Page 1

Waste Water Treatment OPEC CAT391 - Mk II Series PATENT PENDING

Environmental solutions Fat, Oil & Grease Removal


OPEC Ltd is working in partnership with Envirogen Ireland Ltd to provide innovative and cost effective solutions for the removal of fat, oil and grease (FOG). Based on our well proven technology, we have developed a range of unique FOG recovery and separation systems for the waste water treatment industry. Our team of engineers has over 35 years experience in developing separation technology that is widely used across multiple industry sectors such as municipal, dairy, food and beverage, meat processing, poultry, bakery, green grocer, waste oil recycling, power generation, chemical and pharmaceutical. In many of these applications FOG is a much higher concentration and more troublesome. Our industrial range of systems are capable of a high volume recovery rate of up to 9000 l/hour and offer complete design flexibility which can be adapted to almost all applications within a Waste Water Treatment Works (WwTW). Our technology has not only been proven to reduce the cost of chemicals, waste disposal, energy, operator costs, but also to increase the overall process efficiency. This will make a major contribution toward ensuring compliance with the legal requirements such as EU Water Framework Directive (WFD).

Why is FOG a problem? The process Biological treatment process The idea behind all biological methods of wastewater treatment is to introduce contact with bacteria (cells), which feed on the organic materials in the wastewater, thereby reducing its BOD content. Typically, wastewater enters the treatment plant with a BOD higher than 200 mg/L, It needs to exit the treatment works to the local water course (river) with the BOD content less than 2-3 mg/L. Thus, needs to accomplish a 6- fold decrease in BOD. To achieve this reduction, effective dilution of the BOD is required within the primary settling process before entering the biological treatment component. With the introduction of additional and higher than usual FOG wastes into a treatment plant will increase the BOD loading which will place the primary process under significant strain and will result in additional downstream process equipment and operational problems. Typical examples would be a higher than usual energy demand and chemical use.

Surface FOG on a clarifier

Surface scum in an aeration lane

Scum entering a micro strainer

WWTW’s do not have a specific or dedicated FOG receiving facility. They generally accept FOG as a liquid waste into the liquid treatment process with the incoming flow (indigenous) or by road tanker (import) where it is separated at the primary stage as FOG or scum which is then mixed with the primary sludge. Further downstream, the scum is usually removed using the same method from the secondary stage and is usually then returned to the primary sedimentation tank for removal from site. To achieve this FOG and scum removal within the primary or secondary stages ‘clarifier’, usually involves scrapers, traps and transfer points (scum box) within the primary and secondary settlement tanks. FOG which is not captured at the primary stage of the process will be lost to the secondary treatment process, cling to the walls of basins, channels, or piping, form grease balls, etc. The increased loading (BOD) will then impact negatively on the biological process and equipment further downstream. The waste sludge materials which are collected and then removed from the waste water treatment works are transported for final disposal. Two of the most common methods used for disposal are incineration or anaerobic digestion. However, as a further knock on effect, the manner in which these sludges are processed or pre-conditioned can also impact on the performance of the anaerobic digesters or incinerator and so must be managed properly. It is accepted that there are many operational issues and hidden costs directly associated with FOG and scum and It can often be very difficult to put an accurate figure on these due to the range of variables and factors involved. The only way to deal with all of these issues effectively, is to remove the materials as close to the front end of the treatment works as possible, thus preventing the majority of the downstream issues and costs. Historically the separation of the FOG and scum from the waste streams has been difficult as up until now there has never been an effective means for extraction.

Hidden cost of FOG What is the true cost to your business?


Typical examples of problems experienced at the final waste disposal stage

Incineration 

Can experience flashback - non-consistent feed stock

Air emission exceedances

Dewatering issues which results in a back up of sludge intake

Requires excessive operator intervention ‘on hand’

Excessive downtime for maintenance

Anaerobic Digester 

Grit accumulation in digesters

‘Stuck’ digesters (curtailed methanogenesis)

Clogging of gas collection and handling systems

Fat, Oil & Grease Removal OPEC Equipment Trials & Results Client:

Northern Ireland Water


Strabane, Waste Water Treatment Works


October 2011

Systems were monitored for their ability to remove or reduce FOG, BOD, SS from the waste stream within the Niwater, Waste Water Treatment Works.

Automatic samplers were positioned at two monitoring locations to offer a ‘before and after’ test result.

The first point was at the inlet to the works which measured the incoming flow and the second point was to measure the effluent from the primary clarifier.

