Wastewaters at dockyards result from the removal of paintings from ship hulls and they represent an important point source of toxic contaminants to the aquatic environment. For example, biocides in anti-fouling paints applied to ship hulls are released by discharges of waters from dockyards. In the past, tributyltin (TBT) contamination due to ship navigation and dockyard operations caused severe impacts to non-target aquatic organisms. To remove old paint from ships, sand blasting with post water rinsing or high pressure water blasting is applied. In both cases suspensions with paint and metal flakes, as well as contaminated waters with biocides, copper and zinc are generated. Usually the wastewater is released untreated into the North Sea. Even regulatory measures such as the ban of TBT are being enforced, the problem of heavy metal and biocide contaminated waters will remain in the future if no environmental management strategies are developed and applied.
The projects aims to assist dockyard environmental managers and environmental administrations in the following areas:
- Providing information:
- about the different regulations and criteria applied in the North Sea
- for developing "best available techniques" to treat biocide contaminated waters
- Comparing alternatives to treat waters considering not only treatment targets and costs but also a wider range of environmental impacts
- Expanding the site-specific perspective of process assessment by considering impacts on a life-cycle scale
A common decision supporting tool (DST) will be developed in cooperation with local EPAs, harbour administrations and scientists in order to provide decision makers with an instrument for sustainable management of the marine environment. Additionally cross-border knowledge transfer concerning effects of regulation criteria between policy makers and researchers will be improved.
The project will provide a direct contribution to sustainable development of the North Sea region by introducing an environmental assessment strategy for finding the best environmental practice for treating dockyard waters contaminated with organotins and heavy metals. The decision making tool allows harbour managers and regional environmental authorities to compare treatment costs in relation to long-term environmental targets.
Furthermore a socio-economic study will be performed to evaluate impacts and quantify societal effects. The decision instrument will be developed based on data generated from suitable wastewater treatment processes. Process optimisation and comparison will be conducted to ensure technical and economical practicability and lead to an improvement of the state of the art regarding treatment technologies. This action-oriented project will contribute towards the improvement of the environmental quality in the North Sea by addressing the problem of persistent organic pollutants (POP) and metals input from dockyards in a number of North Sea countries. Tributyltin (TBT), as example for biocides and heavy metals (mainly Cu and Zn), will be used as indicator pollutants. Furthermore the minimisation of water consumption in dockyards by close water cycles can be achieved.
In conclusion, this project will make advances in the managemen
The Green North Sea Docks project aims to develop a decision support tool (DST) to assess and compare alternative processes to treat dockyard waters following a methodology that incorporates the elements of sustainable development.
The concept of sustainability requires the integration of economic, environmental and social factors in management systems. One of the challenges of the project is the combination of those criteria into an innovative scheme for selecting alternative treatment processes and decision-making. The DST will also deliver a common way of assessing processes considering not only target levels of contaminants but also impacts such as consumption of energy, demand of raw materials, etc. Normally such impacts are neglected and are only considered in terms of costs, e.g. costs of raw materials or energy. On the environmental administration level the GNSD project is a platform where administrations discuss the different procedures and criteria used in the participating countries to deal with the discharge of toxic contaminants from dockyard operations.
A deeper insight has been gained about the situation in the participating countries thanks to the exchange of information and research that has been conducted in GNSD.
The project was organised in two entities. The Technical Committee was in charge of the development of the processes to treat contaminated waters, design the assessment strategy, project communication and dissemination of results, and develop the decision-support tool. While the Advisory Board was a body consisting on experts and environmental administrations, which ensured that the work done by the Technical Committee was applicable to real conditions. Besides the institutions involved directly in the project, other local authorities, dockyards and industry were involved by sharing information, participating in meetings and discussions.
In this project some innovative technologies to treat contaminated waters were tested along with other well established technologies already applied in some dockyards in the region. The comparison of the processes was carried out following a strategy based on the concept of sustainability. uring the project it was found out that the heterogeneous situation of discharges from dockyards in the region made it necessary to develop a decision support tool that is flexible enough to compare treatment technologies under the different regulatory scenarios. This issue was implemented in the tool along with the knowledge gained during the development of the processes in order to produce an instrument to help decision-makers, managers and planners to implement the most suitable technology to deal with contamination at the source. This will avoid the discharge of hazardous substances in the North Sea region.
See technical implications for further details.
Parallel to the investigation of discharge criteria in the region, the phase of development of treatment technologies was carried out. The processes tested were arranged in the following process chains:
Process chain 1: Adsorption
After testing several types of sorbent materials, two commercially available materials were selected as the most appropriate to decrease Cu, Zn and organotin concentrations down to the targets required:
Südflock P 294, which is a bentonite + flocculant based sorbent (Süd-Chemie AG)
Norit Sae Super, which is a powdered activated carbon from Norit
The mixture of the two sorbents was mixed with the wastewater and then the sorbents were left to flocculate. A mixing and settlement time of 15 minutes resulted in an optimal pollutant and sorbent removal.
Process chain 2: Flocculation – Electrochemical treatment (coupled with granular activated carbon adsorption)
Flocculation to eliminate copper and zinc was performed with ferric salts. The flocs formed were allowed to settle and separated from the water. Electrochemical treatment was carried out to oxidize organotins. Two anode materials were tested: boron doped diamond anodes and titanium coated with iridium dioxide (Ti/IrO
). It was necessary to perform a post-treatment step after electrochemical treatment to eliminate residual oxidants in the treated effluent. A granular activated carbon adsorption column was designed and tested.
Process chain 3: Flocculation – Photolysis (coupled with granular activated carbon adsorption)
Flocculation to eliminate copper and zinc was performed with ferric salts. The flocs formed were allowed to se
In the North Sea Region there is no uniform set of discharge criteria applicable to dockyard waters. Each country and administrative region has their own criteria in order to issue operation and discharge permits to dockyards.
The results of the process development phase of the project can supply valuable information about the economic and environmental feasibility of the technologies to eliminate contaminants.
As a result of the exchange of information regarding discharge criteria that took place during the project, the outcomes of the process development phases were used in Germany to support the setting of criteria for dockyards in the new Water Ordinance. This is an example of what the project aimed to achieve: to foster communication between problem owners and problem solvers, to exchange knowledge and to support decision-making procedures regarding the problem of water emissions in the North Sea region.