AMORAS - Mechanical Dewatering of Sediment

Port of Antwerp, Belgium

Region: Europe / Middle East / Africa

Service Offering: Engineering & Design, Environmental Planning & Management

Market Sector: Natural Resources & Mining, Ports Waterways & Costal

Client Type: Private Sector

Status: Complete

Description:

The Port of Antwerp needed to dispose of 2,000,000 m³ of polluted harbour sediment (600,000 tons of Dry Matter) each year, to maintain and improve the port’s navigation system for large vessels. Lagooning the sediments was no longer an acceptable solution:  scarcity and cost of land in Antwerp forced the Port to seek a new and sustainable way to deal with its huge amount of harbor sediment.

MWH tested  the feasibility of the approach through a pilot test of sand separation and sediment dewatering with chamber filter presses. During these tests extensive screening (environmental and geotechnical) of the incoming (i.e. sediment) and outgoing products (i.e. filter cakes, filtrate, sand) was performed, as well as a mass balance of the pollutants in the incoming sludge, filter cake, filtrate and sand. 

This screening showed the following important results:

·        Filter cake dry matter content : 62 %

·        Filter cake strength parameters :

·           - Cohesion c : ± 20 kPa

·           - Internal friction angle φ :  ± 22 kPa

·         Filter cake permeability :  1.10-9 m/s

After conditioning with lime and ferric chloride the filter cakes could be processed easily. Because the sand fraction was clean, filtrate and filter cakes contained majority of the pollutants

MWH was then selected as part of a joint venture to design a process and plant for the mechanical separation, conditioning and dewatering of this sediment. 

This process is an cost-efficient, sustainable solution for the treatment of these harbour sediment and includes the separation, conditioning and dewatering of the sediment using membrane chamber filter presses. The plant will treat harbour sediment equivalent to 600,000 tons of Dry Matter annually.

The project represents a total value of 100,000,000 Euro (design and construction of the installation) and is the largest mechanical dewatering plant worldwide that uses this technique. MWH was responsible for the following activities: basic design, detailed engineering, drawing up of the tender documents, selection of the contractor(s), supervision of the execution of the works, start-up assistance and process optimisation.

Project Highlights

The mechanical separation and dewatering of the sediment and inorganic industrial sludges  is technically feasible for the huge amount of sediment.  The risk to the environment is limited and controlled as a result of the separation of ‘dirty’ and ‘clean’ flows. Additionally the excellent compaction properties of the filter cakes ensures an impermeable layer, which also decreases possible environmental risks.  Reuse of the produced filter cakes is possible and research on this is ongoing as more and more applications for the reuse of the filter cakes become available.

Services Provided

·        Acceptance of the harbour sludge

·        Dredging unit

·        Sand separation unit

·        Sludge transport (4 km) with booster pumps 1500 m³/h

·        Mechanical dewatering plant (12 membrane filterpresses 2,0 m x 2,0 m)

·        Water treatment installation (fysico chemical and biological treatment)

·        Disposal site included geotechnical contructions

·        Disposal plan

·        Management of the sediment quality/  Acceptance Plan / Monitoring Plan