The Problem of Removing Seaweed from the Beaches: Review of Methods and Machines

water

Review The Problem of Removing Seaweed from the Beaches: Review of Methods and Machines

Łukasz Warguła * , Bartosz Wieczorek , Mateusz Kukla , Piotr Krawiec and Jakub Wojciech Szewczyk

Institute of Machine Design, Faculty of Mechanical Engineering, Poznan University of Technology, 60-965 Poznan, Poland; [email protected] (B.W.); [email protected] (M.K.); [email protected] (P.K.); [email protected] (J.W.S.) * Correspondence: [email protected]; Tel.: +48-(61)-665-20-42

Abstract: Beach cleaning and algae collection in the shoreline area are important for the tourism industry, mainly for aesthetic reasons, but also to protect human health. In addition, the collected material can be used in many industries such as energy, medicine, cosmetics or catering. The problem of cleaning the shoreline area concerns the need to clear land, water and the strip of shore and land onto which water is thrown from falling waves. The vast majority of available cleaning methods are adapted to cleaning beaches or waters. There is a lack of solutions and machine designs suitable for cleaning the coastal strip, which includes: land, the area of land on which the wave is thrown, shoal and deep water. This area is particularly important for tourism as it is mainly used for water bathing. Pictures from tourist areas that are exposed to intensive water contamination show that measures taken to clear the shoreline area are not very effective, as seaweed in shallow water is thrown ashore with the waves. The paper presents a review of methods for cleaning coastal waters and beaches from contamination. It also shows the author’s conceptual design adapted to clear the shoreline area and sandy beaches.

Keywords: cleaning the beaches; seaweed removal; enhancement of tourist qualities; non-road machinery; small engine; adaptive steering Citation: Warguła, Ł.; Wieczorek, B.; Kukla, M.; Krawiec, P.; Szewczyk, J.W. The Problem of Removing Seaweed from the Beaches: Review of Methods 1. Introduction Water 2021 13 and Machines. , , 736. The 21st century is a period in the history of the world characterized by high levels of https://doi.org/10.3390/w13050736 pollution. The negative effects of human activity are visible on the beaches of lakes, seas and oceans. Anthropogenic pollution [1–3] and natural seaweed and algae [4] are observed Received: 11 February 2021 in those places. Human beings contribute directly to anthropogenic pollution, e.g., through Accepted: 7 March 2021 Published: 8 March 2021 ship recycling [5–12] or accidents of structures that operate on water [13–17]. Human activity contributes indirectly to the second group of natural pollutants by

Publisher’s Note: MDPI stays neutral providing nutrients to aquatic plants [18]. The main factors of this pollution are land- with regard to jurisdictional claims in based agriculture and inefficient or malfunctioning wastewater treatment plants. Improper published maps and institutional affil- storage or excessive use of fertilizers contributes to the enrichment of open water reservoirs iations. with biophilic elements, resulting in an increase in trophy, or water fertility [19]. Ineffective or defective wastewater treatment plants similarly contribute to the eutrophication of water bodies [20]. Excessive levels of nutrients in surface waters, and the parallel overfishing of ocean and marine ecosystems [21], result in an excessive amount of algae in waters. The transport of algae in surface waters depends mainly on the water circulation, and the wind Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. causing waves [22–25]. The density of an algal colony changes and mainly depends on This article is an open access article the daily cycle of irradiation [26,27], but other environmental factors also influence this distributed under the terms and parameter, including: nutrients, radiation intensity, temperature and salinity [28–30]. conditions of the Creative Commons Seaweed pollution in the Caribbean can be seen in Figure1[ 31]. Beach pollution is an Attribution (CC BY) license (https:// important problem for the tourism industry. For some countries this industry is a major creativecommons.org/licenses/by/ source of income [32], allowing for socioeconomic development [33] and national develop- 4.0/). ment [34]. Studies by Tudor and Williams on the opinion of visible pollution on beaches

