Biological Grease Traps

Biological activators

Unlike strong acid or caustic drain cleaners, ACO biological activator works safely, but more slowly. The biological activator can be used to unblock drains and can be used to replace aggressive caustic and acid cleaners. ACO biological activator works in two distinct ways on the FOG wastes that settle in the drainage pipework and grease trap system:

  • The activator introduces an enzyme that assists the natural biological process of breaking down long molecular chain FOG’s into a manageable solution to then be discharged safely into the drainage system.
  • The activator introduces other micro-organ-isms that actively feed on the FOG’s present in the solution. Biological activators will not digest solid residues from the food preparation process quickly, so the sediment basket requires periodic removal for cleaning to ensure efficient operation. ACO Clear biological activator is available in 5 or 20 litre containers.

ACO activator process

Depending upon the application, space availability and physical layout of the area, grease traps can be installed in parallel to share the hydraulic load as shown below:

FSS Grease Trap Technical data

Product dimensions

Model Ref Part No. A (mm) B (mm) C (mm) D (mm) Dry Weight (kg) Inlet dia (mm) Outlet dia (mm) Meals per day Flow rate l/s
FSS50 402614 610 520 440 185 35 110 110 0-50 2
FSS150 402615 760 660 540 285 48 110 110 50-150 4
FSS250 402616 930 660 540 285 65 110 110 150-250 6

Minimum clear distance above top of grease trap required for service access

Model Ref Total clear height requirement
for grease trap and sediment bucket removal
FSS150 755
FSS150 855
FSS250 855



Grease trap connection accessories

Model Ref Part No. Weight
FSS110/50/40 402707 0,9 Stainless steel 110mm to 50mm concentric male / male reducers. Must be ordered two pieces of reducer for one grease trap.
Depending upon installation, flow capacity limitations may be experienced.

FSP Grease Trap Technical dat

Product dimensions

Model Ref Part No. A (mm) B (mm) C (mm) D (mm) Dry Weight (Kg) Inlet dia (mm) Outlet dia (mm) Mealsper day Flow rate l/s
FSP50 49079 610 520 440 205 13 110 110 0-50 2
FSP150 49080 760 660 540 305 21 110 110 50-150 4
FSP250 49081 930 740 540 305 29 110 110 150-250 6


Minimum clear distance above top of grease trap required for service access

Model Ref Total clear height requirement for grease trap and sediment bucket removal
FSP150 755
FSP150 945
FSP250 945




Drawing FSP



Grease trap connection accessories

Model Ref Part No. Weight (kg) Description
FSP110/50 402707 0,9 Stainless steel 110mm to 50mm concentric male / male reducers. Must be ordered two pieces of reducer for one grease trap.Depending upon installation, flow capacity limitations may be experienced.

Dosing System Components


Features and benefits


Mains operated dosing unit (MODD) enables maximum operational efficiency of grease management system to be established quickly.

1. Microprocessor controlled dosing is programmed via convenient LCD display touch pad input panel for easy set up and programme modification where, for example, the operating environment changes due to seasonal variations.

2. Water resistant ABS Enclosure conforms to IP 66M for water and dust ingress prevention.

3. Dosing unit delivers 210ml per minute of biological activator, The unit is programmable to match user requirements and supplied complete with PVC tubing, tube connectors and operating instructions.

4. The unit incorporates battery time clock back up in case of power failure.

5. Efficiently allows up to two traps to be dosed by one dosing unit.

6. Precise delivery extends activator economy significantly over “manual dosing” methods.




















MODD Mains Operated Drain Dosing Unit

Description Part No. Pump spread
Power supply Weight
MODD 49025 210 220 / 240 W 1,5
BODD 49024 75 Battery type ‘D’ 1,0

Mounting frame

1. Manufactured in brushed grade 316 stainless steel.
2. Houses 5 litres of activator.
3. Versatile unit can be floor or wall mounted and has reversible door for right hand or left hand opening.
4. Pre-drilled apertures for mains feed and biological activator feed are supplied with blanking grommets.
5. Pre-drilled for wall mounting and dosing unit fixing.




Mounting frame

Description Part No. Weight
MF 402637 4,0



Biological Activator ACO Clear

1. Available in 5 or 20 litre containers.

2. ACO Clear biological activator introduces an enzyme that assists in breaking down fat, oil and grease deposits. Micro organisms actively feed on fats present in the drainage system or grease trap.

3. The activator can be applied manually, pouring a prescribed amount into the drain directly, or as recommended, via MODD or BODD units.

