Anions in sewage effluent - Determination of Anions in Natural and Treated Waters - page 577

Fig 9.1 Flow diagram of analytical system for oxidised nitrogen (Technicon
Industrial Method Sheet No 16-72E) Hydrogen-copper reagent. To
0.14g HN 2 HN2H 2 SO 4 add 0.3ml copper sulphate (3.9g Cu
SO 4 5H 2 OL -1 ) and make up to 1L. Sulphanilamide reagent. 10g
sulphanilamide plus 100ml conc.phosphoric acid plus 2g N
(naphtyletylene) diamine dihydrochloreid,diluted to IL
Source: Reproduced with permission from the Water Research Center,
UK[11]
T he layout of the apparatus for determining 0.50mg L −1 nitrate plus nitrite and 0.1-
1mg L −1 nitrite are shown respectively in Figs. 9.1 and 9.2.
9.8 Phosphate
9.8.1 Spectrophotometric method
The Department of the Environment UK [12] has issued details of the
Spectrophotometric methods for the determination of orthophosphate in sewage effluents.
These methods are based on reaction with acid molybdate reagent to form a
phosphomolybdenum blue complex which is determined at 882nm. The first method has
a range of 0-0.40mg L −1 (after dilution of sample if required) and the second is mainly
designed for oligotrophic waters with phosphorus contents in the range 0-25µg L −1 . In
addition, the report discusses various methods for converting other forms of phosphorus
to orthophosphate, and the elimination of interference due to arsenic, based on the
reduction of arsenate to arsenite.
Bretscher and Gas [13] discuss reduction reagents for the Spectrophotometric