Materials recovered between these two points would be recorded as a reduction in mg/L and also as a % reduction

Primary clarifier

FOG/scum transfer point

Sludge with high FOG content

Trial results with OPEC FOG equipment installed Tested

A (inlet)

B (effluent from clarifier)

% Reduction


159.75 mg/L 02

66.75 mg/L 02

58.2 %


20.75 mg/L

6.25 mg/L



203.5 mg/L

74.5 mg/L


The reductions illustrated will have a significant positive impact upon the downstream process and equipment.

Fat, Oil & Grease Removal The OPEC CAT391 MKII System

One system to cover most applications within a Waste Water Treatment Works. A unique and compact plug and play design.

 The OPEC range of equipment are well proven FOG and scum recovery & separation systems  No chemicals or coagulants needed Fats Insoluble Chemicals  System also successfully removes the following:  






Bacterial blooms


Petroleum Products

FOG System benefits 

Remove up to 70% of fat, oil & grease (FOG)

Reduces suspended solids by up to 64%

Reduces BOD loading by up to 58%

Extremely low energy consumption

Low maintenance components

Low cost consumable components - 5 year spares program

Contributes toward a reduction in odour issues

Reduce overall operational costs

Reduce overall chemical requirements

Removes scum, foam bulking and de-water for blending to FOG and sludge

Reduces tanker requirements as dewatering or separation at source

Will easily retrofit to existing equipment offering significant capital cost reductions

No process upset during installation of standard systems

Where to install the FOG systems Typical waste water treatment process

Typical Application Guide 1.

Inlet mechanical screen & grit removal


Inter stage (PS) Pumping Station


Storm Tanks


(PST) Primary Clarifier


Grease Tank


Aeration system


(SST) Secondary Clarifiers


Scum Tank


Sludge Mixing tanks

10. Balance Tanks 11. Return Liquor Pumping Station 12. Site Effluent Discharge

Application and installation Northern Ireland Water - Coalisland WwTW Envirogen (Ireland) Ltd proposed to supply and install a suitable OPEC system as a retrofit to the Return Liquor Pumping Station Sump to remove Fats, Oils, Grease & Scum which separate from suspension within the pump sump. A blanket of scum forms on the surface of the water. The incoming directional flow was upgraded to a down pipe to replace the horizontal pipe as illustrated. This acts as a diffuser thus allowing the materials to settle out of suspension more effectively. The materials are then absorbed by the fibrous belt and transferred by the motorised recovery head unit to the FOG system buffer tank which is controlled by a level float switch. When the buffer tank is full, the recovered material is then pumped to the main scum storage tank by the integrated transfer pump for removal by tanker. This is an automated system and is operated as a continuous cycle using the level controls.

OPEC CAT391 FOG recovery and separation system

The objective was to maximise extraction of free floating solids, Fat, Oil & Grease and Scum from the Return Liquor Pumping Station Sump and remove it from the process. The system impacted upon the level of FOG within the mixed liquors with a reduction of 50 mg/L +. We can also provide further dewatering at source minimising the volume of water retained within the scum storage tank. Follow the link below to watch the system in operation. Pump sump

Niwater Coalisland WwTW, Return Liquor Pumping Station

Application and Installation Niwater, Strabane WwTW - Grease Removal Purpose built grease and scum tank After the successful installation of the Coalisland Scum system, Northern Ireland Water have decided on a second system to be installed at the Strabane Waste Water Treatment Works. This will be a purpose built FOG tank application which will allow for the installed OPEC CAT391 FOG removal system to be fully operational on the same day as arrival to site. With the removal of the fat, oil and grease from the waste stream at the primary stage, this will reduce the downstream process and equipment issues experienced at this site.

These typically include the following: 

Belt press dewatering equipment

Transfer equipment

Clogging of pipework

Niwater Strabane WwTW, Grease Removal From Primary Tanks

System Support Information and documentation QR Code tagging of equipment allows for web interface access. Web interface contains all relative information about the installed equipment and provides client with the following for each piece of equipment that has been included on our Planned Maintenance Register (PMR):             

User manual Specification Spares list Site and application drawings GA equipment Installation Images Video clip Details of planned maintenance inspections, commissioning certificates inspection reports Data sheets Risk assessment Method statement

Envirogen Ireland Ltd

OPEC Limited

83 Upper Dunmurry Lane

OPEC House, Martin Street,

Belfast BT17 0QD

Birstall, Batley West Yorkshire WF17 9PJ

m: +44 (0) 7507 702772

p: +44 (0) 1924 442701


f: +44 (0) 1924 471925


e: w:

OPEC Grease Removal Waste Water Treatment  
Read more
Read more
Similar to
Popular now
Just for you