IDENTIFICATION OF THE MOST EFFECTIVE EQUIPMENT FOR THE RECOVERY OF MACRO AND MICROPLASTICS FROM SHORELINES AND NEARSHORE ENVIRONMENT
REPORT PREPARED FOR THE PLASTIC POLLUTION WORKING GROUP (PPWG) OF THE UK & IRELAND SPILL ASSOCIATION ‘GOAL TWO’
DOCUMENT CONTROL RECORD
Project: Microplastics Research & Development
Project Reference: Oil Spill Response Limited Plastics Working Group
Report Title: Identification of the most effective equipment for the recovery of macro and microplastics from shorelines and nearshore environments
Author: Marta Januszewska BSc (Hons) MSc – Consultant – Oil Spill Response Ltd
Checked and Approved By: Rhea Shears BSc (Hons) MRes – Senior Response Specialist –Oil Spill Response Ltd
Tom Fisher BSc (Hons) MIEnvSc - Senior Response Specialist – Oil Spill Response Ltd
Lucy Short – BSc (Hons) MSc - Principal Consultant- Oil Spill Response Ltd
Version No: 2
Issue Status: Issued
Date Issued: 10th March 2023
INTRODUCTION
1. The Plastic Pollution Working Group
1.1.1 Spills involving large amounts of microplastics, most notably in the form of plastic pellets, are relatively recent occurrences. Due to the increased awareness, such incidents attract attention from Oil Spill Response Organisations (OSROs), public, private companies and other stakeholders. Every microplastics incident is an opportunity to learn and shape good practice around removal and recovery strategies from different types of shorelines. The most recent incident, which impacted shorelines of Sri Lanka provided a good amount of data on response to microplastics in sandy environments, however there is still a significant gap in understanding how microplastics will behave in different environments and what are the best practices for their removal
1.1.2 To better understand the issues involving plastic pollution, the UK & Ireland Spill Association and several of its members, formed the Plastic Pollution Working Group (PPWG), in March 2021. The group has set itself ten ambitious goals to improve their understanding of the impacts of plastic pollution, the way we deal with plastic pollution incidents and plastic pollution in general.
1.1.3 The ten goals of the PPWG are as follows:
1. Understand the problem – Understand the sources, pathways and impacts of plastic pollution from rivers to the oceans
2. Identification of the most effective equipment for the recovery of microplastics from shorelines and nearshore environments
3. Establish agreed methods for the assessment of ecological impact of plastics recovery operations
4. Establish agreed methods for qualitative (e.g. SCAT) and quantitative (e.g. laboratory analysis) assessment of macro and microplastics in sediments and waters and effective sampling and monitoring techniques
5. Assessment of environmental and health risks associated with macro and micro plastics to assist in clean up end point determination
6. Develop effective approaches for the surveillance and modelling of macro and microplastics to aid in response efforts, prediction of plastic movement and source identification
7. Develop approach to sustainability assessment with respect to plastics recovery endpoints and final destination of recovered plastics / debris
8. Share information gained through the group through webinars, demonstration days, technical publications and liaison with other appropriate organisations (e.g. EA, IMO, Councils, NGOs)
9. Work with International Spill Accreditation Scheme (ISAS) to ensure the Module for Shoreline Plastic Pollution and Marine Debris Recovery is formally released.
10. Identification of effective tools and equipment for controlling plastics at source (e.g. on site, in drains and in rivers)
1.2 Report Aim
1.2.1 As part of achieving Goal two, highlighted in bold above, this report is intended to identify most effective equipment and strategies for the recovery of microplastics from shorelines and nearshore environment.
1.2.2 The report addresses the current gap in industry good practice and aims to create a valuable source of information on equipment and strategies for response to microplastics to be shared with the industry and the wider audience. Recommendations provided in this report are based on experiences gathered during the most recent microplastics (plastic pellets) spills in Norway and South Africa in 2020 and in Sri Lanka in 2021 It is important to note that research into the best techniques for plastic pellets clean-up is an ongoing venture and will be updated through more equipment trials.