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Water 2021, 13, 736 2 of 11 source of income [32], allowing for socioeconomic development [33] and national development [34]. Studies by Tudor and Williams on the opinion of visible pollution on beachesindicate indicate that pollution that pollution of human of human origin, mainlyorigin, mainly sewage, sewage, is the most is theunfavorable most unfavorable [35,36]. [35,36].Among Among the natural the natural pollutants, pollutants, seaweed seaweed is the main is the problem main problem [35]. In the[35]. evaluation In the evaluation of recre- ofation recreation sites, beach sites, and beach coastal and water coastal cleanliness water cleanliness was a very was important a very important parameter parameter among the amongevaluators the [evaluators36]; hence, [36]; great hence, emphasis great is emphas placedis on is their placed cleanliness. on their cleanliness. A beach assessment A beach assessmentsystem was system developed was anddeveloped implemented and implemented as early as 1989–1991as early as to 1989–1991 rank the mainto rank public the mainrecreational public recreational beaches along beaches the open along seacoasts the open in theseacoasts USA onin thethe basisUSA ofon 50the criteria. basis of The 50 criteria.survey wasThe orientedsurvey was towards oriented beaches towards for swimming, beaches for and swimming, therefore, and water therefore, quality iswater also qualityimportant is also for themimportant [37]. for them [37].

FigureFigure 1. SeaweedSeaweed pollution pollution on on the the coast coast of of the the Dominican Dominican Repu Republicblic in the region of the city of Punta Cana.

BothBoth beachbeach cleaningcleaning and and algae algae collection collection are ofare interest of interest to several to several industries. industries. This includes This includesthe tourism the industrytourism industry and the authoritiesand the authorities of agglomerations of agglomerations that border that polluted border polluted beaches, beaches,mainly for mainly aesthetic for reasons,aesthetic and reasons, to protect and theto healthprotect of the residents. health of However, residents. there However, are also therespecies are of algaealso species used in theof algae medical used [38 ],in cosmetic the medical [39,40 ][38], or catering cosmetic industries [39,40] [or41 ,42catering]. industriesThere [41,42]. are papers available describing technologies that use algae as biomass [43] or biofuelsThere [44 are–46 papers]. M. Hannon available suggests describing that techno algallogies biofuels that may use be algae a viable as biomass alternative [43] or to fossil fuels; however, this technology must overcome many obstacles before it can compete biofuels [44–46]. M. Hannon suggests that algal biofuels may be a viable alternative to in the fuel market and be widely implemented [47]. fossil fuels; however, this technology must overcome many obstacles before it can Kirkman and Kendrick indicated that the ecological and commercial importance of compete in the fuel market and be widely implemented [47]. the harvesting of drifting seaweed deposited on beaches is not clearly recognized, using Kirkman and Kendrick indicated that the ecological and commercial importance of the example of Australia. This is partially because the impact of cleaning the beaches from the harvesting of drifting seaweed deposited on beaches is not clearly recognized, using seaweed on the feeding and nesting of shorebirds is unknown [43]. the example of Australia. This is partially because the impact of cleaning the beaches from In addition, a concept with a proposal for a device to clear the coastal and near-shore seaweed on the feeding and nesting of shorebirds is unknown [43]. belt is presented. The area of application of the device is characterized by specific operating In addition, a concept with a proposal for a device to clear the coastal and near-shore conditions resulting from the action of waves that flood the land. As a result, the devices belt is presented. The area of application of the device is characterized by specific used on water cannot be used to clean water, because of the water level being too low and operating conditions resulting from the action of waves that flood the land. As a result, the possibility of depositing on the shoal. In contrast, land-based cleaning equipment and themethods devices cannot used beon used water because cannot of be the used risk to of clean flooding water, or gettingbecause stuck. of the Algae water and level seaweed being tooleft low in the and cleaned the possibility water of of the depositing coastal and on near-shore the shoal. beltIn contrast, pollute theland-based beach and cleaning make tourists uncomfortable to use of the waters of the coastal and near-shore belt. An additional

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difficulty in the development of such a device is the diversity of beach profiles [48], but the developed design of the device is adapted for use on most sandy beaches. The authors of the article identified the area that most affects the pollution of beaches, according to Figure1. This area is located in the seaward strip that includes the land and water areas and is one of the most important tourist and recreational attractions. The aim of the article is to demonstrate the methods and machines adapted to purify beaches, coastal waters and the area of the coastline. The methods of floating booms used, for example, on the beaches of Puerto Morelos (Mexico), or the method of tractors with sweepers used on the beaches of Cancun (Mexico) [31], seem to be ineffective. In addition, an innovative concept with a proposal for a device to clear the coastal and near-shore belt is presented in this paper.

