First of all, make sure any method you use in lab is accepted by the authority in the country you are conducting the test in. Generally, APHA and EPA water and wastewater examination methods are well accepted worldwide unless specific methods are required by the local authority.
I would recommend the following:
1- APHA, 1992. Standard Methods for the Examination of Water and Wastewater,,
American Public Health Association, Washington, DC.
2- CROMPTON, T.R. 2005 Comprehensive Water Analysis. Volume 2: Treated Waters. ELSEVIER SCIENCE PUBLISHERS LTD. ISBN 0-203-49841-0
3- SCP SCIENCE. Water Analysis Handbook. Vol,. 2. www.scpscience.com
4- United States Environmental Protection Agency (USEPA) - Methods for the Chemical Analysis of Water and Wastes (MCAWW). EPAl600f4-79f020, March 1983.
5- EPA. 2000. A GUIDE TO THE SAMPLING AND ANALYSIS OF WATERS,WASTEWATERS, SOILS AND WASTES. http://www.state.in.us/dnr/fishwild/files/Methods_Analysis_Water_Wastes_USEPA_March1983.pdf..
6- Donald F. Goerlitz and Eugene Brown. 1984. ANALYSIS OF ORGANIC SUBSTANCES itf WATER. UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON. http://pubs.usgs.gov/twri/05a03/report.pdf.
7- Guide Manual: Water and Wastewater Analysis - Central Pollution Control Board, India. http://www.google.ca/url?sa=t&rct=j&q=&esrc=s&source=web&cd=83&cad=rja&uact=8&ved=0CCgQFjACOFA&url=http%3A%2F%2Fcpcb.nic.in%2Fupload%2FLatest%2FLatest_67_guidemanualw%26wwanalysis.pdf&ei=fDYcVfGWEJS2yATSxIDIBg&usg=AFQjCNG2Gr8Bf3qsK1ObBUCKF1EBiG7QCg
8 HACH. Water Analysis Handbook . http://www.hach.com/wah
9- Government of India & Government of The Netherlands. Standard Analytical Procedures for Water Analysis. May 1999.