The Surface Water Quality Standard in Thailand

Surface Water Quality Standard in Thailand

Parameter	Units	Statistics	Standard Value for Class¹⁾					Methods for Examination
Parameter	Units	Statistics	Class1	Class2	Class3	Class4	Class5	Methods for Examination
1. Colour,Odour and Taste	–	–	n	n’	n’	n’	–	–
2. Temperature	C°	–	n	n’	n’	n’	–	Thermometer
3. pH	–	–	n	5-9	5-9	5-9	–	Electrometric pH Meter
4. Dissolved Oxygen (DO)^2/	mg/l	P20	n	6.0	4.0	2.0	–	Azide Modification
5. BOD (5 days, 20°C)	mg/l	P80	n	1.5	2.0	4.0	–	Azide Modification at 20°C , 5 days
6. Total Coliform Bacteria	MPN/100 ml	P80	n	5,000	20,000	–	–	Multiple Tube Fermentation Technique
7. Fecal Coliform Bateria	MPN/100 ml	P80	n	1,000	4,000	–	–	Multiple Tube Fermentation Technique
8. NO₃ -N	mg/l	–	n	5.0			–	Cadmium Reduction
9. NH₃ -N	mg/l	–	n	0.5			–	Distillation Nesslerization
10.Phenols	mg/l	–	n	0.005			–	Distillation,4-Amino antipyrene
11.Copper (Cu)	mg/l	–	n	0.1			–	Atomic Absorption -Direct Aspiration
12.Nickle (Ni )	mg/l	–	n	0.1			–	Atomic Absorption -Direct Aspiration
13.Manganese (Mn)	mg/l	–	n	1.0			–	Atomic Absorption -Direct Aspiration
14.Zinc (Zn)	mg/l	–	n	1.0			–	Atomic Absorption -Direct Aspiration
15.Cadmium (Cd)	mg/l	–	n	0.005* 0.05**			–	Atomic Absorption -Direct Aspiration
16.Chromium Hexavalent	mg/l	–	n	0.05			–	Atomic Absorption -Direct Aspiration
17.Lead (Pb)	mg/l	–	n	0.05			–	Atomic Absorption -Direct Aspiration
18.Total Mercury (Total Hg)	mg/l	–	n	0.002			–	Atomic Absorption-Cold Vapour Technique
19.Arsenic (As)	mg/l	–	n	0.01			–	Atomic Absorption -Direct Aspiration
20.Cyanide (Cyanide)	mg/l	–	n	0.005			–	Pyridine-Barbituric Acid
21.Radioactivity - Alpha - Beta	Becqurel/l	–	n	0.1 1.0			–	Gas-Chromatography
22.Total Organochlorine Pesticides	mg/l	–	n	0.05			–	Gas-Chromatography
23.DDT	µg/l	–	n	1.0			–	Gas-Chromatography
24.Alpha-BHC	µg/l	–	n	0.02			–	Gas-Chromatography
25.Dieldrin	µg/l	–	n	0.1			–	Gas-Chromatography
26.Aldrin	µg/l	–	n	0.1			–	Gas-Chromatography
27.Heptachlor & Heptachlorepoxide	µg/l	–	n	0.2			–	Gas-Chromatography
28.Endrin	µg/l	–	n	None			–	Gas-Chromatography

Remark:	1) DO value is minimum value
	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

Based on Standard Methods for the Examination of Water and Wastewater recommended by APHA : American Public Health Association, AWWA : American Water Works Association and WPCF : Water Pollution Control Federation

Notification of the National Environmental Board, No. 8, B.E. 2537 (1994), issued under the Enhancement and Conservation of National Environmental Quality Act B.E.2535 (1992) , published in the Royal Government Gazette, Vol. 111, Part 16, dated February 24, B.E.2537 (1994).

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