2. CLEAN UP STRATEGIES OVERVIEW
2.1 Phases of shoreline response to plastic
The Phased approach can be described as:
pellets
2.1.1 Phase 1 - The initial stage of the response is to focus on triage of any large volumes of plastic pellets that come ashore as a priority, this will be assessed when first reported. This is to limit the risk of remobilisation of the plastic pellets during tidal cycles to potentially a different area of higher environmental or socio-economic value Concerns of potential toxic risks, or sources of additional pollution will be addressed accordingly. If only physical presence is a concern the debris will be treated within the subsequent phases of the response primarily by means of manual or mechanical recovery
2.1.2 Phase 2 – Removal of bulk accumulations of contamination, primarily exhibited as ‘’high’’ concentrations of plastic pellets and macro pollution following surveying each impacted site Recovery is more efficient in concentrated patches and reduces the risks of wider contamination, as a result this is where response efforts should focus as a matter of priority. Background contamination, organic debris and solid waste should be removed and segregated in accordance to waste treatment good practice to increase the efficiency of plastic pellet collection. Collected pellets are likely to need separating from sand and assorted debris via
sieving and/or floatation. Clean-up methods in this stage will primarily be manual and mechanical removal methods (depending on available equipment and access to the location).
2.1.3 As an effort to reduce the spread of contamination, it is also necessary to maintain a team of workers at the furthest extent of the reported contamination to ‘backstop’ the extent of the plastic pellets. This is also essential to minimise the accumulation of buried plastics pellets pits should be dug along the shoreline to confirm presence or absence during surveying the extent of the impact and should be continued throughout the response.
2.1.4 Phase 3 – Removal of medium accumulations of contamination. This category covers a wide geographic area including several shoreline types, a wide variety of shoreline pollution conditions, and a varying extent of background contamination and organic debris. Plastic pellets will likely be condensed into regular groupings found as swath lines along the shore and potentially in the supratidal, sediments may be wet or dry and access to the shoreline extremely diverse.
2.1.5 Phase 4 - The penultimate stage of the clean-up will be to address light contamination where possible, removing more sporadic plastic pellets The ongoing shoreline assessments conducted by the survey teams can support if sign-off is possible within areas previously cleaned after being impacted. Clean-up methods can include spot treatment of residual impact areas and specific treatment of highly sensitive areas where appropriate.
2.1.6 Phase 5 – The final stage will be ongoing monitoring. The activities of this stage will be periodic shoreline surveys to monitor the presence of contamination at areas of natural accumulation. Frequency of these surveys should be agreed by all stakeholders involved in the response. The period between surveys may increase as the contamination levels decrease.
2.1.7 It is important to note that different locations may be going through different phases of the response at the same time and that all collected material should be taken from the shoreline in suitably protected transport as soon as possible to avoid release of the collected contaminate The transportation and storage plan should be developed as soon as clean-up teams are in place on site, so this is not a barrier for removing the collected material from each site location.
2.1.8 Further to this, it is important to recognise that it will not be possible to remove all microplastic contamination. Response actions should always have a net positive effect on the environment when dealing with a pollution incident. If the response is potentially causing more harm than good (for example large plant and many people on a very lightly contaminated beach) it would be more beneficial for the environment to cease operations. This is similar to the good practice established for oil spill response and should be adapted in the same way when deciding on endpoints during the initial days of the clean-up being initiated.
2.2 Offshore and Nearshore Response Techniques
2.2.1 Offshore and nearshore response should be considered if the incident allows this to be viable. Some reasons for this could be safety, security, window of opportunity for shoreline impact
or instantaneous release instead of a continuous release There are two options for both offshore and nearshore techniques that could be implemented as part of the overall plastic pellet clean-up strategy.
2.2.2 Containment and recovery
Capturing any free-floating plastic pellets with the use of containment booms could reduce shoreline impact and potential contamination with Hazardous and Noxious (NHS) contained in the plastic. Contained plastic pellets can then be retrieved manually using sieves. This strategy could only be utilized during an offshore response depending on the incident or in still water conditions and sheltered locations nearshore.
2.2.3 Protection
Protection booming, prior to impact of the plastic pellets, should be considered as a priority to reduce the risk of the microplastics entering highly sensitive areas such as saltmarsh and mangroves. However, depending on the incident, this may or may not be possible with the window of opportunity prior to impact, however a continuous release offshore could warrant this method being used.
