Removal of Persistent Organic Pollutants and Compounds of Emerging Concern in Public-Owned Sewage Treatment Works: A Review - Environmental Contamination: Health Risks and Ecological Restoration - page 158

much.higher,.ranging.from.550.to.1300.ng/mL..The.high.removal.eficiency.
(more.than.60%).for.trimethoprim.at.the.Shatin.STW.was.signiicantly.dif-
ferent.from.other.studies.(Snyder.et.al..2007).and,.thus,.is.also.worth.noting.
OtherTreatmentMethodstobeIncorporatedintoPOSTWs
Not.much.research.has.been.conducted.focusing.on.the.removal.of.POPs.and.
CECs. from. POSTWs.. USDI. 2009. had. reviewed. major. advanced. treatment.
technologies.for.the.removal.of.POPs.and.CECs.from.river.waters..The.data.
from.this.review.have.been.extracted.and.presented.for.hormones.and.anti-
biotics. (Tables. 8.5,. 8.9,. and.8.13),. and. other. pharmaceutical. (Tables. 8.6,.8.10,.
and.8.14),.agricultural,.and.industrial.compounds.(Tables.8.7,.8.11,.and.8.15).
Activated Carbon Adsorption
AC. is. a. family. of. carbonaceous. adsorbents,. with. a. highly. crystalline. form.
and.extensively.internal.pore.structure..By.using.different.production.tech-
niques.and.sources.of.raw.material,.markedly.different.characteristics.of.AC.
products. are. available. from. different. suppliers.. Surface. area,. BET-N2,. is. a.
measurement.using.nitrogen.gas.(N 2 ),.to.obtain.the.extent.of.the.pore.surface.
developed.within.the.matrix.of.the.AC..Surface.area.of.AC.is.a.primary.indi-
cator.of.the.activity.level.based.on.the.indings.that.the.greater.the.surface.
area,. the. higher. the. number. of. available. adsorptive. sites.. Using. 1.g. of. AC.
can.have.a.surface.area.in.excess.of.500.m 2 .due.to.its.high.degree.of.micropo-
rosity..Traditionally,.AC.is.grounded.into.ine.granules.of.less.than.1.0.mm.
in. size.. Granular. activated. carbon. (GAC). is. deined. as. AC. being. retained.
on. a. 50-mesh. sieve. (0.297.mm),. and. the. American. Society. for. Testing. and.
Materials. (ASTM). classiies. powdered. activated. carbon. (PAC). as. smaller.
than.an.80-mesh.sieve.(0.177.mm)..GAC.are.sold.in.different.size.of.granules..
A. 20. ×. 40. GAC. carbon. is.made. of. particles. that. will. (more.than.85%). pass.
through.a.U.S..Standard.Mesh.Size.No..20.sieve.(0.84.mm).but.will.be.(more.
than.95%).retained.on.a.U.S..Standard.Mesh.Size.No..40.sieve.(0.42.mm).
AC. removes. normal. organic. matter. and. organic. compounds. from. water.
through.hydrophobic.interactions..AC.total.surface.area.and.pore.structure.
has.a.large.inluence.on.adsorption.capacity.and.kinetics..The.AC.adsorption.
process. works. in. three. stages.. First,. the. compound. adheres. to. the. surface.
of.the.AC,.the.moves.into.the.large.pores,.and.is.inally.adsorbed.onto.the.
smaller.pores.and.inner.surface.of.the.AC..When.the.carbon.hits.its.break-
point,. it. is. referred. to. as. “spent”. and. is. needed. to. be. replaced. or. removed.
and.sent.off.to.be.reactivated..PAC.is.too.small.for.reactivation,.and.GAC.is.
typically.the.only.form.of.AC.to.be.sent.for.the.treatment.(reactivation)..The.
reactivated.carbon.is.then.sent.back.for.reuse.