Armfield Engineering Education
WATER TREATMENT PROCESSES
W11 Aerobic Digester - Issue 6
The continuous activated sludge process has been successfully employed in public health engineering installations for nearly a century.
The Armfield bench top Aerobic Digester is designed as a comprehensive study facility of this biological water treatment process.
A synthetically prepared waste water may be used to gain a working knowledge
of the operational parameters and purification efficiencies.
ORDERING SPECIFICATION
• A 10 litre bench mounted aerobic reactor, complete with peristaltic feed pump, air compressor and temperature control system.
• Dissolved oxygen and pH probes and meters are included.
• The reactor consists of a cylindrical porous liner held in position with sealing rings between the lid and the base to facilitate removal for cleaning and replacement.
• Suspended solids are thus held within the reactor volume, whilst treated water permeates through the porous liner into an outer annular exit chamber.
• The water level is maintained by an adjustable constant head overflow device.
• This digester system is designed to operate safely and reproducibly for periods of many days.
• The equipment is mounted on a moulded plastic base, equipped with an internally moulded drain channel, designed to cope with spillages and wash-down water.
Practical Training Exercises
> Acclimation of a completely mixed biological reactor
> Measurement of COD and MLSS changes as criteria of performance
> Establishing the stoichiometry and kinetics of aerobic biological processes
> Gas/liquid mass transfer
> Residence time distributions
> 100% scale-up to industrial requirements
> Studying the effect on effluent quality of:-
• inflow substrate concentration ('loading rate')
• liquid flow rate and reactor volume ('detention time')
• air flow rate
• temperature
• pH stability
• nutrient deficiency
Description
The equipment consists of a ten litre reactor vessel mounted on a vacuum formed plastic base, with a liquid feed pump, air supply and instrumentation for monitoring and controlling the process.
The cylindrical wall of the reactor is made from a porous plastic material to retain the suspended solids while allowing treated water to pass through to the outer, annular exit chamber. This design allows the essential features of the aerobic treatment process to be studied without the distractions of having to settle the solids adequately enough for external recycle - a well known laboratory problem.
The porous liner is removable for cleaning, and a spare liner is supplied.
Waste water is drawn from a floor-standing feed tank (not supplied) by a DC motor driven peristaltic pump. Rotational speed and thus flow rate, are accurately set by a ten-turn potentiometer. The pump delivers the feed to the reactor vessel through a transparent lid.
Air is supplied at a measured rate by a small compressor, and discharges
into the base of the reactor via a spider-arm dispenser, designed to prevent
blockages as well as to produce sufficient bubbling for stirring and reaction.
The liquid level in the reactor is maintained at a constant value of 5-10
litres, by an adjustable overflow device connected to the outer annular
chamber of the vessel. Discharge is by gravity to a floor-standing product
tank (not supplied).
The reactor temperature is maintained by a 3-term controller which varies power to an immersion heater within the vessel. Any temperature between ambient and +35°C may be selected, the best conditions being a few degrees above the diurnal maximum in the user's laboratory.
Dissolved oxygen and pH probes and meters are included.
The reactor lid contains a gas exit port, suitable for sampling the gases for subsequent analysis.
Technical Details
Feed pump: 24V DC, peristaltic, 0-30rpm corresponding to 0-40 litres/day
Air compressor: 240V /120V, 0-3.0 litres/minute (STP)
Reactor vessel: 10 litres maximum capacity
pH meter: Range: 0.00 to 14.00
Dissolved oxygen meter: Range: 0-100% saturation
Resolution: 2%
Reactor heater: Toughened glass, electrical immersion 200W
Temperature controller: 3-term PID
Temperature limit set at 35°C
Optional Accessories
CW -16 - chilled water circulator. For simulation of low ambient temperature conditions.
Essential Accessories
(not supplied by Armfield)
Plastic feed and product tanks - capacity typically 30-50 litres. Floor
standing
Requirements
Electrical supply:
W11-A: 220/240V/1ph/50Hz
W11-B: 120V/1ph/60Hz
W11-G: 220/240V/1ph/60Hz
Shipping specification
Volume 0.5m3
Gross weight: 40kg
Overall dimensions
Height: 0.5m
Width: 1.0m
Depth: 0.5m
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DATA SHEET
PRODUCT CATEGORY:
Engineering Education