2. Beach Cleaning Methods and Equipment Various types of solutions are known in the state of technology to clear the beach from seaweed or other sediments. They are based on structures that are built on trailers and dragged along the sand. A scraper blade shaves a layer of sand and debris from the sand surface. A continuous conveyor transports the sand and debris over sifter bars within the chassis of the beach cleaner. A foraminous sifter separates debris and permits sand to fall back to the beach [49–53]. This type of construction is also known from the production of the company Kassbohrer Gelandfahrzeug AG (Laupheim, Germany) and the common feature of these machines is cleaning by the sieving of sand from dirt. The machines manufactured by Kassbohrer Gelandfahrzeug AG—in their series of machines for beach and sand cleaning—use a shaft equipped with short colters. They move the sand and transport it to the sifter by means of a transmission belt designed for this purpose. The belt is subjected to vibrations in order to accelerate the sieving process. This functionality is offered by the exemplary machine BeachTech 3000. Another solution in its series of machines for beach sand cleaning is used by the company P.F.G. (Longiano, Italia) and Metaljonica S.R.L. (Roseto degli Abruzzi, Italia). In these manufacturers’ machines, the working element (wedge) plunges into the sand, performing a reciprocating movement. The nature of the movement of the working element and the appropriate shaping of the sifter have been used in the transport of impurities from the puriﬁed material. Solutions based on this principle have been used in machines, such as the NEMO by P.F.G. and the Evolution 165 by Metaljonica S.R.L. In addition, P.F.G. offers machines that operate in a manner similar to that used in the BeachTech series. The main design difference is of the element that moves the sand, which uses blades in place of colters. Apart from this element, the rest of the design of these machines is similar to that used in other machines of this company. The unit separating the impurities from the sand is a perforated sheet, or a metal grate with suitable openings. The perforated plate improves the cleaning process. To further improve the cleaning process, the characteristic movement of the working element is used. Most of the other machines available use solutions that are similar or identical to those indicated. These machines are built in the form of trailers or stand-alone land units. Another group of designs are beach cleaners mounted in the rear of agricultural tractors [54] or in the front of trucks [55]. There are designs that use agricultural tractors with a loading scoop. In the cleaning process, they use its front part for collecting larger debris, and the rear part of the tractor, to which a cleaning system is ﬁtted, for collecting smaller fractions of debris [56]. An atypical machine is a construction of a low-speed vehicle, which cleans the beaches from pollutants originating from oil spills. The machine moves along the beach and sprays liquid nitrogen onto the contaminated area, thus solidifying the oil and sand mixture, so that the mixture can be separated from the uncontaminated sand lying below and is effectively removed from the beach [57]. The limitations of these methods are related to the vehicles used to transport the working elements of the cleaning machines. Another form of beach cleaning is the use of manual tools. This involves raking up debris left on the beach and loading it behind transport trailers that are pulled from the beach by farm tractors. Water 2021, 13, 736 4 of 11

from the beach [57]. The limitations of these methods are related to the vehicles used to transport the working elements of the cleaning machines. Another form of beach cleaning is the use of manual tools. This involves raking up debris left on the beach and loading it behind transport trailers that are pulled from the

