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#water remediation

2 public questions tagged with this topic.

Bioremediation

Rhizofiltration is mainly used for removal of contaminants from:

Rhizofiltration specifically uses plant root systems grown hydroponically in greenhouse to develop extensive fibrous mass before transfer to contaminated water to filter, adsorb and absorb contaminants from groundwater, effluents and radioactive ponds. Dense mats of sunflower Helianthus annuus accumulating uranium and cesium, Indian mustard Brassica juncea removing lead and chromium, and bulrush Scirpus for selenium provide 10 to 20 square meters surface per plant coated with mucilage and biofilm containing phytochelatins that precipitate and chelate metals via ion exchange. Mechanism involves physical filtration of suspended particles, apoplastic uptake and symplastic transport via IRT1 transporter, vacuolar sequestration and microbial degradation in rhizosphere for organics. Water flows with retention hours to days achieving efficiencies above 90 percent for radionuclides Cs-137, Sr-90, lead at 0.1 to 10 mg per L. After saturation indicated by breakthrough curves, plants harvested, dried and ashed for disposal, making technique suited to low to moderate strength wastewaters rather than highly contaminated soils where metals less mobile and root contact limited.

Ref: Dushenkov et al. Environmental Science Technology 1995 Rhizofiltration of radionuclides; EPA Rhizofiltration overview; PubMed water phytoremediation 1997.

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Bioremediation

Phytoremediation uses:

Phytoremediation integrates botanical processes with rhizosphere microbial ecology for contaminant removal, transformation, containment or detoxification using living plants and their associated microbiome. Roots actively exude low-molecular-weight organic acids such as citrate, malate, oxalate, sugars like glucose, amino acids and flavonoids that function as chemoattractants recruiting plant-growth-promoting rhizobacteria including Rhizobium, Pseudomonas fluorescens, Burkholderia and mycorrhizal fungi like Glomus that colonize root surface and interior, forming beneficial biofilm carrying catabolic genes for pollutant mineralization. Plant contributions encompass uptake of water-soluble organics via transpiration stream, translocation, sequestration in vacuoles mediated by tonoplast transporters, enzymatic transformation via cytochrome P450 monooxygenases, glutathione S-transferases, dehalogenases and peroxidases, plus hydraulic control preventing plume migration through high evapotranspiration rates 5 to 10 liters per day per mature poplar. Associated microbes enhance bioavailability through biosurfactant production, siderophore mediated iron competition, and mineralize petroleum hydrocarbons to carbon dioxide while plant supplies habitat and oxygen via aerenchyma. Animals do not actively contribute to primary mechanism; purely microbial approach excluded because phytoremediation definition inherently requires plant component providing photosynthetically driven solar remediation engine.

Ref: Pilon-Smits Phytoremediation Annual Review Plant Biology 2005; EPA Phytoremediation overview 2000; PubMed plant-microbe interaction.

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