ACO Clear biological activator

Description Part No. Volume
ACO Clear 5 litres 49020 5 5
ACO Clear 20 litres 49022 20 20

Operation and Maintenance

Biological dosing regime

Table 1 – dosing times

Meals per
ACO Clear
Dosing times
50 50 0:14
100 100 1:20
150 150 2:00
200 200 2:40
250 250 3:20
300 300 4:00
350 350 4:40
400 400 5:20
500 500 6:40
600 600 8:00
700 700 9:20
800 800 10:40
900 900 12:00
1000 1000 13:20

Once installed, grease trap performance can be optimised by using the following procedure:

  • Establish total dosing time using table 1 opposite, referring to section “Grease Trap Sizing” to arrive at ‘meals per day’. Then convert the dosing times to seconds for the MODD or dosing unit (Table 1).
  • Establish hourly load on grease trap by considering daily average patterns for all facilities connected to the trap. Table 2 below gives an example of a sixteen hour period with a total capacity of 700 meals per day. Load percentages are shown in row A, row B multiplies load percentage by total dosing time for a MODD unit in order to arrive at the time to be entered into dosing unit programme at the start of that period. For example the unit should be programmed for 30 seconds running at 10am, one minute at 2pm and so on. Programme the unit accordingly.
  • Alternatively, where the load on the grease trap is variable, the dosing can be programmed at the end of the working period, preferably when the trap will not be used for a few hours.

Table 2 – dosing periods

D1 (mm) 7 -10 11 12 13 14 15 -17 18 19 20 21 22 23 Total
Percentage Load 15% 30% 20% 35% 100%
Dosing Time (s) 30 s 60 s 40 s 70 s 200 seconds
Minutes / seconds for programming time
Programming Time (min/s) 0:30 1:00 0:40 1:10 3:20 min/s
  • Shock dosing of the grease trap is an important element to start the biological process. To rapidly establish a biomass within the grease trap, dose the system with 3 or 4 days of maintenance activator to begin the process, either by pouring ACO Clear activator directly through a sink during a quiet period of the working day when there is no drainage activity or by running the dosing pump in priming mode as per the instructions supplied with the pump.

Operation during first 2 weeks

  • Inspect sediment basket daily at first to establish how often the bucket needs to be emptied. If the basket fills rapidly (less than 2 weeks, for example), then it is necessary to provide additional filtration upstream of the trap.

Note: Do not connect macerators to the trap.

  • Inspect the contents of the trap, increasing the dosing frequency and period if:
  • solidified grease is apparent on the surface and/or near the walls of the trap.
  • significant pools of oil are present on the surface
  • flow is impaired at the outlet pipe. This can be established by removing the access point cap.

Ongoing operation

  • Adjust dosing period and frequency for known seasonal variations – establish regular sediment basket removal regime.
  • Drain, clean and inspect the trap twice annually or at more regular intervals if silt build up at the base of the trap exceeds 5cm.

Trouble Shooting

Once ongoing operation is established ACO Biological Grease Traps should provide excellent service. Should problems become apparent, check the following variables.

  • MODD operation, electricity supply and programming.
  • Pipelines from dosing unit.
  • Load on trap in meals per day.
  • Dosing period and frequency.
  • Influent temperature and temperature within trap.

ACO LIPATOMAT Grease Separation Systems

Galley water must first pass through a Grease Separator unit before entering any membrane wastewater treatment plant as FOG´s can have an adverse effect on membrane performance and life expectancy.


  • Resistant to high temperatures
  • Hygienic material stainless steel AISI 316L
  • Rigid construction to withstand vessel movement and vibration
  • Resistant to organic solvents

Operating principles:

By locating the inlet and outlets slightly above the separation chamber the resulting small hydrostatic pressure makes Lipator and Lipatomat Grease Separators the only units of their kind whose separation efficiency is completely unaffected by vessels movement and vibration. The grease accumulates in the upper cone whilst the sediment drops to the lower cone. The heating element located in the upper cone ensures the grease remains liquid. Clean water passes freely and continuously through the grease separator. Accumulated sediment and grease is drained to independent collecting barrels fitted with level sensors which provide indication to the operator when they need to be emptied or replaced with exchange units. Grease and Sediment lift pumps as well as treated water lift station, can also be integrated into the system depending on installation requirements aboard the vessel.


  • small hydrostatic pressure with no free surface ensures that the separation process is unaffected by vessel movement and vibration.
  • the ACO patented internal design ensures flow velocity profiles through the separation chamber produce effective separation of grease and sediments even during periods of high demand.
  • grease and sediment removal is fully automated on the Lipatomat range (manual on the Lipator).
  • no operator contact with grease and sediments.
  • grease and sediment removal occurs without interrupting separator operation. No process down-time.
  • the separation technology ensures the greases and sediments are highly concentrated, only grease and sediments are disposed of with no surplus water; so often the case in conventional static systems.
  • effective heating and short residence time within the separation chamber ensures that no grease is deposited on the chamber walls. Internal maintenance and cleaning is therefore reduced to an annual inspection only.
 Type  NS  DN  Total Weight
 Largest single component
Height (mm)
 LIPATOR  2 100  130 680 x 1050 85
 4  100  320 1380 x 800 70
 7  150  320 1380 x 800 70
 10  150  580 1830 x 600 95
 15  200  595 1830 x 600 95
 LIPTOMAT  2  100  130 680 x 1050 85
 4  100  320 1380 x 800 70
 7  150  320 1380 x 800 70
 10  150  580 1830 x 600 95
 15  200  595 1830 x 600 95


Treated water lift station (option)

Challenger Cruise Ship: 2x Lipatomat NS 10 with Lift station

Clarimar MF Biological Sewage Treatment System

The ACO Clarimar MF biological sewage treatment plant incorporates ACO-MF filtration technology eliminating the requirement for settling and chlorination stages. Disinfection of the treated effluent is by in-line mounted UV lamp with no requirement for chemicals in any part of the ACO MF process.