2.3 Shoreline Response Techniques
2.3.1 Determining the most appropriate response strategy is a complex decision-making process. Questions should be asked about the impact, such as the coverage, depth of contamination and sensitivity of that shoreline to gather as much information about the situation as possible. Response strategies can then be chosen based on producing the optimum solution for the area
2.3.2 If possible, potential impact areas should be established and their sensitivities understood so the correct clean-up techniques are used. Promoting the use of NEBA/SIMA principles and good practice as we know them to be for oil spill response will help dictate the chosen methods/techniques available for plastic pellet clean-up. This topic will be covered in full through the Goal five of the Plastic Working Group.
2.3.1.1 Manual
This method is a labour-intensive technique This is often seen as the primary collection options for microplastics spills, employed across wide areas and involving large numbers of people collecting plastic pellets using the necessary tools spades, shovels, rakes, buckets, sieves and trommels
2.2.1.2 The following methods should be used on light to moderate levels of contamination and dry sand where access to mechanical equipment is limited; small sieves,(Figure 1 and Figure 2) floatation (figure 3) and hand turned trommels (Figure 4).
2.2.1.3 When using sheet sieves, the collected contaminated sediment is agitated through the sieve causing smaller particles (mainly sediment) to fall through the mesh. Larger debris (including the plastic pellets) will remain on top where they can be recovered into waste bags. A consideration is to check the mesh size on the sieves to make sure the collected plastic pellets are not too small to pass through and remain collected.
2.2.1.4 Wet sand can clump together with limits the sieving ability. In this circumstance, or when sediment grains are similar size to the plastic pellets, filtration based on density (floatation) is recommended. This can be done in-situ with the use of buckets, spades, sieves and basins or within the main storage collection area in a larger setup as a secondary separation method.
2.2.1.5 Half-filling a container with water and then shovelling in contaminated sand, causes sediment and natural debris (shells etc) of greater density to sink whereas plastic pellets will float. Pouring the water from the bucket through a sieve (while leaving the sand in the bottom of the bucket) allows the plastic pellets to be recovered while the remaining (plastic pellet free) sand can be deposited back on the beach (Figure 3) – the bottom layer or sand may need agitating to remove any contained plastic pellets in the substrate. Pouring the water through the sieve into a larger basin allows for the water to also be reused.
Figure 1 Sheet sieves constructed on site in Sri Lanka.
Figure 2 Double layered sieve constructed in Sri Lanka to improve background debris separation
Figure 3 Plastic pellets being separated from sediment by floatation filtration.
2.2.1.6 Trommels (Figure 4) are used industrially for waste separation and within the construction industry. They work by having collected waste fed into them, wherein the material is sorted by size. This can be used to sort sand and plastic pellets from larger debris, or to sort the pellets from finer sand. Once again, checking the mesh sizes to make sure they separate and collect the plastic pellet as desired is paramount to the success of this method.
2.2.1.7 Sweeping, raking, and scraping plastic pellets into piles and collecting the pile of plastic pellets can assist with increasing the selectiveness of plastic pellet removal. However, this will then require a method to increase the separation of the plastic pellets to the substate.
2.3.2.1 Vacuum
The choice of vacuum techniques as response strategy for a plastic pellet spill should be subject to the size of contaminated area and its accessibility (supratidal). This method is more efficient with dry sand rather than the wet sand because the plastic pellets and sand could clump and clog up the machine Vacuums are recommended for superficial pollution only. The consideration should be given to the labor-intensive element of this strategy when using backpack vacuums over longer periods of time and the availability of the right equipment in country
2.3.2.2 Even though the strategy could be used for all types of environments as stated in the matrix below (Table 1), its application should be considered due to the noise pollution and its potential to disturb wildlife. Seasonality should be taken into consideration, when deciding on this strategy in environments with rich wildlife.
2.3.2.3 Available vacuum types include: backpack vacuum (Figure 5), wheeled vacuum or trailer vacuum. Vacuums are commonly used in cleaning up pellet spills when they occur during their production, transfer or use. Specific vacuum equipment used for litter collection may be effective at collecting the plastic, however, the time taken to collect plastic pellets in large concentrations using this method means it is frequently less efficient than manual recovery techniques. With more suction and adaptors for the nozzle there is potential for them to be effective at recovering plastic pellets from riprap and vegetated low banks where manual recovery techniques are not applicable.
