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Introduction

Construction

The Evac MBR is a compact design that includes an

equalizing tank, a membrane tank and an effl uent tank. It is

delivered as a complete, factory tested unit with all of the

components mounted on a single skid. The Evac MBR’s

treatment process is fully automated, but may be controlled

through a PLC.

The Structure of the Submerged
Membrane Unit

The membrane unit consists of a membrane case and a

diffuser case. The membrane case accommodates multiple

membrane cartridges, which are connected to a manifold with

transparent tubes. The diffuser case contains a diffuser pipe.

The Structure of the Membrane Cartridge

The membrane sheets are ultrasonically welded on both

surfaces of the membrane panel. Evac uses high quality

membranes that are made from chlorinated polyethylene,

with a nominal pore size of 0.4μm. Once the mixed liquid fl ow

has permeated through the membrane sheets and internal

spacers, it comes out as treated water through the nozzle.

Evac has more then 30 years of experience in the design,

manufacture and marketing of wastewater collection and

treatment equipment for the shipbuilding industry.

Evac offers a complete range of products for wastewater

collection and treatment:

Sewage treatment plants

•

Vacuum collecting units

•

Vacuum toilets

•

With a proven track record of reliable deliveries, worldwide

support and tested effl uent results, Evac’s vacuum

collecting units and treatment plants are the natural choice

for shipbuilders. Since conventional equipment no longer

meet the revised effl uent standards and performance tests

for sewage treatment plants as a result of the new IMO

MARPOL resolution MEPC.159(55), Evac has developed

a new wastewater treatment technology – the Evac

Membrane Bioreactor (MBR).

Regulations

The Evac MBR is certifi ed to fulfi ll the requirements

introduced by the new IMO MARPOL resolution

MEPC.159(55) and all other existing regulations. This

enables vessels equipped with the Evac MBR to operate all

around the world – including environmentally sensitive areas.

The IMO testing procedure outlined in MEPC.159(55)

requires the infl uent concentration of total suspended

solids to be at least 500mg/l. In order to ensure reliable and

smooth operation, even in demanding conditions, the Evac

MBR has been tested with an infl uent concentration of over

2100mg/l. This makes the Evac MBR the ideal solution for

treating black water collected by vacuum.

Advantages

Extremely low running costs and energy consumption

•

Resistant to clogging and fouling of the membrane

•

Expected lifetime of membranes over 10 years

•

Small footprint

•

Low sludge yield

•

Disinfection not required

•

Available in stainless steel

•

Available also as a combined treatment plant with

•

integrated vacuum system

Filtration with Air Scouring

Aeration from the bottom of unit creates

upward fl ow of mixed liquid in between

membrane cartridges. The upward fl ow

prevents the membrane surface from fouling.

Permeate

Water

Mixed Liquid Flow

Discharge parameters

IMO MARPOL

MEPC 159 (55)

Navy NIAG

2015 Target

Alaska

Evac MBR test results

TSS, mg/l

150

< 5

BOD5, mg/l

< 5

COD, mg/l

125

< 30

Faecal/Thermotolerant coliforms,

cfu/100 ml

100 thermotolerant

coliforms

100

below detection limits

Residual Chlorine, mg/l

< 0.5 mg/l

0.01

no disinfection

6.0–8.5

6.5–8.5

within limits

Evac MBR -
principles of operation

The Structure of the Submerged Membrane Unit

The Structure of the Membrane Cartridge

The Evac MBR is an advanced wastewater treatment

plant that treats wastewater to meet all current and future

standards.

Wastewater Collecting, Equalizing and Mixing

Knowledge of the ship’s operating profi le and the source,

the amount, and the collection methods of the wastewater

streams is the key in optimizing the most effi cient treatment

process. Even though wastewater is produced unevenly

throughout the day, the best results are achieved by

ensuring a constant feed to the treatment plant.

Pre-treatment

While heavy objects are separated by sedimentation, other

foreign objects (e.g. towels, rubber gloves, rings, etc.) have

to be removed from the wastewater before the treatment

process. Any remaining waste is macerated.

Biological Process

The biological wastewater treatment process converts

organics into carbon dioxide, water, and biomass (MLSS).

The Evac MBR is designed to operate even on elevated

concentrations of biomass, making the bioprocess stable

and reliable. An oxygen supply for the biomass is secured

via air diffusers.

Membrane Filtration

Clean water is separated from the biomass by membrane

fi ltration. The membrane fi lter is a physical barrier that

permeates infl uent wastewater, producing treated water

absent of solids. The pressure difference for the process is

created by a slight vacuum. Once the process is complete,

the treated water requires no further disinfection, and can

be discharged directly into the sea. The Evac MBR does not

require dilution water, backfl ushing or constant chemical

cleaning, making it the most economical and maintenance-

friendly membrane solution available.

Principles of Operation

BLACK WATER

BLACK/GREY

WATER

BLOWERS

SLUDGE RECYCLING

PUMP

BIOLOGICAL PROCESS

AND FILTRATION

FEEDING

PUMP

WATER EQUALIZING

AND MIXING

VACUUM

GENERATING

(OPTIONAL)

VACUUM

UNIT

SLUDGE

MEMBRANE TANK

EQUALIZING TANK

PERMEATE

PUMP

MEMBRANE

MODULE

EFFLUENT TANK

EFFLUENT

PUMP