Water 2021, 13, 736 beach by farm tractors. 4 of 11

3. Methods and Equipment for Water Treatment One way to keep beaches clean is to clean the coastal water of pollutants. Water purification3. methods Methods and and devices Equipment can be for divide Waterd Treatmentinto those that are able to cleanse the seabed, and thoseOne that way are to not. keep Cleaning beaches me cleanthods is tocan clean be divided the coastal into watertwo catergories: of pollutants. Water manual andpuriﬁcation those using methodsa water unit. and In devices the manual can be method, divided employees into those separate that are seaweed able to cleanse the with manualseabed, tools and and then those collect that areit with not. ne Cleaningts or vacuum methods pumps. can Machines be divided for intothe water two catergories: cleaning ofmanual plant debris, and those in most using of a waterthe avai unit.lable In thesolutions, manual use method, a conveyor employees belt separateas the seaweed working element.with manual An example tools and of such then a collect machin it withe is the nets Algea or vacuum Harvester pumps. [58] or Machines the ILH6- for the water 300 from Inlandcleaning Lake of Harvesters, plant debris, Inc. in (Burli mostngton, of the VT, available USA). solutions,In addition, use some a conveyor designs belt as the of water unitsworking for water element. cleaning An example are equippe of suchd with a machine a trimmer is the that Algea cuts Harvesterthe seaweed [58 ]to or the ILH6- enable the harvesting300 from Inland of rooted Lake plants. Harvesters, Anothe Inc.r method (Burlington, is to mount VT, USA). the rotating In addition, wings some to designs collect debrisof water[59], vacuum units for pumps water [60,61] cleaning or arebooms equipped with nets with to a catch trimmer algae that [62] cuts on the the seaweed to water unit. enableThe limitations the harvesting of these of rootedmethods plants. are due Another to the methodvehicles is used to mount to transport the rotating the wings to working elementscollect debrisof the sediment [59], vacuum cleaning pumps machines [60,61] on or the booms water with unit. nets to catch algae [62] on the The onlywater device unit. identified The limitations by the authors of these for methods cleaning are the due coastal to the and vehicles near-shore used tostrip transport the from pollutionworking is a structure elements adapted of the sediment mainly for cleaning cleaning machines it from on oil. the The water design unit. is based on the use of vacuumThe only pumps device and identified is transported by the authors by a land-based for cleaning unit, the coastale.g., an and agricultural near-shore strip from tractor [63,64].pollution is a structure adapted mainly for cleaning it from oil. The design is based on the use of vacuum pumps and is transported by a land-based unit, e.g., an agricultural tractor [63,64]. 4. Innovative Concept for Cleaning the Shoreline Area from Algae in Particular 4. Innovative Concept for Cleaning the Shoreline Area from Algae in Particular Available designs identified by the authors are characterized by the lack of possibility Available designs identiﬁed by the authors are characterized by the lack of possibility to clean the coastal and near-shore strip from pollution due to the used transport units of to clean the coastal and near-shore strip from pollution due to the used transport units of the working elements of the cleaning machines. The authors propose a solution consistent the working elements of the cleaning machines. The authors propose a solution consistent with the patentwith application the patent application P.429660 [65]. P.429660 The solution [65]. The according solution according to the invention to the invention allows allows us us to cleanto both clean coastal both coastal waters waters and sand and sandbeaches beaches in the in thecoastal coastal strip, strip, from from algae algae and and seaweed seaweed inin particular, particular, using using a aland land vehicle vehicle and and a amotorboat motorboat for for the the movement movement (Figure (Figure 2).2).

Figure 2. ConceptFigure for cleaning 2. Concept the coastalfor cleaning and near-shore the coastal strip and from near-sho algaere in strip particular: from algae 1—land in vehicle,particular: 2—motorboat 1—land and 3—cleaning device.vehicle, 2—motorboat and 3—cleaning device.

A device forA cleaning device for water cleaning and sand water beache and sands in the beaches coastal in and the coastalnear-shore and strip near-shore from strip from algae is shownalgae in is Figure shown 2, inwhere Figure it 2is, wheredepicted it is in depicted its entirety in itsunder entirety operating under conditions. operating conditions. The cleaningThe device cleaning is mounted device is to mounted a land unit to aand land to unita water and unit to a waterwith a unitpower with engine. a power engine. This type ofThis mounting type of will mounting enable willthe cleaning enable the of cleaningthe coastal of theand coastalnear-shore and near-shorestrips, where strips, where sand and watersand are and cleaned. water are The cleaned. entire cleaning The entire module cleaning is illustrated module is illustratedin Figure 3, in where Figure 3, where the modulethe frame, module which frame, is adapted which isfor adapted mounting for to mounting a water unit to a waterand for unit mounting and for to mounting a to a land unit, is shown. The mountings are articulated and provide freedom of movement of the coupled units. The cleaning device is independently driven by a drive unit, which transmits power via a linkage gear to the reducer and then via a clutch to the working shaft

