ASTM_G_29_-_96_2010.pdf

Designation:G2996(Reapproved 2010)Standard Practice forDetermining Algal Resistance of Plastic Films1This standard is issued under the fixed designation G29;the number immediately following the designation indicates the year of originaladoption or,in the case of revision,the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscriptepsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This practice covers the determination of the suscepti-bility of plastic films to the attachment and proliferation ofsurface-growing algae.1.2 The values in SI units are to be regarded as the standard.The inch-pound units given in parentheses are for informationonly.1.3 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Summary of Practice2.1 In this practice,test strips of plastic film are suspendedin glass jars maintained at room temperature.The test strips areexposed to fluorescent light and in direct contact with astandardized inoculum of the filamentous blue-green algaOscillatoria in culture medium.The sample test jars arereinoculated with fresh alga every second or third day.Acontrol using untreated plastic film is used as a basis ofcomparison.The inoculum is prepared with the help of apropagation apparatus made from a small fish tank.The test isterminated at the end of two weeks,or whenever the test filmshows dense algal growth.3.Significance and Use3.1 Bodies of water,such as swimming pools,artificialponds,and irrigation ditches often are lined with plastic films.Algae tend to grow in such bodies of water under the properatmospheric conditions,and they can produce slimy andunsightly deposits on the film.The method described herein isuseful in evaluating the degree and permanency of protectionagainst surface growth of algae afforded by various additivesincorporated in the film.4.Apparatus4.1 Propagation Tank2(see Fig.1):4.1.1 A small fish tank(10 gal)is used to contain asimulated cooling tower,made of redwood slats,over whichculture medium is recirculated through a plastic tube with holespunched in the bottom.This design was developed in order toprovide ideal conditions for propagation of the algae that serveas inocula for each test.Three redwood slats are joined by twosupports in such a way that water cascades over each slat inturn from a distributor tube above the upper slat.A small,fullyimmersed recirculating pump3rests on the bottom of the tankand operates continuously to deliver the tank contents to thedistributor tube.The light required for algal propagation isprovided by a 100-W bulb placed 300 mm(12 in.)away fromthe redwood slats.A timing device turns the light on for 12 heach day.4.1.2 The propagation tank,that is used as the permanentsource of inoculum,is filled to approximately one-third capac-ity with the culture medium.4Heavy growth of Oscillatoriarapidly develops on the redwood tower and,at different phases,this growth appears light green,dark green,or black.4.2 Test Chambers(see Fig.2):4.2.1 One-litre(1-qt)wide-mouth glass jars,170 mm(634in.)high by 76 mm(3 in.)in inside diameter serve as testchambers wherein water containing an inoculum of the algalorganisms and strips of the plastic film are maintained incontact.4.2.2 The jars in 4.2.1 are placed in a 38-L(10-gal)fishtank,508 by 267 by 305 mm(20 by 1012by 12 in.)high,thatis illuminated by four 20-W“cool white”fluorescent bulbs,arranged two on each long side of the tank,at the level of thegrowing algae in the jars.The lamps are mounted on a bracketthat holds the outer surface of the bulbs 25 mm(1 in.)from thewall of the tank.The tank is filled with water to within 25 mmof the top of the exposure jars in order to create uniformtemperature conditions for all jars.1This practice is under the jurisdiction ofASTM Committee G03 on Weatheringand Durabilityand is the direct responsibility of Subcommittee G03.04 on BiologicalDeterioration.Current edition approved June 1,2010.Published June 2010.Originallyapproved in 1971.Last previous edition approved in 2002 as G29 96(2002).DOI:10.1520/G0029-96R10.2The redwood tower should be soaked in water before use,until the water iscolorless.Water is changed daily.3Model 1 MA manufactured by the Little Giant Corp.,3800 N.Tulsa Ave.,Oklahoma City,OK 73107,has been found suitable for this purpose.4Culture medium in the propagation tank is discarded,and the tank is refilledwith fresh medium at monthly intervals.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 4.3 HomogenizerAny suitable commercial homogenizerfor preparing the algal inocula.5.Reagents and Materials5.1 Purity of ReagentsReagent grade chemicals shall beused in all tests.Unless otherwise indicated,it is intend