In-Water Cleaning and Capture to Remove Ship Biofouling: An Initial Evaluation of Efficacy and Environmental Safety

Mario N Tamburri,Graeme J Inglis,Christopher Scianni,Katherine Newcomer,Matthew R First,Gregory M Ruiz,Eugene T Georgiades,Janet M Barnes,Ian C Davidson

doi:10.3389/fmars.2020.00437

Abstract

Biofouling is a long-standing challenge for ships because it can interfere with operations and increases vessel drag, fuel consumption and exhaust emissions. More recently, ship biofouling has also been recognized as a leading vector for global transfers and introductions of marine non-indigenous species. Ship in-water cleaning and capture (IWCC) systems, to remove and collect macrofouling organisms and associated antifouling coating compounds, are now becoming available as a possible solution to both problems. However, independent and rigorous evaluations of IWCC efficacy and environmental safety are needed to facilitate technology maturation, support vessel operator biofouling management decisions, aid IWCC approvals and permitting, and future biosecurity regulations. We developed a formal protocol for evaluating an IWCC system, on two ships with varying biofouling levels and under different environmental conditions, to quantify biofouling removal and capture efficacy as well as impacts on water quality. The IWCC system reduced hull biofouling by 82 - 94%. Concentrations of dissolved and particulate Cu and Zn in effluent from the IWCC onshore processing varied by orders of magnitude between trials, in one case greatly exceeding water quality standards. Our results demonstrate that rigorous, quantitative assessments of IWCC system performance are possible, even under challenging conditions. This initial evaluation also identifies the major factors that impact performance of in-water cleaning, and key needs for future research, to consider in advancing standardized testing and independent evaluations needed for all in-water cleaning systems.

Highlights

Like all substrates placed in coastal waters, the wetted surfaces of ships are quickly colonized by a succession of diverse sessile or sedentary micro- and macro-organisms (Flemming, 2002)
The U.S Department of Transportation (DOT) Maritime Administration’s (MARAD) NS Savannah (Vessel 1), based in Baltimore, Maryland, is a retired, former nuclear-powered ship that had a 10-year-old, copperbased antifouling coating and an extensive accumulation of biofouling across hull surfaces consisting of barnacles, hydroids, mussels, tubeworms and bryozoans [FR 100 using the fouling rating [FR] scale developed by the United States Navy, Naval Ships’ Technical Manual Naval Sea Systems Command [Navsea] (2006)]
Our results show that statistically appropriate measures of the performance of in-water cleaning and capture (IWCC) systems are feasible and practicable

Summary

Introduction

Like all substrates placed in coastal waters, the wetted surfaces of ships are quickly colonized by a succession of diverse sessile or sedentary micro- and macro-organisms (Flemming, 2002). This biological fouling (biofouling) of ships has been a longstanding challenge for vessel owners and operators (Woods Hole Oceanographic Institute [WHOI], 1952), increasing drag, the cost of ship operations, and sometimes corrosion. A multi-billion-dollar antifouling industry has developed to combat the negative consequences of biofouling accumulation on ships This is primarily achieved through application of surface paints that inhibit macrofouling attachment (using biocides) or reduce adhesion (non-biocidal) to wetted surfaces (Dafforn et al, 2011). There are substantial areas of ships’ wetted surfaces that are challenging to coat (e.g., dry-dock blocking areas) or sub-optimal for coating performance (e.g., niche areas) and often act as biofouling hotspots on ships (Coutts and Taylor, 2004; Davidson et al, 2009; Davidson et al, 2016)

Objectives

Methods

Results

Conclusion