assembly. The working shaft assembly is shown in Figure4 in its entirety. This assembly is attached to the frame via bearing supports. The working shaft assembly is built up from the working shaft shown in Figure5. The working shaft consists of a hollow shaft with the bearing pins tightly ﬁtted and welded. Spring mountings, to which the torsion springs are ﬁtted on a bolt are screwed onto the work shaft with spring mounting bolts. The collected WaterWater 2021 2021, ,13 13, ,736 736 55 of of 11 11

landland unit,unit, isis shown.shown. TheThe mountingsmountings areare articulatedarticulated andand provideprovide freedomfreedom ofof movementmovement ofof thethe coupledcoupled units.units. TheThe cleaningcleaning devicedevice isis independentlyindependently drivendriven byby aa drivedrive unit,unit, whichwhich transmitstransmits powerpower viavia aa linkagelinkage geargear toto thethe reducerreducer andand thenthen viavia aa clutchclutch toto thethe workingworking shaftshaft assembly.assembly. TheThe workingworking shaftshaft assemblyassembly isis shownshown inin FigureFigure 44 inin itsits entirety.entirety. ThisThis assemblyassembly isis attachedattached toto thethe frameframe viavia bearingbearing supports.supports. TheThe workingworking shaftshaft assemblyassembly isis builtbuilt upup fromfrom thethe workingworking shaftshaft shownshown inin FiguFigurere 5.5. TheThe workingworking shaftshaft consistsconsists ofof aa hollowhollow Water 2021,shaftshaft13, 736 withwith thethe bearingbearing pinspins tightlytightly fittedfitted andand welded.welded. SpringSpring mountings,mountings, toto whichwhich thethe 5 of 11 torsiontorsion springssprings areare fittedfitted onon aa boltbolt areare screwedscrewed ontoonto thethe workwork shaftshaft withwith springspring mountingmounting bolts.bolts. TheThe collectedcollected algaealgae oror seaweedseaweed areare depositeddeposited onon thethe springssprings andand thenthen transferredtransferred toto aa conveyorconveyor beltbelt transportingtransportingalgae or seaweed themthem are fromfrom deposited outsoutsideide on thethe the treatmenttreatment springs and area.area. then The transferredThe flexibilityflexibility to a of conveyorof thethe belt torsiontorsion springssprings enablesenablestransporting themthem toto them overcomeovercome from outside terrainterrain the obstacles,obstacles, treatment area. suchsuch The asas stones, ﬂexibilitystones, andand of theallowsallows torsion forfor springs the cleaning of sandyenables soils them and to waters overcome with terrain variable obstacles, ground such as contours. stones, and The allows drive for unit the cleaning is of the cleaning of sandysandy soils soils and and waterswaters with with variable variable ground ground contours. contours. The drive The unit drive is mounted unit is in the mounted in the frame closer to the land unit, but optionally, it can be mounted anywhere mounted in the frameframe closer closer to thethe land land unit, unit, but but optionally, optionally, it can it be can mounted be mounted anywhere anywhere on the frame that onon thethe frameframe thatthat doesdoesdoes notnot interfere interfereinterfere with withwith the thethe working workingworking shaft shaftshaft assembly. assembly.assembly. The operation TheThe operationoperation of the cleaning ofof thethe unit can cleaningcleaning unitunit cancan bebe managedmanaged by byby the thethe controller controllercontroller of the ofof drive thethe unit,drivedrive to unit,unit, which toto the whichwhich parameter thethe parameter recorders,parameter switches recorders,recorders, switchesswitchesand andand emergency emergencyemergency stop switches stopstop swsw areitchesitches connected areare connected toconnected the control toto panel thethe through controlcontrol electrical panelpanel cables throughthrough electricalelectrical cableslocatedcables located inlocated the water inin thethe unit waterwater or land unitunit unit. oror landland unit.unit.

