On-line measurement of anions - Determination of Anions in Natural and Treated Waters - page 766

Chapter 17
On-line measurement of anions

On-line process analysers are used throughout the water industry in applications such as
the monitoring of rainwater, water in distribution systems, potable water and effluent and
sewage treatment processes. A wide range of instrumentation is available from various
suppliers. Some instruments determine single parameters and some are multi-parameter
instruments. It is convenient to discuss these under separate headings.
Industrial scale on-line instrumentation supplied by Kent Instrumentation Ltd. for the
determination of anions (chloride, nitrate, phosphate, ammonia, fluoride and silica) in
various types of water are reviewed in Table 17.1. All of these instruments are
microcomputer-based and, with the exception of silica, have autocalibration built-in.
Generally the sensitivities are adequate for the requirements of the water industry.
In addition Iskra produce an industrial-scale cyanide analyser (model MA 540). This is
a sensitive instrument based on the flow electrode measuring cyanide at concentrations
down to 1µg L −1 and, as such, might be of interest in the water industry for cyanide
monitoring of effluents or reservoir water. PHOX also supply a digital ammonia
monitoring module with auto-clearing.
Some multi-parameter instruments are reviewed in Table 17.2. The Kent System 19
has been specifically designed for use in the water industry. In these systems continuous
single-point and multi-stream analytical instruments gather data for data logging or
transmission by telemetry to a control station. Control features of this component are the
model 7975 multi-parameter water quality monitor which can analyse up to six streams
simultaneously and the 8080 series microprocessor. In abstraction from rivers, reservoirs
or boreholes, the instrumentation and systems allow raw water to be monitored
continuously before and during pumping to the water treatment plant.
Additionally, mobile or permanent water-quality monitoring stations can be supplied to
check environmental conditions and either log the data locally or transmit it by telemetry
to a central station. The data thus

Table 17.1 Single-parameter microprocessor-controlled on-line industrial anion and
cation analysers from Kent Instrumentation Ltd.

Parameter Samples
type

Model
No.

Ranges Accuracy Description

Concn.
µg L −1

Flow Temp.
(°C)

Pressure
(lb in −2 )

Anions