600
	16. Fluroride (F)	mg/dm³	0.7	1.0
	17. Nitrate (NO₃)	mg/dm³	45	45
	18. Alkylbenzyl Sulfonates (ABS)	mg/dm³	0.5	1.0
	19. Phenolic substance (as phenol)	mg/dm³	0.001	0.002
Toxic elements Toxic elements	20. Mercury (Hg)	mg/dm³	0.001	–
	21. Lead (Pb)	mg/dm³	0.05	–
	22. Arsenic (As)	mg/dm³	0.05	–
	23. Selenium (Se)	mg/dm³	0.01	–
	24. Chromium (Cr hexavalent)	mg/dm³	0.05	–
	25. Cyanide (CN)	mg/dm³	0.2	–
	26. Cadmium (Cd)	mg/dm³	0.01	–
	27. Barium (Ba)	mg/dm³	1.0	–
Bacterial	28. Standard plate count	Colonies/cm³	500	–
	29. Total coliforms	MPN/100cm³	< 2.2	–
	30. E. coli	MPN/100cm³	None	–

Remarks:	mg/dm³	=	milligram per cubic decimeter
	MPN	=	Most Probable Number
	a	=	These values are allowed for tap water or ground water that is used as temporary drinking water. Such water with a parameter between the maximum acceptable concentration and the maximum allowable concentration cannot be certified as standard drinking water for industrial products and stamped with the standard logo.
	b	=	If the calcium concentration is higher than the standard and magnesium concentration is lower than the standard, calcium and magnesium will be identified in terms of total hardness with a standard value of less than 300 mg/dm³ (as CaCO₃)
	c	=	If a sulphate concentration of 250 mg/dm³ is reached, magnesium concentration must not be more than 30 mg/dm³.

Source: Notification of the Ministry of Industry, No. 322, B.E. 2521 (1978), issued under the Industrial Products Standards Act B.E. 2511 (1968), published in the Royal Gazette, Vol. 95, Part 68, dated July 4, B.E. 2521 (1978).

Available at: https://wepa-db.net/archive/policies/law/thailand/std_drinking.htm

Water Quality Standard in Thailand by Provincial Waterworks Authority

Properties	Parameter	Units	Specification
Physical	1. Appearance Colour	Platinum-Cobalt (Pt-Co)	15
	2. Taste and Odour	–	Non-Objectionable
	3. Turbidity	NTU	5
	4. pH	–	6.5 - 8.5
Chemical	5. Total Dissolved Solids	mg/l	1,000
	6. Iron (Fe)	mg/l	0.3
	7. Manganese (Mn)	mg/l	0.3
	8. Copper (Cu)	mg/l	2. 0
	9. Zinc (Zn)	mg/l	3.0
	10. Total hardness as CaCO₃	mg/l	300
	11. Sulfate (SO₄)	mg/l	250
	12. Chloride (Cl)	mg/l	250
	13. Fluoride (F)	mg/l	1.5
	14. Nitrate as NO₃	mg/l	50
	15. Nitrate as NO₂	mg/l	3.0
Bacterial	16. Total Coliform bacteria	MPN/100cm³	None
	17. E. coli	MPN/100cm³	None
	18. Staphylococcus aureus	MPN/100cm³	None
	19. Salmonella spp.	MPN/100cm³	None
	20. Clostridium perfingens	MPN/100cm³	None
Toxic elements	21. Mercury (Hg)	µg/l	1
	22. Lead (Pb)	µg/l	10
	23. Arsenic (As)	µg/l	10
	24. Selenium (Se)	µg/l	10
	25. Chromium (Cr hexavalent)	µg/l	50
	26. Cyanide (CN)	µg/l	70
	27. Cadmium (Cd)	µg/l	3
	28. Barium (Ba)	µg/l	700
Pesticides	29. Aldrin and dieldrin	µg/l	0.03
	30. Chlodane	µg/l	0.2
	31. DDT	µg/l	1
	32. Heptachlor and heptachlor epoxide	µg/l	0.03
	33. Hexachlorobenzene	µg/l	1
	34. Lindane	µg/l	2
	35. Methoxychlor	µg/l	20
Trihalomethanes	36. Chloroform	µg/l	300
	37. Bromodichloromethane	µg/l	60
	38. Dibromochloromethane	µg/l	100
	39. Bromoform	µg/l	100
	40. Sum of ratio	-	1
Radioactivity	41. Gross alpha activity	Bq/l	0.5
	42. Gross beta activity	Bq/l	1

Free Residual Chloride = 02 mg/l

Source: Water Quality Standard in Thailand by Provincial Waterworks Authority 2023

Available at: https://www.mwa.co.th/wp-content/uploads/2022/12/%E0%B8%A1%E0%B8%B2%E0%B8%95%E0%B8%A3%E0%B8%90%E0%B8%B2%E0%B8%99%E0%B8%99%E0%B9%89%E0%B8%B3%E0%B8%9B%E0%B8%A3%E0%B8%B0%E0%B8%9B%E0%B8%B2%E0%B8%82%E0%B8%AD%E0%B8%87%E0%B8%81%E0%B8%B2%E0%B8%A3%E0%B8%9B%E0%B8%A3%E0%B8%B0%E0%B8%9B%E0%B8%B2%E0%B8%AA%E0%B9%88%E0%B8%A7%E0%B8%99%E0%B8%A0%E0%B8%B9%E0%B8%A1%E0%B8%B4%E0%B8%A0%E0%B8%B2%E0%B8%84.pdf