FigureFigureFigure 3. Cleaning 3.3. CleaningCleaning device: 1—frame,device:device: 1—frame,1—frame, 2—surface 2—surface for2—surface mounting forfor to a mountingmounting water unit, to 3—surfaceto aa waterwater for unit,unit, mounting 3—surface3—surface to a land forfor unit, 4—drivemountingmounting unit of thetoto aa working landland unit,unit, element 4—drive4—drive of the cleaningunitunit ofof thethe machine, woworkingrking 5—linkage elementelement gear, ofof 6 thethe and cleaningcleaning 8—bearing machine,machine, supports 5—linkage of5—linkage the working shaft,gear,gear, 7—working 6 6 and and 8—bearing 8—bearing shaft, 9—clutch supports supports and 10—reducer. of of the the working working sh shaft,aft, 7—working 7—working shaft, shaft, 9—clutch 9—clutch and and 10—reducer. 10—reducer.

FigureFigureFigure 4. Working 4.4. WorkingWorking shaft of shaftshaft the cleaning ofof thethe cleaning machine:cleaning 1—torsionmachine:machine: springs,1—t1—torsionorsion 2—spring springs,springs, ﬁxing 2—spring2—spring screws, 3—mounting fixingfixing screws,screws, screws 3—3— for springmountingmounting mountings screwsscrews and 4—spring forfor springspring mounting. mountingsmountings andand 4—spring4—spring mounting.mounting.

Water 2021, 13, 736 6 of 11

5. Coupling of the Speed Control of a Land Unit and a Water Unit An important issue for the developed design is how to control the speed of the land and water unit in such a way as to ensure that the cleaning device moves nearly perpendicular to the direction of movement of the land unit, whose direction of movement is determined by the coastline (Figure 5b). Assuming that the land unit is decisive for the direction and speed of movement due to the greater danger of operation and the possibility of encountering more terrain obstacles, it is necessary for the Water 2021,motorboat’s13, 736 drive to have the possibility of position correction, which can be disturbed 6 of 11 by strong winds and sea currents.

