FAQs

OxyMem has deployed a broad number of installations (at varying scales) across the globe. By way of example MABR has been trialed and/or installed in the following countries ; UK, Ireland, Canada, Sweden, Spain, Saudi Arabia, Brazil, China, Denmark, New Zealand and Japan.

OxyMem membranes have been operated on a UK client's site from 2011 to 2018, at which time the client indexed to full scale commercial units. 

The membranes did not deteriorate in the municipal wastewater and were never removed, chemically cleaned or mechanically scrubbed at any time.

Anticipated life expectancy of our membranes in municipal wastewaters is 20 years.  Best to trial materials first for harsh/industrial applications 

The membranes in the OxyMem MABR do not contain any pores and due to the structural integrity of the membranes the lumen does not experience the external hydrostatic pressure.

Similar to a swimming snorkel, the air in the membrane fibres does not need to overcome hydro-static head when in operation, as compared to conventional aeration systems which need to "push" against a water depth to create a bubble. This allows the system to operate as much lower pressures and thus provide significant energy savings.  Typical operating pressure is ~400mbar at the module.

Any that are biologically degradable.

OxyMem has a complete range of solutions for you to try MABR.

We have lab scale offerings, mini MABRs for field use, and large-scale packaged systems for onsite demonstration. 

OxyMem manufactures its own membranes.

They are made from dense PDMS (Silicone) and have no pores. The external diameter is 510µm and the internal diameter is 300µm. Oxygen transfers across the membrane wall via diffusion, dependent on a concentration gradient. Oxygen travels from inside the micro bore tubes (where oxygen concentration is greatest), across the wall and into the biofilm (low in oxygen) where is consumed.

PDMS membranes are ideal for gas transferring application as they have no pores. They have high gas permeability, are easy to manufacture and are robust.

The MABR does not rely on bubbles to deliver oxygen.

It uses hollow fibre, gas permeable membranes, to support a fixed film ecosystem for the biology which allows for direct delivery of oxygen to the micro-organisms.

OxyMem MABR will perform well in any environment where these challenges arise:     

- Energy neutrality/ low process emissions and/or sustainability is a goal     
- Existing treatment system is overloaded    
- Nitrification is a challenge    
- Asset can no longer meet consent    
- Existing asset (tank) needs to be upgraded    
- Footprint is limited on site

Absolutely, OxyMem solves energy intensive wastewater treatment with an innovative ‘Drop in’ or ‘IFAS style’ deployment for wastewater aeration. OxyMem MABR can compliment existing treatment systems by delivering up to 50% additional biological capacity in an existing aeration basin (without emptying the tank!). It can also be used for replacing a legacy aeration system entirely.

Each module (modular unit) has the following specification:

Material                                        Stainless Steel 
Length                                            2.1 m 
Width                                              1.05 m 
Height                                             2.1 m 
Weight (Dry)                                   950 kg
Volume                                             4.6 m³ 
Membrane Surface Area             <2200 m²
Specific Surface Area                   478 m²/m³

By installing the reactors in series more effective treatment and use of the reactors may be achieved. Also, it allows for better management of the air being supplied (similar to long activated sludge tanks where more air is supplied to the beginning of the tank).

There will not be any significant change in CAPEX but there may be a significant increase in performance.

OxyMem systems are sized on process load, not hydraulic flow, although flow is considered.

Freeboard exists below each module and the OxyMem units are usually deployed to ensure zero surcharging of a treatment system should there be a power outage or similar for a period.

Scouring can be used to minimise biofilm growth within a module.

This depends on the effluent quality required. If it is a standalone OxyMem MABR system we typically design with three reactors in series to achieve N-NH4 concentrations of less than 1mg/l.

If the OxyMem system is being deployed as an additional aeration capacity, then it can be added to any aerobic part of the current treatment process. Our engineering team will work with you to determine an ideal location for product.

This will depend on many variables as with any biological system, Temperature, nature of wastewater, pH but typically 14-60 days.

This depends on the nature of the wastewater to be treated and what quality the wastewater must be treated to.

The determining quantity is the rate of treatment per m² of membrane surface area.

 It is important to note that unlike other fixed film applications, the OxyMem carrier (membrane) is delivering the oxygen which means the biofilm is <100% active and available for treatment.

Another important aspect is the amount of oxygen transferred per m² of surface area, the higher this is the more treatment that can be affected.

Biofilm maintenance and control can be assisted and accomplished automatically by an optional "biofilm control" system. 

Since the membrane is dense and has no pores, no special cleaning is required.  Membranes are not subject to drying; they can be stored indoors, in dry conditions as long as they are protected from sunlight and physical damage.

Modules should be cleaned well prior to storage if they have already been in operational use.

As the load increases the oxygen supplied can be increased by increasing the airflow through the membranes. This results in an increase in overall oxygen concentration within the membranes resulting in increased performance instantaneously.

Alternatively in systems where there is a large variation in aeration demand, the Oxygen transfer rate could possibly be increased by increasing the % of oxygen in the air supplied . This may result in more kg of oxygen being transferred for a given membrane surface area.

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OxyMem systems use a patented biofilm measurement technique, which determines an effective biofilm thickness on the membrane. When the control system determines that the biofilm has grown too thick for the treatment process required, the system takes steps to automatically remove the excess biofilm. 

The frequency of cleaning is dependent on the growth rate of the biofilm and the nature of the treatment process, but can vary from once a day to ~10 times per day if biofilm is growing fast (eg. Industrial loads). 

Self cleaning will typically last 1-5 mins in duration, so the energy burden us negligible.

