These processes allow to reduce the sludge production and to produce fuel gas. The Bench Top Anaerobic Digester is designed as a comprehensive study facility of water treatment process involving bacteria in absence of air. The unit is supplied with manuals that describe each component of the system, installation and utilization procedures and give many exercises.
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The anaerobic digester comprises two 5 litre upward-flow packed bed reactors with feed rate and temperature control facilities to allow steady, continuous operation at up to seven litres per day over periods of many days.
The temperature of each reactor is controlled by an electric heating mat wrapped around the external wall. The temperature distribution within each reactor is maintained to ±0.5°C. Reactor temperatures may be separately set at any desired value in the range ambient to 55°C.
The reactors may be operated in series or parallel. The flow rates to the vessels are set and controlled by calibrated peristaltic pumps. A buffer vessel between the reactors permits discharge of excess flow from the first reactor when the second reactor is operated in series but at a lower flow rate.
Liquid and gas sampling points are located at all strategic points around the reactors. Non-return valves and liquid seal syphon breaks are included in the process pipework to ensure each reactor operates at a constant volume without the ingress of air or the danger of accidental syphonic action.
The equipment is mounted on a vacuum formed plastic base with an integral drain channel to cope with spillages and wash down.
The gas off-take from each reactor is taken to a volumetrically calibrated collector vessel operating by water displacement. The collected gas can be exhausted from the vessel and the volume re-filled with water during a run without breaking the liquid seal. A constant head, liquid seal device ensures that the gas pressure in the reactor is maintained at a constant value throughout the test run.
A synthetically prepared waste water may be used to gain a working knowledge of the operational parameters and purification efficiencies. The Bench Top Aerobic Digester is designed as a comprehensive study facility of biological water treatment process by means of the continuous activated sludge. The unit is supplied with manuals that describe each component of the system, installation and utilization procedures and give many exercises.
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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 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.
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.
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.
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 +35deg C may be selected, the best conditions being a few degrees above the diurnal maximum in the user's laboratory.
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.