FigureFigure 5. Possible 5. Possible position position of the water of the unit water in relation unit toin therelation land unit: to the (a) delayedland unit: water (a) unit,delayed (b) water water unit unit, in optimal (b) positionwater in relation unit in to optimal the land unitposition and (c in) overtaking relation waterto the unit, land where: unit 1—landand (c) unit,overtaking 2—water water unit and unit, 3—cleaning where: device.1— land unit, 2—water unit and 3—cleaning device. 5. Coupling of the Speed Control of a Land Unit and a Water Unit The maintenance-freeAn important adaptation issue of forthe the water developed unit to design the land is how unit to with control combustion the speed of the propulsion is ensuredland andby the water system unit inand such co antrol way concept as to ensure developed that the cleaningby the authors. device moves The nearly mounting to the landperpendicular unit used to for the the direction control of movementprocess is of equipped the land unit, with whose a sensor direction module of movement is determined by the coastline (Figure5b). Assuming that the land unit is decisive for for the position ofthe the direction water unit and in speed relation of movement to the land due unit to the (Figure greater 6). danger Its purpose of operation is to and the measure the angularpossibility position of encountering of the water more unit terrain in relation obstacles, to it the is necessary land unit for thethrough motorboat’s the drive edge sensors. The tomodule have the is possibility made up of of position a sensor correction, for the whichextreme can position be disturbed overtaking by strong the winds and land unit, a sensorsea for currents. the extreme position of the delayed movement of the water unit and a sensor for the idleThe position maintenance-free of the wate adaptationr unit. ofThe the sensors water unit are to activated the land unit by with a lever, combustion propulsion is ensured by the system and control concept developed by the authors. The which is coupled to the position of the cleaning module. Signals from the sensor module mounting to the land unit used for the control process is equipped with a sensor module of the position of thefor thewater position unit ofin therelation water unitto the in land relation unit to theare landdirected unit (Figure to the6 air). Its throttle purpose is to controller of the drivemeasure unit the of angularthe water position unit, ofadjusting the water its unit position in relation in relation to the land to unitthe land through the unit. The signal of edgeactivation sensors. of The the module sensor isof made the extreme up of a sensor position for the overtaking extreme position the land overtaking unit the reduces the tiltingland angle unit, of athe sensor throttle for the of extremethe water position unit ofto thethe delayedidle position, movement limiting of the the water unit speed of the unit movement.and a sensor The for theactivation idle position sign ofal theof the water sensor unit. of The the sensors extreme are activatedposition byof a lever, which is coupled to the position of the cleaning module. Signals from the sensor module the delayed water unit movement increases the tilting angle of the throttle of the water of the position of the water unit in relation to the land unit are directed to the air throttle unit to a positioncontroller of higher of theengine drive load, unit of increasing the water unit, the adjusting speed of its positionthe water in relationunit. The to the land acceleration processunit. ends The with signal a of signal activation from of the the sensoroptimum of the position extreme positionsensor. overtakingThe activation the land unit signal of the optimumreduces position the tilting sensor angle allows of the throttle us to ofcontrol the water and unit support to the idlethe position,selection limiting of the the optimum speedspeed of the of the land unit unit movement. to the water The activation unit. Optionally, signal of the a sensor centrifugal of the extreme clutch position in of the drive system thecan delayed disconnect water unit the movement drive at increases low speed, the tilting e.g., angle during of the idle throttle operation. of the water unit to a position of higher engine load, increasing the speed of the water unit. The acceleration Another optional processcontrol endsfunction with amay signal be from to engage the optimum the brake position or sensor.reverse The direction activation of signal the of the drive screw by activatingoptimum the position signal sensor from allows the sensor us to control of the and extreme support position the selection overtaking of the optimum the land unit, realizingspeed of the landanalogous unit to the process water unit. of Optionally,changing athe centrifugal throttle clutch angle in the in drive the system motorboat engine.can disconnect the drive at low speed, e.g., during idle operation. Another optional control function may be to engage the brake or reverse direction of the drive screw by activating the signal from the sensor of the extreme position overtaking the land unit, realizing the analogous process of changing the throttle angle in the motorboat engine.

Water 2021, 13, 736 7 of 11 Water 2021, 13, 736 7 of 11

FigureFigure 6. 6.Concept Concept of aof system a system for positioningfor positioning a water a water unit in unit relation in relation to a land to unit: a land 1—land unit: unit, 1—land unit, 2—water2—waterunit, unit, 3—joint 3—joint attached attached to the waterto the unit, water 4—joint unit attached, 4—joint to attached the land unit, to the 5—sensor land unit, mod- 5—sensor ule,module,6—extreme 6—extremeposition position sensor overtaking sensor overtaking the land unit, the 7—idle land unit, position 7—idl sensore position of the water sensor unit, of the water 8—extremeunit, 8—extreme position sensor position of the sensor delayed of movement the delayed of the watermovement unit and of 9—sensor the water activation unit lever.and 9—sensor activation lever. 6. Discusion 6. DiscusionIncreased invasion of beaches by seaweed has been observed over the last decade of the 21st century; hence, there are scientiﬁc articles describing this issue along with the Increased invasion of beaches by seaweed has been observed over the last decade of methods and consequences of dealing with this problem [66]. In the Riviera Maya of Mexico,the 21st 4400 century; people hence, were employed there are to scientific clean beaches articles in 2015, describing but this onlythis targetedissue along 10% with the ofmethods the coast. and The consequences scale of the phenomenon of dealing indicates with this the problem need for [66]. the mechanization In the Riviera of Maya of theMexico, process 4400 or the people use of were hybrid employ techniquesed to [clean31,67]. beaches In 2019, in tractors 2015, withbut this sweepers only targeted that 10% combedof the coast. the beaches The scale were of used the for phenomenon cleaning, which indicates somehow the improved need for thethe qualitymechanization of the of the beaches,process but or these the machinesuse of hybrid did not techniques have the ability [31, to67]. clean In water;2019, thus,tractors the cleaningwith sweepers did that notcombed fully satisfy the beaches the tourists were [ 31used]. At for the cleaning, same time, which in selected somehow cities improved in this area, the water quality of the barriersbeaches, were but applied these machines to limit the did ﬂow not of have seaweed the ab toility the beach,to clean without water; specifying thus, the cleaning the did not fully satisfy the tourists [31]. At the same time, in selected cities in this area, water barriers were applied to limit the flow of seaweed to the beach, without specifying the method of catching them [68]. In 2016, Hindus et al. indicated that manual beach cleansing resulted in less sand removal from the beach [69]; however, systems are currently being developed to rake collected seaweed. Scientists recognize that the use of sand screening devices is less beneficial to the coastal ecosystem than the innovative solution proposed

