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


Aco Marine

As the only Australian Authorised Agent, Cullys proudly supplies ACO Marine products. ACO Marine is a leading supplier of Advanced Wastewater Management Solutions. IMO has adopted RESOLUTION MEPC 227(64) with revised guidelines for effluent standards and performance test procedures for sewage treatment plants. This new resolution is applicable to all sewage treatment plants installed on existing ships on or after 1 January 2016 and on new ships whose keels are laid on or after this date. Vessels of 400 GRT and above and ships of less than 400 GRT which are certified to carry more than 15 persons are required to comply with effect from that date. The ACO Maripur NF and Clarimar MF range of wastewater and sewage treatment plants are fully certified to the IMO MEPC 227(64) including the section 4.2 standards.