Sludge Blanket Measurement
Avocet monitors the sedimentation and scum accumulation in
remote settlement tanks and clarifiers in water treatment
works, waste water reclamation works and factories with treatment
The Avocet is particularly suited for identifying auto-desludging
and overspill alarm signals and for monitoring the general
biological health of thick sludge blankets.
Designed to operate in most if not all aspects of sludge level
monitoring the Avocet system comprises three components.
The outstation consists of an ultrasonic sensor and a local
programmable instrumentation unit, which provides a histogram
display of the sedimentation layer.
Telemetry Link (optional)
The telemetry link enables the local data to be transmitted
to a base station
up to 2km away.
Base Station – pc based (optional)
The base station will centrally monitor and display the information
from multiple outstations via the telemetry link.
Principle of Operation
ultrasonic sensor is immersed just below the surface of the
effluent pointing directly to the bottom of the tank. The
Avocet 2000 uses time of flight echo processing to determine
the distribution of solid particles scattered throughout the
settling effluent. Scum formation is detected by the attenuation,
backscatter and reflection time of the ultrasonic signal as
it passes through the sedimentation.
This is then displayed in a histogram form on the local display.
The Avocet 2000 has 2 integral programmable relays for alarm
Typically the outstation is fixed to the handrail of the scrapper
gantry on the settlement tank. The instrument panel displays
the sediment relative density throughout the tank. During
normal operation the signal strength will vary due to many
factors but one these will be the build up of solids on the
sensor. To overcome this an air purge facility is installed
and at across the sensor which removes debris and reduces
the need for continual maintenance.
The base station comprises of a pc based monitoring system.
This enables each outstation to be consecutively polled to
display real time information of the individual settlement
tanks. Alarm states can be programmed for sensor failure/scum
detection and high level sedimentation. A data storage facility
will enable the operator to observe the sedimentation performance
over any historical period.
|| 7.0 metres
||25mm @ 5 metres
||-20 to +60°C for the internal temperature
of the outstation
||110 VAC, 240 VAC
||2 x single pole change over contacts;
4 –20 mA
||Site specific ranges up to 2km can be
specified dependent of topography.
All brackets and sensor mounting requirements have been designed
to be clamped onto the handrails or similar structure on the
scrapper. The compressor for the air purge is installed in
the same support structure and forms an integral part of the
measuring outstation package.