Figure 4 Hand turned trommel2.3.3.1 Mechanical Sieving
The sieving technique as described in paragraph 2.2.1.5 could be scaled up by constructing mechanical trommels, vibrating tables or larger sieves units that can be pulled by tractors or All-Terrain Vehicles (ATVs). This larger scale operation will be more suitable for large stretches of fine-medium grained sandy shoreline or to have a setup within the main waste storage area to assist with secondary separation
2.3.3.2 The advantage of sieving the sand and plastic pellets in situ is that it minimises removal of organic material from the beach and minimises the amount of waste being transported to storage facilities. As the sieving only filters based on size, some larger natural debris (such as shells etc) will still be present and so further separation by floatation may be necessary.
Figure 5 Backpack vacuum.
Figure 6 Mechanical trommels and industrial scale vibrating sand tables.
2.3.4.1 Beach Combing
To expedite clean-up in large areas of plastic pellet contaminated sediment, the material can be recovered by mechanical equipment, such as beach cleaners (Figure 7). Beach cleaners can only be applied for fine, dry sand with no inclination, may need to have the mesh size adapted to suit the plastic pellets and it has been proven that training for those using the machines will be required to maintain effective and efficient collection. There is also potential for these machines to not be present in country so time of manufacture and transportation will need to be considered – this would also impact the global footprint of the response. As such, other types of recovery of plastic pellets from the substrate would be recommended over this strategy.
2.3.5.1 Mechanical excavation
Other specialist machines such as motor graders, elevating scrapers, loaders and bulldozers (Figure 8) can be used to remove plastic pollution from the surface sediments. This approach can lead to high levels of waste production and the areas where it is applied need to be carefully selected for suitability and the type of grading that is required. For example, sorting large debris to allow a secondary collection of plastic pellets, or using a finer mesh to sort plastic pellets from sand are separate objectives. Care needs to be taken as the heavy machinery can damage sensitive environments – irreversible change to the beach profile or increased substrate erosion through over-removal of the substrate.
2.2.5.2 This method can be used on shorelines where the surface is amenable, where there is suitable access and the machinery is available Basic training and briefing on correct recovery of the plastic pellets should be completed with the machine operator prior to starting the operation
Figure 7 Example of beach cleaners.
Figure 8 Examples of mechanical recovery for microplastic clean-up
2.3.6.1 Flushing
A response technique where volume and pressure of water is applied on the contaminated site to help remobilize microplastic from the substrate Remobilised plastic can then be contained in a boom or recovered using other strategies such as vacuum or sieving. Both the pressure and volume needs to be considered based on the shoreline type. Depending on the type of the environment, low pressure (for marshes and mangroves) or high pressure (for exposed shores and riprap) of flushing could be used (Figure 9). The flushing could be performed using perforated hoses with a spate pump or manual lances.
2.4 Matrix
Recovery techniques Exposed rocky shores (supratidal)
* This should be completed on the outskirts of the area due to the high sensitivity of these shoreline type – responders entering this area is not advocated
** Protection booming strategy should be considered due to the high sensitivity of these shoreline type – reducing impact to these areas instead of implementing other clean-up techniques is advocated
2.4.1 Table 1 is a proposed matrix based on proven techniques used in previous plastic pellet cleanup response as well as combining generic oil spill clean-up techniques against the different environments. Through understanding the behavior of plastic pellets against oil, these techniques are proposed to be most suitable and effective. Some environment types are yet to be trialed to check the applicability of the identified recovery techniques so this will be updated as trials are completed.
Figure 9 Equipment setup for flushing technique
Table 1 Matrix of recovery techniques and its application in different environments.
Sandy beach Gravel beach Riprap structures Exposed tidal flats
2.5 Response technique considerations
2.5.1 Important considerations when using any of these techniques are:
• Ensuring the safety of all personnel involved in the response,
• Ensuring the welfare of the clean-up responders,
• Ensuring correct and adequate training and supervision of the clean-up responders,
• Ensuring the personnel involved are removing the contamination as selectively as possible,
• Ensuring waste management is aligned with common good practice principles, and
• Ensuring consideration of the overall global footprint of the response but utilising equipment choices that are available in country, where possible.
3 CLOSING REMARKS
3.1 As the industry’s experience in responding to microplastics spills is still very limited, the techniques and equipment outlined above may not include all existing technologies. Increased awareness of an issue of plastic pellets on shorelines will provide more opportunities to test different techniques and recommend the most efficient and environmentally considerate tools in the future. Further trials and research by PPWG are planned with some of the techniques described above, which may lead to significant findings and updates of the current report.