The unique properties of the ACO ‘bio-sword’ allow operation with bio-mass concentrations in the activation chamber up to four times higher than those of conventional settling type sewage treatment plants. By operating at such high concentrations, a greatly reduced activation tank volume is achieved with a significant reduction in both the footprint and maintenance envelope requirement.

  • Type Approved to IMO MEPC 159(55) and MED Module B
  • Type Approved to IMO MEPC 227(64) and EC MED Module ‘B’
  • Self-cleaning ‘Bio-Sword’ with ACO-MF filtration technology dramatically exceeds all IMO requirements
  • Modular design concept
  • Lowest running costs of any sewage treatment plant on the market with minimal operator intervention
  • Unaffected by ship movement or vibration
  • The ACO Clarimar MF biological sewage treatment plant incorporates ACO-MF filtration technology eliminating the requirement for settling and chlorination stages.
  • No requirement for chemicals in any part of the ACO MF process.

Maripur NF Advanced Membrane Wastewater Treatment Systems

ACO Maripur NF – the highest standard of wastewater treatment plants for all marine applications.

  • Type Approved to IMO MEPC 227(64) including the section 4.2. and EC MED Module B by Bureau Veritas.
  • Compact process enabling limited space on ships and other marine structures to be used more efficiently.
  • The combination of a biological process with ultra-filtration
  • Simple automated operation requires minimal operator intervention and maintenance.
  • Designed to treat all wastewaters (black and grey water) in one reactor reducing the need for more costly, heavier and larger alternative solutions

Effluent values and its comparison with alternative standards

Caliform bacteria [n/100ml] Total suspended solids [mg/l] BOD5 [mg/l] COD [mg/l] Ntot [mg/l] Ptot [mg/l]
IMO MEPC.2(VI) 200 100 50
USCG 33CFR 159 PT1-300 200 150
USCG/Alaska 33CFR 159.309 20 30 30
IMO MEPC 159 (55) 100 35 (70 at sea) 25 125
IMO MEPC 227 (64) 100 35 25 125 20 1
ACO Maripur NF IMO MEPC 227 (64)  certified values 17,5 2,4 7,3 60 7,2 0,3

Process Description

The wastewater passes into bioreactor where biological purification of the sewage water by activated sludge, a mixture of a number of micro-organisms, occurs.

The process is an aerobic one where the oxygen for respiration of the activated sludge must be delivered into the tank. The blowers continuously deliver air into the system which is then distributed into the bioreactor via the aeration elements. This air, whilst serving to keep the filtration modules clean, also ensures delivery of the required amount of oxygen to the micro-organisms within the process. Simultaneously the volume of the bioreactor is mixed to ensure the contact of sewage water with the activated sludge.

The first stage is continuously re-circulated to the membrane compartment by means of the recirculation pump. This membrane compartment maintains a constant level by overflowing back into the first stage compartment.

This feature allows for much greater flexibility during maintenance where it is no longer necessary to discharge the entire contents of the tank for internal access. The purified water is separated from the activation sludge by means of filtration modules. The filtration modules create safe, physical, barriers for the activation sludge, bacteria and some viruses. As a result, the filtered water does not need to be further disinfected.

The purified water is removed under a small vacuum created on the clean side of the filtration elements by the progressive cavity filtrate/permeate discharge pump with frequency converter.

The filtration modules are continuously cleaned to prevent fouling by the activated sludge. This is achieved by locating the aeration elements uniformly under the filtration modules. An integrated cleaning chamber is included in the main stainless steel tank for periodic membrane cleaning (using the reversible permeate discharge pump).This applies to ACO Maripur NF 100+. Smaller sizes are cleaned by externally prepared cleaning agent.

The amount of sludge in the bioreactor increases during operation. The sludge concentration design value is in the range 10-12,000 mg/l. The sludge concentration is controlled by means of a timer function on the effluent pump after a pre-programmed number of running hours. If the biological loading per litre is equal for all compliment conditions this feature will control concentration very simply and effectively. The surplus sludge is discharged periodically from the second chamber by the recirculation pump.

During operation some foaming may occur on the surface level of the bioreactor. This is suppressed by the integrated antifoam dosing system.

Sizing and design

The ACO Maripur NF was developed as a modular system of seven nominal sizes from 25 – 250. ACO Marine also offer bespoke solutions to even the most specialist of requirements for such markets as Cruise, Military, Megayacht and Offshore.

ACO Maripur NF Designed hydraulic load Major Dimensions
m3/d LxWxH mm
25 5,75 2190x1560x1800
50 11,5 2650x2630x2160
75 17,25 2590x2350x2440
100 23 3610x2600x2280
150 34,5 4600x2430x2320
200 46 4840x2270x2730
250 57,5 6100x2310x2230