The new patent variation allows the incorporation of a crossflow membrane into the Vairox system, enabling filtration to be achieved at the same time as oxygenation, aeration and mixing, without requiring additional energy.
Process
The wastewater treatment occurs in bioreactor tanks using pure oxygen as the main oxygen source.
The process is able to operate at higher biomass concentrations and at higher dissolved oxygen concentrations than air-based MBRs or conventional activated sludge plants. Consequently, faster COD oxidation takes place and less COD is converted to surplus biomass which would need removing off site.
With far less undissolved gases leaving the surface, the tendency for foaming is minimal and there is far less heat lost to atmosphere. The resulting warmer operating temperature leads to a more active biomass.
Mixed liquor of suspended solids (MLSS) concentrations can be up to 30,000mg/l without adverse effect on flux rates. The warmer operating temperatures and lower viscosity counter the increase in solids concentration; this is pumped through the membrane banks which are external to the bioreactor.
The biomass return to the bioreactor is used for the dissolution of oxygen introduced by venturis and controlled by DO probes. The pH is also continuously measured and controls the addition of air in order to strip out dissolved CO2 and maintain neutral or indeed any desired operating pH regime.
Bioreactor tank
Here, the wastewater treatment occurs in bioreactor tanks using both pure oxygen and air.
It is able to operate at higher biomass concentrations than air-based MBRs or conventional activated-sludge plants. This means bioreactor sizes are between 25% and 50% of conventional plant size, hence a very small footprint.
pH control
Precise control of both dissolved oxygen levels and pH enables the biological process to be operated at performance levels far above conventional air-based systems.
Operating at higher dissolved oxygen levels than economically achievable with air enables high rates of biomass metabolism i.e. more COD oxidation and minimal sludge growth.
A single process system provides oxygenation, aeration, mixing and membrane separation for minimum energy requirements and minimum of pumped systems.
Water quality
Exceptional final effluent water quality from UF membranes is suitable for feed to Reverse Osmosis plants and enables a high degree of water recycling.
High strength wastewater
Higher strength industrial wastewaters from food, beverage, pharmaceutical or chemical industries are most suitable for the Oxy-MBR process.
Permeate quality is excellent, with BOD and suspended solids figures of <5 mg/l readily achievable. This means river discharge is certainly an option; water recycling to potable water quality by the inclusion of a reverse osmosis stage is easily engineered.
The resulting plants are compact, having comparatively low energy requirements, low waste sludge production and low maintenance.
Customer trials
BOC has a newly-built containerised pilot plant, complete with a small laboratory, enabling detailed trials to be undertaken at customer sites.
Trial results form the basis of process design and performance guarantees.
To build these plants, BOC worked with Aquabio who have unrivalled expertise in designing and building MBRs.
A full turnkey service is available from trial work to building, training and even remote monitoring and operational assistance.
For more information about AXENIS™ oxy-air membrane bioreactor email us
