Efficacy of hull cleaning operations in containing biological material. I Risk assessment. Floerl, O., Norton, N., Inglis, G., Hayden, B., Middleton, C., Smith, M., Alcock, N., & Fitridge, I. Technical Report NIWA, Christchurch, August, 2005.
Efficacy of hull cleaning operations in containing biological material. I Risk assessment [link]Paper  abstract   bibtex   
Executive summary In January 2003 the Ministry of Fisheries (MFish) contracted NIWA to assess the risk posed to marine biosecurity by New Zealand’s commercial hull cleaning facilities. The specific objectives of this project were: 1. To investigate for a variety of hull cleaning situations the types, amounts and viability of fouling organisms discharged and assess whether the effluent control methodology used is successful in reducing the amount of viable material reaching the coastal marine area. 2. To discuss and make recommendations on control methodologies that would be most effective in minimizing the release of viable organisms from hull cleaning situations taking into account the efficacy, practicality and cost of using effective methodologies in an existing or new hull cleaning situation. Between May and August 2003, NIWA staff visited hull cleaning facilities in Lyttelton, Auckland, Whangaparaoa and Tauranga, where vessels are removed from the water for cleaning (dry-dock and haul-out facilities) or where fouling organisms are removed in situ by divers. In Objective 1, 19 vessels were sampled, ranging from 10–105 m in length. Sampling of fouling organisms and liquid effluent was done at all stages of the hull cleaning and waste treatment process. Macrofouling was sampled before, and immediately following its removal from vessel hulls by freshwater blasting or manual scraping (in-water cleaning). Liquid fouling waste was examined before it entered settlement tanks and filters, and following treatment prior to discharge into the sea. In all cleaning operations examined, physical removal of fouling assemblages from vessel hulls did not result in mortality of all organisms. The overall viability of organisms removed from hulls was lowest in haul-out (16 percent) and dry-dock (43 percent) facilities, where fouling organisms were often exposed to air, high-pressure freshwater blasting and trampling. However, viability was high for (1) hard-bodied organisms not directly attached to hull surfaces (epibiota), and (2) organisms associated with clumps of mussels in the protected sea chests of large ships. Survival and viability of organisms following in-water cleaning by divers, which did not involve exposure to air or high-pressure water blasting, was significantly higher (72 percent) than in shore-based operations. The multi-chamber settlement tanks used by the facilities examined to remove solid particles from liquids (water blast effluent) were effective at killing and removing most biota suspended in the liquid effluent. Concentrations of intact animals, propagules and unicellular organisms in the first settlement tank chamber were 39–100 percent lower than those in the cleaning run-off. Liquids sampled in the last chamber of the settlement tanks had 99– 100 percent of all animal and unicellular biota removed, and it is likely that few or none of the remaining organisms were viable. In some cases, freshwater taxa were encountered in the tanks. No biological material occurred in the final effluent of facilities that subject settlement tank contents to filtration (sandfilter) prior to discharge into the sea. The results of Objective 1 suggest that: 1. In-water hull cleaning without collection of fouling waste poses the highest risk to marine biosecurity. This excludes in-water operations that collect and contain fouling organisms following their removal from vessel hull, as such operations were not included in this study. 2. Operations that clean vessels in shore-based facilities and discharge solid and liquid fouling waste into the sea without any treatment pose a more than minor risk to marine biosecurity. 3. Operations that clean vessels out of the water and employ settling tanks to separate fine particulates from liquid waste prior to discharge into the sea pose a relatively low risk to marine biosecurity, providing there is an adequate residency time of liquid waste in the tanks. 4. Operations that clean vessels out of the water and employ settling tanks and filters (for example, sandfilters) to separate fine particulates from liquid waste prior to discharge into the sea pose negligible risk to marine biosecurity. 5. The residency period of water blasting effluent in settlement tanks is likely to vary between seasons because far more vessels are cleaned per day during summer months than during winter. Actual residency time will be a function of the capacity of the settlement tanks and the number of vessels cleaned per day (and, therefore, the volume of water entering the tanks). We recommend that a repetition of settlement tank sampling be carried out during summer months when far more boats are cleaned per day and the residency period of cleaning effluent in settlement tanks is likely to be shorter. A review of existing legislation and waste treatment methods used at existing cleaning facilities in New Zealand and elsewhere was conducted as part of Objective 2. Our review suggests that although few of New Zealand’s Regional Coastal Plans deal explicitly with managing risks to marine biosecurity, concerns about the release of toxic contaminants from cleaning facilities and their effects on the coastal marine environment have meant that many of the larger Regional Authorities have moved to discourage return of untreated solid and liquid wastes to the marine environment. We recommend fouling waste treatment systems described in (3) above are a desirable standard for hull cleaning facilities where there is a risk of contamination by unwanted marine organisms. For operators that already have some form of collection and settling tank treatment system, the most cost-effective option is likely to be retain and/or modify the existing system to achieve the characteristics listed in (3) above. For operators that do not currently have treatment systems, the simplest and most cost-effective option is likely to be that described in (3) above. This recommendation is based simply on the fact that currently this is the most commonly used system in New Zealand and it is a system that has been shown to be effective at reducing biosecurity risk (Objective 1). This recommendation does not preclude the use of other, possibly more sophisticated systems. There are likely to be significant benefits of including additional filtration steps or other more sophisticated treatment technologies as ‘add-ons’ to the treatment process. First, such steps will offer an additional buffer of confidence in reducing risks to marine biosecurity, for example by providing a final ‘catch all’ removal of particles greater in size than the ‘particle standard’ of 60 μm proposed by McClary and Nelligan (2001). Second, they will improve the removal of fine particulates and associated antifouling chemicals. This is important for operators who not only need to manage marine biosecurity risk, but who also may need consents for discharges to the sea under the Resource Management Act, or may need permission to divert hull-cleaning waste to local community wastewater treatment plants.

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