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method of catching them [68]. In 2016, Hindus et al. indicated that manual beach cleansing resulted in less sand removal from the beach [69]; however, systems are currently being developed to rake collected seaweed. Scientists recognize that the use of sand screening devices is less beneﬁcial to the coastal ecosystem than the innovative solution proposed by the authors, as the screens remove animals, insects or eggs buried in sand [70], while the proposed design only rakes up pollutants from the surface.

7. Conclusions The available methods of cleaning beaches without the use of machinery seem to be ineffective. On the other hand, machine-based beach cleaning methods are divided into two types of sand-cleaning land-based machines and water-purifying water machines. Most of them are based on sieve screens, the disadvantages of which include shaking animals, insects and eggs out of the sand, and taking up relatively large amounts of sand with the organic material. There are many methods for cleaning beaches and coastal waters. However, the available technical solutions do not meet the requirement of cleaning the shoreline belt area, which is important from the tourism point of view. The construction concept presented in this paper may ﬁll in this gap in the area of technical solutions for the simultaneous cleaning of the land (beach), the wave-fall area on the shore, coastal shoals and waters allowing the passage of boats. The conceptual solution was built up from three modules, of which the land unit (e.g., tractor) and the water unit (e.g., motorboat) are commonly available machines, while the cleaning mechanism is a specialized device that can be built from standard components used in agricultural machines. In addition, the cleaning module has its own independent drive, allowing it to work with different land and water units. The solution can be operated by a single operator as the design allows for matching the position of the water unit to the land unit, realized in such a way that the water unit follows the land unit.

8. Patents The design solution described in this paper is subject to a patent application in Poland by Szewczyk, J.W. and Warguła, Ł. The device for cleaning the coast and coastal areas, in particular from algae (original text in Polish: Urz ˛adzeniedo oczyszczania pasa brzegowego i przybrzeznego˙ w szczególno´sciz alg) was patented at Poznan University of Technology, Pozna´n,Poland, application number: P.429660, date of ﬁling 17.05.2019.

Author Contributions: Conceptualization, Ł.W. and J.W.S.; methodology, Ł.W., B.W. and M.K.; validation, Ł.W., P.K., M.K. and B.W.; formal analysis, Ł.W., J.W.S., P.K., M.K. and B.W.; investigation, Ł.W., J.W.S., P.K., M.K. and B.W.; resources, Ł.W., P.K., M.K. and B.W.; data curation, Ł.W., P.K., M.K. and B.W.; writing—original draft preparation, Ł.W., P.K., M.K. and B.W.; writing—review and editing, Ł.W., P.K., M.K. and B.W.; visualization, Ł.W. and J.W.S.; supervision, Ł.W., P.K., M.K. and B.W.; project administration, Ł.W.; funding acquisition, Ł.W. All authors have read and agreed to the published version of the manuscript. Funding: The research was carried out as part of the funding of the Polish Ministry of Science and Higher Education for the Poznan University of Technology as part of the project “Design, research and analysis of parts, assemblies of machines and vehicles for the purpose of searching for innovative solutions” no. 0611/SBAD/0115. Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable. Data Availability Statement: Not applicable. Conﬂicts of Interest: The authors declare no conﬂict of interest. Water 2021, 13, 736 9 of 11

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