 Discover how it works

Sludge is allowed to settle in the bottom of the tank in our OxyFILM arrangement.  Removal of settled sludge from tanks is via well established engineering practices. Removal of sludge is not OxyMem's scope, though we can indeed assist with this.

Sludge is very settable with a concentration of up to 10g/l. In a Retrofit installation, the excess biofilm would form part of the MLSS and need not be removed close to the MABR unit (i.e. MLSS would travel downstream and follow existing process - no changes are required to the sludge removal system).

The plant would need a sludge removal system built into the base of the tank, or operate with a sludge blanket and remove via pump or gravity head etc.  Well established engineering practices can be used. 

The system has been tested up to 30°C.

We can have the temperature up to 50°-69°C in summer, or for industrial water when the wastewater contains a high concentration of food residues.

If the temperature increases OTE may increase and activity and metabolism of bacteria changes.

Above 40°C, "typical" municipal wastewater bacteria stop working. ie. Biology will be affected before the MABR unit materials are affected by temperature.

Where installed, the frequency of biofilm measurement can be adjusted to site requirements. 

A smart controller can be set up to maintain a desired biofilm thickness, varying rates of measurement and control based on historical data/trend data.

Discover how it works

For OxyFAS applications (where MLSS is present) it is best to ensure a homogeneous mix around the modules.

For OxyFILM, the flow to the unit may be sent to a splitter box which will divide the flow equally between the installed process trains.

The Sludge yield in an OxyMem system is 0.1 - 0.15kgTSS per kgs COD removed.

OxyMem membranes have been operated on a UK client's site from 2011 to 2018, at which time the client indexed to full scale commercial units. 

The membranes did not deteriorate in the municipal wastewater and were never removed, chemically cleaned or mechanically scrubbed at any time.

Anticipated life expectancy of our membranes in municipal wastewaters is 20 years.  Best to trial materials first for harsh/industrial applications 

Current OxyMem MABR membranes deliver on average 12g O2 per m² of surface area of membrane, when operating on ambient air.

Using enriched air (containing more than 21% oxygen) to the same MABR module may deliver more oxygen to the system, giving you a lot more treatment capacity for a much lower capital cost. It may not make economic sense to procure more oxygen at times; OxyMem standard approach is to use ambient air for process gas.

Some phosphate removal does occur, but this is only the phosphate required for the biofilm growth. 

Where OxyMem can assist clients with Phosphorous removal is where units can be deployed to intensify an existing system and free up tank volume so that an anaerobic phase can be implemented (BioP).

Currently without trying to achieve denitrification over 50% of the oxidised Ammonia (Nitrate) is removed via denitrification. By limiting oxygen delivery, up to 90% denitrification may be achieved.

Learn more about our simultaneous nitrification and denitrification

Find more information. Read our Case Study.

Standard post-primary municipal wastewater concentrations of FOG usually attaches to the outside of the MABR, biofilm where it is broken down.

The process may require extra oxygen to break down the FOG and reduce the volume of wastewater that can be treated. Best to discuss FOGs with our engineers for an optimum solution.

In line with good engineering practice, it would be preferable to remove FOG in advance of secondary treatment, where possible.

This has to do with mixing intensity and concentration in the reactor; ammonia diffuses faster into the biofilm as it is a smaller molecule, but this is classic mass transfer.

Learn More about mass transfers:

Yes. Each module has an integrated mixing system to move water over the surface of the membranes and improve diffusion of nutrients into the biofilm.  This is our Airlift System, which promotes movement of bulk water through the module 24 hours a day.

As biomass inventory is always at hand and attached to an oxygen source (membrane lumen), the MABR is ideal for tackling process load variations.  

Some clients have seen that the OxyMem system is perfect for locating upstream (to react fast and help remove or level out peaks) and this then allows their downstream biological processes to happily cope with average loads only.

The biofilm in OxyMem MABR is the same as any other biofilm, well attached and difficult to remove (compared to suspended biomasses which are susceptible to washout etc). 

But the MABR biofilm is more robust than usual attached growth biofilms in that, if there is a shock load of acid in the influent, then this may kill off the outer layers of the biofilm, but will take more time and higher concentrations to reach the innermost layers (nitrifying bacteria layer).  The MABR inner layers are protected.

Once the outer layers are sloughed off with scouring, the biofilm can regrow again quickly. Of note, the inner layers of the MABR (nitrifiers) may continue working where standard MBBR or IFAS nitrifying layers (outermost layers) could be rendered useless.

As OxyMem is a biofilm system there is no risk of biomass washout from the reactor.

If there is a higher flow rate then the wastewater will have less time in contact with the membranes and the biofilm (reduced HRT) and it may not be treated as effectively as at normal flow. During stormwater events, the wastewater is typically at lower concentrations and therefore a high percentage of treatment may not be required anyway.

At low flow rates, OxyMem MABR will achieve an improved performance as there is a much higher HRT.

OxyMem systems are designed based on anticipated process loads noted at design phase, not hydraulic flows. We can accommodate high and low volume flows; please discuss all with our engineers.

With OxyFILM (pure biofilm arrangement) we do not typically design with MLSS in mind. This is because we are growing a biofilm on the membranes. A standalone OxyFILM MABR system may have an operating TSS of less than 100mg/l. Where necessary we may consider designing for MABR phase discharges below 35mg/l TSS.

In OxyFAS (IFAS MABR, with MLSS present)  we typically design to operate with MLSS concentrations of 2000- 4000mg/l on conventional plants, but can operate in <8000mg/l in intensified systems.

Depending on the application and wastewater characteristics etc, a 4.6m3 OxyMem MABR unit may contain the equivalent of 6-16000 mg/l TSS.