Water Quality Standard in Thailand by Metropolitan Waterworks Authority

Properties	Parameter	Units	Specification
Physical	1. Appearance Colour	Platinum-Cobalt (Pt-Co)	15
	2. Taste and Odour	–	Non-Objectionable
	3. Turbidity	NTU	1.0
	4. pH	–	6.5 - 8.5
Chemical	5. Total Dissolved Solids	mg/l	1,000
	6. Iron (Fe)	mg/l	0.3
	7. Manganese (Mn)	mg/l	0.08
	8. Free Residual Chloride	mg/l	0.2-2.0
	9. Copper (Cu)	mg/l	1.0
	10. Zinc (Zn)	mg/l	3.0
	11. Sodium (Na)	mg/l	200
	12. Total hardness as CaCO₃	mg/l	300
	13. Sulfate (SO₄)	mg/l	250
	14. Chloride (Cl)	mg/l	250
	15. Fluoride (F)	mg/l	0.7
	16. Nitrate as NO₃	mg/l	50
	17. Ammonia Nitrogen (NH₃ -N)	mg/l	1.5
	18. Nitrate as NO₂	mg/l	3.0
Bacterial	19. Total Coliform bacteria	MPN/100cm³	None
	20. E. coli	MPN/100cm³	None
	21. Heterotrophic Bacteria	CFU/ml	500
	22. Clostridium perfingens	MPN/100cm³	None
	23. Legionella spp.	MPN/100cm³	None
	24. Salmonella spp.	MPN/100cm³	None
	25. Shigella sp.	MPN/100cm³	None
	26. Staphylococcus aureus	MPN/100cm³	None
	26. Vibrio cholerae	MPN/100cm³	None
	27. Cryptosporidium spp.	MPN/100cm³	None
	28. Guardia spp.	MPN/100cm³	None
	29. Hepatitis A Virus	MPN/100cm³	None
	30. Rotavirus	MPN/100cm³	None
	31. Poliovirus	MPN/100cm³	None
Toxic elements	32. Mercury (Hg)	mg/l	0.006
	33. Antimony (Sb)	mg/l	0.02
	34. Lead (Pb)	mg/l	0.01
	35. Arsenic (As)	mg/l	0.01
	36. Selenium (Se)	mg/l	0.04
	37. Total chromium (total Cr)	mg/l	0.05
	38. Cyanide (CN)	mg/l	0.07
	39. Nickel (Ni)	mg/l	0.07
	40. Silver (Ag)	mg/l	0.1
	41. Cadmium (Cd)	mg/l	0.003
	42. Barium (Ba)	mg/l	1.3
	43. Microcysin-total	mg/l	0.001
Pesticides	44. Atrazine	µg/l	2
	45. Carbofuran	µg/l	7
	46. Chlorpyrifos	µg/l	30
	47. DDT	µg/l	1
	48. 2,4-dichlorophenoxy acetic acid	µg/l	30
	49. Glyphosate and AMPA	µg/l	900
	50. Paraquat	µg/l	10
Volatile organic Compound	51. Benzene	µg/l	10
	52. Carbontetrachloride	µg/l	4
	53. 1,2-Dichloroethane	µg/l	30
	54. Ethylbenzene	µg/l	300
	55. Styrene	µg/l	20
	56. Tetrachloroethane	µg/l	100
	57. 1,1,1-Trichlorothane	µg/l	2,000
	58. Toluene	µg/l	700
	59. Trichloroethene	µg/l	8
Trihalomethanes	36. Chloroform	µg/l	300
	37. Bromodichloromethane	µg/l	60
	38. Dibromochloromethane	µg/l	100
	39. Bromoform	µg/l	100
	40. Sum of ratio	-	1
Radioactivity	41. Gross alpha activity	Bq/l	0.5
	42. Gross beta activity	Bq/l	1

Source: Water Quality Standard in Thailand by Metropolitan Waterworks Authority 2022

Available at: https://www.mwa.co.th/wp-content/uploads/2022/12/%E0%B9%80%E0%B8%81%E0%B8%93%E0%B8%91%E0%B9%8C%E0%B8%81%E0%B8%B3%E0%B8%AB%E0%B8%99%E0%B8%94%E0%B8%99%E0%B9%89%E0%B8%B3%E0%B8%9B%E0%B8%A3%E0%B8%B0%E0%B8%9B%E0%B8%B2%E0%B8%81%E0%B8%B2%E0%B8%A3%E0%B8%9B%E0%B8%A3%E0%B8%B0%E0%B8%9B%E0%B8%B2%E0%B8%99%E0%B8%84%E0%B8%A3%E0%B8%AB%E0%B8%A5%E0%B8%A7%E0%B8%87-%E0%B8%9E.%E0%B8%A8.2565.pdf