Biomedical Engineering Reference
In-Depth Information
FIGURE 21.6
Cross.section.of.ceramic.a.100.nm.membrane.supported.on.a.porous.alumina.substrate.
21.6 ApplicationExamples
The.following.brief.examples.demonstrate.the.great.lexibility.that.bio-.and.nano-enabled.
media.have.in.addressing.a.wide.range.of.contaminant.removal.problems.
•. Conversion of nitrates into.nitrogen.gas.can.be.done.at.rates.three.times.faster.than.
those.of.other.media..With.a.contact.time.of.3.minutes,.testing.shows.that.over.30.
g.of.nitrate-nitrogen/L/day.is.achieved,.compared.with.10.g/L/day.reported.for.
other.systems..This.is.done.by.controlling.the.surface.area.and.the.composition.to.
allow.large.colonies.of.heterotrophic.and.autotrophic.bacteria.to.develop..Nitrates.
come.mainly.from.nitrites,.ammonia,.and.organic.nitrogen.compounds.and.are.a.
common.form.of.inorganic.nitrogen.found.in.all.wastewater.treatment.systems,.
industrial. wastewater,. aquacultures,. and. runoff. from. farms. where. fertilizer. or.
manure.handling.exists..Nitrate-nitrogen.compounds.are.found.in.brackish,.salt,.
and.fresh.water.systems..While.nitrates.are.considered.a.plant.nutrient,.concen-
trations.greater.than.5.mg/L.cause.excessive.algae.growth,.leading.to.accelerated.
eutrophication.that.lowers.oxygen.and.kills.aquatic.life..Levels.above.10.mg/L.in.
drinking.water.can.harm.infants.
•. Phosphorous in.water.is.recognized.as.a.major.impairment.to.streams.and.lakes..
Eficient,. low-maintenance. technologies. are. needed. to. lower. discharge. from.
sources.such.as.animal.farms,.septic.systems,.ield.runoff,.and.industrial.waste-
water..Few.phosphorus.removal.approaches.exist,.and.most.are.based.upon.use.
of.iron.compounds..The.most.eficient.commercial.product.is.iron.activated.alu-
mina. (AA).. Nano-enabled. iron,. carried. on. a. porous. ceramic,. has. been. found. to.
remove.signiicantly.more.phosphorous.and.last.longer.when.used.to.treat.water.
collected.from.an.on-site.waste.treatment.system..The.media.had.a.capacity.of.55.
mg.of.phosphorus/g.media.vs..the.AA.of.18.mg/g..Phosphorous.was.still.being.
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