ASTM_G_29_-_16.pdf

Designation:G2916Standard Practice forDetermining Algal Resistance of Polymeric 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.This standard has been approved for use by agencies of the U.S.Department of Defense.1.Scope1.1 This practice covers the determination of the suscepti-bility of polymeric 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 polymeric film are sus-pended in glass jars maintained at room temperature.The teststrips are exposed to fluorescent light and in direct contact witha standardized inoculum of the filamentous blue-green algaOscillatoria in culture medium.The sample test jars arere-inoculated with fresh alga every second or third day.Acontrol using untreated polymeric 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 untreatedcontrol shows dense algal growth.3.Significance and Use3.1 Bodies of water,such as swimming pools,artificialponds,and irrigation ditches often are lined with polymericfilms.Algae tend to grow in such bodies of water under theproper atmospheric 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 Tank:4.1.1 A small fish tank(10 gal)is used to contain an algaepropagation system where culture medium is recirculatedthrough a polymeric tube with holes punched in the bottomover the top of a polymeric mesh screen inside of the tank.Thisdesign was developed in order to provide ideal conditions forpropagation of the algae that serve as inocula for each test.Thepolymeric mesh is supported in such a way that water cascadesover the top from a distributor tube above.A small,fullyimmersed recirculating pump rests 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 polymeric mesh.A timing device turns the light on for thedesired light cycle each 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.Heavy growth of Oscillatoriarapidly develops on the polymeric mesh screen and,at differentphases,this growth appears light green,dark green,or black.NOTE1Culture medium in the propagation tank is discarded monthlyand replaced with fresh media.4.2 Test Chambers:4.2.1 One-litre(1-qt)wide-mouth glass jars,170 mm(634in.)high by 76 mm(3 in.)in inside diameter,orequivalent,serve as test chambers wherein water containing aninoculum of the algal organisms and strips of the polymericfilm are maintained in contact.4.2.2 The jars in 4.2.1 are placed in a suitable glasscontainer,such as a 38-L(10-gal)fish tank that is illuminatedby four 20-W“cool white”fluorescent bulbs,arranged two oneach long side of the tank,at the level of the growing algae inthe jars.The lamps are mounted on a bracket that holds theouter surface of the bulbs 25 mm(1 in.)from the wall of thetank.The tank is filled with water to within 25 mm(1 in.)of thetop of the exposure jars in order to create uniform temperatureconditions for all jars.4.3 HomogenizerAny suitable commercial homogenizerfor preparing the algal inocula.1This practice is under the jurisdiction ofASTM Committee G03 on Weatheringand Durability and is the direct responsibility of Subcommittee G03.04 onBiological Deterioration.Current edition approved Dec.1,2016.Published March 2017.Originallyapproved in 1971.Last previous edition approved in 2010 as G29 96(2010).DOI:10.1520/G0029-16.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade(TBT)